d mann-case studies in triz-fretting failure in automotive electrical components

7/30/2019 D Mann-Case Studies in TRIZ-Fretting Failure in Automotive Electrical Components

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Case Studies In TRIZ:Fretting Failure In Automotive Electrical Components

Tressia HobeikaDepartment of Mechanical EngineeringAmerican University of Beirut, Lebanon

Tomasz LiskiewiczSchool of Mechanical Engineering

University of Leeds, UK

Darrell MannSystematic Innovation Ltd, UK

Introduction

This article summarises a short study programme applying TRIZ to the problem of frettingcorrosion failure in automotive electrical contacts. Fretting corrosion is a form of accelerated

atmospheric oxidation occurring at the interface of contacting materials subjected to smallcyclic relative motion. The main external agents leading to fretting are mechanical vibrations,shocks, differential thermal expansion and contraction of the contacting metals, and junctionheating as power is turned on and off. Such situations cause very small relative movementsof the two mating parts of a contact thus leading to relative displacements and wear on theinterface. This wear may produce oxides which form an interface thus increasing the electricalresistivity and ultimately causing electrical failure.

The main issue targeted during the study centred around the contradictory requirements ofelectrical contacts: the need for sliding action for an easy installation and connection on onehand and the fact that this sliding action is also the origin of fretting corrosion and destructionof the mating surfaces.

Two classic connectors are used nowadays in the automotive industry. The most used one isa connector with a tin (Sn) top layer which is worn out after long-time operation leading toelectrical and mechanical problems in cars. As for the other connector, it is mainly coated byGold (Au), a noble material who has been found to be more durable and more reliable than tinbut at the same time, has become more and more expensive for automotive use.

Problem Definition 1) Problem ExplorerThis part of the problem definition process is frequently the most critical stage to identify theproblem in question and lead to the selection of the suitable solving tools for the electricalcontacts problem. It consists of three parts: problem hierarchy explorer, identification of

resources and sore point analysis. We will explain illustrate each case.

Problem Hierarchy ExplorerHere, we shed light on the space surrounding the originally stated problem leading to a list ofdefinitions which broaden and narrow the problem (Figure 1).


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-High contact electricalresistance.

-inadequate coating.

electrical systemintegrity

fretting corrosion leads to thedestruction of the electricalintegrity of the automotiveelectrical contacts, especiallynext to the engine.

-external conditions vibrations,shocks, junction h eating.

-internal conditions oxidation,wear.

-cost of noble materials gold.

Original Problem(start here)

Broader Problem

Narrower Problem

Whydo I want to solvethis problem?Why else?

Whats stopping mesolving this problem?

Whatelse?

fretting corrosion of

automotive electricalcontacts.

need for assembly/dis-assembly

permanent ANDremovable assembly

Narrower Problem

Figure 1. Problem Hierarchy Explorer

Identification of ResourcesThe following tool, also called system operator analysis, confirms that the system should bestudied on time and scale levels thus pushing the problem solver to see the problem fromdifferent perspectives. Recall that a resource is anything in or around the system that is notbeing used to its maximum potential. The 9-Window tool will be used to demonstrate thisstage of the problem definition (Figure 2).

Figure 2. 9-Window Tool

Packaging, in-

storepresentation.

Engine, weight, load, frequency,

user, cycle rate, electricity.

Mechanical vibration,

differential thermal

expansion andcontraction of the

contacting materials,

shock

Oxidation,

friction, wear,

coating wearing

Selection of

materials and

coating.

Manufacturing

of the electrical

contact.

Failure,

destruction of

electrical

integrity.

Electrical contacts: connectors,

relays, switches.

Two mating parts of the contact,

coating, interface between

components.


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Sore PointThe sore point of a system is the element which prevents it from delivering the requiredbenefits. Therefore, to ameliorate the functioning of the electrical contacts, we have to treator eliminate this sore point. The following scheme clarifies the idea explained above (Figure3).

Figure 3. Sore point analysis

Problem Definition 2) Function and Attribute Analysis

This element of the problem definition process clarifies the functioning of a system. Moreover,it will guide the selection of the solving tools. Conducting a function and attribute analysismeans constructing the related diagram, which will systematically define the problem inquestion. We will also examine how time can affect the system (figure 4.1-2-3-4).

TYPES OF INTERACTIONSEffectiveMissingInsufficientExcessiveHarmful

SYMBOLS

Mechanical vibrations, shock, differential thermal expansion and contraction of thecontacting materials, junction heating as power is turned ON and OFF

(M) MUF: Main Useful Function

SIMPLE SYSTEM

Mating part 1Mating part 2

Figure 4.1. Simple Two-Component Manufacture System

Reliability of electrical contacts, durability,

material selection.

Interface between the two mating parts of an

electrical contact, external factors, cost of noble

materials, and fretting failure of non-noble

materials.


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PAST

Mating part 1 Mating part 2

slides (M)

holds (M)

Figure 4.2. During Installation and Before Operation

PRESENT


Conducts (M)

holds (M)

External Agent

Slides

Thermal expansion or contraction

moves moves

Figure 4.3. During Operation

FUTURE


conducts (M)

holds (M)

External Agent

slides

Thermal expansion or contraction

Non-

conductive

film

holds (M)

moves moves

Figure 4.4. After Long-Time Operation

Problem Definition 3) Ideal Final Result

The notion of an Ideal Final Result is one of the cornerstones of TRIZ. The ideal system isone that requires no materials to build, consumes no energy, and does not need space and


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time to operate: the required function is fully performed. A useful definition of ideality can berepresented using the following equation:

HarmCost

BenefitsPerceivedIdeality

+

=)(

Which means that if we want to increase ideality in a certain system as an evolutionary

direction, we have to either increase benefits (perceived by the customer) and/or decreasecost and harm. We will further develop this equation in the S-Curve Analysis section.

The Ideal Final Result concept (IFR) can help guide our problem definition thinking through asimple questionnaire:

1. What is the final aim of the system?A life lasting durability of electrical contacts.

2. What is the Ideal Final Result outcome?Electrical contacts that behave as a single part.

3. What is stopping you from achieving this IFR?The fact that I have two mating parts instead of one.

4. Why is it stopping you?I need the two parts for the installation process yet the interface between them is thesource of fretting problems.

5. How could you make the thing(s) stopping you disappear?If the mating parts could solder themselves

6. What resources are available to help create these circumstances?Coating, electricity, atmosphere, user, heat, vibrations.

After the above IFR definition, we notice that it has identified future options. Therefore, wetake steps back along the IFR definition space (figure 5).

How might you work back from the IFR to a practical solution?

Figure 5. IFR Definition Space

IFR

Electrical contacts that

behave as a single part

Electrical contacts

mating parts solder to

eliminate the interface,

thus a behavior as a

single part

Electrical contacts that

have a smart interface

between the mating

parts, that can adapt to

the environment


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As a matter of fact, having mapped the steps back from the IFR to the nearest presentgenerates indeed some useful ideas that might lead to the solution of our problem.

Problem Definition 4) S-Curve Analysis

The characteristic manner of the S-curve describes the evolution and the goodness ofsystems in function of time. The ideality of a system is examined using the S-curve whichconsequently determines if there is potential for further improvement of the system or whethera new approach is required. Figure 6 shows the significant positions of the S-curve.

Figure 6. Generic S-Curve Characteristic

Moreover, as we will see in the coming sections, the S-curve analysis leads to the selection ofthe problem solving tools and helps prioritize which problems to deal with, thus bridging the

gap between the experimental/technical solutions and market requirements.

In this section, we will tackle two quantitative properties of the system proposed by Altshuller,which translates into the performance of the system in the S-curve and analyze the idealityequation presented in the previous section.

Number of inventions or patents over timeCorrelating between the S-curve position and the number of inventions over time is a powerfulway to help establish where a system stands on its s-curve. This is best done by analyzingpatents related to the system. Finding the number of inventions over time in this case wasperformed using a combination of online patent databases with the keywords: Automotiveelectrical contact from 1960 until 2008. The below graphs compare between a generic S-curve and the curve related to the number of inventions (figure 7).


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Figure 7. Number of Automotive Electrical Contact Inventions

The analysis of generic Number of Inventions graphs states that the first jump of the curvefollowed by a relatively small decline, as we can see in the graph above, determines theposition of the system along its S-curve. According to Figure 7 we might begin to concludethat we currently have a system between infancy and growth stage or youth and maturity.

Level of inventiveness over timeAnother way to identify where a system stands on its current S-curve is to analyze thetechnical focus of inventions. Figure 8 identifies a number of generic steps in the types ofpatents being granted for a given system over the course of its evolutionary life:

Time

Figure 8. Correlation between S-Curve Position and Invention Focus

In fact, by tracking this evolution, we obtain a reliable estimate of the system maturity whichis, in this case, standing between maximize performance and efficiency. Indeed, we shouldwork more to improve the efficiency of the electrical contacts, which confirms our goal toimprove durability and adaptability of the contacts.

Ideality EquationAs we have seen in a previous section, the definition of ideality was represented by anequation called the ideality equation:

HarmCost

BenefitsPerceivedIdeality

+

=)(

Ideality

MINIMIZE COST

MAXIMIZE RELIABILITY

MAXIMIZE EFFICIENCY

MAXIMIZE PERFORMANCE

MAKE IT WORK PROPERLY

MAKE IT WORK


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As stated before, the most used electrical contact is coated by tin (Sn) which is worn out afterlong-time operation leading to electrical and mechanical problems in cars. On the other side,other contacts are coated by Gold (Au), a noble material who has been found to be moredurable and more reliable than tin but at the same time, has become more and moreexpensive for automotive use. The following graphs (figures 9-10) illustrate the evolution ofGold and Tin prices over time.

Figure 9. Tin Prices in USD$/Kg over time

Figure 10. Gold Prices in USD$/troy ounce over time

Indeed, the price of Gold is much higher than the price of Tin and we notice from the abovegraph that the most common market anomaly is a sudden increase in the dominance of thecost element in the ideality equation. Which means that, using Tin for the coating of electricalcontacts, the cost is low but the benefits are also low due to a limited durability of the tin-coated contacts. Consequently, to increase ideality, boosting the benefits would benecessary.

Select Solving ToolsIt is known that one of the most essential problems faced by new users of TRIZ is knowinghow to find the most relevant solving tools to the problem. Many methods help determiningmany solving tools.


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In our case, we will start by examining the position of the system on its current S-curve (figure7): in fact, the system seems to be reaching the end of the first half of its evolution. Accordingto the Hands-On Systematic Innovation select solving tool method, it means that the systemcontains contradictions.

Next, from the FAA model (figure 4), we identify the contradictions from the existence of

components which have positive and negative interactions with other components. In fact, themating parts both slide and hold/conduct. This means that the Physical Contradictionseparated in Time, followed by the Technical Contradiction are the most important tools forour problem. From the same model, we also notice the existence of excessive actions; thisleads us to use the Knowledge/Effects tool followed by Trends of Evolution. We also havemissing action (hold/conduct) which leads to the use of S-Field Analysis.

Problem Solving Tools

ContradictionsThe first tool problem solving tool offered by TRIZ is the recognition that an invention comes

as the result of the resolution or elimination of a contradiction. In TRIZ terminology, thecontradiction toolkit has two main forms: technical and physical. A technical contradiction ortwo-parametrical contradiction occurs when there are two parameters in conflict with eachother (ex. High strength and Low weight), or when all the following conditions are fulfilled:

(i) there is a desired function in a system,(ii) there is a conventional mean to realize this function and,(iii) the realization is opposed by harmful factors (figure 11).

Desired Function

Harmful Factor

Figure 11. Definition of a technical contradiction

In graphical terms, the conflict between the two parameters can be illustrated as a hyperbolic

curve which gets shifted towards the origin of the graph when trying to eliminate acontradiction (figure 12).

Contradiction


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Figure 12. Graphical Representation of a Technical Contradiction

As for the physical or one-parametrical contradiction, it occurs in occurs in a situation ofconflicting values of one parameter (ex. High weight and Low weight), where we desiredifferent properties of a certain parameter. Tackling our problem, in other words, solving thecontradictions can be achieved by a three-step systematic process, whether technical orphysical:Step 1:Identify the contradiction.Step 2:Determine the generic inventive principles successfully used in the past to resolvecontradictions.Step 3:Apply the generic principles to our specific problem.

As proposed by the analysis in the Select Solving Toolsection, we will start by analyzing thephysical contradiction present in our system then head towards the technical contradictionand interactions between technical and physical contradictions.

Physical contradictionStep 1:Identification of the physical contradiction.

One of the contradictions present in the electrical contacts case is a physical contradictionbecause the electrical contact is needed to SLIDE during installation and NOT SLIDE duringoperation for the prevention of fretting corrosion at the interface between the two matingparts. Indeed, the conflict SLIDE/NOT SLIDE generates our physical contradiction based onconflicting values of one parameter, which is the sliding action.Step 2:Determination of the generic inventive principles.One important result of Altshullers comprehensive patent analysis is the 40 inventiveprinciples. In fact, his major discovery was based on the fact that a large number of inventionswere only related to a small number of generic principles. Three basic methods of separatingphysical contradictions are generally used:

(i) In space (where?)(ii) In time (when?)(iii) On condition (if?)

The where, when and if questions can be used to establish which of the three strategies ismost likely to resolve the SLIDE and NO SLIDE contact requirements:

a) Where do I want the mating part to slide? - On the other mating part.Where do I want the mating part not to slide? - On the other mating part.In this case, the answer both times is the same which means that the problem isnot amenable to solution by separation in space.


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b) When do I want the mating part to slide? During installation.When do I want the mating part not to slide? During operation.In this case, we get two different answers which mean that the contradiction isamenable to elimination by separation of time.

c) I want the mating part to slide if? I am installing the system.I dont want the mating part to slide if? The system is operating.As is often the case, here we also get the differing answers seen in (b), whichmeans that we can also examine the separate on condition strategies to resolve theproblem.

Table A.1, which can be found in the Appendix, represents an important TRIZ tool: it lists theInventive Principles for each separation category in order of descending frequency of use byother problem solvers. As a matter of fact, the separation in time and condition strategiescontained in table A.2 gives us a host of inventive principles:

Time & Condition 11, 16, 19, 20, 23Time 9, 10, 18, 21Condition 6, 8, 12, 33, 38, 39

The most productive solutions generated using these triggers headed in the direction ofadding additional actions to the system. Given that the electrical contact is intended to be afundamentally simple component, costing, in most cases, a few cents, it was felt that, whilstthese solution directions shouldnt be eliminated, it would be preferable to look at possiblystronger directions. In general terms, this means looking at the Inventive Principles that dontrelate to any of the separation strategies. Looking again at Appendix A1, this meansPrinciples:

2, 3, 4, 5, 13, 22, 24, 25, 32, 35, 36

Rather than exploring these Principles directly, at this point it was decided to examine thecontradiction story in more detail through the technical contradiction route. Recently, therehave been many debates about the importance of the physical versus the technicalcontradiction, especially that both tools generated high numbers of ideas. The emergingstandard template for examining both physical and technical contradictions together is thetemplate shown in Figure 13. This template represents a modified version of the EvaporatingCloud worldview described in the Theory Of Constraints:


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Figure 13. The Modified Evaporating Cloud Scheme

In fact, evaporating the cloud or solving the problem necessitates at least one of thelinks between adjacent ovals to be broken or evaporated. The parameters A and Arepresent the physical contradiction whereas the Conflict Parameters 1 and 2, the technicalcontradiction. We now apply the scheme to our system (Figure 14).

durable

operation

operational

flexibility

long life

sliding

no

sliding

AND AND

2, 3, 45, 13, 22

24, 25, 35

32, 36

Figure 14. The Modified Evaporating Cloud Scheme with contradictions

One of the outcomes of the Figure 14 analysis is that some of the Inventive Principlesemerged as frequently used for most or all six of the conflict pairs identified from the template.These were, in decreasing frequency order:

3, 13, 35, 1, 4, 17


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Ideating around these Principles and especially 3, 1, 4 and 17 gave a fairly clear steertowards the use of non-smooth surfaces. For example, incorporating (asymmetric) grooves,ridges, dips and protrusions.

As is often the case, Principle 35 offers a very broad-ranging set of possible solutiondirections. Looking at all of the material attributes present in the mating surfaces of the

electrical contacts, and more specifically looking for step-changes in those attributes revealedtwo intriguing directions, the first involving a possible change of state, and the second lookingat substantial changes in hardness of the material. Coupled with Principle 13, emerged theclue of moving in the counter-to-common-sense direction of decreasing rather than increasinghardness.

Knowledge/Effects

At this point in the proceedings, it was decided that a check on the potential validity of thessolution directions was needed. Consequently, a search of the patent databases of the world wamade using the state change, hardness change and surface profile change clues obtained from

the contradiction analysis. Essentially what we are doing here is using keywords from thPrinciples to guide a search of the literature along the lines indicated by Figure 15:

contact,

mate,

conductelectrical contact

conductor

corrosion

fretting

melt, hardness,

rib, groove,roughen,

asymmetry

CONTEXT Words

SOLUTION DIRECTION Words

Figure 15. Principle-Guided Patent Search Strategy

Of the melting searches, by far the most intriguing solution was US patent applicatio20040241403, published on December 2, 2004: Composite material for producing an electricontact surface, in addition a method for creating a lubricated, corrosion-free electric contacsurface, the abstract of which describes:


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A modification of frictional state and surface condition of an electrical contact surface to reduce theinsertion forces for establishment of an electrical plug connection and also to achieve protection fromoxidation and fretting corrosion is provided. By controlled melting of a contact surface that is appliedonto a support material, a lubricant film applied onto the contact surface is diffused, by using a laser,substantially without modification into the liquefied contact surface and re-solidified together with thelatter, so that the lubricant film is incorporated into the contact surface.

Figure 16. US20040241403

Regarding the ribs/grooves/roughening searches, the most interesting solution seemed to be onfrom Palo Alto Research. US6,966,784, Flexible Cable Interconnect Assembly was granted iNovember 2005. Although intended for a somewhat more sophisticated application than thelectrical contact under consideration here, the solution derived by the inventors appears to havsome relevance to our problem. Heres what the invention disclosure has to say about the frettincorrosion issue:

FIG. 17 is a simplified cross-sectional side view showing a connector apparatus 150S incorporatinmicromachined alignment structures according to another embodiment of the present invention. The highdensity interface arrangements described above depend on accurate alignment and securing between thflexible cables extending from the associated mating boards. A general alignment structure is describe

above for positioning the respective cables to facilitate a successful coupling procedure. As indicated iFIG. 27, further x-y alignment accuracy may be obtained by providing micromachined alignment structure2710 and 2712 on contact structure 153S, and complementary micromachined alignment structures 272and 2740 on cables 120S and 140S, respectively. Such micromachined alignment structures can bfabricated during the spring formation process, thereby minimizing additional cost. Note sucmicromachined alignment structures can also provide accurate alignment in z-axis film-based structurebecause they can be produced to provide stops, which are important for controlling overdrive and insuringuniform compression, and thus wear of the contacts. In addition, current pressure contacts frettinexperiments suggest that multiple touchdowns in the same scrub helps to clear debrisand insure glitchfree performance. Precision alignment mechanisms that repeatedly hit the same scrub area would bnecessary to make this scrub/tip cleaning technique possible.

Figure 17. US6966784


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Trends of Technological Evolution

The results of the patent searches were next used as a guide to construct a map of therelative maturity of the designs in and around the electrical contact domain. The mostproductive means of achieving this kind of analysis is the evolutionary potential radar plot.Evolutionary potential is the difference between the current maturity of a system within one

domain and maximum evolution achieved by others in other domains. In a typical analysis,the system under consideration is compared to each of the 38 known trends of technologicalevolution, taking into consideration that they are heading toward an increasing systemideality. The Evolutionary Potential Radar Plot is then necessary to map how far along eachof the TRIZ trends the current system has developed (figure 18). According to the plot, thesystem should evolve and exploit the remaining evolutionary potential or resources to get tothe Ideal Final Result. And in so doing will resolve some or all of the problems associated withthe current system including the fretting corrosion problem under consideration here. In thisregard, the Evolution Potential concept works somewhat differently from the contradiction toolanalysis that preceded it: the contradiction tool starts from the definition of a problem, andtakes the user through a series of steps to get to an answer, or set of answers. Conversely,the evolution potential tool highlights a series of answers (trend jumps) first and then promptsthe user to identify what problems such jumps might resolve. Evolution potential analysis, inother words, works 180degrees different to the contradiction (and as it turns out all of theother TRIZ/SI) tools.

Figure 18. Composite Evolution Potential Radar Plot For Electrical Contact

Perhaps the most striking first aspect of the radar plot is the level of untapped potential withinthe system. This, in fact, is not an uncommon state of affairs for a component as simple andlow cost as an electrical contact. The low cost expectation, however, is also likely to be thelimiting factor in terms of which trend jumps are affordable and which are not. Combininglikelihood of solving the fretting problem with this affordability limitation indicated that thefollowing trend jumps were the most likely to deliver viable solutions:

Use of ribbed and roughened surfaces (i.e. a reinforcement of the ideas generatedfrom the contradiction analysis)


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Use of composite materials or material structures a potentially good way ofseparating the conflicting conduction and fretting resistance demands

Use of curvature/v-channel shapes i.e. geometries that cause fretting forces to beself-cancelling or self-stabilising

S-Field Analysis/Inventive StandardsAt this point, it could have been determined that we had sufficient solution direction clues toterminate the ideation session. However, in the spirit of completeness, it was decided that ashort S-Field analysis be completed. The S-Field tool is made of 76 Inventive Standardswhich include rules which transform an initial technical system, thus solving specific problems.In fact, they are based on the analysis of previous inventions that found solutions to similarproblems. In this section, a basic deployment strategy, suggested in Hands on SystematicInnovation, will be used to solve the electrical contacts problem.

1. Function DefinitionWe define, in simple terms, the function that the current system is supposed to deliver:

Conduct Electricity.

2. Substances/Fields DefinitionIn a certain system, in order to successfully deliver the necessary function conduct

electricity, a minimum of 2 substances (things, to be simpler) and a field (any form of energypresent in the system) are required. We therefore define the substances as the mating parts 1and 2, thus leading to 2 substances in addition to the mechanical field which dominates thethermal field, thus leading to 1 field.

In order for the system to deliver the conduct electricity function, it must satisfy thefollowing validity test that lies in the center of the S-field tool. Note that answering thequestions is based on the Function and Attribute analysis performed in a previous section(FAA model, figure 4).

a. Are the minimum 2 substances and a field present? Yes, the 2 mating parts and a field.

b. Is this a measurement problem? No.

c. Are there any harmful relationships in the system? Yes. So, we use the list of inventivstandards especially formulated for situations containing modify/add/transition. Their sequence ithe list starts with solution suggestions offering minimum disruption to the system to solutions thainvolve more profound changes. This will be confirmed in the following analysis.

3. S-Field DiagramThe transition from the FAA model to the S-field diagram is quite simple. However, some

modifications to the FAA scheme need to be done:

When drawing the S-field model (figure 19), we need to conduct some kind of fielsummation. Knowing that a field is any source of energy within the system that is helping (opreventing) the delivery of the required function, we find 2 fields: mechanical (vibrations) anthermal (expansion and contraction). In fact, adding mechanical + thermal equates to the fact thain its current state, the system has a harmful field (due to the thermal field) or an excessive fiel(due to the mechanical field). But which of them dominate the other?Therefore, we have a look at the general points stated in the book:


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- If there is only a harmful field, there can be no hope of achieving a useful solution.- In order to achieve the state whereby we do achieve a useful solution, the net sum of a

fields present must equate to a single composite field acting efficiently.So, the best modification to be done on the FAA model is to join the actions of the external agen(now mechanical and thermal field) into one excessive instead of thermal, which underlies the facthat the action of the vibrations dominate the thermal expansions and contractions of the electrica

contacts. Therefore, now the s-field model differs from the FAA model in that it has a mechanicafield instead of an external agent but with an excessive action. The other parts of the model arleft intact.

As for the harmful interactions of the system, they only exist between the 2 mating parts othe electrical contact, in other terms, between the 2 substances of the S-field model. Thereforethe model enables us to see how other people have successfully tackled this generic type oharmful effect between 2 substances model.

Figure 19. S-Field Diagram

4. Inventive StandardsThe harmful interaction between the 2 substances should be resolved by examining the

inventive standards for harmful interactions. Because the harmful interaction exist between the substances (rather from the field), we should look first to the standards associated witmodification of fields in the harmful effects section of the list. But in our case, the field cannobe modified which means that we will first look at the modification of existing substance. Thes

standards should be then used as solution triggers to generate specific solutions to our electricacontacts problem.

Of the possible modify existing substance solution directions indicated by the relevant InventiveStandards, no new solution directions emerged. The Standards, however, did tend to reinforcsome of the already generated ideas i.e. profiled surfaces, composite structures.

Conclusions And Next Steps

Although the main purpose of this case study was to run through the TRIZ/SI problem

definition tools in order to obtain new perspectives on the fretting corrosion problem, severalof the solution directions suggested through the course of the analysis have subsequentlybeen tested in a programme of experimental testing. Figure 20, for example, shows a micro-graph picture of one of the profiled-surface solutions undergoing test. A theoretical analysis ofthe likely benefits of this solution direction derived the thought that the valleys formed into thesurface would act as a place where wear debris caused by fretting could migrate so that theythen found themselves in a position where they would cause no further wear damage. Therelative size and shape of the peaks and valleys need merely to be sufficient to contain themaximum volume of wear debris producible during the intended life of the component.


Mechanical Field


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0

1.8 mm

50

25

2.3 mm

m

Figure 20. Micrograph of the First Tested Surface Profile Modification

Although not yet tested, another potentially interesting surface profile design direction wouldsee the peaks and valleys oriented in directions such that relative motion between matingsurfaces would cause the debris to pass along the valleys towards and ultimately beyond theedge of the contacts.

Initial test results on the Figure 20 profile suggest that the first iteration surface profile(actually created very cheaply by scratching the contact surfaces with a medium-coarse

glass-paper chosen for its low cost productionisation opportunities) would be sufficient toachieve the desired life improvement and to thus overcome the fretting corrosion problem forall but the most demanding applications.

REFERENCES

Mann, D., Hands-On Systematic Innovation, 2nd Edition IFR Press, 2007.

Mann, D., Matrix 2010, IFR Press, 2010.

Sreebalaji V.S., Saravanan R., Advanced Electrical Discharge Machining andTRIZ,The TRIZ Journal, June 2009.

Mann, D., Evaporating Contradictions: Physical and/or Technical,The TRIZJournal, March 2007.

Mann, D., BetterTechnology Forecasting Using Systematic Innovation Methods. www.sciencedirect.com www.infomine.com

APPENDICES

A.1: Physical Contradiction Solution Strategies


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TIMECONDITION

SPACE

14, 17, 26, 29

6, 8, 12, 3338, 39

9, 10, 18, 21

2, 3, 45, 13, 22

24, 25, 35

1, 28, 3031, 40

11, 16,19

20, 23

7, 15, 2734, 37

2, 3, 45, 13, 22

24, 25, 35

32, 36

A.2: Matrix 2010 Parameter List

1. Weight of moving object2. Weight of stationary object3. Length of moving object4. Length of stationary object5. Area of moving object6. Area of stationary object7. Volume of moving object8. Volume of stationary object9. Shape

10. Amount of Substance11. Amount of Information

12. Duration of action - moving object13. Duration of action - stationary object14. Speed15. Force/Torque16. Use of energy by moving object17. Use of energy by stationary object18. Power19. Stress/Pressure20. Strength

21. Stability22. Temperature23. Illumination Intensity24. Function Efficiency25. Loss of Substance26. Loss of Time27. Loss of Energy28. Loss of Information29. Noise30. Harmful Emissions31. Object Generated Side Effects

32. Adaptability/Versatility33. Compatibility/Connectability34. Ease of Operation35. Reliability36. Repairability37. Security38. Safety/Vulnerabilty39. Aesthetics40. Object affected harmful effects


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41. Manufacturability42. Accuracy of manufacturing43. Automation44. Productivity45. System Complexity

46. Control Complexity47. Positive Intangibles48. Negative Intangibles49. Ability to Detect/Measure50. Measurement Precision

d mann-case studies in triz-fretting failure in automotive electrical components

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