The AMPTIAC Quarterly, Volume 9, Number 1 9

MaterialE A S E

Material Failure Modes, Part I

A Brief Tutorial on Fracture, Ductile Failure, Elastic Deformation, Creep, and Fatigue

Benjamin D. CraigAMPTIACRome, NY

29AMPTIAC

What do design engineers and failure analysis experts have incommon? Answer: material failure. These two groups are thebookends to a materials life. While materials selection is some-times left up to a bona fide materials engineer, designers are typ-ically responsible for determining what environments and oper-ating conditions a component will encounter during service. Inmany cases designers are also responsible for performing thetask of materials selection. This combined role essentially deter-mines the fate of a material and quite possibly the system.Failure analysis specialists explore the questions of how and whya particular system, and more precisely, a material failed. Topreclude failure the designer should consider the questions ofwhen and how the system, and more specifically, the materialwill fail. The first step toward preventing failure is understand-ing how it might occur.

If a material were resistant to all failure modes in all envi-ronments, a system or component could theoretically have aninfinitely long life. Unfortunately, all materials are susceptibleto failure. Even the best engineered materials are prone to fail-ure given a sufficiently harsh service environment, or if they arepoor choices for a specific application. Furthermore, there are anumber of mechanisms and combinations of mechanisms thatcause materials to fail. The goal of the design engineer is tocost-effectively design a system that operates at its maximumefficiency for the longest possible period of time without havingto be replaced or overhauled. To meet this goal it is importantfor the designer to be aware and have a certain level of under-standing about how materials can fail.

The intent of this article is to provide an educational refer-ence for designers and other engineers on the common modes ofmaterial failure. Understanding potential failure modes in theearly stages of system design can lead to a more appropriateselection of materials, prevent premature system failure and pos-sibly lengthen system life; ultimately resulting in increased safe-ty in some cases and reduced cost of ownership.

INTRODUCTION TO FAILUREThe failure of a material is not restricted to fracture or total disintegration; it can also consist of a change in shape, loss ofmaterial or the alteration of mechanical properties. When amaterial becomes unable to execute the function that it was orig-inally intended or designed to perform, it has failed.

Environmental conditions and operating loads are often theprimary causes leading to a materials failure. Examples of harshenvironments that commonly induce failure include corrosive,high temperature, and high energy environments. Stress, impact,and frictional loading are examples of operating conditions thatfrequently cause a material failure. Combinations of harsh envi-ronments and mechanical loads often lead to a more rapid mate-rial wearout and failure.

There are several failure prevention methods that can beemployed, but often the first critical step is to properly select thematerial or material system that will be used to construct thegiven system component. Further prevention measures (e.g. pro-tective coatings, cold working, etc.) can be implemented depend-ing on the application, the conditions found in the operationalenvironment, mechanical loading, and the failure modes thatthe selected material is traditionally susceptible to in a given sys-tem configuration. The rest of this article is devoted to providinga background on the most common material failure modes.

FAILURE MODESThere are more than twenty different recognizable ways a mate-rial can fail, including the most common forms: fracture,fatigue, wear, and corrosion.[1] Each of these and other commonfailure modes are described briefly in the following sections orwill be featured in the next two issues of MaterialEASE.

Brittle FractureBrittle fracture occurs when mechanical loads exceed a materi-als ultimate tensile strength causing it to fracture into two or

This issue of MaterialEASE is Part One of a three part series on material failure modes. It introduces the concept of material failure and covers a number of failure modes, including brittle and ductile failure, elastic distortion, creep, and fatigue.Future MaterialEASE articles will cover other important failure modes including impact, wear, thermal shock and corrosion.This series will make a valuable desk reference for any professional making material selection and design decisions. - Editor

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MaterialE A S E

more parts without undergoing any significant plastic deforma-tion or strain failure. Material characteristics and defects suchas notches, voids, inclusions, cracks, and residual stresses arethe typical initiation points for the formation of a crack leadingto brittle fracture (Figure 1). Once the crack is initiated thematerial will undergo catastrophic failure fairly quickly under asustained load. There is little energy absorbed (compared to duc-tile fracture) during the brittle fracture process. This failuremode commonly occurs in brittle materials such as ceramicsand hard metals.

Eliminating or minimizing surface and internal materialdefects is an important method in improving a materials resist-ance to brittle fracture. Many of these defects originate duringmaterial fabrication or processing steps. Therefore, it is impor-tant to give these early stages in the life cycle proper attention inorder to reduce the materials susceptibility to brittle fracture.Fabricating a part with a smooth surface is also important in pre-

venting brittle fracture. For instance, sharp textures and notcheson the surface of the material can initiate brittle fracture. Carefulhandling of the material after its produced will also help to pre-vent unnecessary mechanical damage such as scratches andgouges, which can ultimately lead to brittle fracture. Finally, anappropriate materials selection process to choose a suitablematerial for the intended application is important in ensuringthat it will be capable of handling the applied mechanical loads.

Ductile FailureDuctile materials that are subjected to a tensile or shear stress willelastically or plastically strain to accommodate the load andabsorb the energy. Yielding occurs when the materials yieldstrength is exceeded and can no longer return to its original shapeand size. This is followed by ductile fracture which occurs whenthe deformation processes can no longer sustain the applied load.Both of these failure modes are described in more detail below.

Figure 1. BrittleFracture Surface ofa High-StrengthChain. FractureBegan in a SmallCrack Resultingfrom a HeatTreating Problem(Photo Courtesy ofSachs, Salvaterra& Associates, Inc.).

Figure 2. YieldingFailure of UH-1Helicopter EngineShaft and BearingComponents[2].

Figure 3. (a) Ductile Fracture of 2 1/2 Inch Hose Fitting (b) Close-up of the Deformed Region Where a Pin Joining the Ears BecameFree from the One on the Right Causing the Deformation and Fracture of the One on the Left (Photos Courtesy of Sachs, Salvaterra & Associates, Inc.).

a b

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A D VA N C E D M AT E R I A L S A N D P R O C E S S E S T E C H N O L O G YAMPTIAC

YieldingYielding failure (also known as gross plastic deformation) occurswhen a material subject to mechanical loading exhibits sufficientplastic deformation such that it can no longer perform its intend-ed function. This mode of failure results in deflected, stretched, orotherwise misshapen components, and is typical in ductile mate-rials such as metals and polymers. Ceramics and very hard metalsare inherently brittle materials and therefore yielding is not a sig-nificant concern. An example of this type of failure is oftenobserved in ductile materials subjected to a tensile stress. Thesemalleable materials tend to absorb the applied load by undergo-ing plastic deformation, which causes an elongation of the mate-rial. Yield strength is a measurement of a materials resistance toyielding failure, and it denotes the stress at which the materialbegins to exhibit a disproportionate increase in strain withincreasing stress. Figure 2 shows a picture of several misshapenhelicopter components that experienced yielding failure.

Ductile FractureA failure mode that is somewhat opposite in nature to brittle frac-ture is ductile fracture. Ductile fracture occurs when a materialexperiences substantial plastic deformation or strain while beingstressed beyond its yield strength and is consequently torn in twopieces. An extensive amount of energy is absorbed during thedeformation process. Similar to brittle fracture, however, cracksare typically nucleated at material defects, such as voids andinclusions. As ductile materials experience plastic deformation,existing voids coalesce to form the crack tip. The actual crackpropagation process in ductile fracture is generally a slow processwith the crack growing at a very moderate rate as voids coalesceat the fracture surface. An obvious but important consideration isthat this type of failure is common in ductile materials, typicallymetals and polymers.

Failures attributed only to ductile fracture are not common,but rather this mechanism is typically a contributing factor inthe overall material failure. When a material does fail due to

ductile fracture it is most likely because the stress exceeded thematerials strength limits. This indicates that the material cho-sen during design did not meet the performance requirements,the loads applied were more than what was predicted, the materi-al was improperly or poorly fabricated, or defective raw materialswere used for component fabrication.[3] Figure 3 shows picturesof a component that failed by ductile fracture.

The best method for preventing a part from failing due toductile fracture is to perform proper materials selection duringthe design stages of a system. In addition, appropriate qualitycontrol procedures should be in place for producing the materi-als in order to reduce the number of defects. An appropriatematerials selection process will ensure that the operating loadsimposed as stresses on the chosen material will not exceed itsmechanical limits. However, design errors such as inaccuratelypredicting mechanical loads have been known to occur. Under-estimating a load for instance, could lead to ductile fracture.

BucklingBuckling occurs when a material subjected to compressive or tor-sional stresses can no longer support the load, and it consequent-ly fails by bulging, bending, bowing or forming a kink or otherunnatural characteristic. Bars, tubes, and columns are shapesthat are commonly susceptible to failure by buckling. In addi-tion, I-beams and other more complex geometries may experi-ence buckling under compressive or torsional loads. Strength andhardness properties do not indicate a materials susceptibility tobuckling. Buckling is dependent on the shape and respectivedimensions of the material as well as the modulus of elasticity,which is dependent on temperature. Therefore, buckling is morelikely to occur at higher temperatures where the modulus of elas-ticity is lower, since materials have a tendency to soften whenthey are heated. Figure 4 (a) shows a picture of a cylindricalmetal component after buckling under compressive stress, and(b) a picture of a cylindrical aircraft component that failed bytorsional buckling.

Elastic DistortionA material can fail without being permanently changed when itis elastically deformed to such an extent that it fails to performits intended function. Elastic deformation occurs when a materi-al is subjected to a load that does not exceed its yield strength.This non-permanent distortion can cause the material, for example, to obstruct another component in a system resulting infailure. Elastic distortion can be induced by a load and affectedby a change in temperature. For example, a materials elasticmodulus is temperature dependent, and if an unanticipated temperature change occurs the material may undergo elasticdeformation at a smaller load than it would at the normal oper-ating temperature. Selection of a material with a sufficientlyhigh modulus to withstand loads without experiencing elasticdeformation can prevent this type of failure from occurring,

Figure 4. (a) Compressive Buckling Failure of Metal Cylinder, (b) Torsional Buckling Failure of an F-18 Engine Shaft[2].

a b

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MaterialE A S E

especially if there is an unanticipated temperature change.Control over operating conditions so that the material does notobserve load or temperature changes that would compromise itsability to withstand elastic deformation will also help prevent thistype of failure from occurring.

CreepCreep is a time-dependent process where a material under anapplied stress exhibits a dimensional change. The process is alsotemperature-dependent since the creep or dimensional changethat occurs under an applied stress increases considerably astemperature increases. A material experiences creep failure whenthe dimensional change renders the material useless in perform-ing its intended function. Sufficient strain or creep can result infracture, known as stress rupture, which is discussed briefly in asubsequent section. Figure 5 shows the time-dependent nature ofcreep failure.

Creep occurs when vacancies in the materials microstructuremigrate toward grain boundaries that are oriented normal to thedirection of the applied stress. As this happens atomic diffusionoccurs in the opposite direction to fill the voids, resulting in anelongation of the grain in the direction parallel to the appliedstress. Other mechanisms of creep include those where vacanciesmigrate along grain boundaries, dislocations move to accommo-date the applied stress in the form of strain, and adjacent grainsslide along their common grain boundary also to accommodatethe applied stress.[5]

Materials experience thermally activated creep at differenttemperatures. For example, some materials, such as nickel-based

superalloys, are susceptible to creep at relatively high tempera-tures (e.g. 1000 - 1200C), while others, such as polymers or tin-lead solder, can be susceptible to creep at much lower temper-atures (e.g. 25C). Generally, creep should be a considerationwhen a material is operating at a temperature that is greaterthan 0.3Tm, where Tm is the materials absolute melting temper-ature. At 0.5Tm creep is very much a concern.[5]

Creep can occur in ceramics at temperatures above 0.4 to0.5Tm, although it is much more common in metals and poly-mers.[6] Ceramics have a very high resistance to deformation bycreep partly because of their characteristically high melting tem-peratures. However, at extremely high temperatures ceramics canexhibit a considerable amount of creep.

To prevent failure due to creep deformation it is very impor-tant to know the operating conditions of the system when select-ing materials for an application. Creep has been a particularproblem for turbine engine blades since they experience a sus-tained stress over time at a relatively high temperature. As aresult, materials with high melting temperatures are often select-ed for such an application. Furthermore, it is important to ensurequality material fabrication and processing in order to reducematerial defects and voids.

Creep BucklingCreep buckling is a failure mode that occurs when the creepprocess renders a material unable to support loads it could other-wise handle, and as a result the material buckles.

Stress RuptureStress rupture, also known as creep fracture, is a mechanism thatis closely related to creep except that the material eventuallyfractures under the applied load. As discussed in the previous sec-tion, creep is the time- and temperature-dependent elongation ofa material that is subjected to a stress. When this stress over-comes the materials ability to strain, it will rupture. Crackingthat precedes the rupture of the material can be either transgran-ular or intergranular*.

Thermal RelaxationThermal relaxation is a process related to the temperature-dependent creep failure mode. Failure by thermal relaxationcommonly occurs in fastener materials or other materials thatare prestressed such that they could support a greater load thantheir non-prestressed counterpart. As the material undergoescreep at high temperatures their residual stresses are relievedwhich may render the material unable to support the givenload.

Figure 5. Creep and Rupture Data for 4130 Steel at 1000F[4].

AppliedStrain

0.1 1 10 100 1000

50

45

40

35

30

25

20

15

Time (hours)

Stre

ss (k

si)

1000F

28% - RuptureOccurs

0.5% 1%

2% 5%

0.5%1%2%5%28%

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FatigueFatigue is an extremely common failure mode and deserves con-siderable attention because it can inflict damage on a material ata stress level that is far less than the materials design limit.Fatigue has been attributed with playing a role in approximately90% of all material structural failures.[6]

A material that fractures into two or more pieces after beingsubjected to a cyclic stress (fluctuating load) over a period oftime is considered to have failed by fatigue. The maximum valueof the cyclic stress (stress amplitude) for fatigue failure is lessthan the materials ultimate tensile strength. It is often the casethat the maximum value of the cyclic stress is so low that if itwere applied at a constant level the material would be able to eas-ily support the load without incurring any damage. Cyclic loadscause the initiation and growth of a crack, and ultimately, whenthe crack is significant enough such that the material can nolonger support the load, the material fractures.

The fatigue failure mechanism involves three stages: crackinitiation, crack propagation, and material rupture. Similar toboth ductile and brittle fracture, fatigue cracks are often initiat-ed by material inhomogeneities, such as notches, grooves, sur-face discontinuities, flaws, and other material defects.[7] Theseinhomogeneities or initiation points act as stress raisers wherethe applied stress concentrates until it exceeds the local strengthof the material and produces a crack. The best way to preventfatigue failure is to keep fatigue cracks from initiating, whichcan be accomplished by removing or minimizing crack initiators,or by minimizing the stress amplitude. Once fatigue cracks havebeen initiated they will seek out the easiest or weakest path topropagate through the material. Therefore, minimizing thenumber of internal material defects, such as voids and inclu-sions, will increase the time it takes a crack to propagate. Finally,when the crack has weakened the material to a point such that it

can no longer support the applied load it will rupture, which canoccur by shear or by tension.[7]

Fatigue is not so much dependent on time as it is the numberof cycles. A cycle consists of an applied stress being increasedfrom a starting value (in some cases, zero or even negative) up toa maximum positive value (material loaded in positive direction)and then decreasing past the starting point down to a minimumvalue (in some cases this is a maximum negative loading), andfinally back up to the starting value. This cycle is illustrated inFigure 6, where there is positive and negative loading. However,negative loading is not required for fatigue to occur; rather, itcan be a fluctuating positive load. Moreover, the stress cycles donot need to be symmetric, but can be randomly changing. Ingeneral, ferrous, or iron alloy, materials do have a fatigue(endurance) limit (SL), which is the stress level (amplitude)under which no failure will occur regardless of the number of

Figure 6. Fatigue Loading Cycle. Figure 7. S/N Curves for Ferrous and Non-Ferrous Metals[8].

Figure 8. Torsional Low-Cycle Fatigue Fracture of a Shaft. (PhotoCourtesy of Sachs, Salvaterra & Associates, Inc.)

Stress Amplitude

Ferrous Metals

Non-Ferrous Metals

1 Cycle

Cycles to Failure (Nf)

104 105 106 107 108

Stre

ss

Stre

ss A

mpl

itude

(S)

Time

(+)

(-)

SL

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cycles. On the other hand, by increasing the stress amplitude, thefatigue failure will commence after a smaller number of cycles.Non-ferrous alloys, such as aluminum and titanium, do not havea fatigue limit. This concept is demonstrated in Figure 7.

Metals and polymers are typically susceptible to fatigue fail-ure, while ceramics tend to be resistant. There are several differ-ent types of fatigue including high-cycle fatigue, low-cyclefatigue, thermal fatigue, surface fatigue, impact fatigue, corro-sion fatigue, and fretting fatigue. Each of these will be discussedin some detail in the following sections.

High-Cycle FatigueHigh-cycle fatigue is defined as fatigue where the material is sub-jected to a relatively large number of cycles before failure occurs.Generally, for the fatigue mechanism to be considered high-cyclefatigue the number of cycles required to produce failure is greaterthan 10,000. The deformation exhibited by a material subjectedto high-cycle fatigue is typically elastic.

Low-Cycle FatigueA fatigue failure that occurs after a relatively small number ofcycles is considered to be low-cycle fatigue. Typically, when amaterial fails due to fatigue after less than 10,000 cycles, it isconsidered to be low-cycle fatigue. The mechanisms of crack

growth for materials experiencing low-cycle fatigue are similarto the crack growth of a material subjected to a constant stress.The deformation exhibited by a material subjected to low-cyclefatigue is typically plastic (Figure 8). Since the plastic strains inlow-cycle fatigue are usually greater than in high-cycle fatigue,the surface defects of the material are not as important as thebulk material properties.[9]

Thermal FatigueSimple temperature fluctuations or repeated heating and coolingcan impose stresses on a material leading to fatigue damage andpotentially failure. Materials generally exhibit a dimensionalchange or strain to some extent in response to temperaturechanges. This response can be significant in some materials,especially metals, and can induce thermal stresses on the materi-al if it is mechanically confined in some way. When a material isexposed to conditions of fluctuating temperatures it can causecyclic fatigue loading, which can result in crack growth and pos-sibly fracture. This process is referred to as thermal fatigue.

Mechanical loading is not required for thermal fatigue to occur,and this failure mode is different from fatigue under fluctuating stress at high temperature. If there is a temperaturegradient within the material that is exposed to fluctuating temper-atures, it may experience thermal fatigue since different

MaterialE A S E

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Table 1. Methods for Reducing or Eliminating Fretting Fatigue[10].

Principle of Abatement or Mitigation Practical Method

Reduction in surface shear forces Reduction in surface normal forces Reduction in coefficient of friction with coating or lubricant

Reduction/elimination of stress concentrations Large radii Material removal (grooving) Compliant spacers

Introduction of surface compressive stress Shot or bead blasting Interference fit Nitriding/heat treatment

Elimination of relative motion Increase in surface normal load Increase in coefficient of friction

Separation of surfaces Rigid spacers Coatings Compliant spacers

Elimination of fretting condition Drive oscillatory bearing Remove material from fretting contact (pin joints) Separation of surfaces (compliant spacers)

Improved wear resistance Surface hardening Ion implantation Soft coatings Slippery coatings

Reduction of corrosion Anaerobic sealants Soft or anodic coatings

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sections of the materials microstructure will respond unequally tothe temperature changes. Failure from thermal fatigue can occurnot only from fracture but also from a permanent change in shape.

Thermal fatigue is a significant concern in certain applica-tions such as internal combustion engines, heat exchangers, andturbine engine blades. Metals are especially susceptible to ther-mal fatigue because they often have a microstructure that is temperature dependent. Composites are susceptible to thermalfatigue because they consist of multiple unique materials which respond differently to temperature changes. For example,upon temperature fluctuations the reinforcing material canexhibit significant strain while the matrix material experiencesminimal strain. This leads to a fatigue type loading on thematrix material, which can result in the initiation of a crack.The best way to mitigate thermal fatigue in composite materialsis to choose a reinforcement material and a matrix material that have similar thermal expansion coefficients.[5]

Surface FatigueThe MaterialEASE in the next issue of the AMPTIAC Quarterlywill contain a brief description of this failure mode.

Impact FatigueImpact fatigue occurs when a material is subjected to repeatedimpacts to a localized area causing the initiation and propaga-tion of a fatigue crack. This repeated impact loading can ulti-mately result in fatigue fracture.

Corrosion FatigueFor an in-depth discussion on corrosion fatigue and how it differs from stress corrosion cracking read the article in this issue of the AMPTIAC Quarterly entitled: Environmentally-Assisted Cracking.

Fretting FatigueFretting damage on the surface of a material can act as anucleating point for a crack. Under cyclic loading (typicallysmall amplitude loading) the nucleation of a crack at the loca-tion of fretting damage and the subsequent crack propagationand fracture of the material constitutes fretting fatigue. Frettingof a component under fatigue conditions will lead to a muchquicker nucleation of cracks than fatigue of a component notsubjected to fretting. Furthermore, cracks can be initiated byfretting damage at a much lower stress than if the material is in a normal, undamaged condition. The fatigue strength of amaterial can be reduced by up to 70% under fretting condi-tions.[10] Fretting fatigue is a particularly problematic failuremechanism because it can occur in hidden areas and result inthe sudden, catastrophic failure of a component. Joints, bear-ings, axles and shafts are typically very susceptible to frettingfatigue.[10, 11] Methods for reducing damage by fretting fatigueare briefly described in Table 1.

Creep-Fatigue InteractionAt elevated temperatures creep and fatigue can act simultaneous-ly to produce a concerted, harmful effect on a material. A mate-rial operating in high temperature conditions can experienceboth creep strains and cyclic strains that can seriously compro-mise the materials expected lifetime. For example, if a materialexperiences creep strains while undergoing fatigue cycling, itsfatigue life can be greatly reduced. Similarly, if a material expe-riences fatigue cycling while undergoing creep, its creep life canbe significantly reduced. The combined effect of creep andfatigue can pose serious problems for those designing a system toperform for a defined lifetime. There has been significantresearch into predicting the combined effects of creep and fatigueon materials in various operating conditions.[12]

FAILURE PREVENTIONIn general, the most effective ways to prevent a material fromfailing is proper and accurate design, routine and appropriatemaintenance, and frequent inspection of the material for defectsand abnormalities. Each of these general methods will bedescribed in further detail below.

Proper design of a system should include a thorough materi-als selection process in order to eliminate materials that couldpotentially be incompatible with the operating environment andto select the material that is most appropriate for the operatingand peak conditions of the system. If a material is selected basedonly on its ability to meet mechanical property requirements, forinstance, it may fail due to incompatibility with the operatingenvironment. Therefore, all performance requirements, operat-ing conditions, and potential failure modes must be consideredwhen selecting an appropriate material for the system.

Routine maintenance will lessen the possibility of a materialfailure due to extreme operating environments. For example, amaterial that is susceptible to corrosion in a marine environmentcould be sustained longer if the salt is periodically washed off. Itis generally a good idea to develop a maintenance plan before thesystem is in service.

Finally, routine inspections can sometimes help identify if amaterial is at the beginning stages of failure. If inspections areperformed in a routine fashion then it is more likely to prevent acomponent from failing while the system is in-service.

CONCLUSIONFrom a research standpoint, engineers must consider all plausible material failure modes when developing and maturing anew material or when evolving an old material. However, materi-al failure can often be the result of inadequate material selection bythe design engineer or their incomplete understanding of the con-sequences for placing specific types of materials in certain environ-ments. Education and understanding of the nature of materials andhow they fail are essential to preventing it from occurring. Simplefracture or breaking into two pieces is not all-inclusive in terms of

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failure, because materials also fail by being stretched, dented orworn away. If potential failure modes are understood, then criticalsystems can be designed with redundancy or with fail-safe featuresto prevent a catastrophic failure. Furthermore, if appropriate effortis given to understanding the environment and operating loads,keeping in mind potential failure modes, then a system can bedesigned to be better suited to resist failure.

MaterialEASE 30 will be published in AMPTIAC Quarterly,Volume 9, Number 2, and will contain the next installment offailure modes. These will include: Impact, Spalling, Wear,Brinelling, Thermal Shock, and Radiation Damage.

ACKNOWLEDGEMENTThe author would like to thank Sachs, Salvaterra & Associates,Inc. for their contribution of photos included in this article.

NOTES & REFERENCES* Transgranular indicates that a crack proceeds through grainboundaries and across the grain, whereas, intergranular indi-cates that a crack navigates around or between grain boundaries. Fretting wear is a damage mechanism whereby two surfacesthat are in intimate contact with each other and subjected to asmall amplitude relative motion (cyclic in nature) tend to incurwear. The MaterialEASE in the next issue of the AMPTIACQuarterly will contain a brief description of this failure mode. Fatigue strength is the maximum stress that a material canendure without failure for a given number of cycles.[1] J.A. Collins and S.R. Daniewicz, Failure Modes: Perfor-mance and Service Requirements for Metals, M. Kutz (editor),Handbook of Materials Selection, John Wiley and Sons, 2002, pp.705-773

[2] Visual Examples of Various Structural Failure Modes,Naval Postgraduate School, www.nps.navy.mil/avsafety/gouge/structures/structures.ppt[3] Ductile and Brittle Fractures, Metals Handbook, 9thEdition, Vol. 11: Failure Analysis and Prevention, ASMInternational, 1986, pp. 82-101[4] J.M. Holt, H. Mindlin, and C.Y. Ho (editors), Structural AlloysHandbook, Vol. 1, CINDAS/Purdue University, 1997, p. 74[5] J. P. Shaffer, A. Saxena, S.D. Antolovich, T.H. Sanders, Jr., andS.B. Warner, The Science and Design of Engineering Materials,2nd Edition, McGraw-Hill, 1999[6] R.E. Hummel, Understanding Materials Science: History Properties Applications, Springer-Verlag, 1998[7] Failure of Gears, Metals Handbook, 9th Edition, Vol. 11:Failure Analysis and Prevention, ASM International, 1986, pp.586-601[8] H.E. Boyer (editor), Atlas of Fatigue Curves, ASMInternational, 1986[9] J. Schijve, Fatigue Crack Growth under Variable-Amplitude Loading, ASM Handbook, Vol. 19: Fatigue andFracture, ASM International, 1996, pp. 110-133[10] S.J. Shaffer and W.A. Glaeser, Fretting Fatigue, ASMHandbook, Vol. 19: Fatigue and Fracture, ASM International,1996, pp. 321-330[11] Wear Failures, Metals Handbook, 9th Edition, Vol. 11:Failure Analysis and Prevention, ASM International, 1986, pp.145-162[12] J.B. Conway, Creep-Fatigue Interaction, Metals Handbook,9th Edition, Vol. 8: Mechanical Testing, ASM International, 1986,pp. 346-360

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... Dont forget to look for

Material Failure Modes Parts 2 & 3

in upcoming issues of MaterialEASE!

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