Designation: A938 − 07 (Reapproved 2013)
Standard Test Method for
Torsion Testing of Wire 1 This standard is issued under the fixed designation A938; the number immediately following the designation indicates the year of original origin al adoption or, in the case of revis revision, ion, the year of last revision. revision. A number in paren parenthese thesess indicates the year of last reappr reapproval. oval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
clamping clampin g hea head d sha shall ll be equ equipp ipped ed wit with h a dev device ice cap capabl ablee of applying the necessary tensile load. 5.1.3 The clamping heads shall clamp the wire firmly firmly,, but should not damage it to the extent that fracture occurs at the clampin clam ping g poi point nt dur during ing twi twistin sting. g. The dis distanc tancee bet betwee ween n the clamps is the test length. The wire shall be twisted only along thee tes th testt le leng ngth th,, an and d no nott at th thee po poin intt of cla clamp mpin ing. g. Th Thes esee requirements can be satisfied by bending a short section at each end of the specimen to an angle of about 90° to the wire axis, as described in 6.3 6.3..
1. Sco Scope* pe* 1.1 This test method describes describes the torsion torsion (or twist) testing of metallic wire. 1.2 Th 1.2 Thee va valu lues es st state ated d in U. U.S. S. cu cust stom omar ary y un units its ar aree to be regarded as the standard. The SI equivalents of U.S. customary units may be approximate. standard d doe doess not purport purport to add addre ress ss all of the 1.3 This standar safet sa fetyy co conc ncer erns ns,, if an anyy, as asso socia ciated ted wi with th it itss us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use.
5.2 Revolution Counter— A mechan mechanism ism to count the number number of twists shall be provided. 5.3 Protective Shield— A protective shield shall be provided to protect the operator from flying fragments in cases when the wire breaks into more than two pieces.
2. Referenc Referenced ed Documents Documents 2.1 ASTM Standards:2 E6 Terminology E6 Terminology Relating to Methods of Mechanical Testing 3. Terminology
6. Specimen Preparation Preparation
3.1 Definitions— The The defi definit nition ionss rel related ated to tor torsio sion n test testing ing appearing in Terminology E6 E6 shall shall be considered as applying to the terms used in this test method.
6.1 Straightening— The The test piece, consisting of a length of wire, should be straight before being tested. If straightening is necessary, it shall, unless otherwise specified, be done by hand. Other straightening straightening techni techniques ques are permitt permitted ed prov provided ided surf surface ace damage is avoided. Since the shear stress is maximum at the surface of the wire during testing, even slight surface damage such su ch as pi pits ts or sc scra ratch tches es ca can n cau cause se ea earl rly y fr fract actur ure, e, an and d th thee results may not be indicative of the full capability of the wire.
4. Sign Significan ificance ce and Use 4.1 The complex stress stress and strain conditions conditions that occur in thee sa th samp mple le du duri ring ng th thee to tors rsio ion n te test st ar aree se sens nsiti itive ve to mi mino norr variations in materials, making the torsion test a useful tool in assessing wire ductility under torsional loading.
NOTE 1—During straightening, it is important that the properties and cross sec cross sectio tion n rem remain ain unc unchan hanged ged as far as pos possib sible. le. In par particu ticular lar,, the specimen shall not be subjected to any twisting.
5. Appar Apparatus atus
6.2 Test Length: 6.2.1 Recomm Recommended ended test length is 8 in. (203 mm) (distance (distance between the clamping heads). Sufficient material must also be provided to allow for gripping. 6.2. 6. 2.2 2 Other Other te test st le leng ngth thss ma may y be us used ed as ag agre reed ed up upon on betwee bet ween n the producer producer and pur purcha chaser ser or as spe specifie cified d in the appropriate product specification. 6.2.3 When a test length other other than 8 in. (203 mm) is used, used, the minimum torsions shall be revised in direct proportion to thee ch th chan ange ge in th thee ja jaw w sp spac acin ing, g, or as de dete term rmin ined ed by th thee following formula:
5.1 Clamping Heads: 5.1.1 The torsion test apparatus apparatus must have clampin clamping g heads that will remain coaxial (within 10°) during the test. 5.1.2 One clamping clamping head shall be easily displaceable displaceable in the directi dir ection on of the wir wiree axi axis. s. This lon longitu gitudin dinally ally dis displac placeab eable le
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This test method is under the jurisdiction of ASTM Committee A01 Committee A01 on Steel, Stainless Steel and Related Alloysand is the direct responsibility of A01.03 of A01.03 on on Steel Rod and Wire. Curren Cur rentt edi editio tion n app approv roved ed Apr April il 1, 201 2013. 3. Pub Publis lished hed Apr April il 201 2013. 3. Ori Origin ginall ally y approved approv ed in 1975. Last previous edition approved approved in 2007 as A938 – 07. DOI: 10.1520/A0938-07R13. 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at
[email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.
T x 5
~ T ! ~ L ! ~ L ! L
x
L
where:
*A Summary of Changes section appears at the end of this standard Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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A938 − 07 (2013) T x T L L x L L
= = = =
position positio n of fra fractu cture, re, defi defined ned as com comple plete te sep separa aratio tion n of the brok br oken en en ends ds.. If th thee nu numb mber er of tu turn rnss do does es no nott sa satis tisfy fy th thee requir req uiremen ements ts of the spe specific cificatio ation, n, and the ini initial tial fra fractur cture, e, defined as complete separation of the broken ends, location is within two times the wire diameter from the clamps, the test is considered invalid and shall be repeated.
minimum torsions minimum torsions for new new length, length, minimum minimu m torsions torsions for 8 in. (203 (203 mm) length, length, new len length gth,, and and 8 in. in. (203 (203 mm) mm)..
Preparati paration— on— To pre 6.3 End Pre preven ventt the gri grippe pped d end endss fro from m slipping tangentially in the clamps, a minimum of 1 ⁄ 2 in. (12.7 mm) of each end of the wire is often bent approximately approximately 90° to the axis of the test sample. The end sections need not be exactly parallel to each other. See Fig. See Fig. 1. 1.
NOTE 2—Specimens often break into more than two pieces, subsequent fractures resulting from the rapid untwisting of the wire following the initial fracture. In many cases, the initial fracture will have a smooth surface perpendicular to the wire axis. The above validity test applies only to the location of this initial break.
7. Pro Procedu cedure re
8. Repor Reportt
7.1 Tensile Force— Clamp Clamp the specimen in the clamps of the testt ap tes appa para ratu tuss wi with th its lo long ngitu itudi dina nall ax axis is co coax axial ial wi with th th thee clamp cla mpin ing g he head adss an and d in su such ch a man manne nerr th that at th thee sp spec ecime imen n remains rem ains as str straig aight ht as pos possib sible le dur during ing tes testing ting (see 5.1.1). 5.1.1). Unle Un less ss sp speci ecifie fied d ot othe herw rwis ise, e, th this is ca can n be ac acco comp mplis lishe hed d by applyi app lying ng a sma small ll tens tensile ile for force ce to the specimen. specimen. This for force ce should be just sufficient to prevent the specimen from deflecting away from the axis of rotation during twisting. Recommended tensile forces are shown in Table 1. 1.
8.1 The following following information information shall be included in the test report: 8.1.1 Specim Specimen en identification, identification, 8.1.2 Wir Wiree diameter, diameter, 8.1.3 Test length, and 8.1.4 Total turns to fracture. fracture. NOTE 3—If a minimum number of turns is specified and this number is exceeded, the test need not be continued to fracture. It is then sufficient to record that no fracture occurred.
7.2 Speed of Twisting— The The speed of testing should be such that the wire is not heated appreciably during the test since exces ex cessi sive ve sp speed eed re resu sults lts in a lo lowe weri ring ng of to tors rsio ion n va valu lues es.. Recommended maximum speeds are shown in Table 2. 2.
9. Pre Precisi cision on and Bias 9.1 Precision— Suff Sufficien icientt mul multilab tilabora orator tory y test testss hav havee not been bee n com compar pared ed to est establi ablish sh the rep reprod roduci ucibili bility ty of this test method. Test variables that affect precision include: (1) initial length and straightness of the wire, ( 2) the amount of tensile stress, (3) the speed of testing, and ( 4) location of the fracture.
7.3 Number of Turns: 7.3.1 After placing placing the test specimen in the machine, rotate onee cl on clam amp p at a re reas ason onab ably ly co cons nsta tant nt sp spee eed d un unti till th thee te test st specime spe cimen n fra fractu ctures res,, defi defined ned as a com complet pletee sep separa aratio tion n of the broken ends. 7.3.2 If the number of turns turns is satisfactory, satisfactory, the test specimen is co cons nsid ider ered ed as ha havi ving ng pa pass ssed ed th thee tes test, t, re rega gard rdle less ss of th thee
9.2 Bias— Determ Determina ination tion of the bias of a test method method requires ref quires refere erence nce stan standar dard d val values ues for one or mor moree mate materia rials ls based on many measurements. Such standard reference values are not available for this test method. Therefore, Therefore, the bias of the method is not known. 10. Keyw Keywords ords 10.1 coa 10.1 coaxia xiall clam clampin ping; g; fra fractu cture; re; revolution revolution counter; counter; test length; torsion; torsion testing; twisting rates; wire; wire axis; wire ductil ductility ity
FIG. 1 Sketch Showing Showing 90° Bends at Ends of Wire Twist Twist Test Test Specimen
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A938 − 07 (2013) TABLE 1 Applied Load for Torsion Testing Applied LoadA Diameter of Wire In c h e s Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over A
Up to 0.010 0 .0 1 0 to 0 . 0 1 5 0 .0 1 5 to 0 . 0 2 0 0 .0 2 0 to 0 . 0 3 0 0 .0 3 0 to 0 . 0 4 0 0 .0 4 0 to 0 . 0 5 0 0 .0 5 0 to 0 . 0 6 0 0 .0 6 0 to 0 . 0 7 0 0 .0 7 0 to 0 . 0 8 0 0 .0 8 0 to 0 . 0 9 0 0 .0 9 0 to 0 . 1 0 0 0.100 to 0.110 0.110 to 0.120 0 .1 2 0 to 0 . 1 3 0 0 .1 3 0 to 0 . 1 4 0 0 .1 4 0 to 0 . 1 5 0 0 .1 5 0 to 0 . 1 6 0 0 .1 6 0 to 0 . 1 7 0 0 .1 7 0 to 0 . 1 8 0 0 .1 8 0 to 0 . 1 9 0 0 .1 9 0 to 0 . 2 0 0 0 .2 0 0 to 0 . 2 1 0 0 .2 1 0 to 0 . 2 2 0 0 .2 2 0 to 0 . 2 3 0 0 .2 3 0 to 0 . 2 4 0 0 .2 4 0 to 0 . 2 5 0
Pounds Force (lbf) mm
Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over Over
Newtons (N)
M i ni m u m
M ax i m u m
M i n i m um
Max i mum
0. 50 1 .0 1 .5 2 .0 3 .0 4 .0 5 .0 6 .0 7 .0 8 .0 9 .0 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
2 .0 4. 0 6. 0 8. 0 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96
2 .2 4 .4 6 .7 8 .9 13 18 22 27 31 36 40 44 49 53 58 62 67 71 76 80 85 89 93 98 1 02 1 07
8 .9 18 27 36 53 71 89 1 07 1 25 1 42 1 60 17 8 19 6 21 4 23 1 24 9 26 7 28 5 30 2 32 0 33 8 35 6 37 4 39 1 4 09 4 27
Up to 0.25 0 .2 5 to 0 .4 1 0 .4 1 to 0 .5 1 0 .5 1 to 0 .7 6 0 .7 6 to 1 .0 2 1 .0 2 to 1 .2 8 1 .2 8 to 1 .5 3 1 .5 3 to 1 .7 9 1 .7 9 to 2 .0 4 2 .0 4 to 2 .3 0 2 .3 0 to 2 .5 5 2 .5 5 to 2 .8 0 2 .8 0 to 3 .0 6 3 .0 6 to 3 .3 1 3 .3 1 to 3 .5 7 3 .5 7 to 3 .8 2 3 .8 2 to 4 .0 7 4 .0 7 to 4 .3 3 4 .3 3 to 4 .5 8 4 .5 8 to 4 .8 4 4 .8 4 to 5 .0 9 5 .0 9 to 5 .3 4 5 .3 4 to 5 .6 0 5 .6 0 to 5 .8 5 5 .8 5 to 6 .1 0 6 .1 0 to 6 .3 5
For 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 Speeds Wire Diameter, in. (mm)
Twisting Speed (Rpm)
<0.040 (1.02) 0.040 to <0.142 (1.02 to <3.61) 0.142 and larger (3.61 and larger)
90 60 30
SUMMARY OF CHANGES Committee Committ ee A01 has identified the location of selected changes changes to this standard since the last issue, A938 – 04, that may impact the use of this standard. (Approved Sept. 1, 2007.) Table 1 to sho show w min minimu imum m and maximum maximum loa load d (1) Revised Table values and wire sizes larger than 0.160 inches (4.06mm) in. diameter. ASTM International International takes no positi position on respecting the validi validity ty of any patent rights assert asserted ed in connec connection tion with any item mentio mentioned ned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible respon sible technical technical committee, which you may attend. If you feel that your comments have not receiv received ed a fair hearing you should make your views known to the ASTM Committee on Standards, 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 above address addr ess or at 610610-832832-9585 9585 (pho (phone), ne), 610610-832832-9555 9555 (fax (fax), ), or serv service@ ice@astm astm.org .org (e-m (e-mail) ail);; or thro through ugh the ASTM webs website ite (www.astm. (www .astm.org). org). Permission Permission rights to photocopy the standa standard rd may also be secure secured d from the Copyri Copyright ght Clearance Center, Center, 222 Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/
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