1、Designation: B279 13Standard Test Method forStiffness of Bare Soft Square and Rectangular Copper andAluminum Wire for Magnet Wire Fabrication1This standard is issued under the fixed designation B279; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method, known as the low-stress elongation(LSE) test, covers the procedure for
3、determining the stiffnessof bare soft square and rectangular copper and aluminum wirein terms of the permanent elongation resulting from theapplication of a tensile stress.1.2 The SI values for the mass of the specimen are regardedas the standard. For all other properties, the inch-pound valuesare t
4、o be regarded as standard and the SI units may beapproximate.2. Referenced Documents2.1 The following document forms a part of this test methodto the extent referenced herein:2.2 ASTM Standards:2E4 Practices for Force Verification of Testing Machines3. Significance and Use3.1 This test method is des
5、igned as an inspection or accep-tance test of new bare soft square and rectangular wire intendedfor subsequent fabrication into magnet wire.NOTE 1Since the applied unit stress and the time of application areconstant for all wire sizes, the test enables comparisons of stiffness to bemade between wire
6、s of the same or different size on the basis of thepermanent elongation resulting from the application of a low unit stress.4. Apparatus4.1 Tensile testing machines used for the low-stress elonga-tion test shall conform to the requirements of Practices E4.5. Test Specimens5.1 The test specimens shal
7、l be taken from the finished reelor coil with a minimum amount of handling and distortion,retaining the original curvature of the package to the greatestextent possible. Test specimens having the full cross-sectionalarea of the wire shall be used. The standard gage length for themeasurement of elong
8、ation of wire shall be 10 in. (254 mm).The total length of the specimens shall be at least equal to thegage length plus the length of wire required for the full use ofthe grips employed.6. Procedure6.1 Straighten the test specimens carefully by hand with aminimum amount of distortion or cold work. I
9、mproperlyprepared test specimens often cause unsatisfactory test results.6.2 Cut off a test specimen of sufficient length as describedin 5.1. Measure the length to the nearest 0.01 in. (0.25 mm)with any measuring device accurate to 0.1 % (Note 2). Mea-sure the mass of this specimen to the nearest 0.
10、01 g on abalance accurate to 0.1 %. The load required to apply a stressto the specimen equal to 15 000 psi (103 MPa) for copper, and8 000 psi (55 MPa) for aluminum shall be obtained from thefollowing:P 5KWLwhere:P = Required load, lbs (N),W = mass of specimen, g,L = length of specimen, in., andK = 1
11、02.74 for copper specimens, length in in., requiredload in lb, orK = 11 612.7 for copper specimens, length in mm, requiredload in N, orK = 180.5 for aluminum specimens, length in in., requiredload in lb, orK = 20 401.9 for aluminum specimens, length in mm,required load in N.NOTE 2Where a large numbe
12、r of specimens are to be tested, thecalculation of the required load (P) can be simplified by careful cutting ofall test specimens to equal lengths. The use of a jig or a pair of vices withjaws set at a predetermined length apart can facilitate the cutting of equallength specimens. With all specimen
13、s having an equal length, the1This test method is under the jurisdiction of ASTM Committee B01 onElectrical Conductors and is the direct responsibility of Subcommittee B01.02 onMethods of Test and Sampling Procedure.Current edition approved Sept. 1, 2013. Published September 2013. Originallyapproved
14、 in 1953. Last previous edition approved in 2004 as B279 04 which waswithdrawn in January 2013 and reinstated in September 2013. DOI: 10.1520/B0279-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStan
15、dards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1specimen mass becomes the only variable and the required load (P) willvary proportionately speci
16、men to specimen with the specimen mass.Where the mass of the test specimen exceeds the capacity of theavailable balance, a shorter length specimen may be used to determine themass of the test specimen. The shorter specimen shall be cut from thesame coil or reel immediately adjacent to where the test
17、 specimen was cut.The length of the short specimen shall be measured with an accuracy ofat least 0.2 % and the mass of the short specimen shall be determined inaccordance with the requirements of 6.2. The mass of the test specimenmay be calculated by multiplying the ratio of the test specimen length
18、divided by the short specimen length by the mass of the short specimen.6.3 Mark the 10-in. (254-mm) gage marks by any suitablemethod that will eliminate the possibility of fracture at the gagemarks.6.4 Place the test specimen, properly marked with 10-in.(254-mm) gage marks, in the tensile testing ma
19、chine andslowly and uniformly apply the load determined in 6.2. Holdthe load for 30 s and then remove the load.6.5 After the load has been removed, measure the perma-nent elongation of the test specimen between the gage marks tothe nearest 0.01 in. (0.25 mm) using dividers and scale or othersuitable
20、 means.7. Low-Stress Elongation7.1 The low-stress elongation shall be recorded as theincrease in length of the gage length, expressed in percent.8. Precision and Bias8.1 PrecisionThis test method has been in use for manyyears. No statement of precision has been made and no workhas been planned to de
21、velop such a statement.8.2 BiasThis test method has no bias because the value for(tensile) stiffness of wire is determined solely in terms of thistest method.9. Keywords9.1 aluminum wire; copper wire; soft square and rectangularaluminum wire; soft square and rectangular copper wireASTM International
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23、n 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 ad
24、dressed 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, a
25、t 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 610-832-9585 (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/).B279 132
