1、Designation: D732 17Standard Test Method forShear Strength of Plastics by Punch Tool1This standard is issued under the fixed designation D732; 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 p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the procedure for determiningthe she
3、ar strength of plastics in the form of sheets, plates, andmolded shapes in thicknesses from 1.27 to 12.7 mm (0.050 to0.500 in.).1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address a
4、ll 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.NOTE 1There is no known ISO equivalent to this standard.1.4 Th
5、is international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade
6、 (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD4000 Classification System for Specifying Plastic Materi-alsD5947 Test Methods for Physical Dimensions of SolidPlastics SpecimensE4 Practices for Force Verification of Testing MachinesE691
7、 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 shear strengththe maximum load required to shearthe specimen in such a manner that the moving portion of theload fixture has completely cleared the stationary portion,divid
8、ed by the sheared area. It is expressed in mega-pascals (orpounds-force per square inch) based on the area of the shearededge or edges.4. Significance and Use4.1 Shear strength obtained by the use of punch-type toolingis one of the recognized methods of comparing materials, orobtaining data for engi
9、neering design purposes, or both.However, it must be recognized that for end-use applicationsthere are likely to be many factors not taken into account in thistest method, such as stress-concentrating geometries and ratesof shear, which can profoundly affect the measured shearstrength. Moreover, the
10、 fact that the shear strength is calculatedby dividing the load by the area of the sheared edge (punchcircumference X specimen thickness) does not interpret asindicating the shear strength value so obtained is solely amaterial property, independent of thickness.4.2 For many materials, it is possible
11、 that there is aspecification that requires the use of this test method, but withsome procedural modifications that take precedence whenadhering to the specification. Therefore, it is advisable to referto that material specification before using this test method.Table 1 of Classification System D400
12、0 lists the ASTMmaterials standards that currently exist.5. Apparatus5.1 Testing MachineAny suitable testing machine of theconstant-rate-of-crosshead movement type. The testing ma-chine shall be equipped with the necessary drive mechanismfor imparting to the crosshead a uniform, controlled velocityw
13、ith respect to the base. The testing machine shall also beequipped with a load-indicating mechanism capable of show-ing the total compressive load carried by the test specimen.This mechanism shall be essentially free from inertia-lag at thespecified rate of testing and shall indicate the load with a
14、n1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved May 1, 2017. Published June 2017. Originallyapproved in 1943. Last previous edition approved in 2010 as D732 10. DOI
15、:10.1520/D0732-17.2For 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.*A Summary of Changes section appears at th
16、e end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for t
17、heDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1accuracy of 61 % of the indicated value or better. Theaccuracy of the testing machine shall be verified in accordancewith Practices E4.5.2 Shear To
18、olA shear tool of the punch type which is soconstructed that the specimen is rigidly clamped both to thestationary block and movable block so that it cannot bedeflected during the test. A suitable form of shear tool is shownin Fig. 1.5.3 MicrometersApparatus for measuring the thickness ofthe test sp
19、ecimen shall comply with the requirements of TestMethods D5947.6. Test Specimen6.1 The specimen shall consist of a 50-mm (2-in.) square ora 50.8-mm (2-in.) diameter disk cut from sheet material ormolded into this form. The thickness of the specimen is limitedfrom 1.27 and 12.7 mm (0.050 and 0.500 in
20、.). The upper andlower surfaces shall be parallel to each other and reasonablyflat. A hole approximately 11 mm (716 in.) in diameter shall bedrilled through the specimen at its center.6.2 A minimum of five specimens of each sample materialshall be tested. If fewer than five specimens are tested, the
21、report shall reflect that results are based on a modified versionof the standard.7. Conditioning7.1 Pre-Test ConditioningCondition the test specimens inaccordance with Procedure A of Practice D618 unless other-wise specified by contract or the relevant ASTM materialspecification. Conditioning time i
22、s specified as a minimum.Temperature and humidity tolerances shall be in accordancewith Section 7 of Practice D618 unless specified differently bycontract or material specification.7.2 Test ConditionsConduct the tests at the same tempera-ture and humidity used for conditioning with tolerances inacco
23、rdance with Section 7 of Practice D618 unless otherwisespecified by contract or the relevant ASTM material specifica-tion.8. Procedure8.1 Measure the thickness of each test specimen to thenearest 0.025 mm (0.001 in.) at a minimum of three points ona circle approximately 12.7 mm (0.500 in.) from its
24、center.Average the readings and record as the specimen thickness.8.2 Place the specimen over the 9.5-mm (38-in.) threadedpin of the punch and fasten it in place by securing the washerand nut tightly.NOTE 1In case of difficulty in obtaining hardened dowels and bushings, the entire shear tool may be m
25、ade from a fairly good grade of steel,eliminating all of the bushings shown. The actual working surfaces will wear faster than when hardened tool steel is used. When they show signs ofappreciable wear, the shear tool can then be bored out to take either hardened or unhardened bushings, depending upo
26、n which are available.FIG. 1 Punch-Type Shear Tool for Testing Specimens 0.127 to 12.7 mm (0.050 to 0.500 in.) in ThicknessD732 1728.3 Center the specimen and punch on the support fixtureand complete the assembly of the clamping fixture being sureto tighten the bolts securely.8.4 Load the test speci
27、men at a crosshead speed of 1.27 mm(0.05 in.)/min. The tolerances shall be 1.3 6 0.3 mm (0.050 60.010 in.)/min.8.5 Push the punch far enough through the specimen so thatthe sheared section clears the specimen proper. The specimenwill then be adjacent to the necked-down portion of the punch,and it ca
28、n then be readily removed from the tool.NOTE 2For thick specimens of some materials the punched-out piecetends to stick in the die. If the test is continued only to the point wheremaximum load has been developed and starts to fall off rapidly, thespecimen may be readily removed from both punch and d
29、ie.9. Calculation9.1 Calculate shear strength in mega pascals, MPa, (orpounds-force per square inch, psi), determined by dividing theload required to shear the specimen by the area of the shearededge, which shall be taken as the product of the thickness of thespecimen by the circumference of the pun
30、ch.10. Report10.1 Report the following information:10.1.1 Complete identification of the material tested, includ-ing type, source, manufacturers code number, form, principaldimensions, previous history, etc.,10.1.2 Method of test, type of test specimen, anddimensions,10.1.3 Atmospheric conditions in
31、 the test room,10.1.4 Conditioning procedure used,10.1.5 Diameter of punch,10.1.6 Load in newtons (or pounds-force) required to sheareach specimen, and the average value, and10.1.7 Shear strength in megapascals (or pounds-force persquare inch) for each specimen, the average value, and thestandard de
32、viation.11. Precision and Bias311.1 Table 1 is based on a round-robin test conducted in1983, in accordance with Practice E691, involving six materi-als tested by eleven laboratories. Each “test result” was theaverage of five individual determinations. Each laboratoryobtained one test result for each
33、 material. (WarningThefollowing explanations of r and R (11.2 11.2.3) are intendedonly to present a meaningful way of considering the approxi-mate precision of these test methods. The data given in Table1 should not be applied rigorously to the acceptance orrejection of materials, as those data are
34、specific to the roundrobin and may not be representative of other lots, conditions,materials, or laboratories. Users of this test method shouldapply the principles outlined in Practice E691 to generate dataspecific to their laboratory and materials, or between specificlaboratories. The principles of
35、 11.2 11.2.3 would then bevalid for such data.)11.2 Concept of r and R in Table 1If Srand SRhave beencalculated from a large enough body of data, and for test resultsthat were averages from testing five specimens for each testresult, then:11.2.1 RepeatabilityTwo test results obtained within onelabor
36、atory shall be judged not equivalent if they differ by morethan the r value for that material. The r value is the intervalrepresenting the critical difference between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laboratory.1
37、1.2.2 ReproducibilityTwo test results obtained by differ-ent laboratories shall be judged not equivalent if they differ bymore than the R value for that material. The R value is theinterval representing the critical difference between two testresults for the same material, obtained by different oper
38、atorsusing different equipment in different laboratories.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D20-1120.TABLE 1 Shear StrengthMaterialAValues Expressed in Units of Pound-Force per Square InchAverageThickness, in.Mean S
39、rBSRCrDRERIM 0.134 2900 32 155 92 439HDPE 0.071 3410 27 135 76 382Polyester 0.128 8580 57 278 163 788SMC 0.210 14 700 304 569 862 1610PolyesterF0.0104 10 200 384 1950 1080 5530PCTFEF0.0076 7900 528 2730 1490 7740AThe complete designations for the materials in Table 1 are: reaction injection molding
40、(RIM), high-density polyethylene (HDPE), sheet molding compound (SMC), andpolychlorotrifluoroethylene (PCTFE).BSris the within-laboratory standard deviation for the indicated material. It is obtained by pooling the within-laboratory standard deviations of the test results from all ofthe participatin
41、g laboratories: Sr5ff sS1d21sS2d21sSnd2g /ng1/2.CSRis the between-laboratory reproducibility, expressed as standard deviation: SR5hSr21SL2j1/2where SLis the standard deviation of laboratory means.Dr is the within-laboratory critical interval between two test results = 2.8 Sr.ER is the between-labora
42、tory critical interval between two test results = 2.8 SR.FValues for 0.010 in. thick polyester specimens and 0.007 in. thick PCTFE specimens are included in Table 1 to show that the repeatability and reproducibility of shearstrength values were greatly inferior to corresponding data obtained on spec
43、imens of 1.780 mm (0.070 in.) minimum thickness. Therefore, the scope of this test methodwas revised to limit test specimen thickness to the range from 1.27 to 12.7 mm (0.050 to 0.500 in.).D732 17311.2.3 The judgments in 11.2.1 and 11.2.2 will have anapproximately 95 % (0.95) probability of being co
44、rrect.11.3 BiasIt is not possible to make any statement aboutthe bias of this test method, as there is no standard referencematerial or reference test method that is applicable.12. Keywords12.1 punch tool; shear strengthASTM International takes no position respecting the validity of any patent right
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