ASTM_B_598_-_14a.pdf

Designation:B59814aStandard Practice forDetermining Offset Yield Strength in Tension for CopperAlloys1This standard is issued under the fixed designation B598;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope*1.1 This practice establishes the requirements for determin-ing offset yield strength(0.01%,0.02%,and 0.05%offset)atroom temperature.It is intended for copper alloys in temperscommonly used for spring applications,and materials thickerthan 0.010 in.(0.25 mm).1.1.1 The primary application of this practice is intended forflat strip materials that are used for springs;however,thispractice can be used for other product forms,such as wire,rod,and bar.1.2 UnitsValues stated in inch-pound units are to beregarded as standard.The values given in parentheses aremathematical conversions to SI units which are provided forinformation only and are not considered standard.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 of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B846 Terminology for Copper and Copper AlloysE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE8/E8M Test Methods for Tension Testing of Metallic Ma-terialsE83 Practice for Verification and Classification of Exten-someter Systems3.Terminology3.1 For definitions of terms related to copper and copperalloys,refer to Terminology B846.3.2 For definitions of terms related to mechanical testing,refer to Terminology E6.4.Summary of Practice4.1 To determine the offset yield strength,it is necessary toacquire data(autographic or numerical)from which a stress-strain diagram may be drawn.The stress at which a specifieddeviation of strain from the linear portion of the stress-straincurve occurs is the yield strength at that particular offset.5.Significance and Use5.1 This practice may be used for approximating a limitingdesign stress at room temperature and,in some cases,forapproximating the range of elastic behavior.Elastic limit,orthe greatest stress that a material is capable of sustainingwithout any permanent strain remaining upon complete releaseof the stress,is a more technically accurate design parameter;however,the elastic limit is extremely difficult to measure inroutine testing.Caution should be used in applying such valuesto predict the behavior of flat or wire springs in bending,torsion or other stress modes,or at temperatures other than thatat which the determination is made.6.Apparatus6.1 Standard testing machine of adequate capacity,con-forming to the requirements of Practices E4.6.2 Class B-1 or more accurate Extensometers,conformingto the requirements of Practice E83 and suitable to the tensiontest specimen required for the application.6.3 Extensometer Calibrator,or similar device accurate to0.00002 in.(0.0005 mm).7.Test Specimen7.1 Tension test specimens shall be selected from TestMethods E8/E8M as appropriate for the product form.1This practice is under the jurisdiction ofASTM Committee B05 on Copper andCopper Alloys and is the direct responsibility of Subcommittee B05.06 on Methodsof Test.Current edition approved Sept.1,2014.Published September 2014.Originallyapproved in 1974.Last previous edition approved in 2014 as B598 14.DOI:10.1520/B0598-14A.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.*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 States1 8.Procedure8.1 Follow the accepted practices for preparation to performa tension test in accordance with Test Methods E8/E8M.Special care in the preparation of thin-gage samples,includingcontour and edge preparation should be used.8.2 Select the load range so that the yield strength fallswithin the upper half of the chart load range used.Choose astrain magnification so that the 0.0001,0.0002 or 0.0005-in./in.(or mm/mm)increment of strain can be readily determinedfrom the chart.8.3 Apply a preload of nominally 10%of the known oranticipated offset yield strength to the test specimen to align thegrips and to remove all slack and curvature from the specimen.8.4 Seat the extensometer firmly on the test specimen whilemaintaining the preload.Apply the load uniformly until thedesired testing speed i