1、Designation: E2789 10Standard Guide forFretting Fatigue Testing1This standard is issued under the fixed designation E2789; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates
2、 the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide defines terminology and covers generalrequirements for conducting fretting fatigue tests and reportingthe results. It describes the general types of fretti
3、ng fatiguetests and provides some suggestions on developing and con-ducting fretting fatigue test programs.1.2 Fretting fatigue tests are designed to determine theeffects of mechanical and environmental parameters on thefretting fatigue behavior of metallic materials. This guide is notintended to es
4、tablish preference of one apparatus or specimendesign over others, but will establish guidelines for adherencein the design, calibration, and use of fretting fatigue apparatusand recommend the means to collect, record, and reporting ofthe data.1.3 The number of cycles to form a fretting fatigue crac
5、k isdependent on both the material of the fatigue specimen andfretting pad, the geometry of contact between the two, and themethod by which the loading and displacement are imposed.Similar to wear behavior of materials, it is important toconsider fretting fatigue as a system response, instead of ama
6、terial response. Because of this dependency on the configu-ration of the system, quantifiable comparisons of variousmaterial combinations should be based on tests using similarfretting fatigue configurations and material couples.1.4 This standard does not purport to address all of thesafety concerns
7、, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic
8、SpecimensE4 Practices for Force Verification of Testing MachinesE466 Practice for Conducting Force Controlled ConstantAmplitude Axial Fatigue Tests of Metallic MaterialsE467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing SystemE468 Practice for Presentati
9、on of Constant Amplitude Fa-tigue Test Results for Metallic MaterialsE1012 Practice for Verification of Test Frame and SpecimenAlignment Under Tensile and Compressive Axial ForceApplicationE1823 Terminology Relating to Fatigue and Fracture Test-ingE1942 Guide for Evaluating Data Acquisition SystemsU
10、sed in Cyclic Fatigue and Fracture Mechanics TestingG15 Terminology Relating to Corrosion and CorrosionTesting3G40 Terminology Relating to Wear and ErosionG190 Guide for Developing and Selecting Wear Tests3. Terminology3.1 Definitions and symbols used in this guide are inaccordance with Terminology
11、E1823. Relevant definitionsfrom Terminology G15 or G40 are provided in 3.2. Additionaldefinitions specific to this guide are provided in 3.3.3.2 Definitions: Terms from Terminologies G15 and G40.3.2.1 coeffcient of friction (COF)The dimensionless ratioof the tangential force, Q, between two bodies t
12、o the normalforce, P, pressing these bodies together when the two bodies areslipping with respect to each other, =Q/P.3.2.1.1 DiscussionUnder partial slip conditions, the ratioof the tangential force to the normal force is less than the COF.In addition, when COF is defined as the ratio of Q to P, th
13、emeasured COF is an average along the interface. In reality, theCOF can vary along the interface. Hence, a local definition isoften used, given by (x,y)=q(x,y)/p(x,y) where q(x,y) is theshear traction distribution along the interface and p(x,y) is thenormal pressure distribution. The COF is often gr
14、eater in theslip regions of a partial slip interface compared to the stickregions due to the disruptions in the surface caused by fretting.G403.2.2 frettingSmall amplitude oscillatory motion, usuallytangential, between two solid surfaces in contact.3.2.2.1 DiscussionThe term fretting refers only to
15、thenature of the motion without reference to the wear, corrosion,1This guide is under the jurisdiction of ASTM Committee E08 on Fatigue andFracture and is the direct responsibility of Subcommittee E08.05 on CyclicDeformation and Fatigue Crack Formation.Current edition approved Nov. 1, 2010. Publishe
16、d January 2011. DOI: 10.1520/E2789.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last appro
17、ved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.fatigue, or other damage that may occur. It is discouraged touse the term fretting to denote fretting corrosion or o
18、ther formsof fretting wear due to the ambiguity that may arise. As theamplitude of fretting increases, the condition eventually be-comes reciprocating sliding and the interaction should nolonger be referred to as fretting.3.2.3 fretting corrosionThe deterioration at the interfacebetween contacting s
19、urfaces as the result of corrosion andslight oscillatory slip between the two surfaces. G153.2.4 fretting wearWear that occurs as the result offretting action. G403.3 Definitions of Terms Specific to This Standard:3.3.1 displacement amplitudeThe peak-to-peak relativedisplacement divided by two or to
20、tal cycle displacementdivided by four.3.3.1.1 DiscussionThe displacement amplitude is typi-cally based on a remote reference location. Note that thedefinition of displacement amplitude in the context of frettingwear and tribosystems testing sometimes refers to the fullpeak-to-peak relative displacem
21、ent, rather than the definitiongiven here, which is consistent with the use of the termamplitude in Terminology E1823. Hence, whenever the termdisplacement amplitude is used, it should be clearly defined ora reference made to this guide.3.3.2 fretting damageThe pits, scarring, disruptions andmateria
22、l transfer on the surface due to fretting.3.3.2.1 DiscussionCracks may be associated with thefretting damage, though in many cases they may not be presentor be sufficiently small, such that the fatigue life is notsignificantly degraded. Hence, the disturbed appearance andlevel of roughness of the fr
23、etting damage cannot be reliablyused to determine whether the fatigue life is reduced. In somecases the directionality of roughness, also called the surfacetexture, can be determined via profilometry methods. Thistexture may be correlated to the directionality of fretting and insome cases the charac
24、teristics of the texture can provide auseful screening metric for fretting damage.3.3.3 fretting fatigueThe process of crack formation at afretting damage site, progressive crack growth, possibly cul-minating in complete fracture, occurring in a material sub-jected to concomitantly fretting and fluc
25、tuating stresses andstrains.3.3.3.1 DiscussionFretting fatigue is generally character-ized by a sharp decrease in the fatigue life at the same stresslevel of a standard specimen, attributed to the shortened time toform a crack and the acceleration of the crack growth under thecoupling of the frettin
26、g and bulk cyclic stresses and strains.3.3.4 fretting fatigue knockdown factorThe reduction infatigue strength due to the presence of fretting, defined as thedifference in the fatigue limit and fretting fatigue limit dividedby the fatigue limit.3.3.4.1 DiscussionThis knockdown factor may also bebase
27、d on the fretting fatigue strength defined either as the stresslevel (maximum stress or stress amplitude for a given meanstress or stress ratio) for failure at a certain number of cycles orthe stress level at which a percentage of the population wouldsurvive a certain number of cycles.3.3.5 fretting
28、 fatigue limitThe limiting value of themedian fatigue strength when fretting is present as the fatiguelife becomes very large.3.3.5.1 DiscussionThe fretting fatigue limit strongly de-pends on the fretting conditions.3.3.6 fretting fatigue reduction factorThe reduction infatigue strength due to the p
29、resence of fretting, defined as theratio of the fretting fatigue limit and fatigue limit.3.3.6.1 DiscussionThis reduction factor may also bebased on the fretting fatigue strength defined either as the stresslevel (maximum stress or stress amplitude for a given meanstress or stress ratio) for failure
30、 at a certain number of cycles orthe stress level at which a percentage of the population wouldsurvive a certain number of cycles.3.3.7 fretting fatigue damage thresholdThe combinationof fretting fatigue loading conditions and number of frettingcycles that can be sustained before degradation of fati
31、gue lifeis observed.3.3.7.1 DiscussionThe fretting fatigue loading conditionsmay include combinations of the normal force, the displace-ment amplitude, the tangential force amplitude, and the bulkfatigue loading. The concept of a fretting fatigue damagethreshold is related to the development of an i
32、nitial crackcharacterized with a maximum and range in stress intensity thatexceeds the threshold value for crack growth. Generally, afterthe fretting fatigue damage threshold has been reached, remov-ing the source of fretting, while maintaining the fatigueloading, in configurations where they can be
33、 separated, hasminimal effect on the remaining life.3.3.8 gross slipThe condition for which all points incontact experience relative slip over a complete cycle, asillustrated in Fig. 1.3.3.9 normal forceForce normal to the contact interface.3.3.9.1 DiscussionDue to the accumulation of debriswithin t
34、he contact or wear in the slip regions, this force maynot remain constant but change during the test.3.3.10 normal pressureResultant of the normal forcedivided by the contact area.3.3.10.1 DiscussionTo be considered an average only.The true distribution of pressure within the contact areadepends on
35、the exact profile and roughness of the contactingsurfaces. Analytical or computational methods may be used todetermine this pressure; for example, see Ref. (1)4. Wear willcause the profiles of the contacting bodies to change during thetest. If wear occurs, the size of the non-conforming contacts(for
36、 example, flat on cylindrical, cylindrical on cylindrical,sphere on flat, and so on) will typically increase.3.3.11 partial slipThe condition for which only a portionof the interface of the contacting bodies experience relative slipover a complete cycle, as illustrated in Fig. 1.3.3.12 plain fatigue
37、Often used to describe fatigue withoutpresence of fretting.3.3.13 reciprocating slidingThe condition when the con-tact area at the two extremes of the cycle do not overlap, asillustrated in Fig. 1.4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.E2789 102
38、3.3.13.1 DiscussionUnder fretting conditions, at least aportion of the contact areas always overlap at the extremes ofthe cycle.3.3.14 relative slipThe amount of tangential displacementbetween a point on the interface of one body and a point on thesurface of the second body.3.3.14.1 DiscussionThe po
39、int on one of the bodies servesas a reference, which is often defined as the location when thetwo bodies first come into contact under application of thenormal pressure at the interface. The relative slip may bedefined as a local or remote reference. Fundamentally, a localmeasure is desired, however
40、, experimentally a remote displace-ment is measured and in many times controlled.3.3.15 slipLocal movement of surfaces in contact.3.3.16 tangential forceForce acting parallel to the contactinterface.4. Significance and Use4.1 Fretting fatigue tests are used to determine the effects ofseveral frettin
41、g parameters on the fatigue lives of metallicmaterials. Some of these parameters include differing materi-als, relative displacement amplitudes, normal force at thefretting contact, alternating tangential force, the contact geom-etry, surface integrity parameters such as finish, and theenvironment.
42、Comparative tests are used to determine theeffectiveness of palliatives on the fatigue life of specimens withwell-controlled boundary conditions so that the mechanics ofthe fretting fatigue test can be modeled. Generally, it is usefulto compare the fretting fatigue response to plain fatigue toobtain
43、 knockdown or reduction factors from fretting fatigue.The results may be used as a guide in selecting materialcombinations, design stress levels, lubricants, and coatings toalleviate or eliminate fretting fatigue concerns in new orexisting designs. However, due to the synergisms of fatigue,wear, and
44、 corrosion on the fretting fatigue parameters, extremecare should be exercised in the judgment to determine if thetest conditions meet the design or system conditions.4.2 For data to be comparable, reproducible, and correlatedamongst laboratories and relevant to mimic fretting in anapplication, all
45、parameters critical to the fretting fatigue life ofthe material in question will need to be replicated. Becausealterations in environment, metallurgical properties, frettingloading (controlled forces and displacements), compliance ofthe test system, etc. can affect the response, no generalguidelines
46、 exist to quantitatively ascertain what the effect willbe on the specimen fretting fatigue life if a single parameter isvaried. To assure test results can be correlated and reproduced,all material variables, testing information, physical procedures,and analytical procedures should be reported in a m
47、anner thatis consistent with good current test practices.4.3 Because of the wear phenomenon involved in fretting,idealized contact conditions from which the fretting contactarea and pressure may be calculated exist only at the onset ofthe test. Although it is still possible to calculate an averagefr
48、etting pressure using the initial contact area, the pressurewithin the contact area may vary considerably.4.4 Results of the fretting fatigue tests may be suitable forapplication to design when the test conditions adequatelymimic the design service conditions.5. Background5.1 Interfacial Conditions:
49、When designing a test program to mimic the design serviceconditions, one must first identify whether the interface con-ditions are partial slip or gross slip. This will help determinewhich type of fretting fatigue test may be more relevant. In Fig.2, a running condition fretting map is shown (2). Two primaryvariables in fretting are the normal force and displacementamplitude. The latter is linearly related to the tangential forceamplitude under partial slip conditions. On this map, threefretting regimes can be identified: the partial slip regime (PS
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1