ASTM_B_279_-_13.pdf

Designation:B27913Standard 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 case 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 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 to 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 designed as an inspection or accep-tance test of new bare soft square and rectangular wire intendedfor subsequent fabrication into magnet wire.NOTE1Since the applied unit stress and the time of application areconstant for all wire sizes,the test enables comparisons of stiffness to bemade between wires 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 shall 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 elongation 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.Improperlyprepared 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 0.01 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=102.74 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.NOTE2Where a large number 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 specimens 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 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 ASTMStandards 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 States1 specimen mass becomes the only variable and the required load(P)willvary proportionately specimen 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 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 len