ASTM A938-2007(2013) Standard Test Method for Torsion Testing of Wire《钢丝扭转测试的标准试验方法》.pdf

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1、Designation: A938 07 (Reapproved 2013)Standard Test Method forTorsion Testing of Wire1This standard is issued under the fixed designation A938; 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

2、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 describes the torsion (or twist) testingof metallic wire.1.2 The values stated in U.S. customary units are to beregarded as the

3、 standard. The SI equivalents of U.S. customaryunits may be approximate.1.3 This standard 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 t

4、he applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical Testing3. Terminology3.1 DefinitionsThe definitions related to torsion testingappearing in Terminology E6 shall be considered as applyingto the terms u

5、sed in this test method.4. Significance and Use4.1 The complex stress and strain conditions that occur inthe sample during the torsion test are sensitive to minorvariations in materials, making the torsion test a useful tool inassessing wire ductility under torsional loading.5. Apparatus5.1 Clamping

6、 Heads:5.1.1 The torsion test apparatus must have clamping headsthat will remain coaxial (within 10) during the test.5.1.2 One clamping head shall be easily displaceable in thedirection of the wire axis. This longitudinally displaceableclamping head shall be equipped with a device capable ofapplying

7、 the necessary tensile load.5.1.3 The clamping heads shall clamp the wire firmly, butshould not damage it to the extent that fracture occurs at theclamping point during twisting. The distance between theclamps is the test length. The wire shall be twisted only alongthe test length, and not at the po

8、int of clamping. Theserequirements can be satisfied by bending a short section at eachend of the specimen to an angle of about 90 to the wire axis,as described in 6.3.5.2 Revolution CounterA mechanism to count the numberof twists shall be provided.5.3 Protective ShieldA protective shield shall be pr

9、ovidedto protect the operator from flying fragments in cases when thewire breaks into more than two pieces.6. Specimen Preparation6.1 StraighteningThe test piece, consisting of a length ofwire, should be straight before being tested. If straightening isnecessary, it shall, unless otherwise specified

10、, be done by hand.Other straightening techniques are permitted provided surfacedamage is avoided. Since the shear stress is maximum at thesurface of the wire during testing, even slight surface damagesuch as pits or scratches can cause early fracture, and theresults may not be indicative of the full

11、 capability of the wire.NOTE 1During straightening, it is important that the properties andcross section remain unchanged as far as possible. In particular, thespecimen shall not be subjected to any twisting.6.2 Test Length:6.2.1 Recommended test length is 8 in. (203 mm) (distancebetween the clampin

12、g heads). Sufficient material must also beprovided to allow for gripping.6.2.2 Other test lengths may be used as agreed uponbetween the producer and purchaser or as specified in theappropriate product specification.6.2.3 When a test length other than 8 in. (203 mm) is used,the minimum torsions shall

13、 be revised in direct proportion tothe change in the jaw spacing, or as determined by thefollowing formula:Tx5TL!Lx!LL!(1)where:1This test method is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloysand is the direct responsibility of A01.03 on SteelRod and Wire

14、.Current edition approved April 1, 2013. Published April 2013. Originallyapproved in 1975. Last previous edition approved in 2007 as A938 07. DOI:10.1520/A0938-07R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual B

15、ook of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Tx= minimum tors

16、ions for new length,TL= minimum torsions for 8 in. (203 mm) length,Lx= new length, andLL= 8 in. (203 mm).6.3 End PreparationTo prevent the gripped ends fromslipping tangentially in the clamps, a minimum of12 in. (12.7mm) of each end of the wire is often bent approximately 90 tothe axis of the test s

17、ample. The end sections need not be exactlyparallel to each other. See Fig. 1.7. Procedure7.1 Tensile ForceClamp the specimen in the clamps of thetest apparatus with its longitudinal axis coaxial with theclamping heads and in such a manner that the specimenremains as straight as possible during test

18、ing (see 5.1.1).Unless specified otherwise, this can be accomplished byapplying a small tensile force to the specimen. This forceshould be just sufficient to prevent the specimen from deflect-ing away from the axis of rotation during twisting. Recom-mended tensile forces are shown in Table 1.7.2 Spe

19、ed of TwistingThe speed of testing should be suchthat the wire is not heated appreciably during the test sinceexcessive speed results in a lowering of torsion values.Recommended maximum speeds are shown in Table 2.7.3 Number of Turns:7.3.1 After placing the test specimen in the machine, rotateone cl

20、amp at a reasonably constant speed until the testspecimen fractures, defined as a complete separation of thebroken ends.7.3.2 If the number of turns is satisfactory, the test specimenis considered as having passed the test, regardless of theposition of fracture, defined as complete separation of the

21、broken ends. If the number of turns does not satisfy therequirements of the specification, and the initial fracture,defined as complete separation of the broken ends, location iswithin two times the wire diameter from the clamps, the test isconsidered invalid and shall be repeated.NOTE 2Specimens of

22、ten break into more than two pieces, subsequentfractures resulting from the rapid untwisting of the wire following theinitial fracture. In many cases, the initial fracture will have a smoothsurface perpendicular to the wire axis. The above validity test applies onlyto the location of this initial br

23、eak.8. Report8.1 The following information shall be included in the testreport:8.1.1 Specimen identification,8.1.2 Wire diameter,8.1.3 Test length, and8.1.4 Total turns to fracture.NOTE 3If a minimum number of turns is specified and this number isexceeded, the test need not be continued to fracture.

24、 It is then sufficient torecord that no fracture occurred.9. Precision and Bias9.1 PrecisionSufficient multilaboratory tests have notbeen compared to establish the reproducibility of this testmethod. Test variables that affect precision include: (1) initiallength and straightness of the wire, (2) th

25、e amount of tensilestress, (3) the speed of testing, and (4) location of the fracture.9.2 BiasDetermination of the bias of a test method re-quires reference standard values for one or more materialsbased on many measurements. Such standard reference valuesare not available for this test method. Ther

26、efore, the bias of themethod is not known.10. Keywords10.1 coaxial clamping; fracture; revolution counter; testlength; torsion; torsion testing; twisting rates; wire; wire axis;wire ductilityFIG. 1 Sketch Showing 90 Bends at Ends of Wire Twist TestSpecimenA938 07 (2013)2SUMMARY OF CHANGESCommittee A

27、01 has identified the location of selected changes to this standard since the last issue, A938 04,that may impact the use of this standard. (Approved Sept. 1, 2007.)(1) Revised Table 1 to show minimum and maximum loadvalues and wire sizes larger than 0.160 inches (4.06mm) in.diameter.ASTM Internatio

28、nal takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their

29、 own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be

30、 addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards

31、, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9

32、585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).TABLE 1 Applied Load for Torsion TestingApplied LoadADiameter of Wire Pounds Force

33、(lbf) Newtons (N)Inches mm Minimum Maximum Minimum MaximumUp to 0.010 Up to 0.25 0.50 2.0 2.2 8.9Over 0.010 to 0.015 Over 0.25 to 0.41 1.0 4.0 4.4 18Over 0.015 to 0.020 Over 0.41 to 0.51 1.5 6.0 6.7 27Over 0.020 to 0.030 Over 0.51 to 0.76 2.0 8.0 8.9 36Over 0.030 to 0.040 Over 0.76 to 1.02 3.0 12 13

34、 53Over 0.040 to 0.050 Over 1.02 to 1.28 4.0 16 18 71Over 0.050 to 0.060 Over 1.28 to 1.53 5.0 20 22 89Over 0.060 to 0.070 Over 1.53 to 1.79 6.0 24 27 107Over 0.070 to 0.080 Over 1.79 to 2.04 7.0 28 31 125Over 0.080 to 0.090 Over 2.04 to 2.30 8.0 32 36 142Over 0.090 to 0.100 Over 2.30 to 2.55 9.0 36

35、 40 160Over 0.100 to 0.110 Over 2.55 to 2.80 10 40 44 178Over 0.110 to 0.120 Over 2.80 to 3.06 11 44 49 196Over 0.120 to 0.130 Over 3.06 to 3.31 12 48 53 214Over 0.130 to 0.140 Over 3.31 to 3.57 13 52 58 231Over 0.140 to 0.150 Over 3.57 to 3.82 14 56 62 249Over 0.150 to 0.160 Over 3.82 to 4.07 15 60

36、 67 267Over 0.160 to 0.170 Over 4.07 to 4.33 16 64 71 285Over 0.170 to 0.180 Over 4.33 to 4.58 17 68 76 302Over 0.180 to 0.190 Over 4.58 to 4.84 18 72 80 320Over 0.190 to 0.200 Over 4.84 to 5.09 19 76 85 338Over 0.200 to 0.210 Over 5.09 to 5.34 20 80 89 356Over 0.210 to 0.220 Over 5.34 to 5.60 21 84

37、 93 374Over 0.220 to 0.230 Over 5.60 to 5.85 22 88 98 391Over 0.230 to 0.240 Over 5.85 to 6.10 23 92 102 409Over 0.240 to 0.250 Over 6.10 to 6.35 24 96 107 427AFor sizes larger than 0.250 in. (6.35mm), the tensile force of 1 % of the nominal maximum load of the wire is recommended.TABLE 2 Recommended Maximum Twisting SpeedsWire Diameter, in. (mm) Twisting Speed (Rpm)0.040 (1.02) 900.040 to 0.142 (1.02 to 3.61) 600.142 and larger (3.61 and larger) 30A938 07 (2013)3