1、Designation:A93807(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 parenth
2、eses 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 standard.The
3、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 the applica-bility o
4、f 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 used in this test meth
5、od.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 Heads:5.1.1 The torsion
6、 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 the necessary tensile load
7、.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 point of clamping.Theserequiremen
8、ts 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 CounterAmechanism to count the numberof twists shall be provided.5.3 Protective ShieldA protective shield shall be providedto protect the operator fro
9、m 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,be done by hand.Other straightening te
10、chniques 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 capability of the wire.NOTE1During straigh
11、tening,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 clamping heads).Sufficient material must also beprovided
12、 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 be revised in direct proportion tothe change in the
13、 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.Current edition approved April 1,2013.Published Apri
14、l 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 Book of ASTMStandards volume information,refer to the standards
15、 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 States1Copyright by ASTM Intl(all rights reserved);Tx=minimum torsions for new length,TL=mi
16、nimum 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 of12in.(12.7mm)of each end of the wire is often bent approximately 90 tothe axis of the test sample.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