for show or safety

For Show or Safety? - A Study on Structure,Ballistic Performance and Authenticityof Seventeenth Century Breastplates

Sylvia Leever

MSc ThesisAugust 2005Supervision by dr. J. Dik and dr. ir. J. Sietsma

For Show or Safety? Master Thesis August 2005

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Abstract

In the seventeenth century soldiers usually wore some form of armour,most notably breastplates, to protect themselves against firearms. However,firearms became more and more powerful in time and the thickness of armourhad to be increased to be able to offer enough protection. After armour had lost itprotective quality and soldiers abandoned wearing armour, leaders still worearmour to indicate their status, so the armour was for show. But how muchprotection would a breastplate really offer the wearer?

To determine the amount of protection 17th century breastplates wouldgive, two specimens have undergone ballistic testing. The results from theballistic testing will be linked with results obtained through non-destructivetesting. A model is proposed, based on experiments and literature, which linksthe weapon parameters to the critical thickness of armour (below whichperforation of the breastplate is likely). The material properties of the breastplatewill determine how the critical thickness is influenced by the weapon parameters.A prediction of the protective quality of other original breastplates can be madewith this model, although more investigation towards the parameters influencingthe relation between critical thickness and weapon properties is necessary.Ideally only parameters that can be measured non-destructively, like thicknessand hardness, are necessary to predict ‘perforation’ or ‘no perforation’ due to abullet, of which the size, mass and speed at variable distances are known. Thisway a prediction of the protection offered by breastplates can be done throughnon-destructive testing of the specimens only, and future destructive research onoriginal armour can be limited.

Other tests to determine the properties like composition, microstructureand hardness of the breastplates were also performed.One of the two breast-plates turned out to be a nineteenth century replica, as indicated by its shape,microstructure, texture and low variable thickness. The other, original 17th

century breastplate shows a layered microstructure, which indicates the forging ofplates of iron together to increase the thickness for better protection.


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Acknowledgements

First of all I would like to thank the Delft Centre for Materials for fundingmy research under the Young Wild Ideas (YWI) flag, without this funding most ofthis research would not have been possible, or at least had become very difficultto pursue. Thanks also to David Starley and Thom Richardson of the RoyalArmouries in Leeds, England, who have encouraged me to do some research on17th century armour, and without them, I would not have thought of this project.

I am indebted to Dirk Visser of the Physics department of the NetherlandsOrganisation for Scientific Research (NWO) for arranging and making it possibleto go to England for neutron diffraction analysis at the ISIS facility at RutherfordAppleton Laboratory. I would also like to thank, in no particular order, thefollowing people for helping me on various parts of my research: Koen Herlaar,PML; Peter van Doorn, TNO; Arjan Rijkenberg, Corus; Bram Huis, Erik Peekstokand Ben Oude Engberink, DUT; Robert Douglas Smith for proof reading thisreport and for giving additional data; Winfried Kockelmann at ISIS for helping outwith the neutron diffraction analysis and texture analysis; Joop Hubers forproviding original bullets; Fred Hammers for taking the photographs of thebreastplates as received, and everybody else who has supported me during thisproject.


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Contents

Abstract ..................................................................................................... iiAcknowledgements ..................................................................................... iiiList of Figures ............................................................................................ viList of Tables .............................................................................................vii1 Introduction .............................................................................................1

1.1 Goal ..................................................................................................11.2 Methods of testing...............................................................................11.3 Examined breastplates .........................................................................21.4 Outline of the report ............................................................................3

2 History on armour in the 17th century ..........................................................42.1 Warfare in the seventeenth century .......................................................42.2 Weapons effectiveness on the battlefield.................................................52.3 Equipment of soldiers...........................................................................72.4 Production of armour ...........................................................................92.5 Testing of armour.............................................................................. 112.6 Modern research on armour ................................................................ 12

2.6.1 Microstructure and Composition ..................................................... 122.6.2 Hardness .................................................................................... 122.6.3 Thickness ................................................................................... 122.6.4 Tensile testing ............................................................................. 132.6.5 Test firing 17th century weapons .................................................... 13

2.7 Importance of destructive testing ........................................................ 143 Analytical techniques and sample preparation ............................................. 15

3.1 Sampling of the breastplates............................................................... 153.2 Breastplates ..................................................................................... 16

3.2.1 Composition ................................................................................ 163.2.2 Microstructure ............................................................................. 173.2.3 Hardness .................................................................................... 173.2.4 Thickness ................................................................................... 183.2.5 Tensile testing ............................................................................. 183.2.6 Neutron diffraction ....................................................................... 19

3.2 Bullets ............................................................................................. 223.2.1 Composition ................................................................................ 223.2.2 Casting....................................................................................... 223.2.3 Compression Test ........................................................................ 23

3.3 Ballistic testing.................................................................................. 234 Results .................................................................................................. 24

4.1 Breastplates ..................................................................................... 244.1.1 Composition ................................................................................ 244.1.2 Microstructure ............................................................................. 244.1.3 Hardness .................................................................................... 314.1.4 Thickness ................................................................................... 334.1.5 Tensile testing ............................................................................. 354.1.6 Neutron diffraction ....................................................................... 36

4.2 Bullets ............................................................................................. 414.2.1 Composition ................................................................................ 414.2.2 Compression Test ........................................................................ 41

4.3 Ballistic testing.................................................................................. 414.3.1 Test results ................................................................................. 414.3.2 Energy versus thickness................................................................ 45


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5 Discussion ............................................................................................. 475.1 Introduction...................................................................................... 475.2 Authenticity of BP2 ............................................................................ 475.3 Layered structure of BP1 .................................................................... 485.4 Critical thickness of armour................................................................. 49

6 Conclusion ............................................................................................. 557 References............................................................................................. 56Appendices ............................................................................................... 57


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List of Figures

Figure 1: The examined breastplates, BP1 (left) and BP2...................................3Figure 2: Battle of Breitenfeld, 1631, depicted in a contemporary drawing ...........4Figure 3: 17th century flintlock musket and pistol .............................................6Figure 4: Cuirass (c. 1590) of Prince Maurice of Orange with named parts ...........7Figure 5: Armour for a pikeman (left) and for a harquebusier/musketeer.............8Figure 6: Weaponsmith in the seventeenth century ........................................ 11Figure 7: Experiment in Graz, 1989, before (left) and after shooting ................. 14Figure 8: Sample locations for chemical and microstructure analysis ................. 15Figure 9: Sample locations for microstructure analysis .................................... 16Figure 10: Test rod dimensions in mm for tensile testing ................................. 16Figure 11: Schematic view of the ROTAX instrument....................................... 19Figure 12: Locations on the breastplates that have been scanned by ROTAX ...... 20Figure 13: Sample orientation in GEM analysis............................................... 21Figure 14: Original seventeenth century bullet mould...................................... 22Figure 15: Experimental setup at PML for ballistic testing ................................ 23Figure 16: Microstructure of BP1A ................................................................ 26Figure 17: Microstructure of BP1B ................................................................ 27Figure 18: Microstructure of BP2.................................................................. 27Figure 19: Twinning in BP1-Iy ..................................................................... 28Figure 20: Absence of pearlite bands in outer rim of cross-section of BP1 .......... 28Figure 21: Pearlite bands in centre of cross-section of BP1............................... 29Figure 22: Pearlite in between ferrite grains .................................................. 29Figure 23: Layer boundaries in cross-section of BP1........................................ 30Figure 24: Microhardness of BP1.................................................................. 32Figure 25: Microhardness in the centre of BP1 ............................................... 33Figure 26: 3D scan of BP1 with thickness profile in mm................................... 34Figure 27: 3D scan of BP2 with thickness profile in mm................................... 35Figure 28: Zoomed diffraction pattern .......................................................... 37Figure 29: Difference in diffraction pattern of BP1 and BP2 .............................. 37Figure 30: Difference in diffraction pattern of BP1 .......................................... 38Figure 31: Pole figures of (110) planes of rolled and annealed bcc iron.............. 39Figure 32: Pole figures for BP1 and BP2 ........................................................ 40Figure 33: Displacement in BP1 in mm.......................................................... 43Figure 34: Displacement in BP2 in mm.......................................................... 44Figure 35: Energy vs. thickness as measured................................................. 46Figure 36: Critical thickness of armour.......................................................... 50Figure 37: Critical thickness at various distances............................................ 51Figure 38: Critical thickness of armour through time....................................... 52Figure 39: Average thickness of breastplates through time .............................. 53

Figure on title page: Cavalry Battle, Jan van Huchtenburg (1647 – 1733)


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List of Tables

Table 1: Hardness in HV of some pieces of armour ......................................... 12Table 2: Thickness values in mm of several pieces of armour ........................... 13Table 3: Results of chemical analysis with elements in weight % ...................... 24Table 4: Hardness in HV of various samples of BP1 and BP2 ............................ 31Table 5: Results from tensile testing............................................................. 36Table 6: Phase analysis of GEM and ROTAX data ............................................ 38Table 7: Elements present in lead bullets in wt% with standard error ................ 41Table 8: Results of ballistic testing ............................................................... 42Table 9: Weight loss of bullets..................................................................... 44Table 10: Test firing selected 17th century weapons........................................ 51


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1 Introduction

In the sixteenth and seventeenth centuries the use of firearms graduallyincreased and the firearm became the main weapon on the battlefield. Wearingsome form of armour was the traditional way to dress in combat. For makingarmour in the seventeenth century, iron was favoured instead of steel, becausesteel is more difficult to work with than iron, and was also much more expensivein that period. The thickness of iron plates was increased to improve theprotection armour would offer. The armourers in the seventeenth century wereknown to make their armour proof against impacts from at least pistol bullets. Inthis research two breastplates of alleged 17th century origin are put to the test.Were they able to protect the wearers against bullet impacts from either pistolsor muskets? Also attention is paid to the quality of the breastplates with respectto the metallurgy. The composition and microstructure can give valuableinformation about the performance of the plates. Various analytical techniquesare used to determine the different properties of the material. The battletechniques and weapon performances in the period of the origin of thebreastplates are discussed, and the production and testing procedures of armourare described.

Technological research on armour has not been very extensive. Mostresearch to date is restricted to non-destructive research like hardnessmeasurements and local microstructure examination of flakes or rims of armour.Almost no destructive testing of original samples has been done. There has beensome testing on hardening and tempering of two pieces of sixteenth centuryarmour, an Italian vambrace (arm defence) of c.1570, and an Innsbruck pauldron(shoulder defence) of c. 1550, of which the composition was determined by SEManalysis and the carbon content by metallography. The samples were also testedon yield stress and elongation with tensile testing [Williams, 2003]. Onbreastplates no destructive testing is known to date, with the exception of a 1570Augsburg breastplate, which had one bullet fired at it [Krenn, 1989].

1.1 Goal

In this research the focus lies on determining the amount of protection thebreastplates will offer against bullet impacts. To do this, it is necessary to find outwhat the properties like microstructure, hardness and thickness of the material ofthe breastplates are. A critical thickness will be determined for ballisticperformance. The results from the ballistic testing will be linked with resultsobtained through non-destructive testing, also with results from earlier research.This way a prediction of the protection offered by breastplates can be donethrough non-destructive testing of the specimens only, and future destructiveresearch on original armour can be limited.

1.2 Methods of testing

In order to determine the properties of the material of the breastplates,several tests should be performed. The composition of the material can givevaluable information about the concentration of elements and thus indicates whatphases can form given certain circumstances. This can be verified by looking atthe microstructure, which can give information on the history of the material,whether any heat treatments were performed on the material or if anydeformation on a microscopic scale is present. Another way of finding out whatphases are present in the material is diffraction. X-Ray diffraction will give


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information about the top layer (10 – 20 µm) of the material, whereas neutrondiffraction will give the average phase composition of the bulk material. Thislatter technique is therefore used. Also with neutron diffraction a texture analysiscan be carried out which can give information about a preference in orientation ortexture. This can indicate a certain technique that has been used to make theobject in question (e.g. cast, rolled or minted materials each give differenttextures).

The hardness of the material is an indication for the performance on yieldstrength and impact strength. To find out whether the material has a goodperformance under tensile stress, a tensile test is performed. The performance ofthe breastplates is also dependent on the (local) thickness. With 3D scanning athickness profile with an accuracy of 0.1 mm has been made.To find out what the protective quality of the breastplates is, ballistic testing isperformed. Lead bullets were fired at the breastplates with varying speeds to findout where the limit of protection of either breastplate lies.

Some of the testing techniques mentioned above, especially the ballistictesting, tensile testing and in a lesser degree the composition and microstructureanalysis, will (partially) destroy the object in question. This is necessary becausewithout destructive testing it is not possible to determine some properties of thematerial. In this research it is not possible to solve the key problem - the amountof protection the breastplates offer the wearer – without destructive testing.However, damage to the object is generally not desired or permitted whenhandling antiques. Therefore, as much information as possible should be obtainedthrough non-destructive testing. This research will also try to limit futuredestructive testing of original armour by linking the results from destructivetesting to those results obtained through non-destructive testing.

1.3 Examined breastplates

For this research two seventeenth century breastplates were available, thefirst of which was purchased from Andrew Lumley, an arms and armour dealer inEngland. It is a relatively heavy breastplate, weighing 5.48 kg, and has muchsurface corrosion. According to Lumley, the breastplate was made between 1600and 1630 in Northern Europe, probably Germany. It is of a type that was used inthe Thirty Years War. The provenance is a collection in England where it has beenfor the last 15 years. In this report this breastplate is referred to as ‘BP1’.

The second breastplate was obtained through West Street Antiques, adealer in Antique Arms & Armour and Period Furniture, in Dorking, Surrey,England. According to the salesmen of WSA, it is an English cavalry trooper’sbreastplate from the English Civil War period, c. 1645. It is probably of NorthEuropean manufacture, possibly Dutch. In this report this breastplate is referredto as ‘BP2’. The weight of the breastplate is much less than of the first one, only2.42 kg. The surface appears to have undergone a treatment with an angle-grinder to remove some corrosion; the inside is painted black, which wasprobably done to prevent the inside from corroding due to body heat and sweat.

Also a few original bullets from the seventeenth century (found in anarchaeological dig of a cesspool in Groenlo, the Netherlands) were available forstudy. These were made in the Eighty Years War and probably used during thesiege of Grol in 1627 (as Groenlo was called in the 17th century).


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Figure 1: The examined breastplates, BP1 (left) and BP2

1.4 Outline of the report

In the next chapter the production, use and testing of armour in theseventeenth century, the effectiveness of weapons on the battlefield and the wayof warfare in that period are discussed. In paragraph 2.6 all relevant moderntesting of armour is described and results up to date are given. In the lastparagraph of chapter two the importance of destructive testing with respect tothis research is indicated. In the third chapter all analysing techniques andequipment used are described, and the procedure at each testing is made clear.The following chapter contains the results of each technique, which are discussedand where possible compared with the results of other, similar research. Inchapter five three main topics that arose from the results are specificallydiscussed, in order to reach a conclusion and give some recommendations inchapter six.


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2 History on armour in the 17th century

2.1 Warfare in the seventeenth century

There was much turmoil in Western Europe in the seventeenth century.The Dutch Republic was fighting for her independence against Spain in the EightyYears War (1568 – 1648), and in Germany the Thirty Years War (1618 – 1648)was fought, a war between Imperialists (Protestants) and Catholics. Not onlyGermany was involved in this war, but France, Spain, Poland, Denmark andSweden were also trying to gain influence in the German case.

Figure 2: Battle of Breitenfeld, 1631, depicted in a contemporary drawing(selection)

Under the influence of Prince Maurice of Orange the Dutch armiesdeveloped new tactics, which were partially copied by Gustavus Adolphus, theSwedish King. Some of these innovations were: the drawing up of the infantry insix, later three ranks, and its ability to perform spectacular wheelingmanoeuvres; the deployment of the line in the attack and the use of light artilleryin the offensive. This required a strict discipline of the infantry, and when theywere not fighting, they were training every day. Also field defences were built bythe soldiers themselves. This was not only a tactical defensive move, but alsoensured the continual discipline of the troops. Another example of the disciplineof the soldiers can be found in the loading and firing of a musket. This processwas broken down into forty-three separate actions, which had to be learned bycontinuous daily drill. All steps have been illustrated and written down in 1607 inDe Gheyn’s The Exercise of Armes. Also drills for pikemen and other soldiers havebeen written down and illustrated in the beginning of the 17th century.

The ratio between pikemen and musketeers gradually changed in thesixteenth and seventeenth century from about 5 : 1 to the opposite, one pikeman


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for five musketeers. Also the general number of soldiers that formed an armyincreased, owing to financial and organisational improvements and thestandardisation of weapons. However, financial, logistical and personal factors allset limits on the size and the actual dedication of armies. Seventeenth-centurysources indicate that between 30,000 and 40,000 troops in the field was theabsolute maximum. And these could only be maintained for a brief period. Suchlarge armies had also a large influence on society; citizens were highly taxed tofinance the army, while the armies themselves plundered and destroyedindiscriminately.

The tactical revolution, the increase in scale, and the greater influence ofthe army and war on the civil society did not evolve in the brief period around theend of the sixteenth and the beginning of the seventeenth century, but was agradual process, pertaining particularly to the eighteenth century. Most battleswere still fought along traditional lines and victories were rarely determined bythe implementation of new tactical principles. Just as these had been in earliertimes, warfare and the results of battles were determined by a large number offactors, which were not definitively influenced by a better organized army andtactical innovations: climate and terrain, disease and desertion, leadership andpersonal capacities of the officers and generals among them.

The ultimate outcome of a battle was decided during the combat of managainst man, in the midst of a general mêlée of troops. No matter how advancedthe army might be in other matters, however subtle the manoeuvres of thetroops were in the face of the advancing infantry of its opponent, the battle wasultimately decided in the chaos of man-to-man fighting. The tactical formula thatGustavus Adolphus applied was the following [Moor in: Van der Hoeven ed.,1997]: first the enemy infantry would come under fire from the artillery and themusketeers, then cavalry charges, and finally attacks made by the infantry usingshort pikes should give a decisive outcome to the battle. He reduced the basicorganisation to three or four companies, which together formed a battalion (500men). He carried out daily training, exercises, and arms drill with the samestrictness as Maurice of Orange.

2.2 Weapons effectiveness on the battlefield

Battles were fought at very close quarters. Cheaply manufactured militarymuskets, not equipped with sights, were by no means reliable. The distance overwhich it could contribute to the battle was less than 200 metres, whereas theeffective range lies between 30 and 100 metres. The theoretical effectiveness wasdetermined through test-firing muskets at a static target of 1.75 m by 3 m[Hughes, 1974]. It was found that the percentage of shots actually hitting thetarget drops off quickly with increasing distance beyond 100 m, to less than 20%at distances greater than 250 metres. In the actual battle however, shots werefired on animate targets, which lowers the theoretical effectiveness of themusket. Also, the musket was subject to technical failures, which can partly beattributed to the experience of the firer. The amount of powder could beinaccurate, which would cause variations in the performance of the weapon,particularly with regard to the range. The firing mechanism was unreliable andmisfires occurred frequently. Matchlock guns were of no use in wet weather.Errors related to stress and pressure of the men in battle should not beunderestimated. A strong nerve is needed to aim a musket accurately when theenemy is charging at you and there would be only time for one or two shotsbefore the charge would crash in. Training and discipline could ensure that fewernerves would break down at the critical moment.

Another aspect with respect to the effectiveness of the firepower of theinfantry is human fatigue. The musketeers often had to perform on the battlefieldafter a long and tiring march to get there in the first place. In most cases they


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had not been properly fed and at the critical moment, the musket would feelheavy and the point would drop, thus causing the shot to be inaccurate. Infantrycould not load and fire on the move, so they engaged when static at a distance ofaround 50 metres.

The ammunition supply also influenced the firepower of the armies. TheBritish infantryman carried 60 rounds on his person, and this seems to have beensufficient for most battles. In more elongated battles the firer could run out ofammunition. In more isolated posts, it was difficult to replenish the stock.

When firing a musket, the exploding gunpowder leaves a dense whitesmoke. The batteries of soldiers would be enveloped in the smoke, so that thesoldiers were not able to see the enemy ranks. This reduced the time in whichartillery could maintain its maximum potential rate of fire.

Figure 3: 17th century flintlock musket (c. 1650) and pistol (c. 1645)

All of the factors described above lead to the conclusion that theeffectiveness of the weapons on a 17th century battlefield is not very great. Thechance of actually being hit by a bullet is definitely not negligible, but that ismainly because of the large numbers of muskets that were in play during thebattle. Most musketeers did not wear any armour, but if they did, like thepikemen, the question remains whether it would have saved the wearer againstthe impact of a bullet. What energy would a bullet from a seventeenth centurymusket or pistol have at 30 or 100 metres? Would this energy be sufficient todefeat certain armours? If the armour would not give enough protection, mostsoldiers would have abandoned wearing them, because of the weight that wouldslow them down and tire them more quickly. The fact that still a lot of soldierswore armour in the early seventeenth century should indicate that it had asignificant effect. When the common soldiers abandoned wearing armour at theend of the seventeenth and in the eighteenth century, the generals and otherleaders would still sometimes equip themselves with decorated armour. Theprotection these armours would give the wearer was not sufficient, so from thatpoint onwards armour would have a decorative function only and indicated thestatus of the wearer, who was able to afford the armour. Wearing armour wascompletely abandoned after around 1660, and for a considerable period beforethat the common soldier was wearing less and less armour.


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2.3 Equipment of soldiers

Figure 4: Cuirass (c. 1590) of Prince Maurice of Orange with named parts

In the army of the seventeenth century there were different units withdifferent tasks - infantry, cavalry and artillery. Within the infantry there weredifferent roles: there is mainly a distinction between the pikeman, the one whocarried a pike of over 5 metres long, and the musketeer, with a matchlock orflintlock musket. Aside from the very long pike, the pikeman also had a shortsword, and wore armour suitable for hand-to-hand combat with other similarlyequipped men. The pikemen’s armour consisted of a brimmed pot, a gorget, abreastplate with tassets and a backplate (see Figure 5). The musketeer worearmour to be protected from cavalry assaults, though this seemed not to have


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been always the case, and was in the second half of the seventeenth centurymore an exception than a rule. If any armour were worn, then it would only be apot with often a triple-bar face defence, a breast- and backplate fitted with a highneck and worn without a gorget. Protection of the arms by pauldrons, vambracesand gauntlets appear to have become redundant at least for the infantry in theseventeenth century.

Figure 5: Armour for a pikeman (left) and for a harquebusier/musketeer

The cavalry was equipped with a sword and one or two pistols in holstersthat were attached to the saddle and they generally had more armour than theinfantry. A harquebusier, light cavalry with a carbine, a short musket, wore a pot,a back- and breastplate and left gauntlet over a leather buff coat. The heavycavalry, armoured cuirassiers firing pistols or carbines, usually had a close helminstead of a pot and cuisses that came down to the knee to protect the completeupper leg (see Figure 4). Pauldrons, vambraces and gauntlets seem to have beenworn by the cavalry after the infantry had disposed of them. The breast- andbackplates of the cavalry were commonly of thicker, and thus heavier, quality,because the horse did part of the carrying. The cuirass of Prince Maurice ofOrange (1567-1625) that was made in 1590 in the Netherlands is considered tobe the prototype of the cuirass for cavalry in the seventeenth century from theNorth-Netherlands.

The artillerymen operated the guns on the battlefield and generally woreno armour or helmet, because the range of the guns was much greater than thatof muskets, and it would encumber them in their movements. After some volleysor direct shots had been made and the battle had proceeded to hand-to-handcombat, the artillery would retreat.


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2.4 Production of armour

Armour is made from iron, a material that is malleable enough to beformed into the various necessary parts. The iron came either from a bloomeryhearth or from a finery. In a bloomery iron ore is reduced to iron by heating ittogether with charcoal at a temperature of about 1200 °C. The iron, which has amelting temperature of 1540 °C, does not melt and has a very low carboncontent. In a finery, cast iron, a brittle form of iron with more than 2 wt% ofcarbon and a melting temperature of 1150 °C, is decarburised by re-melting in anoxidising atmosphere. The wrought iron obtained in either way is essentially thesame; it is pure iron with low concentrations of other elements, and contains acertain amount of slag. This slag is produced during the iron making process fromimpurities in the ore and from the furnace lining itself. The finery process wascheaper and gradually replaced the bloomery hearth in the sixteenth century,although bloomeries were still used on a semi industrial scale until the 20th

century. It is difficult, if not impossible, to distinguish metallurgically betweenwrought iron from the bloomery hearth or the finery, i.e. their microstructuresare very similar.

Wrought iron is relatively soft, but can be hardened by adding a smallamount of carbon, preferably around 0.8 wt%, to make steel. More commonly acarbon percentage between 0.2 and 0.8 is found in surviving specimens of 15th to17th century armour. The difficulty is to get the carbon distributed evenlythroughout the wrought iron. There are several methods to increase the carboncontent in a piece of iron:

• Case-carburisation. A piece of iron; a bar, plate or even the finishedobject, would be wrapped in charcoal or some organic material and heatedred-hot (between 900 and 1000 °C) for a long time. The carbon diffusesinto the iron, but the process results in a greater concentration of carbonat the surface than in the centre. This process was described byTheophilus in the 12th century [Theophilus, 1963]. This method is verysuitable to harden the edges of files, knives and swords, but it is lesssuitable to be used when making armour, and is therefore seldom foundtherein.

• Leaving the bloom longer in the bloomery hearth means that it will spendmore time in contact with CO gas, thus absorbing some carbon. Again,this leads to a greater concentration of carbon at the surface of the bloomthan in the centre.

• Partial decarburisation of cast iron. This was a common practise, but it isvery difficult to stop the ‘fining’ process at just the right time, so a goodknowledge of what was going on was necessary. Pieces of solid wroughtiron could also be put into a pool of liquid cast iron, thus lowering thecarbon content. With this process there will be no clear gradient in carboncontent.

Most of these methods yield very heterogeneous steel, but by folding and forgingthe material one or more times the carbon content would become morehomogeneous. This folding can be seen in the microstructure in the form of bandsof different carbon content.

Steel itself can be hardened by heating it up to 900°C and then quenchingit in water (full quench) or oil (slack quench) and has been done since the earlyfifteenth century. After a full quench the steel can be too hard and also verybrittle. In this case tempering is desired. Re-heating the material to a moderatetemperature for a specific time will result in a softer, but tougher, material. Iron,which contains no carbon, cannot be hardened. The effectiveness of hardeningand tempering depends not only on the skill of the armourer, but also very muchon the actual carbon content. In the fifteenth and sixteenth century most armourswere made of some sort of steel, with some attempts at hardening, whereas in


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the seventeenth century, possibly because of the larger demand, which reducedthe time an armourer had to make armour, most armours were made of pure ironor very low grade steel with up to 0.2% carbon. It is easier to work with iron orvery low carbon steel than with high grade steel which has to be hardened andtempered to optimise the performance.

Once a lump of iron had been obtained it was flattened to a certainthickness by water-powered hammers. Flattening the plate by hand was possible,but very hard work, and using water-powered hammers for flattening waspreferred. From the flattened iron the various pieces of armour were made bycutting the pattern out of the plate and hammering it with various hammers ondifferently shaped stakes or anvils until the desired shape was obtained.Hammering the plate gives a breastplate a rough surface, with many small dentsfrom the hammer impacts. This appearance, ‘rough from the hammer’, seems tohave been the final result for the cheaper breastplates, the more expensive suitsof armour would undergo smoothing out of these dents (planishing) and finalpolishing. A possible advantage of leaving the breastplate ‘rough from thehammer’ is that by hammering the plate, cold work has been put into thematerial, thus hardening the top layers. Planishing could have cold hardened thematerial a bit more, but polishing will warm up the surface and remove some ofthe effects of cold work.

It has been found that on most breastplates the middle region is thickerthan the parts on the wearers sides, which could mean that the starting plate wasof inhomogeneous thickness, or that a second, smaller, plate was forged togetherwith the complete breastplate, to get locally more thickness. In this case a‘duplex’ breastplate was made, which consists of two (or more) layers of ironplates of sometimes variable composition. This was done to give the wearer moreprotection to his vital parts. Also riveting of two breastplates together to improvethe quality was done.

There is no typical thickness for amour plate in general, the armourermade the armour with a purpose, and depending on that purpose, whether itshould be able to withstand bullets or not, the thickness was made high or low.Nevertheless, there seems to have been an average thickness that is constantthrough time, which corresponds to a comfortable weight for a back- andbreastplate. This thickness lies between 1.5 and 3 mm. Apart from that, there isa rise in maximum thickness starting in the late fifteenth century at 3 mm to 6 or7 mm in the mid seventeenth century [Williams, 2003]. A thickness of 7 mmwould imply an uncomfortable weight to carry along in battle, but the protectionwould have been better, and some men might have preferred protection abovecomfort. This thicker armour was supposed to be bullet-proof, or at least pistolproof. For a foot-soldier the extra weight would be cumbersome, so most armourthat is too thick for comfort would have been worn by horsemen.

The quick increase in maximum thickness of the armour plates can also,aside from needing better protection, be explained by the rise in demand ofbreastplates in the seventeenth century. There were on average 20,000 soldiersin an army, many of them needed a breastplate. To meet this demand, thequality of the breastplates was decreased, so the production speed wouldincrease. Because wrought iron is more malleable than steel, the productionwould speed up if the steel is replaced with (pure) iron to make armour. Aconcession that had to be made here is that an iron breastplate has to be thickerthan a steel one in order to give the same amount of protection. Also, and moreimportantly, steel was much more expensive than wrought iron, and if a wholearmy has to be equipped with armour for a limited amount of money, using cheapiron is also a logical thing to do. The knowledge of making good quality steelbreastplates as can be found in examples from the late fifteenth and earlysixteenth century was not lost immediately, but put aside to be able to produceaffordable armour for the large armies.


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Figure 6: Weaponsmith in the seventeenth century (painting by GabrielMetsu, 1629-1667)

2.5 Testing of armour

After breastplates were roughly finished, and before decoration likeetching, gilding and polishing, they were tested. The testing of armour plate hadbeen regularly done since the late 14th century. The plates were tested with anarrow from a longbow or a thrown spear but more commonly with a bolt from acrossbow, either hand-spanned or windlass-spanned, the latter being morepowerful. In the late 16th and the 17th century testing with firearms wasintroduced, because gradually muskets had replaced the longbows and crossbowson the battlefield. Also the ratio of firearms to pikes increased greatly, with in theend more firearms than pikes present. The Archduke Maximilian II is recorded astesting his armour with two pistol and harquebus shots in 1561. Armour that was‘proof’ against the far more powerful firearms thus eventually grew thicker anduncomfortably heavy as a result. The dent that was left in the armour by the testshowed that the armour was ‘of proof’. In most dented armours that are ondisplay in museums the dent is caused by this test of proof, and is not result ofbattle. Also the armour of Prince Maurice of Orange has a dent of proof (seeFigure 4). Not all armours were tested in such way, possibly because the dent ofproof was not a pretty sight in highly decorated armour, or that the makers couldnot be bothered because it was not required in all armouries and they would notbe fined if they did not test their products.


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2.6 Modern research on armour

In this paragraph some relevant results of tests on armour before 2004are listed. All other research on armour is largely done on material from thesixteenth century or before, but the methods of testing are comparable to what isdescribed below.

2.6.1 Microstructure and Composition

A number of pieces of armour from the first half of the 17th century havebeen examined by Alan Williams [Williams, 2003]. The microstructures of most ofthese samples show ferrite with little or no pearlite and some slag. An exceptionon this rule is one or two samples that have a complete fine pearlitic structure ora martensitic structure (with some ferrite). A summary of composition andestimate of carbon content can be found in Appendix A.

2.6.2 Hardness

Some hardness data on armour has been obtained by Alan Williams[Williams, 2003] and by Robert Douglas Smith [R.D. Smith, personalcommunication, 2005]. A selection of the results on these hardnessmeasurements is put together in Table 1. Williams has measured a few locationson the pieces of armour and took the average, which is listed together withminimum and maximum values. Smith has measured on 20 to 30 locationsspread over the breastplate and took minimum value, maximum value, range,mean and standard deviation.

Table 1: Hardness in HV of some pieces of armour

Date Sample Mean Min Max Origin Source Remarkc. 1610 Breastplate 225 158 375 RA Smithc. 1625 Breastplate 282 202 490 RA Smithc. 1625 Backplate 272 166 430 RA Smithc. 1630 Breastplate 244 201 289 HJR Williams p. 450, microhardnessc. 1630 Breastplate 190 186 310 WA Williams p. 713, hussar’s (A)c. 1630 Breastplate 187 109 310 WA Williams p. 713, hussar’s (B)c. 1630 Breastplate 141 98 280 WA Williams p. 713, hussar’s (C)c. 1640 Breastplate 210 130 285 RA Smithc. 1640 Backplate 182 154 224 RA SmithRA = Royal Armouries, LeedsHJR = Hofjagd- und Rüstkammer, ViennaWA = Wawel Armoury, Poland

2.6.3 Thickness

Data on armour thickness has been obtained by Alan Williams [Williams,2003]; the mean value of four measurements on the breastplates, and by RobertDouglas Smith [R.D. Smith, personal communication, 2005]; in a mesh withsquares of 2 by 2 cm laid over the armour the thickness was measured in thecentre points of those squares. Minimum, maximum, range, mean and standarddeviation are listed afterwards. Parts of fifteenth to seventeenth century armourhave been measured, and in Table 2 a selection of seventeenth century data islisted.


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Table 2: Thickness values in mm of several pieces of armour

Date Sample Mean Min Max Origin Source Remarkc. 1610 Breastplate 2.2 0.9 3.6 RA Smithc. 1615 Breastplate 1.9 - - Graz Williams Infantryc. 1615 Breastplate 2.4 - - Graz Williams Infantryc. 1615 Breastplate 2.5 - - Graz Williams Infantryc. 1615 Breastplate 2.8 - - Graz Williams Infantryc. 1620 Breastplate 3.3 - - HJR Williams Horsemanc. 1625 Breastplate 1.6 0.8 2.9 RA Smithc. 1625 Backplate 1.4 0.9 2.2 RA Smithc. 1635 Breastplate 5.2 - - Graz Williams Horsemanc. 1635 Breastplate 5.7 - - Graz Williams Horsemanc. 1635 Breastplate 4.8 - - Graz Williams Horsemanc. 1640 Breastplate 1.2 0.7 2.1 RA Smithc. 1640 Backplate 1.3 0.6 2.4 RA Smithc. 1650 Breastplate 1.8 0.7 3.9 RA Smithc. 1650 Breastplate 1.7 0.7 3.9 RA Smithc. 1682 Breastplate 4.5 - - Graz Williams Horsemanc. 1685 Breastplate 4.3 - - Graz Williams HorsemanRA = Royal Armouries, LeedsGraz = Landeszeughaus, GrazHJR = Hofjagd- und Rüstkammer, Vienna

2.6.4 Tensile testing

Mechanical properties of original material have not been determined ingreat detail, only tensile testing of two historic samples is known. This wasperformed by Williams [Williams, 2003], on an Italian vambrace of c. 1570, apearlitic steel, hardness 183 HV, and an Innsbruck pauldron plate of c. 1550, atempered martensite with 0.5% C and a hardness of 514 HV. The yield strengthof the vambrace is 107 N/mm2, the ultimate tensile strength 426 N/mm2 and theelongation at fracture is 40%. For the pauldron these values are 132 N/mm2, 513N/mm2 and 19% respectively.

2.6.5 Test firing 17th century weapons

Because armour of the seventeenth century is considered antique andmuseums are not likely to approve of destructive testing of their exhibits, it is notpossible to test those specimens with real bullets. For this reason all previousimpact testing was largely done on modern mild steel or ‘Victorian’ wrought iron(puddled iron), with simulated guns and ammunition, or with longbows andbodkin arrows. With these tests the energy of the missile was calculated and theresult (penetration or not) was recorded. There is one known example where anoriginal breastplate has been tested on ballistic performance. The experiment wascarried out at the Landeszeughaus in Graz in 1989 as a secondary test duringresearch on performance of 16th to 18th century weapons. For the experiment a1620 wheellock pistol (used by cavalry) and a 1570 breastplate were used. Thetest was performed under the following conditions. The breastplate was strappedto a sandbag with two layers of fabric (linen) in between. Just left to the middleof the breastplate an old dent was present, presumably from the test of proof inthe sixteenth century. The thickness of the breastplate is 2.8 - 3 mm. The pistolwas positioned at 8.5 m distance from the breastplate, a realistic distance giventhe fighting tactics of the cavalry in that period. The muzzle velocity was 444m/s, the speed on impact 436 m/s. The bullet pierced the breastplate, but had noenergy left to penetrate the sandbag. The heavily deformed bullet was found in


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between the layers of fabric between the breastplate and the sandbag. Thewearer would probably have survived this shot at this range, but at shorterranges and with muskets shooting at it, the breastplate would not offer enoughprotection [Krenn 1989]. The mode of fracture of the breastplate is a form ofpetalling, common for thinner plates.

Figure 7: Experiment in Graz, 1989, before (left) and after shooting

2.7 Importance of destructive testing

As discussed above, some properties like hardness, thickness andmicrostructure of 17th century armour have been determined for a respectablenumber of specimens. Also a number of weapons from that period were tested onperformance. Thus, the properties of both weapon and armour have beenstudied. A missing link in historical weapon research, however, concerns thecombination of both datasets. At present, the performance of historicalbreastplate versus historical weapon is not well understood.

It is known that 17th century armourers tested their breastplates. Anoccasional dent in a breastplate is the only evidence for these tests, all otherparameters of quality control are unknown. The Graz experiment, describedabove, made an attempt to combine the knowledge on weapons and breastplates.The experiment involved a single shot with a historical gun on an originalbreastplate. However, no other properties like hardness and microstructure of thearmour have been examined in that case. Based on these scarce data it is notpossible to establish a general prediction model on the protective quality of 17th

century armour.This research involves multiple test shots on two pieces of armour at

locations of variable thickness. Other material aspects such as composition,microstructure, hardness and tensile strength have also been determined. Withthese results the aim is a model that links the material properties of armour tothe properties of the weapon. This model will predict the performance ofbreastplates against bullet impacts using material properties that can be obtainednon-destructively, most notably hardness and thickness and in a lesser degreethe microstructure. Such a model is of great interest from a historical point ofview and should also help to avoid destructive testing of original material in thefuture.


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3 Analytical techniques and sample preparation

In this chapter the analytical techniques are discussed. Because thesampling of the breastplates may be confusing, first a description of the samplingis made, followed by the description of all techniques used to determine theproperties of the breastplate. After that attention is paid to the analysis of originallead bullets and making replicas. Finally a description of the procedure of theballistic testing is given.

3.1 Sampling of the breastplates

For microstructure analysis and determination of chemical composition,samples from three similar locations on both breastplates were taken. Becauseballistic testing still had to be done on undamaged material, only samples fromthe rims could be taken. The samples were cut out with a bandsaw; see Figure 8for locations A, B and C on BP1 (left) and BP2. One part of each sample was setaside for chemical analysis, while the other was cut in two to get cross-sections inthe horizontal and the vertical planes of the breastplate. In Appendix B thefurther embedding and cutting up of these samples is illustrated.

Figure 8: Sample locations for chemical and microstructure analysis

In Figure 9 the impact locations of the ballistic testing are illustrated oneach breastplate, a grey circle with a letter in it indicates the impact. Afterballistic testing was done, rods for tensile testing were taken out; the locations ofthese rods are indicated by a dotted rectangle with a number in it. Three rodswere taken out of BP1; when looking at the front of the breastplate one in the xand one in the y direction and one at an angle of about 45 degrees to the –x,ydirection. Four test rods were taken out of BP2, in x; y; x,y and -x,y direction(the last two at an angle of about 45 degrees). The cutting was done with abandsaw, and the final shape of the test rod was milled so all samples would havethe same dimensions. The widths w of the test rods were 7.8 mm over a length of20 mm. The width outside this area was about 25 mm. The thickness of the rodsvaried between the three samples of BP1, rod 1 has a thickness t of 3.0 mm, rod2 of 4.0 mm and rod 3 of 3.3 mm. Because the stress is the force per squaremillimetre, this factor won’t influence the results. In Figure 10 the shape anddimension of the test rods can be found. Additional samples for microstructure


16

analysis were taken from internal locations, BP1-I and BP2-I in the x and the ydirection. The cross-section of the right half of BP1 is indicated by cs1, cs2 andcs3, the microstructure of the top side is examined.

Figure 9: Sample locations for microstructure analysis, tensile testingand impact locations of ballistic testing

Figure 10: Test rod dimensions in mm for tensile testing

3.2 Breastplates

3.2.1 Composition

The chemical analysis of the specimens was performed at the R&Ddepartment of Corus in IJmuiden. The sample preparation started with removingthe oxide layer. After the oxide layer had been removed, the samples were cut upinto small pieces with a rotary cultivator. The elements carbon and sulphur wereanalysed in the C/S analyser, in which some milled material is heated togetherwith additional components up to approximately 2000 °C. In this process C and Sburn up and form CO2 and SO2 respectively. Both gases are detected with aninfrared cell. The machinery is calibrated with certificated reference material.


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The standard elements that are measured with Induction Coupled Plasma(ICP) analysis are Si, P, Cr, Mn, Ni, Cu, Mo, Sn, Nb, Ti and V. Some milledmaterial was dissolved in acid in the robotically operated system AMIA. Alloperations, such as weighing and conveying, are performed by a robot. Heatingwas done in an open microwave system; a gravimetric dispenser added thereagents based on weight. The solution was measured by ICP analysis, where thesolution is vaporised in an argon plasma. The atoms reach an agitated state,when they fall back to their normal state, they send out light with an elementspecific wavelength. The amount of light tells how high or low the concentrationof the element is in the solution. In addition to these standard elements, theelements As, Ba, Pb, Sb, Co, Cd and Sb were measured semi quantitatively. Thesolution obtained before was put into ICP again, but now a complete scan wasmade for every element to see whether any are detectable. As, Co, Pb and Sbwere detectably present in the solution, but not in very large amounts.

To see whether the composition changes over the thickness of the cross-section of BP1, a scan with an Electron Probe X-ray Micro-Analysis (EPMA) wasmade. This scan can locally indicate the composition; so if one element is onlypresent in the slag or one specific area, this will become clear. The measurementwas performed with a JEOL JXA 8900R microprobe using an electron beam withenergy of 15 keV and a current of 150 nA. The composition at each analysislocation of the sample was determined using the X-ray intensities of theconstituent elements Fe, Mn, Si and P after background correction relative to thecorresponding intensities of reference materials. A line measurement over thetotal thickness of the sample was made, with measuring steps of 50 µm; the totallength of the line was 6.7 mm.

3.2.2 Microstructure

The samples for microstructure analysis were embedded using a StruersLabo Press-3 where the embedding material was heated to a temperature of 180°C for 10 minutes after which it was water-cooled to harden. This temperature istoo low for phase transformations to occur in steel. The sample from the cross-section on BP1 was too large for this machine. It was cut in three pieces and eachpiece was embedded in a green transparent cold curing resin (Technovit 4071).The embedded specimens were polished and before etching with 2% Nital theywere examined with a microscope to determine the slag content. Somephotographs of various locations on the samples at different magnification weretaken at Corus, IJmuiden, where the chemical analysis was also performed.Based on the microstructure, the more interesting samples were examined with aSEM (Scanning Electron Microscope; LEO 438VP), and local composition wasdetermined with EDS (Energy Dispersive Spectrometry; EDAX LEO 435VP).

3.2.3 Hardness

The bulk hardness was measured with a Rockwell hardness tester. Withthis system, a hardness number is determined by the difference in depth ofpenetration resulting from the application of an initial minor load followed by alarger major load; utilization of a minor load enhances test accuracy. ForRockwell B hardness the minor load is 10 kg, the major load is 100 kg. Theindenter is a 1/16” spherical and hardened steel ball.

The microhardness was measured with a Buehler Omnimet MHT Vickersmicrohardness tester with accompanying software. The applied weight formeasuring the microhardness was 500 g.


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3.2.4 Thickness

The thickness of the breastplates was determined by a 3D scan. This scanwas made at TNO in Eindhoven, with a Hyscan 45C scanner. The surface of thebreastplate should not be too dark (too little reflection for the laser) or to light(shining surface, too much scattering of light). This distorts the measuring. Anopaque grey coating can be applied to the surface in order to be able to scan itproperly. This had to be done to the inside of BP2. The coating can be removedafter scanning. The laser scanner registers up to 10,000 points per second, with ameasuring area of 50 x 50 mm2. The scanner is positioned in a CoordinateMeasuring Machine (CMM) of type Zeiss, UMC 550 S. The whole surface of thebreastplate is scanned with a laser and a CCD camera with a known angle to thelaser bundle determines the position of a point on the surface. The highest lightintensity comes from a point at a straight angle with the laser, when the surfaceis curved the laser dot becomes oval and less intense. A computer registers theobtained data and with software from Innovmetric a picture is made. IM-Alignconnects all the measured dots in a matrix of 0.3 mm and aligns them to formone smooth surface. With IM-Merge the dots are connected to each other withtriangles. IM-Edit is used to smooth everything out, so holes (where the surfacehad too much or too little reflection to give proper data) are closed. Finally withIM-Inspect the two models (of inside and outside) are compared to make thedifference visible, which results in a thickness profile. The accuracy of thethickness lies within a 0.1 mm range.

With the same techniques a second scan after ballistic testing was made tosee how much the material has deformed. The scans from the outer surfacebefore and after shooting are compared with IM-Inspect, so a deviation from theoriginal position is obtained. Also a thickness profile is made of a few impactlocations, to find out the reduction in thickness due to the bullet impact.


For tensile testing it is necessary to specify the dimensions of the testspecimens in order to know the right area the force acts on during testing. Thisway the test results can be compared with test results of tests on other (modern)material. Test rods were taken out of the breastplates in various directions, seeFigure 8 for the locations.

The specimens were tested in a Zwick Z010 test machine, which candeliver a maximum force of 10 kN. The specimens of BP1 were not entirelystraight after cutting and milling, so with a vice the test rods were straightenedgently, so not too much deformation would occur in the region that wouldundergo the test. Due to the fact that the specimens were not completelystraightened, some slip occurred during testing. Samples BP2-1 and BP2-2 weretested with a strain gauge, but slip occurred in the gauge and no strain data wereobtained. After removal of the strain gauge the machine itself measured thestrain. These results led to the decision that the strain gauge was to be omittedfor the remainder of the tests. The test speed was 30 N/mm2s, with a pre-load of10 N. The maximum stress in N/mm2 was measured along with the strain at thatpoint. The yield strength, defined as the point at which 0.2% permanentelongation is experienced by the material, is calculated by the machine, andcompared with values from literature for several kinds of iron and steel. Theelongation at fracture is also determined; to see how much strain the materialcan have before failure.


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3.2.6 Neutron diffraction

At the ISIS facility, at the Rutherford Appleton Laboratory near Oxford,England, the breastplates were measured with the ROTAX time-of-flightdiffractometer and General Materials Diffractometer (GEM) instruments. Theobtained diffraction pattern indicates the phases and corrosion products presentand is obtained in a non-destructive way. During neutron diffraction the scatteredneutron waves show interference producing diffraction peaks at characteristic 2θscattering angles between incoming and outgoing beam. Bragg’s law states thatdiffraction can be regarded as reflection of neutrons by crystal lattice planes:

€

2dhkl sinθ = λ (1)

In Bragg’s law is dhkl the spacing between lattice planes hkl, 2θ is the scatteringangle and λ is the wavelength. In the resulting diffractogram the d-spacing isplotted against the normalised neutron counts. With X-Ray diffraction similarresults are obtained, but only information of the top layer of 10-20 µm of thesample is generated. Neutron diffraction gives information of the bulk of thesample, but the results are averaged, so it is not exactly known where thedifferent phases can be found in the thickness of the sample if the diffractionpattern shows irregularities.

In the ROTAX instrument a time-of-flight neutron diffraction (TOF-ND)pattern is determined. Neutrons produced by shooting high energetic protonsfrom a synchrotron to a target station are slowed down to thermal energiesbefore they travel to the sample position at 15 meters from the moderator (or 17meters in GEM). About 1 million neutrons per second hit the sample withwavelengths between 0.5 and 5 Å, corresponding to neutron velocities from about8000 to 800 m/s. The beam size can range from 5x5 up to 20x40 mm2. In thisexperiment a 10x10 mm2 beam size was used, to ensure a large enough surfaceto be measured, but not too large so that the measurement is not performed atboth dent and undamaged material. Neutrons, diffracted in the sample, arerecorded by three neutron detector banks that measure both the 2θ angles andthe flight times. The three detector banks are positioned at a scatter angle of 30˚(low angle), 70˚ (forward scattering) and 125˚ (backscattering). Time-of-flightspectra are usually normalised to the incident number of neutrons per neutronwavelength. This is necessary in order to evaluate scattered neutrons of differentneutron velocities or wavelengths, but the normalisation also allows to directlycompare data sets of different measuring times.

Figure 11: Schematic view of the ROTAX instrument

Sample


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TOF-ND determines the flight time (t) of a neutron travelling from target todetector. With the flight path (L) known, one obtains the velocity

€

ν =Lt

; the energy 2

2νnmE = and the wavelength

€

λ =h2mnE

. For a detector at

a fixed 2θ angle, the d-spacing is derived from Bragg’s law (Equation (1)). In theequations above h is the Planck constant and mn is the neutron mass.

Figure 12: Locations on the breastplates that have been scanned byROTAX (grey circles are bullet impacts of ballistic testing)

For reference and comparison with GEM results, first the small samplefrom location BP1A was measured in the ROTAX sample tank under vacuum. Afterremoval of the tank a measurement of the air (so without sample) was done,which yielded practically no background scattering. The sample was alsomeasured in the ambient air. To locate the region where the neutrons arescattered on the breastplates a position marker was created that determined theheight of the location, and with an extendable pointer the centre before the beamexit. Each location on the breastplates was put in the ROTAX during half an hour,with one exception, location 0 on BP1, see Figure 12, was measured overnight,for about 10 hours. Longer measurement will make peaks of less strongscattering phases more clear due to better background statistics. On BP1 in totaleight locations and on BP2 in total three locations were measured.

The GEM is a high intensity, high resolution neutron diffractometerequipped with 6 detector banks housing a total of about 6500 detector elementsthat cover a very wide range in scattering angle from 1.1° to 169.3°. Thesedetectors are all around the sample tank, so it is not necessary to rotate thesample to get the texture analysis in the form of pole figures. Texture analysisdetermines the distribution of crystallographic orientations with respect to thesample shape. The sample is considered to be inside an imaginary orientationsphere, the ‘pole sphere’. The orientation of crystallites is represented by crystalplanes and their ‘poles’; the directions perpendicular to the crystal planes. Thepole figure is the two dimensional representation of the pole sphere. In GEManalysis enough data is assembled in one run to create the pole figures and a


21

diffraction pattern of the sample. The texture of a polycrystalline material mayresult from plastic deformations, specific mechanical working processes orthermal treatments (e.g. triggering recrystallisation) during manufacturing. Manyworking processes (casting, rolling, hammering, heating) cause distinct grainorientation distributions. If all crystallite orientations are equally realisedcorresponding to a random distribution of poles in the pole figure, then thematerial is said to be texture-free. Because the GEM sample tank limits the sizeof the object to be measured, for a good result some small pieces of thebreastplate were cut off (location BP1A, BP1C and BP2A). The sample tank isnecessary to provide vacuum for measuring certain samples and it also protectsthe detector elements. The samples are positioned perpendicular to the incomingneutron beam; the long side of the fragments are along the vertical. In Figure 13the samples and the incoming neutron beam are schematically depicted.

The pole figures that depict the texture in the material are calculated withthe MAUD (Materials Analysis using Diffraction) computer program. Each singlepole figure represents the orientation distribution of a specific lattice plane, e.g.(200), with respect to the sample body. Each particular point in a pole figuredenotes a specific direction in the sample. The centre of the pole figurecorresponds to the direction perpendicular to the sample surface. Preferredalignments of lattice planes show up as maxima. Different colour shadings referto different pole densities given as multiples of the random distribution (mrd).Pole figures are normalised with mrd = 1 marking the average distribution. Themaximum mrd-values indicate the texture strength. The pole strength andsymmetry of a pole figure reflects the deformation strength and symmetry of aworking or deformation process. For example, rotation-symmetric pole densitiesindicate a single working direction, e.g. the hammering direction.

Figure 13: Sample orientation in GEM analysis

After analysis on the three small samples, both breastplates were put inthe GEM sample tank, but only one location in the middle of each plate could bemeasured, because there was no room for moving the breastplate in order tomeasure different locations. Moving the breastplates around was possible at theROTAX instrument, where the tank could be removed, for it is not necessary to


22

measure iron in vacuum, because it gives strong Bragg peaks, and is notdistorted by scattering of air.

For the phase analysis with the program GSAS (Generalised Structure andAnalysis Software) the detector elements of each of the six GEM banks werecombined to give six diffraction patterns for each scan. Likewise, each ROTAXacquisition yielded three separate diffraction patterns. The observed patternswere analysed according to the Rietveld method [Young 1993] that is based onan iterative fitting process used to model the measured diffraction patterns interms of the crystal structures of identified mineral or metal phases. The Rietveldmethod imposes strong constraints in terms of the crystal structure models.Mineral and metal phase have to be identified first and then implemented in themodel set of Rietveld, here realised with GSAS. The crystal structure models usedin the Rietveld analysis are listed in Appendix C. The structure models were takenfrom databases ICSD and CrystMet. Structure parameters were kept fixed for thecalculations, apart from the lattice parameters of cementite, for allowing a slightadjustment of the database parameters. The lattice parameters of Fe were keptfixed, and used as internal standard for correction of misalignment of the sampleposition on the GEM and ROTAX samples positions.

3.2 Bullets

3.2.1 Composition

To determine the composition of the original seventeenth century leadbullets EDS (Energy Dispersive Spectrometry) was applied at a few locations, butthis is not a quantitative approach. The results from EDS analysis are not reliable,so the two half bullets were put in a Philips PW1480 XRF (X-Ray Fluorescence)apparatus. The results were processed with the semi quantitative softwareprogram UniQuant5®.

3.2.2 Casting

The lead bullets used for ballistic testing were cast in a soapstone mouldat Archeon, Alphen a/d Rijn. The lead was molten in a ladle that was put on acharcoal fire. The rim on the bullet where the mould closed was polished smoothon a polishing machine. The diameter of the bullets is 15.5 mm ± 0.5 mm, theaverage weight is 21.19 g with a standard deviation of 0.12 g.

Figure 14: Original seventeenth century bullet mould (left) and thereplica used to cast the bullets for ballistic testing


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3.2.3 Compression Test

Two cast bullets were tested in compression, to find out how much energyis needed to deform the bullet. The compression test was performed at the ZwickZ010 test machine, with a compression rate of 5.2·10-3 s-1. Lead has a slowrecrystallisation rate at room temperature, and the way of deformation at highimpact speed, where a temperature rise is likely, is different from that at the lowtesting speed, but this test should give an indication whether the amount ofenergy that is used to deform the bullet is significant with respect to the totalamount of energy available to perforate the breastplate.

3.3 Ballistic testing

The ballistic testing was performed at the Prins Maurits Laboratory of TNOin Ypenburg. The experiments were done in a small bunker, suitable for lowcalibre weapons. A 16 mm barrel was positioned with the barrel mouth at 2.7 mdistance of the target rack on which the breastplates would be set. Betweenbarrel and target a small tunnel was set up through which the bullet passes inorder to measure the speed of the bullet. With a Radar-Doppler system the speedof the bullet was also measured.

At the back of the barrel there is space for the powder chamber which isinserted after a definite amount of gunpowder is put in there. To make sure nopowder falls out, two small round cartons are put in the powder chamber toconfine the powder in the back of the chamber, next to the detonation point. Thebullet is inserted through the mouth of the barrel. At first three pieces of cartonof exactly 16 mm diameter were put in the barrel to ensure an evenly distributedpressure build-up, because the self-cast bullets were not perfect spheres. For thelast three shots the cartons were omitted, because the shooting went quite welland the footage with the high-speed camera would thus not be distorted with bitsand pieces of carton flying past.

The powder is electrically detonated from outside the test chamber, forsafety reasons. The type of powder that is used is N150, a single base (NC)propellant, Nitrocellulose 90-98% in extruded cylindrical grains. This is a powderthat has a moderately slow burning rate. The breastplates were positioned insuch way that the impact of the bullet would always be at a right angle or asclose as possible to that. They were fastened with tension cords to the targetrack, with some cotton bales and pieces of wood to keep everything in place. Intotal twelve shots were fired at the two breastplates, seven of these shots werefilmed with a high-speed camera. See Figure 8 for the locations of the bulletimpacts.

Figure 15: Experimental setup at PML for ballistic testing


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4 Results

4.1 Breastplates

4.1.1 Composition

At R&D of Corus in IJmuiden the composition of the six samples wasdetermined with a C/S analyser and with Induction Coupled Plasma (ICP)analysis. The results are in Table 3, with the more important elements in boldscript.

Table 3: Results of chemical analysis with elements in weight %

BP1-A BP1-B BP1-C BP2-A BP2-B BP2-CC 0.147 0.015 0.012 0.030 0.029 0.031Si 0.012 0.013 0.018 <0.001 <0.001 <0.001P 0.012 0.009 0.021 0.007 0.007 0.007Cr 0.004 0.004 <0.001 0.012 0.012 0.012Mn 0.072 0.073 0.030 0.311 0.312 0.313Ni 0.010 0.019 0.020 0.026 0.026 0.027Cu 0.007 0.011 0.010 0.050 0.051 0.050Mo 0.002 0.003 0.004 0.007 0.007 0.007Sn 0.002 0.001 0.002 0.003 0.003 0.003Nb <0.002 <0.002 <0.002 <0.002 <0.002 <0.002Ti <0.001 <0.001 <0.001 <0.001 <0.001 <0.001V <0.001 <0.001 <0.001 <0.001 <0.001 <0.001S 0.002 0.002 0.002 0.025 0.025 0.024As 0.006 0.006 0.011 0.008 0.008 0.008Ba <0.001 <0.001 <0.001 <0.001 <0.001 <0.001Cd <0.001 <0.001 <0.001 <0.001 <0.001 <0.001Co 0.007 0.013 0.016 0.005 0.005 0.005Pb 0.004 0.004 0.005 0.004 0.004 0.005Sb 0.002 0.002 0.002 0.002 0.003 0.002total 0.29 0.18 0.15 0.49 0.49 0.49

The carbon content of all samples but 1A, which has 0.15% C, is too lowto call the material steel; the breastplates are made of some form of wroughtiron. The total amount of alloying elements is also too low to be able to speak ofconscious or effective alloying. Only in BP2 there is about 0.3% of manganesepresent, which is with respect to composition the only major difference betweenBP1 and BP2. Manganese is not generally present in medieval and renaissancesteels [Williams, 2003].

The EPMA results on phosphorous and manganese in the cross-section ofBP1 do not yield a distinct concentration profile, the concentrations are too low toget a significant difference. Silicon was not present in any of the points along theline scan. The graph with concentrations of P and Mn can be found in Appendix D.

4.1.2 Microstructure

The slag content of the unetched samples as determined with an imageanalysing computer programme is different for both breastplates. For BP1 itvaries between 0.5 and 2 %, with locally slag contents of over 5%, whereas forBP2 the slag content is much lower, between 0.2 and 0.5 %. For wrought iron aslag content between 2 and 3 % is not uncommon. The distribution of the slag inthe various specimens of BP1 is very inhomogeneous. It consists of layers of


25

inclusions at various locations with respect to the thickness. For samples BP1A-Cand BP1-Ix one or two thin layers are visible, but BP1-Iy almost has no slag. Thecross-section of BP1 (cs1-cs3) shows a concentrated amount of slag layers on thefront side of the breastplate and a few thin layers in the middle of the structure(Figure 23). BP2 has many small, randomly distributed slag inclusions, slightlyelongated parallel to the surface of the plate.

The microstructure of the eight samples from BP2 (6 samples BP2A-C,BP2-Ix and BP2-Iy) is very similar; ferritic grains of approximately 30 micrometersize on average. The samples BP1B, BP1C and BP1-I are also similar inappearance, but with very large ferritic grains, some of them about 0.5 mm ormore in diameter. Different areas with different grain sizes can be found next toeach other, with average grain sizes of 30, 60, 100 and 140 micrometer. In thesamples BP1B and BP1C the microstructure changes noticeably around slaglayers. For BP1-Ix and BP1-Iy the regions of different microstructure are morerandom and less clear than in the samples BP1A-C. The cross-section shows alsoareas of different grain size, but also areas of different composition, with orwithout a little pearlite. Sample BP1A has more obvious regions with a variableamount of carbon, see Figure 16. On the front of the breastplate the carboncontent is highest, and areas of pearlite within Widmanstätten ferrite are visible.Near the surface there seems to have been some decarburisation, for only a littleor no carbon is present in the outer layer of a few microns. The region followingupon the carbon rich area, just after a band of slag inclusions, is pure ferritewhich gradually becomes slightly richer in carbon, nearing the second line of slaginclusions. After the second slag line the structure is pure ferrite again, but withvery tiny areas (less than 10 µm2) of pearlite. The amount of pearlite in theregion near the second line of slag is corresponding to an amount of carbon of upto 0.2 wt%, whereas the pearlitic area near the front of the plate wouldcorrespond to a carbon content of about 0.7 wt%. The total amount of carbon insample 1A is 0.15 wt%. The Widmanstätten structure in the carbon rich areaarises during cooling down from the austenite phase (γ-phase) and is atransformation product of coarse γ-grains. The coarse austenite excretes ferrite inthe shape of needles and plates. Widmanstätten structure always arises when theγ-grain is large and if there is a quick cooling down from a higher temperature.

Another feature that is visible in the microstructure of BP1 are twinboundaries, see Figure 19. In the ferrite structure twins form after plasticdeformation through a punch load where a part of the grain switches to the twinposition. Twins are visible in the microstructure of BP1 as lines in a grain, whichstop at the grain boundary. The lines in one grain are parallel to each other, or ata 60-degree angle. The microstructures of samples BP1-Ix and especially BP1-Iyshow many twins. This is because the latter sample was taken near a dent fromballistic testing. BP1-Ix also shows more twins than BP1A-C, but less than BP1-Iy; this sample was taken further away from a dent, which also had caused lessdeformation than the dent near BP1-Iy. No twinning is visible in any sample fromBP2, but the samples were not taken near a dent.

The cross-section of the right side of BP1 shows an interesting structurechange. In the samples cs2 and cs3 layers of different structure can be indicated(Figure 21), in cs1 these are less visible. From the front side of the breastplate tothe inside at location cs2 a slag rich layer with relatively large grains is seen,followed by a layer of small ferritic grains with small inclusions of pearlite on thegrain boundaries. After the layer with some pearlite a layer without pearlite andwith variable grain size is seen, concluded by a band of small grains with againsome pearlite and an area of relatively large grains and a few bands of slag onthe surface on the inside of the breastplate.

Looking at the complete cross-section of the right side of BP1 it can beseen that an extra plate was forged on the inside to thicken the centre part. Theboundary between the forged plates starts halfway through the cross-section and


26

can be distinguished from the rest of the material by a fine line of pearlite thatwidens towards the middle, but can be followed throughout the structure, and bysome slag inclusions on the boundary close to the beginning of the layer, see thered dotted line in Figure 21. At least one other boundary between layers can beindicated in the cross-section, and this one starts at the outside and continues allthe way to the centre. The layer that is more to the front of the breastplate hasmany slag inclusions and relatively large grains, and the boundary can be foundin the area with small grains and with more pearlite and in additional slag layers.The carbon has been introduced to the separate plates before forging while theywere heated up in the (charcoal) forge. Upon forging the carbon has locallyhomogenised through the structure, hence the relatively wide bands of ferritewith small pearlite inclusions. In Figure 23 the layer boundaries are indicated. Theindicated lines are based on the local microstructure variations, but are by nomeans definite, a shift up or down of a few tenths of millimetres is possible. Thetop line that is only indicated in cs2 and cs3 is based on the region with highercarbon content and a thin line of pearlite within a ferrite structure (see alsoFigure 21). The lower line that is indicated in all cross-sections is also based incs2 on the area of heightened carbon content, but also on slag layers, as isindicated in Figure 20. Because the general structure of BP1 is veryinhomogeneous, it is very unlikely that these layers are similar throughout thebreastplate. The different examined locations already show a lot of variation instructure. However, the general trend of two or three layers will be visiblethroughout the breastplate, albeit in different ways.

In Appendix D more details of various microstructures as well as someSEM photographs can be found.

Figure 16: Microstructure of BP1A


27

Figure 17: Microstructure of BP1B

Figure 18: Microstructure of BP2


28

Figure 19: Twinning in BP1-Iy

Figure 20: Absence of pearlite bands in outer rim of cross-section of BP1


29

Figure 21: Pearlite bands in centre of cross-section of BP1

Figure 22: Pearlite in between ferrite grains


30

Figure 23: Layer boundaries in cross-section of BP1


31

4.1.3 Hardness

The hardness of armour is directly correlated to the composition and/orpossible heat treatments. As for the performance of a piece of armour, a higherhardness is desired, but depending on the carbon percentage, not too high,because then it will also be too brittle. The average hardness for pure iron(ferrite) is about 80 HV (hardness on the Vickers scale), for 0.2% carbon steel180 HV and for 0.6% carbon steel 260 HV. Slag inclusions and fine ferrite crystalsmay influence the hardness of the material and measured values for ferriticarmour may be anywhere between 100 and 180 HV.

The three samples from different locations on BP1 and BP2 were analysedwith a Rockwell hardness tester for bulk hardness and with a microhardnesstester with 500 g indentation weight to obtain the microhardness. The cross-section BP1-cs3 was also measured for microhardness, on six lines from front toback. In general the hardness is slightly higher in regions with smaller and/ordeformed grains. The average hardness and minimum and maximum value foreach sample is given in Table 4. The actual measured data of microhardness andthe corresponding locations are given in Appendix E.

Table 4: Hardness in HV of various samples of BP1 and BP2

Sample Mean Min Max RemarkBP1-A 151 94 236 microhardnessBP1-A 108 99 129 from Rockwell BBP1-B 103 74 147 microhardnessBP1-B 83 76 90 from Rockwell BBP1-C 128 91 170 microhardnessBP1-C 92 81 101 from Rockwell BBP1-cs3 100 72 140 microhardnessBP2-A 135 113 205 microhardnessBP2-A 99 88 108 from Rockwell BBP2-B 138 106 176 microhardnessBP2-B 95 89 100 from Rockwell BBP2-C 117 94 138 microhardnessBP2-C 91 86 100 from Rockwell B

When the data in Table 4 is compared with data from previous research(see Table 1), it is found that the microhardness of both BP1 and BP2 is relativelylow, and especially the bulk hardness (converted from Rockwell B hardness) isvery low. Only the hussar’s breastplate (C) measured by Williams is comparablewith BP1-A, all other values are much higher. The average hardness of samplesafter 1625 is about 200 HV, whereas the samples from the beginning of theseventeenth century average 250 HV. The hardness values for BP1 and BP2 are inthe same range, between 100 and 150 HV for average, but the minimum valuesare lower for BP1, this is because the grains in BP1 are much larger than in BP2,as can be seen in the microstructures. The maximum values are again in thesame range. The converted bulk hardness is for all samples lower than themicrohardness, which is understandable, because the plastic behaviour of thematerial with hardness testing plays a role. Upon indentation a gradient in plasticstrain arises; high plastic strain in the centre of indentation and no plastic strainat a certain distance from the centre. For microhardness measuring this gradientis higher (smaller distance over which strain goes to zero), and thus the hardnessis higher. For the same material the nanohardness will even be higher due to thisfact. Also, for bulk indentation small pores or slag inclusions may influence thehardness (indentation is larger due to the inhomogeneity of the material, andmakes the hardness lower).


32

When the measured microhardness is plotted against the percentage ofthickness where it is measured it is possible to see whether specific regions havehigher hardness than others, which might indicate that there are layers present ofdifferent hardness and thus of either different material or that different heattreatment have been applied. As can be seen in Figure 24, the microhardness ofBP1A is slightly higher on the outside of the breastplate, in the carbon-rich area.This was to be expected. Other than that there is too much scattering in the datapoints to be able to draw a trendline. Only the hardness of BP1B is in generallower than for BP1C or BP1A. For BP2 there is no significant variation inmicrohardness throughout the thickness. See Appendix E for the graph ofmicrohardness of BP2.

Figure 24: Microhardness of BP1

In a similar plot for the microhardness measured on the centre of thecrosssection of BP1 a locally heightened hardness is visible corresponding withthe pearlitic band in the microstructure. In Figure 25 the hardness is depicted in agraph with the corresponding microstructure below. On the outer rims thehardness is also locally higher, especially on the front side (near 100%).

0

50

100

150

200

250

0,0 20,0 40,0 60,0 80,0 100,0

Distance from backside (%)

Har

dnes

s (H

V)

BP1A

BP1B

BP1C


33

Figure 25: Microhardness in the centre of BP1

4.1.4 Thickness

The thickness of BP1 fluctuates a lot, the middle part is about 7 mm thick,and the rims are 2 to 3 mm thick. The thicker part in the middle will give thewearer more protection for front-on assaults, the thinning out to the sides willprobably have to do with optimising the comfort by limiting the weight whilemaintaining as much protection as possible. The thickness of BP2 is veryconstant; it is 1.75 mm on average with a deviation of at most 0.3 mm. In themiddle part the breastplate is slightly thinner than on the outsides, opposite tothe situation of BP1. The thickness profiles for the breastplates can be found inFigure 26 and Figure 27.

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60 70 80 90 100

Distance from inside (%)

Har

dnes

s (H

V)


34

Figure 26: 3D scan of BP1 with thickness profile in mm

The difference between minimum and maximum values of the thicknessmeasurements indicates how evenly thick a plate is. If the range - the differencebetween minimum and maximum - is small, that means the plate is very even inthickness. The range for BP1 is very high, 5 mm, and for BP2 very small; 0.6mm. Also this range is very small when compared with measurements done bySmith, see Table 2, the average range for his data lies between 1.5 and 3 mm,which is at least twice the range on BP2.


35

Figure 27: 3D scan of BP2 with thickness profile in mm


The yield strength of samples BP2-1 and BP2-2 could not reliably bemeasured due to lack of strain values. The yield strength for BP2-3 and BP2-4can be determined by looking at what stress level the yield plateau lies. The yieldpoint for the samples of BP1 is less easy to determine, for BP1-3 there is no yieldpoint phenomenon visible. Presumably the real yield point is lower than what themachine has determined, hence the parentheses in Table 5. The maximum stress(or (ultimate) tensile strength) is independent of the strain measurement; sliphas no influence on this value. The strain at fracture is determined by measuringthe original length and surface of the specimen and those values after fracture.Also the results from tensile testing on two historic samples [Williams, 2003] arein Table 5, and for further comparison some values of low grade steels andductile irons [Callister, 1997] are listed. The graphs of tensile testing can befound in Appendix F.

Because of lack of carbon in most tested samples, and only a possiblepresence of up to 0.1 wt% C in BP1, a comparison will be made between theductile irons and the tested specimens. The yield strength of all samples is lowerthan the given range of ductile irons; also all (ultimate) tensile strengths aremuch lower than what would be expected of a ductile iron. The presence of slagparticles and slag layers could explain this. For BP1 both the yield and tensilestrength are lower than for BP2, which is probably caused by the difference in


36

slag distribution, layers in BP1 or small globular inclusions in BP2. The tensilestrength of 1020 steel is lower than for the ductile irons, but still higher than thetested specimens. Vb-1570 and Pd-1550 have high tensile strengths, in the rangeof ductile irons, but the yield strengths are much lower than even the specimensof BP1 and BP2. The strain for all tested samples lies in or above the high regionof the ductile irons. This means that the breastplates can take a lot ofdeformation before fracture, but not much stress is needed to deform the plates.

The fractured surfaces for the samples of BP1 show a layered structure ona macroscopic scale. During necking of the rod the individual layers had separatenecking just before they gave way one after the other. The level of the fracturesurfaces of the different layers is not at the same distance from one end of thesample. Between the layers air pockets are visible that were created just beforeor during fracture.

Table 5: Results from tensile testing

Specimen Yield strengthN/mm2

Tensile strengthN/mm2

ε Break%

BP1-1 210 271 23.5BP1-2 196 271 31BP1-3 (262) 266 25BP2-1 - 327 28BP2-2 - 329 27BP2-3 255 320 30BP2-4 273 328 28Vb-1570a) 107 426 40Pd-1550b) 132 513 19Ductile irons1) 280-370 410-520 26-181020 Steel2) 295 395 36.51040 Steel3) 353 520 30.24140 Steel4) 417 655 25.7

a) Italian vambrace of 1570b) Innsbruck pauldron of 15501) Grade 60-40-18, annealed2) Steel alloy 1020, ca. 0.2% C, 0.45% Mn, annealed at 870°C3) Steel alloy 1040, ca. 0.4% C, 0.8% Mn, annealed at 790°C4) Steel alloy 4140, ca. 0,4% C, 1% Cr, 1% Mn, 0.25% Si, 0.2% Mo, annealed at 815°C

4.1.6 Neutron diffraction

The neutron diffraction patterns collected on GEM (bank 6) of the centreparts of BP1 and BP2 are dominated by the ferrite phase. Other phases haveintensities of at least one order of magnitude smaller and become visible only inthe zoomed diffraction patterns (see Figure 28). The small peaks in the BP1pattern are from cementite, Fe3C. The samples from BP1A and BP1C showdifferent patterns, as can be seen in Figure 29. Fe3C and Fe3O4 are present inBP1A, whilst in BP1C only the oxide Fe3O4 can be found. In the sample from BP2neither phases are present as clear distinct Bragg peaks, only ferrite is visible.The diffraction patterns obtained by ROTAX of sample locations 2 to 7 on BP1(see Figure 30, and Figure 12 for the locations) show that Fe3C can be found inpattern 3 to 5, but not in pattern 2. Pattern 6 shows a very distinct peak at thewustite location, FeO, which is not visible in any other pattern. The pearlitic areaas found in the microstructure of BP1A apparently stretches towards location 3 onthe breastplate.


37

Figure 28: Zoomed diffraction pattern

Figure 29: Difference in diffraction pattern of BP1 and BP2


38

Figure 30: Difference in diffraction pattern of BP1

The results from the Rietveld analysis give the calculated amounts of Fe,FeO, Fe3C and Fe3O4 in wt%. From the values of Fe3C the carbon percentage canbe calculated from the weight fraction ratios. Measurements on industrialstandards show that this calculation will yield an underestimation of the carboncontent. In Table 6 the results of the phase analysis of GEM and ROTAX data arelisted. Because the measuring time on ROTAX was too short for the weak peaksof magnetite to show in the diffraction patterns, these values are not available,except for BP1 S0, the location that was measured overnight. The locations BP1S0 to S7 and BP2 S1 to S3 can be found in Figure 12.

Table 6: Phase analysis of GEM and ROTAX data

wF wC wO wM %CGEMBP1A 97.3 2.5 (7) 0 0.2 0.17BP1C 99.1 0 0 0.9 0BP1 centre 98.9 1.1 (1) 0 0.0 0.07BP2A 99.9 0.0 0.1 0.0 0BP2 centre 99.6 0.2 0.2 0.0 0.01ROTAXBP1 S0 99.2 0.2 (1) 0.6 (4) 0.0 0.01BP1 S1 99.9 0 0.1 0BP1 S2 99.7 0.2 (1) 0.1 0.01BP1 S3 98.1 1.9 (1) 0 0.13BP1 S4 98.4 1.6 (1) 0.0 0.11BP1 S5 97.1 2.9 (1) 0.0 0.19BP1 S6 99.0 0.4 (2) 0.6 (1) 0.03BP1 S7 99.4 0.4(2) 0.2 (1) 0.03BP2 S1 98.7 1.3 0.0 0.09BP2 S2 99.4 0.6 0.0 0.04BP2 S3 98.8 1.2 0.2 0.08wF = w(Fe), wC = w(Fe3C), wO = w(FeO), wM = w(Fe3O4) in wt%Numbers in parentheses are estimated standard deviations


39

The texture evaluation of GEM data was performed on the three fragmentsand on the centre part of BP1. The texture is displayed in terms of pole figures ofrepresentative ferrite lattice planes (110), (200) and (211). Figure 32 shows thepole figures of the three fragments and the scan of the centre of BP1. Maximumpole densities are between 1.2 and 1.4, indicating a rather weak texture for theferrite.

The BP1A sample shows rather circular (axisymetric) pole densities. Thepositions of maxima and minima in (110) and (200) respectively are similar as forBP2. For BP1 there is no distinct unique direction, like a rolling direction, in thetexture. The pole figures of the centre part of BP1 and of BP1C are ratherirregular. Maxima are distributed at random with respect to the plate shape, withno clear indication of a rolling process. The observed type of texture for the BP2sample displays the typical features of a rolling texture of bcc iron, see Figure 31[Wasserman, 1962; Kocks et al. 1998]. Rolling direction is along the vertical,inside the BP2 fragment plane, perpendicular to the incoming beam, and alongthe short side of the sample of location BP2A. This corresponds to a verticalrolling direction when looking at the breastplate from the front. The rollingtexture is characterised by a minimum in the centre of (110) and by twoelongated maxima aligned perpendicular to the rolling direction. The (110) poledensity maxima are complemented by a maximum in the centre of (200).Typically rolled fcc-metals have a pole density streak in the 220 pole figure –representing the (110) crystal plane family.

Figure 31: Pole figures of (110) planes of rolled and annealed bcc iron[Wasserman, 1962]

95% deformation, annealed at570 °C for 50 minutes

95% deformation, annealed at540 °C for 80 minutes


40

Figure 32: Pole figures for BP1 and BP2

BP1A

BP1C

BP1

BP2A


41

4.2 Bullets

4.2.1 Composition

The result of the XRF measurement on the original lead bullets confirmedthe assumption that they were made of pure lead. No significant amount of tin orantimony is present in either of the bullets. The silicon that was detected withEDS while the bullets were in a SEM was also not in very large amounts present.A summary of elements discussed above and those present in a concentrationover 0.1 wt% is given in Table 7. The complete reports can be found in AppendixG.

Table 7: Elements present in lead bullets in wt% with standard error

Pb Sn Sb Si Al FeSmall bullet 98.66

± 0.060.399± 0.025

0.042± 0.012

0.135± 0.015

0.250± 0.027

0.223± 0.025

Large bullet 99.18± 0.04

- -0.0779± 0.0086

0.187± 0.018

0.0195± 0.0048

4.2.2 Compression Test

Under slow compression (

€

˙ ε = 5.2 ⋅10−3 s-1) the amount of energy needed todeform the bullet a certain percentage is equivalent to the surface under the

force – strain diagram;

€

E = Fdv0

v

∫ with F the applied force and v the travelled

distance. To deform the bullet 50%, with v = 8 mm, the required energy is 10.7J. To deform the bullet 60%, with v = 10 mm, the required energy is 62.1 J.These energies are relatively low, and will therefore be neglected when looking atenergy loss due to bullet deformation in the discussion of the ballistic testing. Theforce – strain diagram can be found in Appendix F.

4.3 Ballistic testing

4.3.1 Test results

The test shots showed that the bullets were suitable for the gun and thatsufficiently low speeds could be achieved. Also a general idea about the amountof powder that should be used to get a certain speed for the bullet was obtained.The bullets used at the test shots were not weighed before shooting, thereforethe average weight of the cast bullets is taken. The results of all shootingexperiments are in Table 8.

At BP1 eight bullets were fired, the results of these shots are visible inFigure 33. Two of the bullets perforated the breastplate. At a plate thickness of6.25 mm a bullet travelling with a speed of 451 m/s was stopped. A speed of 470m/s was more than enough for the bullet to perforate the breastplate at alocation of 5 mm thickness; the material that was torn out of the breastplate wasnot found again. At one location on BP1 the bullet left a dent with a crack. Thecrack shows a laminated structure, part of the fracture was parallel to the platesurface. The crack is also very brittle. BP2 had four bullets fired at it, see Figure34, of which two perforated the breastplate. Perforation of BP2 occurred at abullet speed of 271 m/s, since the plate thickness was only 1.75 mm.


42

One bullet was shot at an ARMOX® 500 plate, which hit with 444 m/s andleft a shallow dent comparable with the ones made at 175 or 262 m/s on BP1.In this case perforation or full penetration is achieved when a hole is made in thebreastplate, but without enough remaining energy to inflict damage to the wearerhimself. At this point the ballistic limit is reached, if more energy is put in thebullet, the wearer would be killed or severely wounded and out of action for theremainder of the battle.

Table 8: Results of ballistic testing

Massbullet (g)

Platethickness

(mm)

Speed(m/s)

Energy(J)

Result Powder(g)

Test - 1 (21.19) - 329 1147 - 1.75Test - 2 (21.19) 1.50 232 570 perforation 1.10Test - 3 (21.19) 1.50 116 143 stop 0.75BP11H* 21.06 6.25 175 322 stop 1.851A 21.38 4.50 262 734 stop 1.301B 21.11 4.75 322 1094 stop/crack 1.601C 21.26 4.50 339 1222 stop 1.801G* 21.33 5.75 400 1706 stop 2.001F* 21.10 6.25 451 2146 stop 2.351D 21.27 5.00 470 2349 perforation 2.501E* 21.10 7.00 489 2523 perforation 2.50BP22A* 21.35 1.75 188 377 stop 0.902B* 21.09 1.65 236 587 stop 1.102D 21.30 1.75 271 782 perforation 1.302C* 21.13 1.85 293 907 perforation 1.50ARMOX®armox 21.09 3.60 444 2079 stop 2.40* High speed camera footage available

The displacement of the plate around the bullet impact is made visible bya second 3D scan after the ballistic testing. The displacement of material aroundthe impact locations is depicted in different colours, purple is a displacementbackwards, yellow when the material has come forward. Dark green and lightblue indicate no displacement in comparison with the original state of thebreastplate. As can be seen in Figure 33 and Figure 34 the deformation in BP2 isover a much larger area than in BP1, although the energy was much lower. Thisstands to reason, because the plate is much thinner and therefore easier todeform. In Appendix H a thickness cross-section of three bullet impacts (A, G andF) are given, the thickness reduction is clearly visible.


43

Figure 33: Displacement in BP1 in mm

The weight loss of the bullets (see Table 9) is the amount of lead that hasbeen molten on impact and flew away. The heat of fusion of lead is 24.1 J/g, anapproach to the amount of energy that goes into bullet deformation and meltingcan be calculated by multiplying the weight loss with the heat of fusion of lead.The resulting energy that is lost because of melting the lead of the bullets is onlya small part of the total energy. Also the energy needed to deform the bullet (see§ 4.2.2) is very low. The energy needed to perforate the breastplate is the totalenergy available minus the energy lost on deformation and partially melting ofthe bullet. Because these last two factors are relatively small, and difficult todetermine exactly, in the end the total amount of energy is needed to account forall actions that lead to the perforation of a plate of certain thickness.

A

B

C

DE

F

G

H


44

Figure 34: Displacement in BP2 in mm

Table 9: Weight loss of bullets

Mass before(g)

Mass after(g)

Weight loss(g)

Weight loss(%)

Energy loss(J)

BP22A 21.35 21.00 0.34 1.6 8.32B 21.09 20.66 0.43 2.1 10.42D 21.30 20.56 0.74 3.5 17.82C 21.13 20.35 0.78 3.7 18.7BP11H 21.06 12.02 9.04 42.9 217.81A 21.38 19.06 2.32 10.8 55.81B 21.11 17.91 3.20 15.1 77.01C 21.26 16.82 4.44 20.9 107.01G 21.33 16.23 5.10 23.9 122.81F 21.10 16.95 4.15 19.7 100.01D 21.27 18.04 3.23 15.2 77.81E 21.10 15.93 5.17 24.5 124.7ARMOX®armox 21.09 11.64 9.45 44.8 227.7

A

B

C

D


45

4.3.2 Energy versus thickness

Increasing the thickness of armour is known to have been a commonpractise to offer more protection against bullet impacts. However, it is not verystraightforward how the increase in thickness affects the ballistic performance,i.e. how much more energy the plate can withstand. Because of the variousfactors affecting the ballistic limit and therefore the amount of protection offered,it is not possible to say without some research what the influence of thickness ofthe plate is on the performance. In Figure 35 the measured thickness and energyare plotted. The square data points with a cross indicate the shots that perforatedthe material in question. For the energy error a measuring error of the speed of10 m/s is used. For the error in thickness 0.2 mm for BP1 and 0.1 mm for BP2 isused. A line can be drawn to divide the data points that correspond to perforationand those who do not. This yields an interesting picture; data from both BP1 andBP2 obey more or less to this boundary, and AISI 1137 steel (used for test shots)also seems to obey the line, but because only two points are available, this is notcertain. ARMOX does not, but this is a very different material, especially designedto withstand impacts of various projectiles. This line can be considered to indicatethe energy needed to perforate a plate of critical thickness tc;

€

E =αtc (2)

with α = 2.8·10-3 J/mm, a material dependent constant, due to the position ofthe points of perforation and of no perforation this is a constant value in thiscase.

The straight line is explained when the way of perforation of thebreastplates by the bullet is simplified by comparing it to making a hole in a platewith a (round) punch load. The failure of the plate is assumed to be caused bypure shear stress only, factors like toughening of the material because of partialdeformation will be neglected, because these would make the comparisonunnecessarily complex. The shear area As on which this stress acts is thecircumference of the hole times the thickness of the plate:

€

As = 2πrt (3)

in which r is the radius of the hole (and thus of the bullet) and t is the thicknessof the plate. If a force F is required to make a hole, the average shear stress inthe plate is that force divided by the shear area:

€

τ s =FAs

(4)

This shear stress is required to cause yielding of the material, which will lead tofracture. In this simplified model the critical thickness is proportional to theenergy of the bullet, but, as mentioned before, several factors are neglected inthis approach. The toughening of the material due to partial deformation isneglected, which would mean that with a higher thickness relatively more energyis required to perforate the plate. The reason why the line goes through the originis because no energy is required to perforate a plate of zero thickness.


46

Figure 35: Energy vs. thickness as measured

0

1

2

3

4

5

6

7

8

0 500 1000 1500 2000 2500 3000

Energy (J)

Thic

knes

s (m

m)

BP1BP1 perforatedBP2BP2 perforatedAISI 1137 Steel1137 perforatedARMOX

No Perforation

Perforation

(cracked surface)


47

5 Discussion

5.1 Introduction

In the previous chapter all results are given and discussed. From theseresults three main topics can be distinguished. First, because of the results ofvarying analyses the originality of BP2 is doubted. Secondly the microstructure ofBP1 is very interesting and leads to the conclusion that different pieces of ironwere forged together to form the layers in BP1. Lastly, the ballistic testing yieldedinteresting results and the performance of the material with respect to thethickness and the impact characteristics is discussed.

5.2 Authenticity of BP2

There are four aspects that indicate that the breastplate sold as originatingfrom 1645 is in fact not a seventeenth century breastplate but one made in thenineteenth century, or later. These aspects are the shape, the thickness, thetexture and the microstructure.

The shape of the breastplate in general gives doubts as to the originality;it is not found commonly in other breastplates from the seventeenth century.Most painting of inside (and outside) of armour is of a later date, 19th or 20th

century. There is little or no evidence that armour was painted in the early or mid17th century. However, absence of proof is no proof of absence, and besides, thepaint can in a later stage be put on original specimens as well.

A second indication that BP2 is not a 17th century breastplate but a replicafrom probably the nineteenth century lies with the thickness. The thickness itself,1.8 mm, is not uncommon for armour in the seventeenth century, but the 3Dscan showed that the variation in thickness is very low (Figure 27). The regularthickness points to it being made from a rolled plate. (Hot) rolling was notavailable in the seventeenth century, but became common practise in theeighteenth and especially the nineteenth century during the industrial revolution.Another indication for the use of a rolled plate lies in the fact that in BP2 themiddle part is slightly thinner than the outer regions. If you start with an evenlyrolled plate and try to make a breastplate, you will find that more hammering isneeded to form the vestigial peascod in the middle. More hammering will causethe plate to become thinner. With period breastplates this effect normally seemsto have been cancelled out by making the centre part thicker to start with,although examples where the middle is thinner than the outer parts are alsofound.

The texture analysis at the ISIS facility shows a texture that is commonfor rolled material (Figure 32). This is good proof that it actually is rolled materialinstead of material flattened by hammering.

The microstructure of BP2 is not very common for 17th century material.The main ingredients, ferrite and slag inclusions, are regularly found inseventeenth century armour, but the slag is not that evenly distributedthroughout the 17th century material; randomly distributed bands of slag aremore common. The size of the slag inclusions and the amount of total slag (lessthan 0.8%) give an indication that puddled or Victorian wrought iron is used. Thepuddling technique for making iron only became common practise well after theseventeenth century. The microstructure is very homogeneous throughout thebreastplate, opposite to what is found in BP1 or other original samples [Williams2003].

All factors combined, it can be said that BP2 is a replica from a laterperiod, presumably the nineteenth century, in which period many replicas of 15th


48

to 17th century armour are known to have been made (particularly after 1828,when the organisation of a medieval tournament in England inspired thereproduction of (missing or lost) 15th century armour, which in turn led to thereproduction of other armour – also for decorative purposes, to impress visitorsof the manor where various pieces or suits of armour are displayed).

5.3 Layered structure of BP1

The armourers in the seventeenth century recycled armour. Old fashionedor too thin armour was recycled to form new thicker armour that offered betterprotection. This way layers can be formed, by forging plates of iron on the insideof thin armour. Evidence of these layered structures is best visible in the so-calledduplex breastplates, where turned flanges on the inside show that it consists ofmore than one layer. This forging together is sometimes very crudely done, butcan also be very precise, without an overlap or flange. There are 27 duplexbreastplates available at the Royal Armouries alone, so it is likely that in the restof Europe more specimens can be found [De Reuck et al., 2005]. Forge weldingplates of iron together with steel was done, but this was difficult to do and steel isalso more expensive than iron. Because of the large demand of cheapbreastplates the armourers could not produce armour of high quality steel andthe thickness of the armours is an indication for the amount of protection offered.The mechanical properties of a layered plate with slag inclusions on the forge-welded lines are inferior to a single layered plate without these continuous layersof slag. The slag forms slip planes upon deformation, so the resistance againstslip is lower, also the inclusions are crack initiators, locations where cracks canstart more easily. If no slag was present in the layered structure this differencewould probably be much lower, so the poor quality can be explained largelythrough the presence of large amounts of slag in BP1 (3% on average, locallymore than 5%). The high amount of slag is not uncommon for this period, but isnot considered to be the result of good craftsmanship. Forging plates togethershould help taking out part of the slag, because the forging will take place at atemperature above the melting temperature of slag. Remelting iron in order tostart out with a fresh lump was not done until the nineteenth century, after theBessemer process was invented (patented in 1855). So in order to produce thickiron and not having the opportunity to start with new material, forging old platestogether seems to have been the only logical option.

Layering of armour with different kinds of iron or steel can also be anoption. Bladesmiths especially were very familiar with the different properties ofiron and steel. Knives and swords were sometimes laminated (or pattern-welded)for beauty but also for practicality. A soft iron back with a high-carbon steel tipthat could be sharpened formed the main ingredients of a good knife. There areexamples of consciously laminated armour plates, but this is mostly found inbrigandines, which consist of a number of smaller plates riveted to a leather coat.These small plates were sometimes laminated with a soft outside and a hardinside. Also tin-coating to prevent corrosion was applied. This illustrates theknowledge of armourers and bladesmiths of the different properties of iron andsteel and the ability to apply them correctly. On BP1 however, there is no clearindication, other than the carbon rich area in the upper left corner of thebreastplate, that different materials have been used for layering. So no differentproperties can be combined. Also, on the upper left area the harder area is on theoutside, which is illogical, because a harder surface will crack sooner, and a softerductile outside with a harder inside is preferred when you desire resistance toimpacts. So for this breastplate no real attempt was made to improve thequalities of the breastplate by forging layers of iron together, other than theresulting thickness increase that improves the protective quality of thebreastplate.


49

There are several factors that indicate that BP1 consists of layers of iron,forged together. Delamination at various locations around the edge where twoparts of more or less similar thickness can be seen, indicate a two-layered plate.The microstructure of the cross-section confirms this, but also adds a third layerthat is forged only in the centre part of the breastplate, see Figure 23. Themicrostructure shows in the middle region (cs2 and cs3) two bands of pearliticiron. This locally increased carbon content can be the result of forging the platestogether; before forging the plates were heated in a charcoal fire and thus somecarburisation on the surface of the plates occurred. Through forging andsubsequent heat treatments (enabling quicker diffusion of carbon) the carbon hasspread through the material and the bands of pearlite have locally become sowide that they are no longer distinguishable as bands. This is also the case forcs1 where no bands are visible.

The microstructure is very inhomogeneous, large grains are found next tosmall grains, and slag inclusions are found throughout the samples, but mostlylocalised at the side of the cross-section corresponding with the front of thebreastplate. This inhomogeneity can be explained if bloom iron was used in itsmanufacture. The iron formed in a bloomery is very inhomogeneous [Williams2003]. Local variations in carbon content of 1 wt% are not uncommon. Also, slagconcentrations vary throughout the bloom. When the bloom is flattened throughhammering, the slag areas also flatten and form layers or thin plates of slag inthe iron. A lower grade of iron with higher slag content can have been used toform the outside layer of the breastplate. This higher slag content on the outersurface was not found that clearly in the samples BP1-Ix and BP1-Iy, the totalamount of slag is also much lower in those two samples, almost no slag is visiblein BP1-Iy. This again illustrates the heterogeneous structure of BP1.

5.4 Critical thickness of armour

From the graph in which the energy of the bullet vs. the thickness of theplate on impact location are compared (Figure 35), it has become clear that thereis a definite amount of energy a plate of certain thickness can withstand. InEquation (2) the energy is related to the critical thickness of BP1 and BP2represented by a constant value α. ARMOX, which is designed to withstandimpacts, has a higher α. This graph and division in situations of ‘perforation’ andof ‘no perforation’ only applies to lead bullets of 16 mm diameter. In a moregeneral plot the size of the bullet was taken into account (see Figure 36). Asmentioned in Equation (3), the radius affects the shear area As and therefore theinfluence of a smaller bullet is different than of a large bullet. With this taken intoaccount the following equation can be made:

€

Ec = ′ α 2πrbtc( ) (5)

where rb is the radius of the bullet. In a graph where the critical thickness tc isplotted against the energy divided by the bullet radius, a straight line alsoseparates the situations of ‘perforation’ and of ‘no perforation’, Figure 36, slope is(2πα’)-1. The experiment of Graz (see § 2.6.5) with a perforated breastplate alsoobeys this boundary, perforation occurred at an Ec/rb value of 154 J/mm, as isindicated in Figure 36 with a cross. The properties of the weapon are now on thex-axis (energy of the bullet divided by the radius of the bullet), and the thicknessof the armour plate is on the y-axis. The parameter α ’ is dependent on the

material properties of the armour. With a higher hardness Hv of the material α’will increase (for convenience a first order approach is made, but furtherinvestigation should either confirm or deny this relation):

€

′ α = βHv (6)


50

and with Equation (5) the relation between critical thickness and energybecomes:

€

tcHv =12πβ

Ec

rb (7)

In this approach only hardness and thickness of the material in questionneeds to be measured, both possible in a non-destructive way, to predict theresistance of the plate against a specific weapon at a certain distance. Moreinvestigation on modern material with respect to energy and hardness is neededto give a value to β.

Figure 36: Critical thickness of armour

Selected muskets and pistols from the 16th to 18th century were tested onperformance [Krenn, 1991]. During this test modern gunpowder was used.Seventeenth century gunpowder will not burn as effectively as moderngunpowder does, so the results on speed and thus energy of the bullets given bythese muskets and pistols are higher than what could be achieved in their originaltime. In Table 10 the results of the testing of some 17th century weapons arelisted. The 17.3-gram bullet from the Styrian matchlock musket has a muzzlevelocity of 449 m/s. The corresponding energy-radius ratio (245 J/mm) will causeperforation of a breastplate with similar properties to BP1 and BP2 of a thicknessbelow 5.2 mm (see line M2 in Figure 36). It is high enough to penetrate BP2,even at a range of over 30 meters, when the energy-radius ratio drops to 174J/mm, corresponding with a perforation of plates of less than 3.7 mm thick. Thewheellock musket however has a lower muzzle velocity but a slightly larger bullet,resulting in an energy-radius ratio of 281.5 J/mm (line M3 in Figure 36), which isenough to perforate BP1 on locations where the thickness is below 6 mm. Again,this musket has enough power to perforate BP2, even at a distance of 100 m.BP1 can resist a shot from the wheellock pistol at any distance, while BP2 risksperforation even at 30 m distance. In Figure 37 the critical thicknesscorresponding to muzzle energy of muskets and the energy at 30 m and at 100 mdistance is given. In this plot it is easy to see that BP2, at just 1.8 mm, offerslittle protection. The middle region (above 5 mm thickness) of BP1 is able toresist all shots from pistols (similar values for tc as M1 at muzzle and 30mdistance) and almost all shots from muskets from the early seventeenth centuryat any distance. To be on the safe side, and depending on the type of musket,


51

protection against musket shots is offered at a distance of 30 m and furtheraway. Especially towards the end of the seventeenth century the musketsbecame so powerful, that it was not possible to make breastplates that were ableto offer enough protection and comfort at the same time.

Table 10: Test firing selected 17th century weapons, after [Krenn, 1991]

Weapons Acr

onym

for

wea

pon

Ave

rage

bulle

tw

eight

(g)

Ave

rage

bulle

tca

liber

(m

m)

muzz

le v

eloci

ty(m

/s)

velo

city

at

30m

(m

/s)

velo

city

at 1

00m

(m

/s)

muzz

leen

ergy

(J)

ener

gy

at 3

0m

(J)

ener

gy

at 1

00m

(J)

Wheellock musket, Suhl,1593

M1 10.84 12.3 427 349 238 998 660 307

Matchlock musket, Styria, 1st

quarter 17th C.M2 17.38 14.3 449 378 264 1752 1242 606

Wheellock musket, rifled, 1st

half 17th C.M3 32.06 17.5 392 342 260 2463 1875 1084

Wheellock pistol,Nuremberg, c. 1620

P1 9.56 11.8 438 355 - 917 602 -

Flintlock musket with com-bined matchlock, Suhl, 1686

M4 30.93 17.5 494 426 305 3774 2807 1439

Flintlock musket convertedfrom matchlock c. 1700

M5 27.54 16.8 474 406 291 3094 2270 1166


M6 32.16 17.6 451 391 287 3271 2458 1324


M7 34.25 17.8 467 406 300 3735 2823 1541

Flintlock pistol, Ferlach,c.1700

P2 14.45 13.5 385 323 - 1071 754 -

Figure 37: Critical thickness at various distances

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60 80 100 120

Distance (m)

Critica

l th

ickn

ess

(mm

)

M1M2M3M4M5M6M7


52

As mentioned before, in the second half of the seventeenth century, afterabout 1660, armour was largely discarded, and in Figure 38, a plot where thecritical thickness determined through Equation (5) for energies delivered by theweapons in Table 10 is depicted against the date, it is clear that there is a steadyincrease in critical thickness with time. The corresponding weight of thebreastplate is also given in this plot on the right side. The weight is for a 0.17 m2

plate of a certain critical thickness. This area is based on the weight and thicknessof BP2 and the density of iron, 7,800 kg/m3. As can be seen in the plot, afterabout 1660 the critical thickness at 30 m distance is at least 5 mm, which wouldcorrespond to a breastplate weight of almost 7 kg. In this plot only musket datais used. When the critical thickness in Figure 38 is compared with actual thicknessdata of original breastplates [Williams 2003], see Figure 39, there is anagreement in the rise of maximum thickness and critical thickness. The maximumthickness found lies above the line of critical thickness based on muzzle energiesof the muskets. Also the thickness for breastplates for horsemen is on averagehigher than for infantry, and this indicates that infantry is only protected at largerdistances (100 m or further away) than the cavalry, so that cavalry could engageat closer distances than infantry with less personal risk.

Figure 38: Critical thickness of armour through time

0

1

2

3

4

5

6

7

8

9

10

1580 1600 1620 1640 1660 1680 1700 1720

Year

Critica

l th

ickn

ess

(mm

)

muzzle

30 m

100 m

Linear(muzzle)Linear (30m)Linear(100 m)

Correso

pondin

g w

eight (kg

)

0.0

1.3

2.7

4.0

5.4

6.7

8.1

9.4

10.8

12.1

13.4


53

Figure 39: Average thickness of breastplates through time, after[Williams, 2003]

There is a grey zone around the line that divides ‘perforation’ from ‘noperforation’. Does it always mean with perforation, so with defeat of the armour,that the wearer dies? The definition of perforation or full penetration depends onthe use of the material. Nowadays, full penetration of materials used in the armyis achieved as soon as the top part of the bullet reaches the back of the plate.The ballistic limit consists of parameters (speed, size, mass, hardness etc. ofbullet) with which full penetration is just achieved. Full penetration according toarmy standards does not mean that the wearer is incapacitated; so even with fullpenetration the wearer will sometimes survive. To defeat armour, full penetrationis desired, but with enough remaining energy of the bullet to perforate the fabricworn under the armour and to make a lethal or semi-lethal wound. When thecriteria for full penetration have just been met, the impact can be so severe, thatthe wearer is out of breath and needs time to recuperate before he is into actionagain. But also, in the heat of battle, severe damage to the body can be ignoreduntil the battle is over or until the wounds finally take their toll.

The ballistic limit for projectiles that penetrate solely on the basis of theirkinetic energy is affected by many parameters. For spherical bullets the projectileyaw does not play a role, but the projectile and target hardness, density and yieldstrength affect the ballistic limit, as well as the target thickness and targetobliquity (angle of impact). In the experiments the last parameter was neglected,all impacts were more or less at a right angle. However, these small variations inangle were not taken into account. The hardness of the bullet plays a significantrole with respect to ballistic limit. With increasing hardness of the bullet theballistic limit drops, because less energy goes to plastic deformation of theprojectile, and more into perforation of the target. Even though during testingonly lead bullets were used, it is known that sometimes steel bullets were used inthe 17th century, but this is more an exception than a rule, and extremely rare,because lead bullets are much easier to manufacture and do the job fine enough.But it has to be reckoned with, that if a breastplate is bullet-proof for lead bullets,it does not necessarily mean that it can withstand steel bullets shot with thesame pistol or musket (even though steel bullets have just over half the weight ofsimilar sized lead bullets). The energy that originates from the burned gunpowder

0

1

2

3

4

5

6

7

8

9

1450 1500 1550 1600 1650

Year

Thic

knes

s (m

m)

critical thickness based on muzzle energycritical thickness at 30 mcritical thickness at 100 mbreastplate for horsemenbreastplate for infantry


54

is transferred to the bullet in the gun. For a lighter bullet, this will result in ahigher initial speed. Because steel is much harder than lead and less deformationof the bullet will occur, less energy of the bullet on impact is lost on bulletdeformation, and more energy to perforate the breastplate is available.

To sum things up, by combining various available data on armour it wasshown that in the second half of the seventeenth century the weapons becametoo powerful, and that breastplates able to offer enough protection becameuncomfortably heavy to wear, and were therefore abandoned. The amount ofprotection offered by a breastplate depends on a number of factors: thickness,material properties of the breastplate like hardness, and the speed, size and lessrelevantly the material of the bullet. Most of these factors can be determined in anon-destructive way, and thus a prediction of the amount of protection offered bya certain breastplate can be made. The critical thickness that is needed for abreastplate to protect the wearer against a weapon of certain date correspondsvery well with the actual measured (maximum) thickness of armour throughtime.


55

6 Conclusion

With respect to the authenticity of the breastplates it can be said that BP2is most likely a 19th century replica because of the shape, thickness, texture,microstructure and performance, although original breastplates with low thicknessand therefore low performance are known to exist. There is no reason to doubtthe originality of BP1. The texture analysis as a result from neutron diffraction isa good non-destructive method to prove the non-authenticity of certain pieces ofarmour; it can indicate a rolled texture, which will exclude the likeliness thatarmour was made before the eighteenth century.

The structure of BP1 has proven to be very interesting. The layers in themicrostructure of BP1 arise probably due to forging together of recycled material,or due to reinforcing of old armour that was too thin. The inhomogeneousstructure is likely to have come from the heterogeneous bloom the iron plateswere forged from.

To answer the main question whether the breastplates offer enoughprotection against impacts from bullets from muskets or pistols in theseventeenth century, it can be said that BP1 offers enough protection against apistol at any distance, but at short ranges (less than 30 metres) muskets have afair chance of defeating the breastplate. BP2 does not offer enough protectionagainst a pistolshot, even at 30 m distance, and musket shots will definitelyperforate the breastplate at any distance. The model that links the weaponparameters to the critical thickness of armour (below which perforation of thebreastplate is likely) should help to predict the performance of other pieces ofarmour, although more investigation with respect to the model is necessary.Especially attention has to be paid to finding out the material properties thatdefine the value of α’ (Equation (5)). This can be done with experiments onmodern iron and steel with variable hardness and other material properties thatcan be varied to find the parameters that influence α’. For the ballistic testingthat is needed to investigate this, it is recommended to use lead bullets,preferably also of variable diameter.


56

7 References

Callister, W.D. (1997). Materials Science and Engineering, an Introduction,Canada, John Wiley & Sons, Inc.

Childs, J. (2001). Warfare in the Seventeenth Century, London, Cassell History ofWarfare.

De Reuck, A., Starley, D., Richardson, Th. and Edge, D. (2005). Duplex armour:an unrecognised mode of construction, Arms & Armour, Vol. 2, No. 1. pp. 5-26

Hughes, B.P. (1974). Firepower: Weapons effectiveness on the battlefield, 1630 –1850, London, Arms and Armour Press.

Kocks, U.F., Tomé, C.N. and Wenk, H.-R. eds. (1998). Texture and Anisotropy,Cambrigde University Press. pp. 181-198

Krenn, P. (1989). Von alten Handfeuerwaffen: Entwicklung, Technik, Leistung;Sondernausstellung im Landeszeughaus, Mai-Oktober 1989, Publication of theArmoury in Graz, Austria. pp. 72-73, 109

Krenn, P. (1991) Test-Firing Selected 16th-18th Century Weapons, MilitaryIllustrated 33 (February 1991) pp. 34-38

Laible, R.C. ed. (1980). Ballistic Materials and Penetration Mechanics,Amsterdam, Elsevier Scientific Publishing Company.

Puype, J.P. and Van der Hoeven, M. ed. (1993). Het arsenaal van de wereld. DeNederlandse wapenhandel in de Gouden Eeuw, Amsterdam, De BataafscheLeeuw.

Richardson, Th. (2004) The London Armourers of the 17th Century, Dorchester,The Dorset Press, Royal Armouries Monograph 7.

Theophilus (1963) On Divers Arts (translated by Hawthorne, J.G. and Smith, C.S.from De diversis artibus), New York, Dover Publications.

Van der Hoeven, M. ed. (1997). Exercise of Arms – Warfare in the Netherlands,1568 – 1648, Leiden, Brill. History of Warfare vol. 1. pp.17-32

Wasserman, G. and Grewen, J. (1962). Texturen metallischer Werkstoffe, Zweiteauflage, Springer-Verlag. pp. 354-356

Williams A.R. and De Reuck A. (2002). The Royal Armoury at Greenwich 1515-1649, a history of its technology, Dorchester, The Dorset Press, Royal ArmouriesMonograph 4.

Williams, A.R. (2003). The Knight and the Blast Furnace: a history of themetallurgy of armour in the middle ages & the early modern period, Leiden, Brill,History of Warfare vol. 12.

Young, R.A. ed. (1993). The Rietveld Method, International Union ofCrystallography, Oxford University Press

Zukas, J.A. (1982). Impact Dynamics, New York, John Wiley & Sons.


57

Appendices

Content:

Appendix A: Microstructure of 17th century armour ......................................... 58Appendix B: Sampling for microstructure and composition analysis................... 60Appendix C: Crystal structures for Rietveld analysis........................................ 62Appendix D: Microstructures, optical and SEM, and EPMA results ...................... 63Appendix E: Measured locations of microhardness .......................................... 67Appendix F: Graphs for tensile testing and compression test ............................ 75Appendix G: Composition of lead bullets ....................................................... 77Appendix H: Thickness reduction in bullet impact locations .............................. 79Appendix I: Photographs before and after ballistic testing................................ 81


58

Appendix A: Microstructure of 17th century armour

Microstructure of armour from the first half of the seventeenth century, after[Williams, 2003]

Date Piece Ferrite Pearlite Carbides Martensite Slag % CItalian1600 visor x - x - x -1600 visor/helmet x x - - x 0.11600 gorget x x - - x 0.11600 gauntlet x x - - x 0.21600 breastplate x x - - x 0.31602 backplate x - (isolated) - x -1600 helmet x x - - x 0.31630 helmet x x - - x 0.3German1610 gorget x x - - x 0.11620 demi-shaffron x x - - x 0.61630 breastplate x x x - x 0.21619 burgonet x - x - x 0.21620 gorget x x - - x -1641 vambrace x x x - x 0.61607 backplate x x - - x 0.61609 breastplate x x x - x 0.21630 breastplate x x - - x 0.11630 breastplate

(infantry)x - - - x -

1630 breastplate(cuirassier)

x - - - x -

1630 helmet x - - - x -1640 knee cop x - - - x -Polish1630 12 hussar armours x - - - x -English1608 pasguard x x x - x (0.2)1610 breastplate x - - x ? ?

backplate - - - x ? ?vambrace - - - x ? ?pauldron x - - x ? ?visor - - - x few ?gorget x - - x ? ?gauntlet x - - x ? ?pasguard x - - x ? ?visor x - - x ? ?

1610 grandguard x x - - x ?1610 gauntlet x - x x x ?1610 gauntlet x - x - ? ?1610 grandguard x x x - ? ?1612 bevor x - - x x ?1625 tasset x x - - x 0.31625 helmet x - - - x -1630 greave - x x - ? ?

tasset - x - - ? ?helmet - x - - ? ?

French1610 pauldron x x - - x 0.11640 helmet x - - - x -

breastplate x - - - x -Dutch1610 helmet x - - - x -1640 helmet x - - - x -


59

Most carbides present are small grain boundary carbides (globular cementite),and mostly present in small amounts.The general structure of seventeenth century armour consists of ferrite with no orvery small amounts of pearlite and slag inclusions. Most specimens have low orno carbon content.

Description of armour parts:

Bevor = A chin-shaped defence for the lower face, incorporating a gorget plate.Burgonet = A light, open-faced helmet popular in the sixteenth century as analternative to the close-helmet for light cavalry. It was usually furnished with apeak over the brow, a combed skull, and hinged ear-pieces. The face openingcould be closed by the addition of a falling bevor.Gauntlet = Armored glove mostly consisting of a single plate for the back of thehand and a smaller and flexible part of overlapping plates for the fingersGorget = Close-fitting plate protecting the neck, throat, and upper chest (alsocalled collar).Grandguard = A large reinforcing plate designed for the tilt, attached to the leftside of the breastplate to cover the left shoulder, the upper arm and breastplateand the left side of the visor.Greave = Plate defence for the leg from knee to ankle, initially protecting onlythe front, but later the whole lower leg. Constructed of two plates hinged togetherand shaped to the contours of the muscleKnee cop = Knee protection, varying from single plate to three or morelaminated plates.Pasguard = A reinforcing piece for the left elbow, used in tilting/jousting.Pauldron = Shoulder defenceShaffron = horse armour for horses head (fully or partially (demi) covered)Tasset = Overlapping plates covering the joint of the haunch partVambrace = (lower) arm defenceVisor = Protection for the eyes and face; a plate defence pivoted to the helmet


60

Appendix B: Sampling for microstructure and composition analysis


61


62

Appendix C: Crystal structures for Rietveld analysis

symmetry spacegroup

latticeparameters(Å)

atom positionsatom in x,y,z

FerriteFe

cubic Im3m(bcc)

2.8665 Fe in 0,0,0

CementiteFe3C

orthorhombic Pnma a = 5.082b = 6.743c = 4.522

Fe1 in 0.036,1/4,0.852Fe2 in 0.186,0.063,0.3280C in 0.890,1/4,0.450

WuestiteFeO

cubic Fm3m(fcc)

a = 4.313 Fe in 0,0,0O in 1/2,1/2,1/2

MagetiteFe3O4

cubic Fd-3m a = 8.3941 Fe1 in 1/8,1/8,1/8Fe2 in 1/2,1/2,1/2O in 0.2549,0.2549,0.2549


63

Appendix D: Microstructures, optical and SEM, and EPMA results

Microstructure of BP1A, on the ferrite grain boundaries the pearlite/cementite isvisible as dark with at white boundary.

Slag inclusions in pearlitic area on BP1-cs2


64

Small band of pearlite in ferritic matrix with in top left area a twin boundary (BP1-cs2)

SEM photograph of pearlitic area in BP1A


65

SEM photograph of slag inclusions in BP1B

SEM photo, detail of slag inclusion. With EDS a mapping of elements in andaround this inclusion is made, see next page.


66

Mappings of elements around a slag inclusion

Image Aluminium Calcium Carbon Chlorine

Iron Potassium Magnesium Manganese Oxygen

Lead Phosphor Silicon Sulphur

The intensity of the colours in the mappings indicates how strong thesignal was or in what quantity the element is present on one location (relativevalues). The result of the mapping indicates that the slag inclusion consists ofsilicon and calcium oxides (darker area) and iron oxides (lighter area) and lies inan iron matrix. Also some manganese is present in the slag inclusion, but not inthe iron. The values of this mapping are not absolute, they only give anindication.

The result of the EPMA line-scan through the thickness of the cross-sectionat a location corresponding to the middle of BP1-cs2 yields only data on phosphorand manganese, both of which are not present in large amounts:

0,00

0,01

0,02

0,03

0,04

0,05

0,06

0 20 40 60 80 100 120 140

Measure point

Co

nce

ntr

ati

on

P (

wt%

)

0,00

0,50

1,00

1,50

2,00

2,50

3,00

Co

nce

ntra

tion

Mn

(wt%

)

Phosphor

Manganese


67

Appendix E: Measured locations of microhardness

The thick line in the images indicates the front side of the breastplate.

Sample 1Ax

Location Hardness(HV)

1 110.62 115.63 94.44 120.25 179.26 141.87 116.28 122.19 95.610 130.511 206.012 158.513 157.914 152.215 154.316 222.417 207.418 236.019 177.920 184.021 160.222 180.623 217.624 232.6Average 161.4Min 94.4Max 236.0

Sample 1Ay


1 106.82 116.43 94.44 106.45 182.16 144.47 144.48 151.39 117.210 126.811 171.212 191.013 131.814 138.115 130.516 131.117 157.318 163.919 137.720 130.921 110.022 128.923 176.524 183.6Average 140.5Min 94.4Max 191.0


68

Sample 1Bx


1 98.12 88.13 102.64 93.05 90.56 106.37 83.78 92.79 94.410 100.411 102.112 93.113 96.114 94.815 86.916 104.817 91.718 98.319 99.620 96.8Average 95.7Min 83.7Max 106.3

Sample 1By


1 129.02 102.53 106.94 122.95 92.66 127.97 118.68 113.29 113.310 109.711 144.212 147.213 139.314 120.115 106.716 120.517 75.918 106.619 105.920 90.321 90.322 111.823 73.924 95.925 105.426 111.7Average 110.9Min 73.9Max 147.2


69

Sample 1Cx


1 149.32 139.83 161.54 112.85 133.26 141.47 150.18 170.49 165.210 112.711 123.012 141.313 140.014 156.115 113.416 119.917 129.418 140.3Average 138.9Min 112.7Max 170.4

Sample 1Cy


1 121.52 135.23 140.24 123.85 100.46 102.07 131.08 125.59 123.710 107.911 105.012 91.013 129.014 126.615 109.216 113.917 109.018 113.119 96.9Average 116.0Min 91.0Max 140.2


70

Sample 2Ax


1 131.92 130.03 134.04 142.85 118.06 128.07 121.88 124.59 158.510 141.311 140.912 148.513 204.914 163.315 150.416 153.417 172.718 163.519 170.320 154.421 123.422 126.623 124.624 112.5Average 143.3Min 112.5Max 204.9

Sample 2Ay


1 124.92 119.13 122.64 122.65 125.46 114.97 134.28 151.19 129.410 120.611 130.512 132.8Average 127.3Min 114.9Max 151.1


71

Sample 2Bx


1 146.02 142.53 141.74 142.65 137.06 135.57 137.98 132.49 141.910 138.511 143.312 147.4Average 140.6Min 135.5Max 147.4

Sample 2By


1 114.92 106.13 115.24 122.75 115.06 116.47 110.88 116.59 144.710 140.011 125.812 147.813 142.414 143.215 174.416 175.517 134.618 136.919 129.320 138.5Average 132.5Min 106.1Max 175.5


72

Sample 2Cx


1 110.42 107.73 106.44 132.65 96.26 97.37 108.78 129.79 102.210 93.711 116.712 134.813 98.5Average 110.4Min 93.7Max 134.8

Sample 2Cy


1 124.22 108.13 95.64 102.65 125.16 134.27 132.18 121.49 133.910 137.511 132.212 136.0Average 123.6Min 95.6Max 137.5


73

Microhardness cross-section BP1-cs3, middle part of breastplate

Hardness (HV)Location A B C D E F1 101,6 112,8 114,3 109,0 98,1 103,22 103,8 113,2 108,1 98,8 92,8 92,63 130,5 126,2 126,3 111,4 118,6 103,24 129,2 122,9 140,3 136,4 122,1 106,75 122,2 123,6 119,5 107,8 125,9 112,86 103,6 100,1 92,1 89,7 91,8 84,47 95,4 92,9 93,2 89,9 83,9 88,88 94,2 90,6 94,1 90,4 90,4 99,79 85,7 89,5 85,5 91,1 85,8 94,210 93,6 95,3 89,4 89,1 86,5 86,811 76,8 88,4 94,2 92,8 80,0 83,912 89,7 100,0 90,0 78,3 80,1 9413 95,6 91,5 95,2 88,6 96,1 92,214 103,3 95,1 72,4 97,5 102,6 124,515 102,7 111,6Average 101,9 103,0 101,7 97,9 96,8 97,6Min 76,8 88,4 72,4 78,3 80,0 83,9Max 130,5 126,2 140,3 136,4 125,9 124,5


74

Microhardness profile for BP2:

0

50

100

150

200

250

0,0 20,0 40,0 60,0 80,0 100,0

Distance from backside (%)

Har

dnes

s (H

V)

BP2ABP2BBP2C


75

Appendix F: Graphs for tensile testing and compression test

Tensile testing of BP1

0

50

100

150

200

250

300

0 20 40 60 80 100

Strain (%)

Str

ess

(N/m

m2)

BP1-1 BP1-2BP1-3

shallow slopes due to slip


76

Tensile testing of BP2

Compression test lead bullet

0

50

100

150

200

250

300

350

0 10 20 30 40 50 60

Strain (%)

Str

ess

(N/m

m^

2)

BP2-4

BP2-3

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 2 4 6 8 10 12

Strain (mm)

Str

ess

(N)


77

Appendix G: Composition of lead bullets

MK/ASp TU-Delft SuperQ Visit our website at:Rotterdamseweg 137 k 030 http://www.uniquant.com--------------------------------------------------------------------------------------C:\UQ5\USER\Uni2005\JOB\JOB.092 2005-02-03Sample ident = 09205/02/002 (Large Bullet) Remark = AN 24711480 Rh 60kV LiF220 Ge111 T1Ap Measure Frog.: UniQuantC:\UQ5\USER\Uni2005\Appl\AnySample.kap 2005-01-10Calculated as : Elements Matrix (Shape & ImpFc) : 11TeflonX-ray path = Helium Film type = 1 Prolene4Case number = 0 All knownEff.Diam. = 22.0 mm Eff.Area = 379.9 mm2KnownConc = 0 %Rest = 0 % Viewed Mass = 13425.00 mgDil/Sample = 0 Sample Height = 2.68 mm< means that the concentration is < 20 mg/kg<2e means wt% < 2 StdErr. A + or & means: Part of 100% sumZ wt% StdErr Z wt% StdErr Z wt% StdErr========================= ========================= =========================SumBe..F 0 88.09 29+Cu 0.0289 0.0045 52 Te <11 Na <2e 0.14 30+Zn 0.0098 0.0033 53 I <2e 0.006712 Mg <2e 0.029 31+Ga < 55 Cs <13+Al 0.187 0.018 32 Ge < 56 Ba <14+Si 0.0779 0.0086 33+As 0.041 0.010 SumLa..Lu 0.10 0.1415+Px 0.0147 0.0023 34 Se < 72 Hf <2e 0.01115 P 35+Br < 73 Ta <2e 0.008716+Sx < 37 Rb <2e 0.018 74 W <16 S 38+Sr < 75 Re <2e 0.009317+Cl 0.114 0.030 39 Y <2e 0.0080 76+0s 0.069 0.02818 Ar <2e 0.0071 40+Zr < 77 Ir <19+K 0.0809 0.0090 41 Nb < 78 Pt <2e 0.006220+Ca 0.0684 0.0076 42 Mo <2e 0.0077 79 Au <2e 0.006021 Sc < 44 Ru <2e 0.0064 80+Hg <22+Ti 0.0106 0.0030 45 Rh <2e 0.0063 81+Tl <23 V < 46 pd < 82+pb 99.18 0.0424 Cr < 47 Ag < 83 Bi <2e 0.01225+Mn 0.0082 0.0037 48 Cd < 90 Th <26+Fe 0.0195 0.0048 49 In < 92+U 0.0401 0.004227 Co < 50 Sn < 94+Pu <28 Ni < 51 Sb < 95+Am <==== Light Elements ===== ==== Noble Elements ===== ====== Lanthanides ======SumBe..F 0 88.09 44 Ru <2e 0.0064 57+La 0.0456 0.00684 Be * 45 Rh <2e 0.0063 58+Ce <5 B * 46 Pd < 59 Pr <2e 0.0126 C * 47 Ag < 60 Nd <2e 0.0067 7N * 75 Re <2e 0.0093 62 Sm <2e 0.0118 O * 76+0s 0.069 0.028 63 Eu <2e 0.00639 F < 77 Ir < 64 Gd <

78 Pt <2e 0.0062 65 Tb <79 Au <2e 0.0060 66 Dy <

67 Ho <2e 0.014 68 Er <69 Tm <2e 0.0085 70 Yb <2e 0.0083 71 Lu <

KnownConc= 0 REST= 0 D/S= 0Sum Conc's before normalisation to 100% : 99.0 %


78

MK/ASP TU-Delft SuperQ Visit our website at:Rotterdamseweg 137 k 030 http://www.uniquant.com--------------------------------------------------------------------------------------C:\UQ5\USER\Uni2005\JOB\JOB.093 2005-02-03Sample ident = 09305/02/003 (Small Bullet)Remark = AN 24711480 Rh 60kV LiF220 Ge111 T1AP Measure Prog.: UniQuantC:\UQ5\USER\Uni2005\Appl\AnySample.kap 2005-01-10Calculated as : Elements Matrix (Shape & ImpFc) : 11TeflonX-ray path = Helium Film type = 1 Prolene4Case number = 0 All knownEff.Diam. = 16.5 mm Eff.Area = 213.7 mm2KnownConc = 0 %Rest = 0 % Viewed Mass = 7244.000 mgDil/Sample = 0 Sample Height = 3.31 mm

< means that the concentration is < 20 mg/kg<2e means wt% < 2 StdErr. A + or & means: Part of 100% sumZ wt% StdErr Z wt% StdErr Z wt% StdErr========================= ========================= =========================SumBe..F 0 99.90 29+Cu 0.0487 0.0060 52 Te <11 Na < 30+Zn 0.0113 0.0044 53 I <2e 0.01512 Mg < 31 Ga <2e 0.011 55 Cs <2e 0.01513+Al 0.250 0.027 32 Ge <2e 0.0050 56 Ba <14+Si 0.135 0.015 33 As < Sum1a..Lu 0.08 0.1815 Px 34 Se < 72 Hf <2e 0.01715+P 0.0138 0.0035 35 Br < 73 Ta < 16+Sx < 37+Rb < 74 W <16 S 38 Sr < 75 Re <17+Cl < 39+Y < 76+0s 0.077 0.03118 Ar <2e 0.011 40+Zr < 77+Ir <19+K 0.0322 0.0075 41 Nb < 78 Pt <2e 0.009320+Ca 0.0566 0.0079 42 Mo <2e 0.014 79 Au <21 Sc < 44 Ru <2e 0.013 80 Hg <22 Ti <2e 0.0042 45 Rh <2e 0.013 81+Tl <23 V < 46 Pd < 82+Pb 98.66 0.0624 Cr < 47 Ag < 83 Bi <2e 0.01425 Mn <2e 0.0053 48 Cd < 90 Th <26+Fe 0.223 0.025 49 In < 92+U 0.0184 0.008527 Co < 50+Sn 0.399 0.025 94+Pu <28 Ni <2e 0.0041 51+Sb 0.042 0.012 95+Am <==== Light Elements ===== ==== Noble Elements ===== ====== Lanthanides ======SumBe..F 0 99.90 44 Ru <2e 0.013 57+La 0.0328 0.00964 Be * 45 Rh <2e 0.013 58+Ce <5 B * 46 Pd < 59 Pr <2e 0.0166 C * 47 Ag < 60 Nd <2e 0.00887 N * 75 Re < 62 Sm <8 O * 76+0s 0.077 0.031 63 Eu <2e 0.00919 F < 77+Ir < 64 Gd <2e 0.0090

78 Pt <2e 0.0093 65 Tb <2e 0.009079 Au < 66 Dy <2e 0.018

67 Ho <68 Er <69 Tm <2e 0.01170 Yb <71 Lu <2e 0.011

KnownConc= 0 REST= 0 D/S= 0Sum Conc's before normalisation to 100% : 100.9 %


79

Appendix H: Thickness reduction in bullet impact locations

At three locations the through thickness of bullet impacts is given, and thethickness reduction is clearly visible. The grid is 1 by 1 mm.


80


81

Appendix I: Photographs before and after ballistic testing

Details of BP1


82

Details of BP2


83

Halfway through ballistic testing, left BP1 and right BP2


84

Impact details of BP1