osu 1211986132
TRANSCRIPT
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Path Actuators for Magnetic Pulse
Assisted Forming and Punch-lessElectro-Magnetic Shearing
A THESIS
Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in
the Graduate School of The Ohio State University
By
Scott Michael Golowin, B.S.
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Copyright By
Scott Michael Golowin
2008
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ABSTRACT
Path actuators can be fabricated very quickly and inexpensive, allowing
customized products to be brought to market very quickly. Only one sided tooling is
required, since an electro-magnetic force is used to drive the work sheet. This eliminates
high tolerance problems in matched tooling and could be implemented into a
manufacturing process. The path actuators were successfully used in net shape
calibration forming of doubly bent U channels and three shearing operations.
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The high velocity punch-less shearing method developed here minimizes burrs on
shearing and no slivers have been seen on any of the parts sheared.
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DEDICATION
This is to my Mother, Father, and Sister. They always knew what I was capable of doing
and were always a positive encouragement. Without them I would not have made it this
far.
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ACKNOWLEDGMENTS
This is a relatively long list. First and foremost I need to acknowledge my advisor
Professor Glenn Daehn, whom gave me a chance to work in this wonderful field of
Electro-Magnetic Forming (EMF). Without him, I would not have found this exciting
work environment of explosions and high speed forming, which brings excitement to my
work every day. The next people I would like to thank is my fantastic graduate group I
have worked with: Manish Kamal, Mala Seth, Jianhui Shang, Yuan Zhang, Kristen
Banik, Jacob Portier, Jonathan Evarts, Kinga Uniocic, Geoffrey Taber, Anupam Vivek,
and last but not least Kathy Babusci. These people made work enjoyable and functional.
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VITA
August 30, 1983 .......................................BornColumbus, Ohio
2006..........................................................B.S. Material Science and Engineering, The
Ohio State University
2006Present ..........................................Graduate Researching Associate, The Ohio
State University
PUBLICATIONS
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TABLE OF CONTENTS
ABSTRACT ................................................................................................................ ii
DEDICATION ............................................................................................................ iv
ACKNOWLEDGMENTS ........................................................................................... v
VITA ........................................................................................................................... vi
TABLE OF CONTENTS .......................................................................................... vii
LIST OF FIGURES ..................................................................................................... x
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CHAPTER 3 .............................................................................................................. 13
MAGNETIC PULSE ASSISTED FORMING ................................................... 13
3.1. INTRODUCTION ................................................................................ 14
3.2. EXPERIMENTAL METHOD ............................................................. 17
3.3. ANALYTICAL PROCEDURES ......................................................... 21
3.4. EXPERIMENTAL RESULTS ............................................................. 22
3.5. ANALYTICAL RESULTS .................................................................. 25
3.6. DISCUSSION ...................................................................................... 29
CHAPTER 4 .............................................................................................................. 31PUNCH-LESS ELECTRO-MAGNETIC FORMING ....................................... 31
4.1. INTRODUCTION ................................................................................ 31
4.1.1. OTHER SHEARING METHODS ............................................. 32
4.1.2. HIGH VELOCITY SHEARING ............................................... 33
4.2. EXPERIMENTAL PROCEDURES .................................................... 40
4.2.1. TWO BY TWO PROCEDURES ............................................... 40
4.2.2. ONE BY ONE PROCEDURE ................................................... 42
4 2 3 OHIO SHEARING PROCEDURE 43
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LIST OF REFERENCES .......................................................................................... 77
APPENDIX A. ........................................................................................................... 79
TWO BY TWO SHEARING DESIGN ............................................................. 79
APPENDIX B. ........................................................................................................... 82
ONE BY ONE SHEARING DESIGN ............................................................... 82
APPENDIX C. ........................................................................................................... 86
OHIO CROSS-SECTIONAL SHEARING DATA ............................................ 86
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LIST OF FIGURES
Figure 1.1: The charging circuit stores a large voltage in the capacitor bank, which is
then dumped through a coil and creates a magnetic field. Rogowski probes are used to
measure the voltage dumps. ................................................................................................ 1
Figure 1.2: The fundamental principle of EMF is shown above. (Left) shows a typical
path actuator, this particular one exerts a magnetic field in the shape of a square. Two
legs come off the bottom of the coil and one is connected to the positive, the other to
ground. When a current is passed through the actuator, the current circles the coil fromhot to ground. (Right) when a work sheet is placed in close proximity, a secondary
induced current is created circling in the opposite direction of the primary. These two
opposite force repel each other and is used in EMF. .......................................................... 3
Figure 1 3: Typical current time profiles of the primary and secondary induce current
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Figure 3.1: Shows traditional springback located at the corners of U channels and
sidewall curl from the drawing process around an edge. .................................................. 15
Figure 3.2: Schematic of springback for in-plane strain bending (Choi 2006). .............. 16
Figure 3.3: Mechanical bending setup, the punch in the center is 60 mm wide with 6 mmcorner radii. The punch moves up into the platoon bending sheet metal around the
corners of the punch. ......................................................................................................... 18
Figure 3.4: The magnetic pulse assisted forming setup was made similar to the
mechanical bending setup. The punch (60 mm wide) was embedded with a path actuatorwith 6 mm corner radii. A clamping load was applied using toggle clamps and shims
were used to adjust for material thickness. ....................................................................... 19
Figure 3.5: View of the path actuator (OFHC copper) that circles the bottom of the G10punch. The coil is closely coupled with the bottom of the doubly bent U channels, where
the force is directed into the corners. ................................................................................ 20
Figure 3.6: Setup of the magnetic pulse assisted forming with toggle clamps pressing thecoil into the corners of the U channel. .............................................................................. 20
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Figure 3.11: In plane stress (Left) mechanically bent and still in press, (Right)
springback upon removal. ................................................................................................. 27
Figure 3.12: In plane stress (Left) mechanically bent and magnetically pulse, (Right)
springback of magnetically pulsed sample. ...................................................................... 28
Figure 3.13: Bending moment through the thickness of the sheet for mechanical forming
and magnetic pulse assisted forming. The residual stresses have been alleviated........... 29
Figure 3.14: Results comparing Experiment and FEA for final springback angles in the
DP 600 in the 0.035thick sheet. ..................................................................................... 30
Figure 4.1: Configuration of experimental setup for impact shearing of the MDS
specimen (Klepaczko, 1991, 1994). .................................................................................. 35
Figure 4.2: Wide spectrum of shear strain rate for C-Cr-Mo hot-rolled steel; (a)
Maximum shear stress vs. log of shear strain rate (l/s); (b) Maximum shear strain of
localization versus log of shear strain rate (l/s) (Klepaczko and Rezaig, 1995). .............. 36
Figure 4 3: Stress conditions in Shearing Zone 39
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Figure 4.7: Blue dye is used to position the die in the center of the copper coil. (Left)
shows dye being applied to the die. (Right) shows the transfer of dye when positionedover the coil....................................................................................................................... 44
Figure 4.8: Model setup in AUTODYN simulates shearing of 1mm thick Aluminum6061-O, the refined middle section is given an initial launch velocity to simulate themagnetic repulsion of the path actuator. ........................................................................... 46
Figure 4.9: Shows increasing energy from left to right (1.6, 2.0, 2.2, & 2.4 kJ) where
only the right most sample was termed successful, the red dots show where the cross-sections were taken. .......................................................................................................... 48
Figure 4.10: The following pictures are aluminum 6061-O cross-sections of the two inch
square shearing samples: (a) Energy (E) was 1.6 kJ with an Off-Set (OS) zero, (b) E = 2.0kJ with OS = 0.010, (c) E = 2.2 kJ with OS = 0.020, (d) E = 2.4 kJ with OS = 0.030,
(e) E = 2.4 kJ with OS = 0.040, (f) E = 2.6 kJ with OS = 0.060, and (g) E = 2.4 kJ with
OS = 0.083...................................................................................................................... 50
Figure 4.11: Depicts standard PEMS cross-sections: S(roll) describes the rolloverfeature, S(shear) describes the secondary shearing zone typically a straight section where
rollover ceases, and the third or tertiary zone is noted by a burr formation or S (rupture) a
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Figure 4.14: Aluminum 6061-O cross-sections in the PEMS operation are subjected to
different measurement tools than normal mechanical sheared pieces, however the tertiaryzone is a combination of the rupture and burr zones in mechanical shearing. These two
were combined due to the insignificant amount of the zone. More often than not a
rupture zone happened to be created as large as 62m and one burr was found to be
24m................................................................................................................................. 55
Figure 4.15: The following pictures are aluminum 6061-O cross-sections of the one inch
square shearing samples: (a) Energy (E) was 1.6 kJ with an Off-Set (OS) 0.020, (b) E =
1.6 kJ with OS = 0.062, & (c) E = 2.4 kJ with OS = 0.128........................................... 56
Figure 4.16: A plot of current traces for Copper Ohio shearing shown with increasingenergy. ............................................................................................................................... 59
Figure 4.17: Successfully sheared sample that was to be sectioned in four (marked by the
lines) and to be mounted to examine the cross-sections marked by the 1, 2, 3, and 4. .... 60
Figure 4.18: Averaged results for Ohio shear samples showing percent rollover versusenergy. ............................................................................................................................... 61
i d l f hi h l h i h d h
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Figure 4.23: Autodyn FEM simulation with a launching velocity of 200 m/s was
successful. Above is a timeline of the simulation the pictures are at time: (a) 4.3 s; (b)9.4 s; (c) 14.0 s.............................................................................................................. 67
Figure 4.24: Autodyn FEM simulation with a launching velocity of 300 m/s wassuccessful. Above is a timeline of the simulation the picture are at time: (a) 4.1 s; (b)8.1 s................................................................................................................................. 68
Figure 4.25: 1 x 1 shearing coil after failure at the tap holes, in order for the screws to
provide a sufficient tie down force only a thin path remained for the current to runthrough during forming. .................................................................................................... 69
Figure 4.26: The chart depicts energy as a function of offset distance for two by two and
one by one shearing of aluminum 6061-T6. The maximum energy needed for two inchsquare shearing was 2.6 kJ (offset distance of 0.060) and one inch shearing was 2.4 kJ
(offset distance of 0.128)................................................................................................. 70
Figure 4.27: Both samples above were one inch square shears and both were formed at1.6 kJ. The sample on the (left) was formed at an offset of zero, while the sample on the(right) had an offset of 0.062........................................................................................... 71
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Figure A.1: 2 x 2 coil design (base unit inches)........................................................... 79
Figure A.2: 2 x 2 potting unit (base unit inches).......................................................... 80
Figure A.3: 2 x 2 die (base unit inches)....................................................................... 81
Figure B.1: 1 x 1 coil (base unit inches)....................................................................... 82
Figure B.2: 1 x 1 potting unit (base unit inches).......................................................... 83
Figure B.3: 1 x 1 backing unit (base unit inches)......................................................... 84
Figure B.4: 1 x 1 die (base unit inches)........................................................................ 85
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LIST OF TABLES
Table 3.1: DP 600 0.035 inches thick: list of energy, peak current, rise time, along with
measurements of initial, final and change in springback angle. ....................................... 23
Table 3.2: DP 600 0.057 inches thick: list of energy, peak current, rise time, along withmeasurements of initial, final and change in springback angle. ....................................... 24
Table 4.1: List of candidate materials for Ohio shearing................................................. 45
Table 4.2: Lowest energy required for shearing at various standoff distances. ............... 49
Table 4.3: Lowest energy shears at various standoff distances. ...................................... 57
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CHAPTER 1
INTRODUCTION
This thesis on path actuators lays out the basic fundamentals behind Electro-
Magnetic Forming and informs the reader how a path actuator can be used. Coils can be
used in magnetic pulse assisted forming to alleviate residual stresses and eliminate
springback. Lastly, it shows how coils can be used in a Punch-less Electro-Magnetic
Shearing (PEMS) operation. This type of blanking does away with clearance issues
because magnetic force is used as the punch.
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setup of a capacitor bank and a charging circuit connected to a coil. Rogowski probes are
used to capture the voltage dump profiles and can be converted into current-time profiles.
Figure 1.1: The charging circuit stores a large voltage in the capacitor bank, which is then dumped through
a coil and creates a magnetic field. Rogowski probes are used to measure the voltage dumps.
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its charge. The secondary induced current creates a loop in the opposite direction. For
the efficiency to be high, path actuators must come very close to completing a loop
themselves. To reiterate the primary current is measured using Rogowski coils, but the
secondary current in the work sheet is acknowledged as a fraction of the primary current
(seeFigure 1.3). The better the conductivity of the work sheet the higher the fraction, for
example the induced current in a sheet of Aluminum 6061 may be around 80 percent of
the primary current.
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Figure 1.3: Typical current-time profiles of the primary and secondary induce current. Notice the induced
current is a fraction of the primary and as the conductivity of the work sheet gets smaller so will the
fraction.
Current-time profiles, captured by Rogowski coils, can be used to estimate
-800
-600
-400
-200
0
200
400
600
800
1000
0 100 200 300 400
Time (microsec)
Cu
rrent(KA)
induced current
Primary current
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WhereHis the electro-magnetic field intensity, expressed in amperes per width and 0is
the permeability of free space and equals (4x 10
-7
H/m). Under the assumption that the
induced current is a fraction of the primary current equations (2) & (3) further describe
how the magnetic pressure is calculated. HerePmaxis magnetic pressure and HpandHi
represents the current densities expressed in amperes per width, in the primary and
induced circuits, respectively [2]. A constant not shown in these equations, but plays a
pivotal role, is the path actuators width. Remember, the H terms are expressed in
amperes per width, therefore, as the width is decreased the magnetic pressure increases
due to a higher current density. The induced magnetic field is calculated as a fraction of
the primary. The fraction, F, is related to the conductivity of the work sheet. As the
conductivity decreases so does the multiplying fraction.
=0
2 (2)
Hi = Hp F (3)
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either the raw material itself or the construction must be examined to reduce energy. The
path actuator is an Electro-Magnetic Forming (EMF) technique that is easy to make and
inexpensive. These coils can be used for net shape calibration and shearing.
Path actuator can be made quickly and inexpensively, being water-jet cut from
high conductivity materials like copper. Once machined coils need to be well insulated
and materials like dielectrics, glass fiber reinforced phenolics (G10), and Kapton tapes
are typically used. Most EMF coils are normally embedded in G10 for structural
integrity. Again, these can be water-jet cut negatives of the coil, which means coils and
there insulating materials can be turned around in a short time frame. The big economic
drive that makes path actuators inexpensive is one sided tooling. Since an EM force is
used in forming; only one side of the sheet comes in contact with a die. This eliminates
matched tooling required in bending and shearing operations.
Path actuators can be used to strain material at higher rates over quasi-static
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Figure 1.4: DP 600 (0.057 thick), mechanically bent U channel.
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clearance issues vanish, and more elaborate shapes can be made. The last expectation is
to create an arbitrary shape, the outline of Ohio is chosen (seeFigure 1.5).
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1.3. OBJECTIVES
The objectives of this thesis are to create working path actuators for magnetic
pulse assisted forming and PEMS. The path actuators are created from Oxygen Free
High Conductivity (OFHC) copper and are water-jet cut and machined. The main
concepts used are closely coupling the actuators to the work sheet for forming, while
keeping the designing cheap, simplistic, and product that could be linked into regular
machinery.
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CHAPTER 2
PATH ACTUATORS
Path actuators can be utilized as a very useful tool and could be implemented into
manufacturing lines. The path coil is inexpensive and simple metal forming technique. It
can also be used for a wide variety of operations, such as calibration forming, flanging,
hemming, shearing, tube expansion and compression, extended drawing, embossing, and
welding. Path actuators are simple single-turn coils in which the primary current takes on
a nearly closed-loop path and this is closely inductively coupled to the work piece. This
work piece also has a nearly-closed eddy current path. The near closures of both these
paths give relatively high efficiency to the operation In contrast to these path actuators
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energy are required. If high energies are not an option, steels can be formed using a
copper driver. Basically, the driver sheet is used to give the lower conductivity material a
proper acceleration for forming by driving it into a die.
In mechanical operations, tooling can become very expensive, especially as the
complexity increases. Mechanically formed sheet metal use highly precise matched
tooling. Besides the fact that this is costly; tooling can undergo multiple modifications to
punch and die, to fine tune for product design. In stamped parts tuning is important
because on unloading residual stresses can reopen a part. The tuning is done to meet a
final net shape requirement. With electro-magnetic calibration forming, parts may be
pressed to net shape and pulsed, adding small deformations to retain a specific shape by
alleviating the residual stresses. The coils themselves can be more easily tuned than
highly precise matched tooling sets. As mentioned before, by constricting the width of
the actuator, the current density increases and so does the generate magnetic field at that
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repulsion created by the path actuator. The path coil creates a loop and a closely coupled
work sheet creates a secondary induced loop. A magnetic repulsion is created from the
eddy currents that are induced in the work piece from the primary current in the path coil.
The primary and secondary currents run in the opposite directions. These equal and
opposite forces repel each other. This is the most important concept behind EMF and is
used to launch the sheet metal into the die for calibration forming and shearing. The
main degrees of freedom associated with EMF are current density, location of the coil
with respect to the sheet and die, and energy level. Figure 2.1 shows an example of an
arbitrary path coil, which tailors the current density for harder to form contours, such as
corners. As the width of the coil was reduced the current density increases, also
increasing the magnetic pressure exerted to the work piece.
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CHAPTER 3
MAGNETIC PULSE ASSISTED FORMING
The Ohio State University and The Edison Welding Institute joined forces on a
springback calibration project. The goal of this project was to take doubly bent U
channels and calibrate it to near right angles at the corners by adding plastic deformation
to the bent corners. The mechanical press used to bend the channels was not available,
but a goal was to see if the coil could be used in conjunction with the press. To test a
copy of the dimensions were used in creating the magnetic pulse setup. Experiments
were run in conjunction with analytical model. The material used in the trials was DP
600 a dual phase steel of thickness 0 035 and 0 057 inches The degree of freedom
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3.1. INTRODUCTION
The concept of net shape forming is usually difficult for most metallic materials.
When deforming sheet metal the outer surface is placed in tension while the inner surface
is compressed. These unequal residual stresses maintain equilibrium by springing back
open when the sheet is unloaded. This elastic recovery is termed springback and now the
part no longer meets the net shape requirements. Figure 3.1 shows traditional springback
at corners of a drawn U channel and also shows sidewall curl from drawing the sheet
metal around an edge. Companies have difficulty tuning punch and die to over bend the
sheet metal, so that, when unloaded the sheet meets the final requirements. The
companysjob is harder when the stock sheet metal changes because the tuning process
must be done again. Electromagnetic calibration can be used in net shape dies for high
tolerance parts and can be easily tuned by adjusting energy. Following example deals
with traditional springback where an electromagnetic pulse can be used to calibrate
d bl b t U h l i t th fi l t h
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Figure 3.1: Shows traditional springback located at the corners of U channels and sidewall curl from the
drawing process around an edge.
In 2006 Choi did a study on spring-back in the bending process for low carbon
steel sheet. He states the phenomenon of spring-back in the plane strain bending is
schematically described inFigure 3.2.
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Figure 3.2: Schematic of springback for in-plane strain bending (Choi 2006).
If one assumes that sheet metals exhibit elastically isotropic and an elasticideally plastic
(i.e. non-strain hardening) behavior, the amount of relative spring-back of sheet metals
having a thickness, t can be calculated from the following equation (4): where roand rf
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3.2. EXPERIMENTAL METHOD
U channels of DP 600, 0.035 and 0.057 inches thick, were mechanically bent
using the setup inFigure 3.3. The punch had a width of 60 millimeters and corner radii
of 6 millimeters. Shims were used to adjust for the thickness of the material. One goal
for this project was to design a system that could be coupled with the mechanical bending
operation. Therefore the 60 millimeter width dimension was maintained in the magnetic
pulse assisted forming arrangement and adjusted for thickness by shims, seeFigure 3.4.
The punch and coil were attached and loaded into the U channel. A downward force was
applied by toggle clamps to secure the setup. The coil was designed with 6 millimeter
radii and created a path that circled and closely coupled with the bottom and corners of
the doubly bent U channels. Figure 3.5 shows the combination of the path actuator and
punch used in the setup. Figure 3.6 shows a setup fully loaded and ready for testing.
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Figure 3.3: Mechanical bending setup, the punch in the center is 60 mm wide with 6 mm corner radii. The
punch moves up into the platoon bending sheet metal around the corners of the punch.
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Figure 3.4: The magnetic pulse assisted forming setup was made similar to the mechanical bending setup.
The punch (60 mm wide) was embedded with a path actuator with 6 mm corner radii. A clamping load was
applied using toggle clamps and shims were used to adjust for material thickness.
Clamp
Load
60 mm
Shims to
adjust forthickness
R 6 mm
Constraintbolt
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Figure 3.5: View of the path actuator (OFHC copper) that circles the bottom of the G10 punch. The coil isclosely coupled with the bottom of the doubly bent U channels, where the force is directed into the corners.
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Upon removal from the mechanical bending process, the U channels did not
conform to the 90 sidewall angles. DP 600 at 0.035 and 0.057 thickhad preformed
springback angles of 83.5 and 81.5, respectively. The method to create the desired 90
sidewall angles was using a path actuator. The main tuning variable is energy. A 16
kilojoules Magneform capacitor bank is used and adjusts in increments of 5% from
experiment to experiment. The final springback angles are plotted versus energy.
3.3. ANALYTICAL PROCEDURES
The analytical procedures were setup and completed by Peihui Zhang at The
Edison Welding Institute. The finite element analysis of the magnetic pulse assisted
forming for springback correction was performed in two steps. The first step was
modeling the electromagnetic coupling between the coil and sheet. The couple is
important to generate the magnetic pressure without loss in efficiency The second step
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The electromagnetic modeling was performed using commercial software
Magnet. 3D modeling was chosen to fully capture the current flow and force distribution
in the coil and work sheet. The coil, the work sheet, and the surrounding air were
included in the model. The estimated current waveform data was used as the input to the
coil. To estimate the current waveform, the system capacitance and inductance was used
to solve a RLC equation. To simplify the modeling process and save calculation time,
time harmonic solution was obtained. After completion of the analysis, current,
electromagnetic force, and magnetic field distributions were plotted and analyzed.
The mechanical modeling was done for two cases for results comparison. Case I
is forming of a flat sheet into U-channel and let it springback. Case II is forming of a flat
sheet into U-channel, applying magnetic pulse pressure, and removing the tooling. Both
cases were done using ABAQUS. To save computational time 3D symmetric models
were built.
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0.057 inches thick, respectively. Plotted results for DP 600 of 0.035 and 0.057
thickness are shown in Figure 3.7, which had performed angles of 83.5 and 81.5,
respectively. With a 5.6 kJ discharge an angle of 89-90 was achieved for both thickness
of material. Figure 3.8 shows a before and after picture of the EM calibrated U channel.
With a 4 kilo Joule discharge the springback in the corners was almost completely
eliminated to meet final requirements.
ID
Energy
(kJ)
Max I
(kA)
T rise
(s)Initial
left
Initial
right
Final
left
Final
right left right
30% - 8kJ 2.4 128 10.4 83.20 83.03 86.77 86.72 3.57 3.7040% - 8kJ 3.2 160 10.4 83.44 83.39 87.26 87.19 3.83 3.81
50% - 8kJ 4.0 172 8.8 83.75 83.46 87.91 87.67 4.16 4.21
60% - 8kJ 4.8 184 9.6 83.77 83.83 88.10 88.12 4.33 4.29
70% - 8kJ 5.6 200 9.6 84.13 84.01 88.98 88.86 4.85 4.85
DP 600 - 0.035" thick
Table 3.1: DP 600 0.035 inches thick: list of energy, peak current, rise time, along with measurements of
initial, final and change in springback angle.
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ID
Energy
(kJ)
Max I
(kA)
T rise
(s)
Initial
left
Initial
right
Final
left
Final
right left right
20% - 8kJ 1.6 120 9.6 81.45 81.45 87.19 87.00 5.74 5.56
30% - 8kJ 2.4 132 8.8 81.38 81.21 86.90 86.51 5.52 5.30
40% - 8kJ 3.2 136 9.6 81.41 81.35 87.58 87.19 6.16 5.84
50% - 8kJ 4.0 176 9.6 81.33 81.13 88.20 87.85 6.87 6.71
60% - 8kJ 4.8 188 9.6 81.42 81.46 88.82 88.70 7.40 7.24
DP 600 - 0.057" thick
Table 3.2: DP 600 0.057 inches thick: list of energy, peak current, rise time, along with measurements of
initial, final and change in springback angle.
84
86
88
90
92
lSpringba
ckAngle(degree)
DP 600 - 0.035" left DP 600 - 0.035" right
DP 600 - 0.057" left DP 600 - 0.057" right
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Figure 3.8: U channel in the back was before EM calibration and U channel in the front was after a 4 kJ
discharge.
3.5. ANALYTICAL RESULTS
Peihui Zhang completed the analytical modeling and comments on the results.
Figure 3.9 shows the mesh and setup of the coil and sheet in the electromagnetic
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Figure 3.9: Electromagnetic model setup showing the mesh and how the work piece and coil are coupled.
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Figure 3.11 plots the in plane stress contours of the sheet metal after being
mechanically bent and then after unloading from the machine. As shown in the figure,
the maximum stress in the U-channel is 600 MPa, and the stress was relieved after
removing of the tooling. Figure 3.12 shows the in-plane stress contours of the doubly
bent U channel after magnetic pulse forming and then after unloading from the machine.
The stress level in the grey area exceeds 600 MPa. Comparison between figures
indicates that the magnetic pulse pressure deforms more of the material into the plastic
zone, which has less elastic recovery. The stress state in the removed magnetic pulse
sample further confirms it.
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Figure 3.12: In plane stress (Left) mechanically bent and magnetically pulse, (Right) springback of
magnetically pulsed sample.
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springback can almost be completely eliminated with 100 MPa of magnetic pressure in
DP 600 0.035 thick.
Figure 3.14: Results comparing Experiment and FEA for final springback angles in the DP 600 in the
0.035 thick sheet.
0.0
1.0
2.0
3.0
4.0
5.0
6.0
84.00 85.00 86.00 87.00 88.00 89.00 90.00 91.00
Final Angle (degree)
FormingEnergylevels
(KJ)
0
20
40
60
80
100
120
M
agpulsePressure(Mpa)
Experiment-DP600
FEA simulation-DP600
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CHAPTER 4
PUNCH-LESS ELECTRO-MAGNETIC FORMING
Punch-less Electro-Magnetic Shearing (PEMS) was termed at The Ohio State
University. Mechanical shearing is present everywhere in manufacturing. Two big
problems encountered by industries are burrs and slivers. A burr is a sharp edge created
by a clearance issue. A sliver is an artifact of the shearing process, its an extra chip falls
from the sheared piece. This remnant can cause havoc on subsequent parts formed. The
goal for the PEMS operation is to eliminate clearance issues, to avoid forming burrs and
slivers. A secondary goal is to create a complex shearing shape that industry would not
attempt while staying cost efficient
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few. With an understanding of other shearing methods and relative costs and advantages,
high velocity shearing is explored and compared to the mechanical shearing process.
4.1.1. OTHER SHEARING METHODS
This discussion will be of other shearing methods such as, cookie cutter die,
simple shear tool, control panel die, laser cutting, and water-jet cutting, and of a blanking
geometry that is more complex than a simple linear shear. All of these techniques have
advantages, but each has a disadvantage as well. With a highly detailed shearing
operation, such as the outline of the state of Ohio, the matched tooling sets will have
difficulty with clearance issues. One clear trend is that burr height increases as the
clearance increases and as the blade gets duller (larger edge radius). This suggests that in
conventional shearing using the 0 cutting angle, very small clearances should provide an
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Electro Magnetic (EM) shearing offers a number of advantages over traditional
methods. It is much less equipment-intensive than laser cutting or die cutting. It can deal
well with very thin materials, whereas very precise tooling is required to shear thin
metals and can be very expensive. Also, there are opportunities for integrating forming
and shearing operations. Despite these advantages, this method has not been well
developed. However, there has been some promise shown in this area by Glouschenkov
for hollow tubular billet cropping of an aluminum alloy [6].
4.1.2. HIGH VELOCITY SHEARING
It has been shown recently, that during shear deformation imposed by a high-
velocity; plastic waves excited in a deformed material can completely change the
mechanics of plastic field. Since formulation of the rate independent theory of elasto-
plastic waves in solids by Krman, Taylor and Rakhmatulin, in the late forties and early
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chains: source of light, photodiode and input/output fiber optics [11]. This is
demonstrated inFigure 4.2,where a wide range of strain rates were tested on C-Cr-Mo
hot-rolled steel. Above a strain rate of 103 l/s a substantial increase of the maximum
shear stress is observed. On the contrary, the adiabatic localization strain increases
initially, again up to ~ 103(l/s) and next, in excess of ~ 2 x 10
4l/s, decreases rapidly [11].
The systematic drop in the critical strain of shear localization is observed for low alloy
steel around impact velocity 100 m/s. An existence of the CIV in shear was predicted by
a numerical method by Wu and Freund [3, 7, 8, 11, 12].
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It is clear that the CIV in shear is closely related with adiabatic heating and
thermal softening. The CIV in shear is caused by an instantaneous instability and strain
localization superimposed on plastic wave propagation in shear [11]. Preliminary
numerical estimation of the CIV values for 1018 steel have confirmed the usefulness of
the analytic procedure proposed by Klepaczko in 1995. The value of CIV obtained with
a simplified constitutive relation was Vcr= 98.0 m/s and c= 4.9 x 10
4
l/s for 2.0 mm
gage length, the value very close to the one determined by the MDS direct impact
technique, Vcr= 90 m/s. The experimental technique based on the MDS specimen and
direct impact has been applied so far for determination of the CIV for three steel
materials. Besides 1018 steel, the CIV determined for VAR 4340 steel (52 HRC) was
130 m/s and in the case of hot-rolled C-Cr-Mo steel 100m/s [11].
Unlike the modified double shear technique, mechanical shearing uses different
technique and equipment. Clearance is typically the number one problem in mechanical
shearing. If set to close the cutting edges bind and wear. So during a normal mechanical
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tooling. The horizontal forces result in the frictional forces FH and F'H and the
shearing forces in FVand F'V. The stress condition in the shearing zone during crack
formation is tri-axial. According to Tresca, the flow criterion is given by equation (5)
[14].
=
=
(5)
Where max is the max shear stress, while 1, 2, & f, represents the principal tensile
stress, principal compressive stress, and flow stress, respectively. During the process, the
shear yield stress increases because of the strain hardening effect. As shown in Figure
4.3, the principal stress circle enlarges until the shearing strength is reached [3]. This
strain hardening effect helps describe the morphology of the shearing cross-section. The
shearing begin but is arrested by the hardening effect, after a critical stress is reached the
rest of the shear propagates by fracture of the surface. Many simulations have been done
for the blanking process. It is considered that the crack starts in the punch-die flank at or
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Figure 4.3: Stress conditions in Shearing Zone.
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The Ohio State University developed electromagnetic shearing capability for
sheet metal cutting that should be cost effective and could find wide application in both
small precision applications, such as medical & micro devices, and could also have
significant applications in heavy-duty manufacturing, such as automotive and truck
manufacturing. The process can replace laser cutting of metal, which involves large
amount of capital investment and can also be applied to non-metal cutting, such as foam.
Furthermore, electromagnetic forming and cutting could be integrated in a single step to
save manufacturing cost. The work here will help develop a new agile sheet metal
shearing technique, for shapes not realistic by conventional methods.
4.2. EXPERIMENTAL PROCEDURES
The PEMS experiments were sectioned into three shapes. Two of the shapes were
squares of different sizes: a two by two inch and a one by one inch square The system
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electro-magnetic path actuator. Next, a set of experimental parameters were designed for
a parametric study.
The path actuators were created from OFHC copper and for structural integrity of
the coil a potting units was made from G10. The coil and potting unit were both water-jet
cut. Next, a shearing die was wire EDM from mild steel and was positioned in the center
of path actuators width. This creates a magnetic pressure under the shearing edge.
Figure 4.5 shows the layout of how the coil, supporting unit and die come together. Half
inch alignment holes were used for position and bolts were used for a clamping force.
CAD drawings of the coil, potting unit, and die can be found in Appendix A (Figure A.1,
Figure A.2,&Figure A.3,respectively).
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With the design completed, a list of variables was selected for a parametric study.
Energy was used as the main variable for shearing. A Magneform 16 kilojoules bank was
used for shearing; this was adjusted in increments of 2.5% from experiment to
experiment. The second variable studied was standoff distance. The standoff was
measured as the distance from the work sheet to the shearing die; this was created using
steel shims. The last variable was material: aluminum 6061-T6, aluminum 6061-O and
copper 101. All materials were one millimeter thick.
4.2.2. ONE BY ONE PROCEDURE
The one by one inch square shearing procedures were conducted as follows. This
second set of experiments was setup to examine an energy level effect for a smaller
square shape. The coils were designed similar to the two by two experiments, having the
same coil width and corner radii. This kept the current densities similar when using the
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of 5% of the bank. The standoff distance was also varied using steel shims at alignment
pins. The material list was aluminum 6061-T6, aluminum 6061-O and copper 101.
4.2.3. OHIO SHEARING PROCEDURE
The Ohio shearing setup was constructed slightly different than before. Materials
remained the same. The coil was made from OFHC copper, while the potting unit and
backing plates were made from G10. The Ohio die was wire EDM from 4340 stainless
steel. The die was scaled to one inch east to west across the border of Ohio (seeFigure
1.5). The coil was created by a smoothed scale drawing of the outline of Ohio. This
eliminated sharp edges which can potentially cause arcing. The outer perimeter was
made an eighth inch larger and the inner perimeter was made an eighth inch smaller (see
Figure 4.6). Tapped holes were placed in the back and the die was attached to a second
plate, which contained alignment holes. Blue dye was used to position the dies cutting
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Figure 4.6: The highly detailed wire EDM Ohio shearing die is shown, laid over the smooth water-jet cut
copper coil an eighth inch of the dies cutting edge.
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Once the die is aligned and with the square shearing studies completed. The
results were used to create the Ohio shearing parameters. Energy was chosen as the only
variable. Again, the 16 kilojoules Magneform capacitor bank is adjusted each experiment
in increments of 5%. Once the critical shearing energy is achieved two more parts are
formed at higher energy. This was done to compare the cross-sectional changes in
rollover, secondary shearing zone, and the tertiary zone at increasing energies. The Ohio
shearing trial used a larger subset of materials and is shown in Table 4.1.
Material Density(g/cc)
ElectricalConductivity
(1/cm)
YoungsModulus
(GPa)
YieldStrength
(MPa)
Mg AZ31B-O 1.77 1.09E+05 45 150
Mg AZ31B-H24 1.77 1.09E+05 45 220
Al 6061-O 2.70 2.73E+05 69 55
Al 6061-T6 2.70 2.51E+05 69 276
Al 3003-H24 2.73 2.40E+05 69 145
Al 3003-O 2.73 2.87E+05 69 41
Cu 101 8.90 5.85E+05 115 69-365
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platform for analysis was AUTODYN, interactive non-linear dynamic analysis software.
To save run time a half 2-D model with respect to symmetry was setup to model the one
by one inch shearing (seeFigure 4.8). The sheet was created by joining three sections.
The middle section was designed to be directly position above the coil and was give the
same width. Meshing in this middle section was more refined and given the initial launch
conditions created by the magnetic pressure. Then modeling was run at launch velocities
of 150, 200 & 300 m/s at a zero offset distance. This in return gave a critical velocity for
shearing and cross-sectional characteristics.
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The FEM simulations were setup to demonstrate shearing of Aluminum 6061-O.
The material properties were selected from the database to imitate the experiment. A
Shock equation of state was selected to model the impact from the launch velocity. Next,
a Johnson-Cook strength model (5) was chosen to better accurately describe the yield
stress, when the material experienced work hardening and/or strain hardening.
= + + (6)
Where A, B, and Cwere constants, which were set as 0, 500 MPa, and 0 respectively.
With these constants, the yield stress changes as a function of plastic strain, p, and the
work hardening exponent, n, was set as 0.25. Effects from thermal input were ignored.
Lastly, plane stress and plane strain erosion criteria were implemented. If an element in
the worksheet reaches either a critical stress of 400 MPa or a strain of 0.75, the element
was removed.
4 4 EXPERIMENTAL RESULTS
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induced current in aluminum is assumed to be 80% of the primary current. The lowest
magnetic pressure needed for shearing 270 MPa for aluminum 6061 at a zero standoff
distance. Figure 4.10 shows cross-sections of the two inch square shears. The samples
are laid out as follows: each picture contains two cross-sections both from the same
sample, the bottom piece in each picture is from the side, the piece above is from the top
edge of the sample, & the shearing direction was always oriented in the upward direction.
The figure shows what were termed successful shear for each standoff distance (zero,
0.010, 0.020, 0.030, 0.040, 0.060, & 0.083 inches).
Off-set of 0.030 increase energy from left to right (1.6, 2.0, 2.2, 2.4 kJ)
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2 x 2
Squares
Energy
(kJ)
Standoff
(in)
Peak Current
(kA)
Rise Time
(s)
Pmax
(MPa)
Al 6061 1.6 0.000 116 9.6 270
Al 6061 2.0 0.010 128 9.6 329
Al 6061 2.2 0.020 134 9.6 361
Al 6061 2.4 0.030 140 9.6 394
Al 6061 2.4 0.040 138 9.6 383
Al 6061 2.6 0.060 140 9.6 394
Al 6061 2.4 0.083 136 9.6 372
Table 4.2: Lowest energy required for shearing at various standoff distances.
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(a) (b)
(c)
(e) (f)
(d)
(g)
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The PEMS cross-sections take on a different morphology than mechanically
sheared operation. Figure 4.11 classifies the notation that was used to describe the cross-
sections. It was note worthy, that the rupture zone, a classic shearing characteristic, was
not seen in the majority of the PEMS operation. Therefore, the following picture
describes the high velocity shearing with a rollover, secondary, and tertiary zone. The
tertiary zone was considered a rupture or burr feature. None of the two by two PEMS
samples contained any significant burr. This was tested using a cotton bag, if a burr was
present, with sharp and cutting features; fibers of cotton would be pulled from the cotton
ball. This is a simple test used in some industrial practices. Also no slivers were present
after the shearing operation. The cross-sections depicted nearly 100% combination of
edge rollover and secondary shearing zone. The tertiary zone was negligible in most
samples. Figure 4.12, Figure 4.13, & Figure 4.14 show plots of percent rollover, percent
secondary shear, and the tertiary value, respectively.
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Figure 4.11: Depicts standard PEMS cross-sections: S(roll) describes the rollover feature, S(shear)
describes the secondary shearing zone typically a straight section where rollover ceases, and the third or
tertiary zone is noted by a burr formation or S (rupture) a rupture zone similar to mechanical shearing.
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Figure 4.12: Aluminum 6061-O cross-sections in the PEMS operation are subjected to different
measurement tools than normal mechanical sheared pieces, however the rollover zone is present in bothand the PEMS cross-sections show up to 42% rollover and little at 15% depending on offset (OS) distance
and energy.
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0.0 0.5 1.0 1.5 2.0 2.5 3.0
%Rollover
Energy (kJ)
OS=0.010" OS=0.020" OS=0.030" OS=0.040" OS=0.060" OS=0.083"
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Figure 4.13: Aluminum 6061-O cross-sections in the PEMS operation are subjected to different
measurement tools than normal mechanical sheared pieces, however the secondary zone or sheared zone
are similar. However the PEMS secondary zone often occurs at an angle to the shearing of 65 to 85compared to the normal perpendicular cuts in mechanical shearing. The PEMS operation shows 58% to
84% of the cross-section to be the secondary shearing zone.
50%
55%
60%
65%
70%
75%
80%
85%
90%
95%
100%
0.0 0.5 1.0 1.5 2.0 2.5 3.0
%Shear
Energy (kJ)
OS=0.010" OS=0.020" OS=0.030" OS=0.040" OS=0.060" OS=0.083"
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Figure 4.14: Aluminum 6061-O cross-sections in the PEMS operation are subjected to different
measurement tools than normal mechanical sheared pieces, however the tertiary zone is a combination of
the rupture and burr zones in mechanical shearing. These two were combined due to the insignificantamount of the zone. More often than not a rupture zone happened to be created as large as 62m and one
burr was found to be 24m.
-80
-60
-40
-20
0
20
40
60
80
0.0 0.5 1.0 1.5 2.0 2.5 3.0
TertiaryZone(m)
Energy (kJ)
OS=0.010" OS=0.020" OS=0.030" OS=0.040" OS=0.060" OS=0.083"
BURRFORMATION
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direction. This was similar to how the cross-sections were taken from the two by two
samples. All of the samples contain no significant burr, and no slivers were ever present
after PEMS operation. The operation depicts nearly 100% combination of edge rollover
and secondary shearing zone. The tertiary zone was negligible in most samples. Table
4.3 shows the lowest energy needed for a successful shear for the various standoff
distances, along with peak current, rise time, and magnetic pressure exerted. For the
annealed aluminum samples between zero and 0.062 inches standoff, a magnetic pressure
under 400 MPa was required for shearing.
(a) (a)(b)
(c)
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1 x 1
Squares
Energy
(kJ)
Standoff
(in)
Peak Current
(kA)
Rise Time
(s)
Pmax
(MPa)
Al 6061-O 1.6 0.000 140 14 394
Al 6061-O 1.6 0.010 136 12 372
Al 6061-O 1.6 0.020 138 12 383
Al 6061-O 1.6 0.062 136 12 372
Al 6061-O 2.4 0.128 164 12 541
Table 4.3: Lowest energy shears at various standoff distances.
4.1.3. OHIO SHEARING RESULTS
The Ohio shearing results are complied inTable 4.4,showing energy level, peak
current, rise time, and listing for a successful shear or not. Figure 4.16 shows the
recorded current traces, captured by a Rogowski coil for increasing energy in the copper
samples. The Rogowski loops the path actuator and records the voltage running through
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Material Thickness(in)
Energy(kJ)
Peak Current(kA)
Rise Time(s)
SuccessfulShear
1 Alum 0.0250 4.0 208 11.2 yes
2 Alum 0.0250 4.8 246 10.9 yes
3 Alum 0.0250 5.6 262 11.2 yes
4 Alum 0.0250 3.2 206 10.7 no
1 Copper 0.0200 4.0 221 10.9 no2 Copper 0.0200 4.8 248 10.6 yes
3 Copper 0.0200 5.6 265 10.6 yes
4 Copper 0.0200 6.4 279 10.9 yes
1 Silver 0.0120 3.2 212 10.8 yes
2 Silver 0.0120 2.4 183 10.8 yes
3 Silver 0.0120 1.6 150 10.6 no
4 Silver 0.0120 4.0 228 10.9 yes1 Al 6061-T6 0.0250 4.0 - - no
2 Al 6061-T6 0.0250 4.8 233 11.5 no
3 Al 6061-T6 0.0250 5.6 253 11.1 yes
4 Al 6061-T6 0.0250 6.4 268 11.9 yes
5 Al 6061-T6 0.0250 7.2 290 11.9 yes
1 Al 3003 0.0230 4.0 219 11.3 no
2 Al 3003 0.0230 3.2 199 10.7 no3 Al 3003 0.0230 4.0 218 11.1 yes
4 Al 3003 0.0230 4.8 239 11.9 yes
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Figure 4.16: A plot of current traces for Copper Ohio shearing shown with increasing energy.
The successfully sheared samples were then sectioned and mounted for cross-
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The secondary shear zone was just under half of the material thickness. Most of the
cross-sections recorded no burr formation; however a few samples had the presence of a
small burr. The largest burr recorded was 60 micrometers in Aluminum 6061-T6 (see
Figure 4.21). The majority of the samples lay between burr lengths of 5 to 25
micrometers, barely noticeable to touch and rarely sharp.
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Figure 4.18: Averaged results for Ohio shear samples showing percent rollover versus energy.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
PercentRollover
Energy (kJ)
Alum Copper Silver Al 6061-T6 Al 3003-H24 Mg AZ31-O Mg AZ31-B
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Figure 4.19: Averaged results for Ohio shear samples showing the secondary shear zone percentage versus
energy.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
PercentSecondary
ShearZone
Energy (kJ)
Alum Copper Silver Al 6061-T6 Al 3003-H24 Mg AZ31-O Mg AZ31-B
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Figure 4.20: Averaged results for Ohio shear samples showing the tertiary zone versus energy.
-35
-25
-15
-5
5
15
25
35
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
TertiaryZon
e(m)
Energy (kJ)
Alum Copper Silver Al 6061-T6 Al 3003-H24 Mg AZ31-O Mg AZ31-B
BURR
FORMATION
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Figure 4.21: Aluminum 6061-T6 sheared at 6.4 kJ contained a burr 60 m in length and was taken at 5X
magnification from zone #1.
4.5. ANALYTICAL RESULTS
The modeling was arranged so that a segment of the work piece, no larger than
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determined to be between 150 to 200 m/s. Klepaczko studies were on various steels. He
showed a CIV less than 100 m/s for 1018 steel. However, Klepaczkos approach was
accomplished with impacts by projectiles. This suggests an added mass was used to help
with the shearing process and would effectively reduce the velocity. The PEMS
operation used no projectiles for shearing and would require a higher critical shearing
velocity if the same materials were in question.
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(a)
(d)
(b)
(f)(e)
(c)
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Figure 4.23: Autodyn FEM simulation with a launching velocity of 200 m/s was successful. Above is a
timeline of the simulation the pictures are at time: (a) 4.3 s; (b) 9.4 s; (c) 14.0 s.
(a) (b)
(c)
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Figure 4.24: Autodyn FEM simulation with a launching velocity of 300 m/s was successful. Above is a
timeline of the simulation the picture are at time: (a) 4.1 s; (b) 8.1 s.
4.6. DISCUSSION
The path actuators used for shearing were slightly modified from setup to setup.
These modifications were done to increase the coils lifetime. The two by two square
shearing coil and potting unit were made from different thicknesses of material The
(a) (b)
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and it eventually broke at the legs (seeFigure 4.25). This coil failure could be avoided
by not running the tap holes as deep or using a thicker copper plate. The Ohio shearing
did not encounter any new types of modifications but used the gathered knowledge. The
coil and potting unit were created from similar sized materials, and a backing plate was
used but without the tap holes. At this point of the experiments it was known that zero
standoff gave the best results, and the clamping force of the die restricted the coil from
distorting in-plane thus adding to its lifetime.
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was at a minimal standoff distance; this was zero during trials (Figure 4.26). However,
the one inch square shearing presented no significant difference for zero standoff to a
0.062 inch offset; except a more noticeable texture was picked up from the dies surface
and slight bump formation from the coil (see Figure 4.27). For the two inch square
shearing as the offset distance was increased so was the energy required for a successful
cut. The SS 304 was not successfully sheared. The energy required to begin shearing a
single corner began to warp and distort the path actuators. Therefore, those trials were
stopped.
1.5
2.0
2.5
3.0
ergy
(kJ
)
Two Inch Square Shearing One Inch Square Shearing
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Figure 4.27: Both samples above were one inch square shears and both were formed at 1.6 kJ. The sample
on the (left) was formed at an offset of zero, while the sample on the (right) had an offset of 0.062.
Mechanically sheared pieces typically have a burr and slivers, which are bad in
the manufacturing world. Burrs must be removed are hidden during assembly. These
features arise from a clearance issue between the shearing blades. A rule of thumb is the
larger the clearance the larger the burr. Figure 4.28 shows two cross-sectional
i h f h i ll h d l i l l d
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Figure 4.28: The micrographs above are cross-section views of mechanically sheared aluminum 6061-T6;
(the left) was done on a mechanical shearing machine with a 0.004 clearance, burr height 101m; (the
right) was done by a mechanical pressing using a urethane pad to drive the sheet into the die, burr height
150m.
Figure 4.29 shows sheared samples of the one by one setup with increasing
energy. Figure 4.30 shows a blown up view of the modeling done in conjunction. From
the modeling as the velocity (energy) increased it was expected there would be some
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Figure 4.29: Aluminum shearing, 1 mm thick increasing energy from bottom to top (1.6, 2.0, 2.4, & 2.8 kJ)
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CHAPTER 5
CONCLUSIONS
The path actuators can be fabricated very quickly and inexpensively. Only one
sided tooling is required, since an electro-magnetic force is used to drive the work sheet.
This eliminates high tolerance problems in matched tooling and could be implemented
into a manufacturing process. The path actuators were successfully used for net shape
calibration forming and shearing. The main degrees of freedom were the energy level,
coil with respect to the work sheet and die, and tailored current density.
The path actuator used for calibration forming required tuning of one variable, the
energy to alleviate residual stresses in the material. For both thicknesses of DP 600
(0.035 and 0.057 inches), the doubly bent U channels were formed to 89-90 sidewall
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create a magnetic pressure on both sides of a shearing edge. From results of the two by
two and one by one square shearing setups, a zero offset distance showed the most
promise, shearing at the lowest energy and providing the least distortion. Figure 5.1
shows an energy level effect versus standoff distance, as the standoff increased so does
the energy for shearing. Also, as the standoff increases more of a bump formation is
observed. This was a direct response to the location of the coil below. When passing
similar current densities through the two by two and one by one inch square shearing
coils, a minimal amount of extra energy was required for the scaled up shearing. This
was because the coil had a lower inductance by a removal of 4 out of 8 caps in the
capacitor bank. Lastly, PEMS can be used for more complex shapes, without high
tolerance issues. In most cases large burr formations were avoided and silvers were
never present.
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Figure 5.1: Aluminum 6061-T6 and copper 101.
Standoff Distance
zero
0.010
0.020
0.062
0.128
0.113
2.5kJ 5kJ 7.5kJ 10kJ 12.5kJ 15kJ
Energy Level
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LIST OF REFERENCES
1. Daehn, G.S.,High-Velocity Metal Forming.Forming Processes for Sheet, Strip,
and Plate: p. 406-418.
2. Kamal, M.,A Uniform Pressure Electromagnetic Actuator for Forming Flat
Sheet, inMaterial Science and Engineering. 2005, The Ohio State University:
Columbus. p. 82-94.
3. Grnbaum, M.,Influence of High Cutting Speeds on the Quality of Blanked Parts.
1996, NSF Engineering Research Center for Net Shape Manufacturing, The OhioState University.
4. Choi, S.-H. and K.-G. Chin,Prediction of Spring-Back Behavior in High StrengthLow Carbon Steel Sheets.J. of Mat. Proc. Tech., 2006. 171: p. 385-392.
5. Li, M.,An Experimental Investigation on Cut Surface and Burr in TrimmingAluminum Autobody Sheet.Int. J. of Mech. Sciences, 2000. 42: p. 889-906.
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10. Klepaczko, J.R.,Plastic Shearing at High and Very High Strain Rates.Les
Editions de Physique Les Ulis, J. Phys.(France) IV(France), 1994. 4: p. 35-40.
11. Klepaczko, J.R.,Remarks on Impact Shearing.J. of the Mech. and Phys. of Sol.,1998. 46(10): p. 2139-2153.
12. Wu, F.H. and L.B. Freund,Deformation Trapping Due to Thermoplastic
Instability in One-Dimensional Wave Propagation.J. Mech. Phys. Sol., 1984.
32(2): p. 119-132.
13. Lange, K.,Blanking and Piercing Handbook of Metal Forming. 1985: McGraw-
Hill Book Company. 1216.
14. Lange, K., Umformtechnik III. Blechbearbeitung.Vol. 3. 1990, Berlin,
Heidelberg, New York: Springer.
15. Faura, F., A. Garcia, and M. Estrems,Finite Element Analysis of OptimumClearance in the Blanking Process.J. of Mat. Proc. Tech., 1998(80-81): p. 121-
125.
16. Hatanaka, N., K. Yamaguchi, and N. Takakura,Finite Element Simulaton of theShearing Mechanism in the Blanking of Sheet Metal.J. of Mat. Proc. Tech.,
2003(139): p. 64-70.
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APPENDIX A.
TWO BY TWO SHEARING DESIGN
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APPENDIX B.
ONE BY ONE SHEARING DESIGN
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Figure B.4: 1 x 1 die (base unit inches).
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APPENDIX C.
OHIO CROSS-SECTIONAL SHEARING DATA
Material
Energy
(kJ)
Rollover Section Secondary Section Tertiery Section
1 2 3 4 ave 1 2 3 4 ave 1 2 3 4 ave
Alum 4.0 0.438 0.521 0.583 0.667 0.552 0.563 0.479 0.417 0.333 0.448 -24 0 -24 -12 -15
Alum 4.8 0.474 0.647 0.681 0.686 0.622 0.526 0.353 0.319 0.314 0.378 -24 -48 -24 0 -24Alum 5.6 0.575 0.658 0.695 0.583 0.628 0.425 0.342 0.305 0.417 0.372 -12 0 -12 -24 -12
Copper 4.8 0.665 0.733 0.651 0.571 0.655 0.335 0.267 0.349 0.429 0.345 -12 0 0 0 -3
Copper 5.6 0.713 0.742 0.652 0.719 0.706 0.287 0.258 0.348 0.281 0.294 -18 0 0 -18 -9
Copper 6.4 0.716 0.737 0.663 0.646 0.690 0.284 0.263 0.337 0.354 0.310 0 0 0 0 0Silver 2.4 0.571 0.381 0.391 0.474 0.454 0.429 0.619 0.609 0.526 0.546 0 0 0 -12 -3Silver 3.2 0.524 0.500 0.429 0.386 0.459 0.476 0.500 0.571 0.614 0.541 -12 0 0 0 -3
Silver 4.0 0.571 0.391 0.565 0.652 0.545 0.429 0.609 0.435 0.348 0.455 -24 0 0 0 -6
Al 6061-T6 5.6 0.472 0.382 0.400 0.222 0.369 0.528 0.618 0.600 0.778 0.631 -24 0 0 -24 -12Al 6061-T6 6.4 0.480 0.308 0.451 0.431 0.418 0.520 0.692 0.549 0.569 0.582 -60 0 0 0 -15
Al 6061-T6 7.2 0.434 0.358 0.389 0.481 0.416 0.566 0.642 0.611 0.519 0.584 -12 0 0 -24 -9
Al 3003 4.0 0.604 0.500 0.596 0.604 0.576 0.396 0.500 0.404 0.396 0.424 -24 0 -36 -24 -21
Al 3003 4.8 0.739 0.702 0.771 0.804 0.754 0.261 0.298 0.229 0.196 0.246 -24 -12 -36 -36 -27
Al 3003 5.6 0.667 0.245 0.837 0.612 0.590 0.333 0.755 0.163 0.388 0.410 -24 36 -24 -36 -12
Mg AZ31-O 3.2 0.671 0.480 0.500 0.518 0.542 0.329 0.520 0.500 0.482 0.458 -48 0 0 0 -12
Mg AZ31-O 4.0 0.784 0.571 0.647 0.581 0.646 0.216 0.429 0.353 0.419 0.354 -48 0 0 -12 -15
Mg AZ31-O 4.8 0.591 0.622 0.554 0.598 0.591 0.409 0.378 0.446 0.402 0.409 -48 0 0 0 -12Mg AZ31-B 3.2 0.596 0.560 0.707 0.732 0.649 0.404 0.440 0.293 0.268 0.351 -12 0 0 -36 -12
Mg AZ31-B 4.0 0.590 0.446 0.512 0.509 0.514 0.410 0.554 0.488 0.491 0.486 0 0 24 0 6Mg AZ31-B 4.8 0.434 0.634 0.585 0.519 0.543 0.566 0.366 0.415 0.481 0.457 0 0 48 0 12
Table C.1: Ohio PEMS samples broken into fractional Rollover, Secondary Shear Zone fraction, and Tertiary Zone (m), by zone number and averaged.
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