1、Designation: E238 12E238 17aStandard Test Method forPin-Type Bearing Test of Metallic Materials1This standard is issued under the fixed designation E238; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers a pin-type bearing test of metallic materials to determine bearing yield strength and bearingstrength.NOTE 1Th
3、e presence of incidental lubricants on the bearing surfaces may significantly lower the value of bearing yield strength obtained by thismethod.1.2 UnitsThe values stated in inch-pound units are to be regarded as standard. The values given in parentheses aremathematical conversions to SI units that a
4、re provided for information only and are not considered standard.1.3 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 appl
5、icability of regulatorylimitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the W
6、orld Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE83 Practice for Verification and Classification of Extensometer SystemsB769 T
7、est Method for Shear Testing of Aluminum AlloysB831 Test Method for Shear Testing of Thin Aluminum Alloy Products3. Terminology3.1 Definitions:3.1.1 bearing areathe product of the pin diameter and specimen thickness.3.1.2 bearing stressthe force per unit of bearing area.3.1.3 bearing strainthe ratio
8、 of the bearing deformation of the bearing hole, in the direction of the applied force, to the pindiameter.3.1.4 bearing yield strengththe bearing stress at which a material exhibits a specified limiting deviation from theproportionality of bearing stress to bearing strain.3.1.5 bearing strengththe
9、maximum bearing stress which a material is capable of sustaining.3.1.6 edge distancethe distance from the edge of a bearing specimen to the center of the hole in the direction of applied force(Fig. 1).3.1.7 edge distance ratiothe ratio of the edge distance to the pin diameter.3.1.8 For definitions o
10、f other terms see Terminology E6.1 This test method is under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.04 on Uniaxial Testing.Current edition approved June 1, 2012April 1, 2017. Published August 2012April 2017. Originally approv
11、ed in 1964. Last previous edition approved in 20082017 asE238 84 (2008).E238 17. DOI: 10.1520/E0238-12.10.1520/E0238-17A.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
12、 to the standards Document Summary page on the ASTM website.This document is not 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 chan
13、ges accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Bar
14、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 The data obtained from the bearing test are the bearing ultimate and yield strength. The data provide a measure of theload-carrying capacity of a material edge loaded with a close-fitting cylindri
15、cal pin through a hole located a specific distance fromthe specimen edge.4.2 Bearing properties are useful in the comparison of materials and design of structures under conditions where the pin is notrestricted.5. Apparatus5.1 Testing MachinesMachines used for bearing testing shall conform to the re
16、quirements of Practices E4.5.2 Gripping DevicesVarious types of gripping devices may be used to transmit the measured load applied by the testingmachine to the test specimens.Any grips considered to apply the load axially for tension testing, such as pin connections or wedgegrips, are satisfactory f
17、or use in bearing testing.5.3 PinThe bearing load is generally applied to the specimen through a close-fitting cylindrical pin. The pin shall be harderand stronger than the material being tested. Restraint of movement of the specimen where it is in contact with the pin has aconsiderable effect upon
18、the hole deformation obtained as a function of the load applied. Close control of surface conditions onboth the specimen and pin is needed to assure reproducible results. The pins used should be uniform in diameter, hardness, andsurface roughness. Pin materials, hardness, and surface roughness as sh
19、own in Table 1 are recommended for testing the materialslisted. The pin should be checked carefully after each test to ensure that no metallic residue adheres to it and that it is both straightand undeformed. If there is any question regarding its quality it should be replaced.5.4 Pin SupportThe jig
20、 supporting the pin should position the pin concentric with the hole in the specimen. It should notrestrain the thickening of the specimen as the load from the pin deforms the hole. Bending of the pin should be kept to a minimumby having the jig support the pin close to the specimen. Fig. 2 and Fig.
21、 3 show examples of the types of jig that have been usedand are considered satisfactory.FIG. 1 Bearing Test SpecimenTABLE 1 Characteristics of Pin for Various Materials TestedMaterial Tested Material RockwellHardness Surface Roughness, in. (m) (avg)Aluminum alloys hardened steel C60 to 64 4 to 8 (0.
22、1 to 0.2 m)Beryllium alloys hardened steel C60 to 64 4 to 8 (0.1 to 0.2 m)Copper alloys hardened steel C60 to 64 4 to 8 (0.1 to 0.2 m)Magnesium alloys hardened steel C60 to 64 4 to 8 (0.1 to 0.2 m)Zinc alloys hardened steel C60 to 64 4 to 8 (0.1 to 0.2 m)E238 17a25.5 ExtensometersExtensometers used
23、for measuring the bearing deformation shall comply with the requirements for ClassB-2 or better as described in Practice E83. The bearing deformation measurement shall be made in a manner to obtain the axialbearing deformation with a minimum of other deformations being included such as the bending o
24、f the pin and tensile strain in theFIG. 2 Bearing Test Fixture Used on Aluminum SheetFIG. 3 Schematic Drawing of Bearing Deformation Transfer DeviceE238 17a3specimen. Fig. 2 shows an adaptation of a Templin extensometer system to record bearing deformation. Fig. 3 illustrates amechanism that can be
25、used to transfer the bearing deformation so it can be measured with the same extensometers used for tensiontesting. A method of measuring bearing deformation featuring two linear differential transformers is shown in Fig. 4.6. Test Specimens6.1 Specimen GeometryThe specimen shall be a flat sheet typ
26、e, with the full thickness of the product being used if possible.If the specimen is too thick in relation to the pin diameter, the pin is likely to bend considerably or break before the bearing strengthis obtained. If a specimen is too thin, buckling may occur. A ratio of pin diameter to specimen th
27、ickness of from 2 to 4 has beenused to avoid both conditions. The hole should have approximately the same diameter as for the intended use. For example, if thebearing test results are being used to obtain data for a riveted part, a hole 316 in. or 14 in. (5 or 6 mm) in diameter would be suitable,whi
28、le for a bolted assembly, a larger hole might be desirable. A difference in test results may be obtained with holes of differentdiameters. The width of the specimen shall be 4 to 8 times the hole diameter. diameter of the hole. A wider specimen encouragesthe intended shear-out failure mode. The edge
29、 distance ratio shall be specified and the edge distance held within a tolerance of62 %. Edge distance ratios of 1.50 and 2.00 are commonly used (see Fig. 1).Aclose fit between the specimen and pin is required,since a loose fit will tend to give lower results. The diameter of the hole shall not exce
30、ed the pin diameter by more than 0.001 in.(0.02 mm). The free length between the point of loading and the center of the test pin hole shall be greater than 1.5 times thespecimen width. The total length of the test specimen is not critical and may depend on the method used to grip the specimen. Fig.1
31、 shows a bearing test specimen commonly used.6.1.1 Specimen orientationThe measured bearing properties can depend on the specimen orientation and the direction inwhich the load is applied relative to the grain flow in the specimen. The specimen orientation and the loading direction shall beidentifie
32、d by the following system.6.1.2 The reference grain directions for rectangular shaped products are indicated in Fig. 5. These are suitable for sheet, plate,extrusions, forgings, and other shapes of nonsymmetrical grain flow.6.1.1 Specimen orientationThe two-letter specimen orientation codes are also
33、 shown measured bearing properties can dependon the specimen orientation and the direction in Fig. 5 to describe the specimen orientation and loading directions. which the loadis applied relative to the grain flow in the product from which the specimen is extracted. The specimen orientation and the
34、loadingdirection shall be identified by a two-letter code as illustrated in Fig. 5. The first letter designates the normal to the expected shearplane. The second letter designates the direction of force application. The most commonly used specimen orientations are T-L andL-T for thin products. This
35、orientation code is identical to that used for cylindrical and flat shear specimens in Test Methods B769and B831.FIG. 4 Autographic Measurement of Bearing DeformationE238 17a46.1.2 The orientation codes for rectangular shaped products are indicated in Fig. 5a. The product axes are in the longitudina
36、l(L), transverse (T), and short (S) directions. These are suitable for sheet, plate, extrusions, forgings, and other shapes having arectangle form. The most commonly used specimen orientations are T-L and L-T for thin products. Fig. 5b shows the orientationcodes for cylindrical product forms such as
37、 rod, tube, and pipe, where the product axes are in the longitudinal (L), radial (R), andcircumferential (C) directions.6.2 Specimen PreparationAflat specimen with a hole normal to the face shall be used.Asmooth, round hole with a minimumof cold work on the surface must be obtained. The finished hol
38、e is generally bored, reamed, or ground as a final operation to obtainthe desired degree of roundness.Any burr on the periphery of the hole is indicative of a cold-worked surface on the hole and shouldbe avoided. Removal of the burr will not eliminate the cold work.(a)(b)FIG. 5 Grain Orientations an
39、d Pin Bearing Specimen Orientation Codes for Pin Bearing Specimens Taken from (a) Rectangular Shapesand (b) cylindrical shapes.E238 17a57. Procedure7.1 Measurement of SpecimensMeasure the actual thickness of the specimen and the pin diameter, preferably reading to atleast the nearest 0.5 % of the di
40、mension measured, and in any case to at least the nearest 0.001 in. (0.02 mm). Calculate the stresson the basis of the measured dimensions. Measure the edge distance to the nearest 0.01 in. (0.2 mm).7.2 CleaningClean the specimen, pin, and adjacent areas of the jig of all foreign matter and contamin
41、ation, especiallylubricants, prior to assembly. Keep in that condition until the test is completed. It has been found that oil from human fingerstouching the pin significantly lowers the results of the test. A handle on the pin has been found to help in keeping fingers fromtouching the test area of
42、the pin. Recommended methods of cleaning are given in the Appendix X1.3 The cleaners recommendedfor the materials given in the Appendix X1 are generally satisfactory for cleaning the pin and fixtures, too.7.3 TestingLoad the specimen and obtain simultaneous readings of the load and bearing deformati
43、on.Any convenient methodof load application and system of strain recording may be used. Autographic strain recording equipment can be readily adaptedto measure bearing deformation (see Figs. 1-6).7.4 Conduct the tests at a controlled rate of straining or loading. The recommended rate for metallic ma
44、terials is 0.05 bearingstrain per minute. If a testing speed other than a strain rate of 0.05/min is used, report this fact.8. Determination of Bearing Yield Strength8.1 Determine the bearing yield strength from a graph of the bearing load versus bearing deformation. Fig. 6 is an illustrationof such
45、 a graph. Calculate the yield strength from the load at an offset from the initial straight-line portion of the graph equal to2 % of the pin diameter. Calculate the stress by dividing the load by the bearing area.9. Determination of Bearing Strength9.1 Calculate the bearing strength by dividing the
46、maximum load carried by the specimen by the bearing area.10. Determination of Fracture Mode10.1 Determine the fracture mode of the specimen according to Fig. 7 and the descriptions of the depicted fracture modes.10.1.1 Crushing (C): Deformation to the test pin hole without fracture3 Stickley, G. W.,
47、 and Moore, A. A., “Effects of Lubrication and Pin Surface on Bearing Strengths of Aluminum and Magnesium Alloys,” MTRSA, Materials Researchbearing test; bearing yield strength; metallic materials; pin-typeFIG. 7 Bearing Test Specimen Fracture Modes and Corresponding Descriptions of FailureE238 17a7
48、APPENDIX(Nonmandatory Information)X1. RECOMMENDED METHODS OF CLEANINGX1.1 Recommended methods of cleaning the bearing test specimen, pin, and support assembly to get uniform test results are givenin this Appendix. They are not intended to be exclusive but have been found adequate for the materials i
49、ndicated.X1.1.1 Aluminum AlloysUltrasonic cleaning in a suitable solvent such as acetone.X1.1.2 Magnesium AlloysChemical cleaning with a cleaner such as one consisting of 60 g of NaOH plus 10 g of Na3 PO4 12H2O/L of water at 180 to 200F.SUMMARY OF CHANGESCommittee E28 has identified the location of selected changes to this standard since the last issue(E23884(2008)E238)17) that may impact the use of this standard. (Approved April 1, 2017)(1) Minor revisions to improve clarity(1) Inclusion ofSection 10 a specimen orientation code in 6.
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