1、Designation: D6873/D6873M 08D6873/D6873M 08 (Reapproved 2014)Standard Practice forBearing Fatigue Response of Polymer Matrix CompositeLaminates1This standard is issued under the fixed designation D6873/D6873M; the number immediately following the designation indicates theyear of original adoption or
2、, in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides instructions for modifying static bearing test methods t
3、o determine the fatigue behavior of compositematerials subjected to cyclic bearing forces. The composite material forms are limited to continuous-fiber reinforced polymermatrix composites in which the laminate is both symmetric and balanced with respect to the test direction. The range of acceptable
4、test laminates and thicknesses are described in 8.2.1.2 This practice supplements Test Method D5961/D5961M with provisions for testing specimens under cyclic loading. Severalimportant test specimen parameters (for example, fastener selection, fastener installation method, and fatigue force/stress ra
5、tio) arenot mandated by this practice; however, repeatable results require that these parameters be specified and reported.1.3 This practice is limited to test specimens subjected to constant amplitude uniaxial loading, where the machine is controlledso that the test specimen is subjected to repetit
6、ive constant amplitude force (stress) cycles. Either engineering stress or applied forcemay be used as a constant amplitude fatigue variable. The repetitive loadings may be tensile, compressive, or reversed, dependingupon the test specimen and procedure utilized.1.4 The values stated in either SI un
7、its or inch-pound units are to be regarded separately as standard. Within the text theinch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system mustbe used independently of the other. Combining values from the two systems may result in
8、 nonconformance with the standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitati
9、ons prior to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsD5961/D5961M Test Method for Bearing
10、Response of Polymer Matrix Composite LaminatesE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot orProcessE177 Practi
11、ce for Use of the Terms Precision and Bias in ASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE467 Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing SystemE739 Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and
12、 Strain-Life (-N) Fatigue DataE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases1 This practice is under the jurisdiction of ASTM Committee D30 on Compos
13、ite Materials and is the direct responsibility of Subcommittee D30.05 on Structural TestMethods.Current edition approved March 1, 2008Aug. 1, 2014. Published April 2008September 2014. Originally approved in 2003. Last previous edition approved in 20032008as D6873D6873/D6873M 08.-03. DOI: 10.1520/D68
14、73_D6873M-08.10.1520/D6873_D6873M-08R14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not
15、an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate.
16、 In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1823 Terminology Relating to Fatigue and Fracture Testing3. Terminol
17、ogy3.1 DefinitionsTerminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883defines terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminology E1823 defines termsrelating to fatigue. Terminology E456 and Practice E
18、177 define terms relating to statistics. In the event of a conflict between terms,Terminology D3878 shall have precedence over the other standards.NOTE 1If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter symbol) infundamental di
19、mension form, using the following ASTM standard symbology for fundamental dimensions, shown within square brackets: M for mass,L for length, T for time, for thermodynamic temperature, and nd for non-dimensional quantities. Use of these symbols is restricted to analyticaldimensions when used with squ
20、are brackets, as the symbols may have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 bearing force, P MLT-2, nthe total force carried by a bearing coupon.3.2.2 constant amplitude loading, nin fatigue, a loading in which all of the peak value
21、s of force (stress) are equal and all ofthe valley values of force (stress) are equal.3.2.3 fatigue loading transition, nin the beginning of fatigue loading, the number of cycles before the force (stress) reachesthe desired peak and valley values.3.2.4 force (stress) ratio, R nd, nin fatigue loading
22、, the ratio of the minimum applied force (stress) to the maximum appliedforce (stress).3.2.5 frequency, f T-1, nin fatigue loading, the number of force (stress) cycles completed in 1 s (Hz).3.2.6 hole elongation, L, nthe permanent change in hole diameter in a bearing coupon caused by damage formatio
23、n, equalto the difference between the hole diameter in the direction of the bearing force after a prescribed loading and the hole diameterprior to loading.3.2.7 nominal value, na value, existing in name only, assigned to a measurable property for the purpose of convenientdesignation. Tolerances may
24、be applied to a nominal value to define an acceptable range for the property.3.2.8 peak, nin fatigue loading, the occurrence where the first 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 res
25、idual strength, ML-1T-2, nthe value of force (stress) required to cause failure of a specimen under quasi-staticloading conditions after the specimen is subjected to fatigue loading.3.2.10 run-out, nin fatigue, an upper limit on the number of force cycles to be applied.3.2.11 spectrum loading, nin f
26、atigue, a loading in which the peak values of force (stress) are not equal or the valley valuesof force (stress) are not equal (also known as variable amplitude loading or irregular loading).3.2.12 valley, nin fatigue loading, the occurrence where the first derivative of the force (stress) versus ti
27、me changes fromnegative to positive sign; the point of minimum force (stress) in constant amplitude loading.3.2.13 wave form, nthe shape of the peak-to-peak variation of the force (stress) as a function of time.3.3 Symbols:d = fastener or pin diameterD = specimen hole diameterh = specimen thicknessk
28、 = calculation factor used in bearing equations to distinguish single-fastener tests from double-fastener testsLg = extensometer gage lengthN = number of constant amplitude cyclesP = force carried by specimen = crosshead translation = hole elongationalt = alternating bearing stress during fatigue lo
29、adingbrm = maximum cyclic bearing stress magnitude, given by the greater of the absolute values of max and minmax = value of stress corresponding to the peak value of force (stress) under constant amplitude loadingmaxq = value of stress corresponding to the peak value of force (stress) under quasi-s
30、tatic loading for measurement of holeelongation, given by the greater of the absolute values of max and 0.5 minmean = mean bearing stress during fatigue loadingmin = value of stress corresponding to the valley value of force (stress) under constant amplitude loadingminq = value of stress correspondi
31、ng to the valley value of force (stress) under quasi-static loading for measurement of holeelongation, given by the greater of the absolute values of min and 0.5 maxD6873/D6873M 08 (2014)24. Summary of Practice4.1 In accordance with Test Method D5961/D5961M, but under constant amplitude fatigue load
32、ing, perform a uniaxial test ofa bearing specimen. Cycle the specimen between minimum and maximum axial forces (stresses) at a specified frequency. Atselected cyclic intervals, determine the hole elongation either through direct measurement or from a force (stress) versusdeformation curve obtained b
33、y quasi-statically loading the specimen through one tension-compression cycle. Determine thenumber of force cycles at which failure occurs, or at which a predetermined hole elongation is achieved, for a specimen subjectedto a specific force (stress) ratio and bearing stress magnitude.5. Significance
34、 and Use5.1 This practice provides supplemental instructions for using Test Method D5961/D5961M to obtain bearing fatigue data formaterial specifications, research and development, material design allowables, and quality assurance. The primary property thatresults is the fatigue life of the test spe
35、cimen under a specific loading and environmental condition. Replicate tests may be usedto obtain a distribution of fatigue life for specific material types, laminate stacking sequences, environments, and loadingconditions. Guidance in statistical analysis of fatigue data, such as determination of li
36、nearized stress life (S-N) curves, can be foundin Practice E739.5.2 This practice can be utilized in the study of fatigue damage in a polymer matrix composite bearing specimen. The loss instrength associated with fatigue damage may be determined by discontinuing cyclic loading to obtain the static s
37、trength using TestMethod D5961/D5961M.NOTE 2This practice may be used as a guide to conduct spectrum loading. This information can be useful in the understanding of fatigue behaviorof composite structures under spectrum loading conditions, but is not covered in this standard.5.3 Factors that influen
38、ce bearing fatigue response and shall therefore be reported include the following: material, methods ofmaterial fabrication, accuracy of lay-up, laminate stacking sequence and overall thickness, specimen geometry, specimenpreparation (especially of the hole), fastener-hole clearance, fastener type,
39、fastener geometry, fastener installation method, fastenertorque (if appropriate), countersink depth (if appropriate), specimen conditioning, environment of testing, time at temperature, typeof mating material, number of fasteners, type of support fixture, specimen alignment and gripping, test freque
40、ncy, force (stress)ratio, bearing stress magnitude, void content, and volume percent reinforcement. Properties that result include the following:5.3.1 Hole elongation versus fatigue life curves for selected bearing stress values.5.3.2 Bearing stress versus hole elongation curves at selected cyclic i
41、ntervals.5.3.3 Bearing stress versus fatigue life curves for selected hole elongation values.6. Interferences6.1 Force (Stress) RatioResults are affected by the force (stress) ratio under which the tests are conducted. Specimens loadedunder tension-tension or compression-compression force (stress) r
42、atios develop hole elongation damage on one side of the fastenerhole, whereas specimens loaded under tension-compression force (stress) ratios can develop damage on both sides of the fastenerhole. Experience has demonstrated that reversed (tension-compression) force ratios are critical for bearing f
43、atigue-induced holeelongation, with fully reversed tension-compression (R = 1) being the most critical force ratio (1-3).36.2 Loading FrequencyResults are affected by the loading frequency at which the test is conducted. High cyclic rates mayinduce heating due to friction within the joint, and may c
44、ause variations in specimen temperature and properties of the composite.Varying the cyclic frequency during the test is generally not recommended, as the response may be sensitive to the frequencyutilized and the resultant thermal history.6.3 Fastener Torque/Pre-loadResults are affected by the insta
45、lled fastener pre-load (clamping pressure). Laminates canexhibit significant differences in hole elongation behavior and failure mode due to changes in fastener pre-load under both tensileand compressive loading. Experience has demonstrated that low fastener torque/clamp-up is generally critical for
46、 bearingfatigue-induced hole elongation. (1, 2, 4). It should be noted that in some instances, low torque testing of single shear specimenshas proven unsuccessful due to loosening of the fastener nut/collar during fatigue loading caused by deformation of the pin/bolt.6.4 Debris BuildupResults are af
47、fected by the buildup of fiber-matrix debris resulting from damage associated with holeelongation. The presence of debris may mask the actual degree of hole elongation, and can increase both the friction force transferand temperature within the specimen under fatigue loading. Experience has demonstr
48、ated that non-reversed force ratios (especiallycompression-compression force ratios) exhibit greater debris buildup than reversed force ratios, and that hole elongation can bemost accurately determined if debris is removed prior to hole elongation measurement (1, 2, 4). Therefore, cleaning the speci
49、menhole(s) prior to measurement is recommended to ensure conservatism of hole elongation data.6.5 EnvironmentResults are affected by the environmental conditions under which the tests are conducted. Laminates testedin various environments can exhibit significant differences in both hole elongation behavior and failure mode. Experience has3 The boldface numbers in parentheses refer to the list of references at the end of this standard.D6873/D6873M 08 (2014)3demonstrated that elevated temperature, humid environments
