1、Designation: D 6873 03Standard Practice forBearing Fatigue Response of Polymer Matrix CompositeLaminates1This standard is issued under the fixed designation D 6873; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides instructions for modifying staticbearing test methods to determine the fatigue behavior ofcomposite
3、materials subjected to cyclic bearing forces. Thecomposite material forms are limited to continuous-fiber rein-forced polymer matrix composites in which the laminate isboth symmetric and balanced with respect to the test direction.The range of acceptable test laminates and thicknesses aredescribed i
4、n 8.2.1.2 This practice supplements Test Method D 5961/D 5961M with provisions for testing specimens under cyclicloading. Several important test specimen parameters (for ex-ample, fastener selection, fastener installation method, andfatigue force/stress ratio) are not mandated by this practice;howev
5、er, repeatable results require that these parameters bespecified and reported.1.3 This practice is limited to test specimens subjected toconstant amplitude uniaxial loading, where the machine iscontrolled so that the test specimen is subjected to repetitiveconstant amplitude force (stress) cycles. E
6、ither engineeringstress or applied force may be used as a constant amplitudefatigue variable. The repetitive loadings may be tensile, com-pressive, or reversed, depending upon the test specimen andprocedure utilized.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separ
7、ately as standard. Within the text theinch-pound units are shown in brackets. The values stated ineach system are not exact equivalents; therefore, each systemmust be used independently of the other. Combining valuesfrom the two systems may result in nonconformance with thestandard.1.5 This standard
8、 does not purport to address all of thesafety concerns, 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
9、Standards:D 883 Terminology Relating to Plastics2D 3878 Terminology for Composite Materials3D 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite Materials3D 5961/D 5961M Test Method for Bearing Response ofPolymer Matrix Composite Lami
10、nates3E 4 Practices for Force Verification of Testing Machines4E 6 Terminology Relating to Methods of Mechanical Test-ing4E 122 Practice for Calculating Sample Size to Estimate,with a Specified Tolerable Error, the Average for Charac-teristic of a Lot or Process5E 177 Practice for Use of the Terms P
11、recision and Bias inASTM Test Methods5E 456 Terminology Relating to Quality and Statistics5E 467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing System4E 739 Practice for Statistical Analysis of Linear or Linear-ized Stress-Life (S-N) and Strain-Life (e-N)
12、 Fatigue Data4E 1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in Databases3E 1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases3E 1823 Terminology Relating to Fatigue and Fracture Test-ing43. Terminology3.1 Definit
13、ionsTerminology D 3878 defines terms relatingto high-modulus fibers and their composites. TerminologyD 883 defines terms relating to plastics. Terminology E 6defines terms relating to mechanical testing. TerminologyE 1823 defines terms relating to fatigue. Terminology E 456and Practice E 177 define
14、terms relating to statistics. In the1This practice is under the jurisdiction of ASTM Committee D30 on CompositeMaterials and is the direct responsibility of Subcommittee D30.05 on Structural TestMethods.Current edition approved March 10, 2003. Published April 2003.2Annual Book of ASTM Standards, Vol
15、 08.01.3Annual Book of ASTM Standards, Vol 15.03.4Annual Book of ASTM Standards, Vol 03.01.5Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.event of a conflict between terms, Terminology D 387
16、8 shallhave precedence over the other standards.NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the following ASTM standard sym-bology for fundamental dimensions, shown within
17、square brackets: Mfor mass, L for length, T for time, u for thermodynamic temperature,and nd for non-dimensional quantities. Use of these symbols is restrictedto analytical dimensions when used with square brackets, as the symbolsmay have other definitions when used without the brackets.3.2 Definiti
18、ons of Terms Specific to This Standard:3.2.1 bearing force, P MLT-2, nthe total force carried bya bearing coupon.3.2.2 constant amplitude loading, nin fatigue, a loadingin which all of the peak values of force (stress) are equal andall of the valley values of force (stress) are equal.3.2.3 fatigue l
19、oading transition, nin the beginning offatigue loading, the number of cycles before the force (stress)reaches the desired peak and valley values.3.2.4 force (stress) ratio, R nd, nin fatigue loading, theratio of the minimum applied force (stress) to the maximumapplied force (stress).3.2.5 frequency,
20、 f T-1, nin fatigue loading, the numberof force (stress) cycles completed in 1 s (Hz).3.2.6 hole elongation, D L, nthe permanent change inhole diameter in a bearing coupon caused by damage forma-tion, equal to the difference between the hole diameter in thedirection of the bearing force after a pres
21、cribed loading and thehole diameter prior to loading.3.2.7 nominal value, na value, existing in name only,assigned to a measurable property for the purpose of conve-nient designation. Tolerances may be applied to a nominalvalue to define an acceptable range for the property.3.2.8 peak, nin fatigue l
22、oading, the occurrence where thefirst derivative of the force (stress) versus time changes frompositive to negative sign; the point of maximum force (stress)in constant amplitude loading.3.2.9 residual strength, ML-1T-2, nthe value of force(stress) required to cause failure of a specimen under quasi
23、-static loading conditions after the specimen is subjected tofatigue loading.3.2.10 run-out, nin fatigue, an upper limit on the numberof force cycles to be applied.3.2.11 spectrum loading, nin fatigue, a loading in whichthe peak values of force (stress) are not equal or the valleyvalues of force (st
24、ress) are not equal (also known as variableamplitude loading or irregular loading).3.2.12 valley, nin fatigue loading, the occurrence wherethe first derivative of the force (stress) versus time changesfrom negative to positive sign; the point of minimum force(stress) in constant amplitude loading.3.
25、2.13 wave form, nthe shape of the peak-to-peak varia-tion of the force (stress) as a function of time.3.3 Symbols:d = fastener or pin diameterD = specimen hole diameterh = specimen thicknessk = calculation factor used in bearing equations todistinguish single-fastener tests from double-fastener test
26、sLg= extensometer gage lengthN = number of constant amplitude cyclesP = force carried by specimend = crosshead translationD = hole elongationsalt= alternating bearing stress during fatigue loadingsbrm= maximum cyclic bearing stress magnitude, givenby the greater of the absolute values of smaxandsmin
27、smax= value of stress corresponding to the peak value offorce (stress) under constant amplitude loadingsmaxq= value of stress corresponding to the peak value offorce (stress) under quasi-static loading for mea-surement of hole elongation, given by the greaterof the absolute values of smaxand 0.5 3sm
28、insmean= mean bearing stress during fatigue loadingsmin= value of stress corresponding to the valley valueof force (stress) under constant amplitude loadingsminq= value of stress corresponding to the valley valueof force (stress) under quasi-static loading formeasurement of hole elongation, given by
29、 thegreater of the absolute values of sminand 0.5 3smax4. Summary of Practice4.1 In accordance with Test Method D 5961/D 5961M, butunder constant amplitude fatigue loading, perform a uniaxialtest of a bearing specimen. Cycle the specimen betweenminimum and maximum axial forces (stresses) at a specif
30、iedfrequency. At selected cyclic intervals, determine the holeelongation either through direct measurement or from a force(stress) versus deformation curve obtained by quasi-staticallyloading the specimen through one tension-compression cycle.Determine the number of force cycles at which failure occ
31、urs,or at which a predetermined hole elongation is achieved, for aspecimen subjected to a specific force (stress) ratio and bearingstress magnitude.5. Significance and Use5.1 This practice provides supplemental instructions forusing Test Method D 5961/D 5961M to obtain bearing fatiguedata for materi
32、al specifications, research and development,material design allowables, and quality assurance. The primaryproperty that results is the fatigue life of the test specimenunder a specific loading and environmental condition. Repli-cate tests may be used to obtain a distribution of fatigue life forspeci
33、fic material types, laminate stacking sequences, environ-ments, and loading conditions. Guidance in statistical analysisof fatigue data, such as determination of linearized stress life(S-N) curves, can be found in Practice E 739.5.2 This practice can be utilized in the study of fatiguedamage in a po
34、lymer matrix composite bearing specimen. Theloss in strength associated with fatigue damage may bedetermined by discontinuing cyclic loading to obtain the staticstrength using Test Method D 5961/D 5961M.NOTE 2This practice may be used as a guide to conduct spectrumD6873032loading. This information c
35、an be useful in the understanding of fatiguebehavior of composite structures under spectrum loading conditions, but isnot covered in this standard.5.3 Factors that influence bearing fatigue response and shalltherefore be reported include the following: material, methodsof material fabrication, accur
36、acy of lay-up, laminate stackingsequence and overall thickness, specimen geometry, specimenpreparation (especially of the hole), fastener-hole clearance,fastener type, fastener geometry, fastener installation method,fastener torque (if appropriate), countersink depth (if appropri-ate), specimen cond
37、itioning, environment of testing, type ofmating material, number of fasteners, type of support fixture,specimen alignment and gripping, test frequency, force (stress)ratio, bearing stress magnitude, void content, and volumepercent reinforcement. Properties that result include the fol-lowing:5.3.1 Ho
38、le elongation versus fatigue life curves for selectedbearing stress values.5.3.2 Bearing stress versus hole elongation curves at se-lected cyclic intervals.5.3.3 Bearing stress versus fatigue life curves for selectedhole elongation values.6. Interferences6.1 Force (Stress) RatioResults are affected
39、by the force(stress) ratio under which the tests are conducted. Specimensloaded under tension-tension or compression-compressionforce (stress) ratios develop hole elongation damage on oneside of the fastener hole, whereas specimens loaded undertension-compression force (stress) ratios can develop da
40、mageon both sides of the fastener hole. Experience has demonstratedthat reversed (tension-compression) force ratios are critical forbearing fatigue-induced hole elongation, with fully reversedtension-compression (R = 1) being the most critical forceratio (1-3).66.2 Fastener Torque/Pre-loadResults ar
41、e affected by theinstalled fastener pre-load (clamping pressure). Laminates canexhibit significant differences in hole elongation behavior andfailure mode due to changes in fastener pre-load under bothtensile and compressive loading. Experience has demonstratedthat low fastener torque/clamp-up is ge
42、nerally critical forbearing fatigue-induced hole elongation. (1, 2, 4). It should benoted that in some instances, low torque testing of single shearspecimens has proven unsuccessful due to loosening of thefastener nut/collar during fatigue loading caused by deforma-tion of the pin/bolt.6.3 Debris Bu
43、ildupResults are affected by the buildup offiber-matrix debris resulting from damage associated with holeelongation. The presence of debris may mask the actual degreeof hole elongation, and can increase both the friction force-transfer and temperature within the specimen under fatigueloading. Experi
44、ence has demonstrated that non-reversed forceratios (especially compression-compression force ratios) ex-hibit greater debris buildup than reversed force ratios, and thathole elongation can be most accurately determined if debris isremoved prior to hole elongation measurement (1,2,4). There-fore, cl
45、eaning the specimen hole(s) prior to measurement isrecommended to ensure conservatism of hole elongation data.6.4 EnvironmentResults are affected by the environmen-tal conditions under which the tests are conducted. Laminatestested in various environments can exhibit significant differ-ences in both
46、 hole elongation behavior and failure mode.Experience has demonstrated that elevated temperature, humidenvironments are generally critical for bearing fatigue-inducedhole elongation (1-4). However, critical environments must beassessed independently for each material system, stackingsequence, and to
47、rque condition tested.6.5 Fastener-Hole ClearanceBearing fatigue test resultsare affected by the clearance arising from the differencebetween hole and fastener diameters. Small changes in clear-ance can change the number of cycles at which hole elongationinitiates, and can affect damage propagation
48、behavior (1). Forthis reason, both the hole and fastener diameters must beaccurately measured and recorded. A typical aerospace toler-ance on fastener-hole clearance is +75/-0 m +0.003/-0.000in. for structural fastener holes.6.6 Fastener Type/Hole PreparationResults are affectedby the geometry and t
49、ype of fastener utilized (for example,lockbolt, blind bolt) and the fastener installation procedures.Results are also affected by the hole preparation procedures.6.7 Method of Hole Elongation MeasurementResults areaffected by the method used to monitor hole elongation. Directmeasurement permits an accurate examination of the extent ofdamage and elongation local to the hole surface. However, themeasured elongation may not be uniform through the thicknessof the laminate and may be uneven along the surface of thehole. Additionally, fasteners suc
