1、Designation: B 598 98 (Reapproved 2004)Standard Practice forDetermining Offset Yield Strength in Tension for CopperAlloys1This standard is issued under the fixed designation B 598; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This practice establishes
3、 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
4、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 The values stated in inch pound units are the standard.The SI values given in parentheses are for information only.1.3 This standard does not purport to address
5、 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 The following documents in effect
6、 on the date that thematerial is tested form a part of this practice, to the extentreferenced herein:2.2 ASTM Standards:2E 4 Practices for Force Verification of Testing MachinesE 6 Terminology Relating to Methods of Mechanical Test-ingE 8 Test Methods for Tension Testing of Metallic MaterialsE 74 Pr
7、actice for Calibration of Force Measuring Instru-ments for Verifying the Load Indication of Testing Ma-chinesE 83 Practice for Verification and Classification of Exten-someters3. Terminology3.1 The definitions of terms relating to mechanical testing inTerminology E 6 apply.4. Summary of Practice4.1
8、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 offs
9、et.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 remainin
10、g 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
11、, 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 E 4 and E 74.6.2 Class B-1 or more accurate Extensometers, conformingto the requirements of Practice E 83 and suitable to
12、 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 E 8 as appropriate for the product form.1This practice is under the jurisdiction of A
13、STM Committee B05 on Copper andCopper Alloys and is the direct responsibility of Subcommittee B05.06 on Methodsof Test.Current edition approved May 1, 2004. Published May 2004. Originallyapproved in 1974. Last previous edition approved in 1998 as B 598 98.2For referenced ASTM standards, visit the AS
14、TM 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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr
15、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8. Procedure8.1 Follow the accepted practices for preparation to performa tension test in accordance with Test Methods E 8. Specialcare in the preparation of thin-gage samples, including contourand edge preparation should be
16、 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
17、 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 is attained. The r
18、ate of stress applicationshall not exceed 100 000 psi/min (12 MPa/s). Take care that therecording equipment is functioning correctly and indicating theload properly.8.5 Remove the extensometer when the curve indicatesadequate departure from linear behavior to reveal the desiredoffset, without stoppi
19、ng the test.8.6 Determine the offset yield strength from the stress-straindiagram as described in Test Methods E 8.9. Calculation and Report9.1 Determine the load where the offset line intersects thestress-strain curve. This load in pounds divided by the originalcross section area is the yield stren
20、gth and is reported as yieldstrength (offset value).10. Precision and Bias10.1 PrecisionThe following parameters are reported toimpact upon the precision of this practice:10.1.1 Characteristics of the specimen such as orientation ofgrains relative to the axial stress, grain size, residual stress,pre
21、vious strain history, dimensions, and eccentricity.10.1.2 Testing conditions such as alignment of the speci-men, speed of testing, temperature, temperature variations,conditions of test equipment, ratio of error in load to the rangein load values, and ratio of error in extension measurement tothe ra
22、nge in extension values.10.1.3 Interpretation of data such as whether graphical ordigital data were taken, calibration of recording or data-loggingdevice, number of data pairs used to obtain slope of stress-strain curve.10.2 BiasA statement of bias of this practice requiresreference standard values
23、for one or more materials based onmany measurements or round-robin test data. Such standardreference values or test data are presently not available.11. Keywords11.1 offset yield; tensile test; yield strengthSUMMARY OF CHANGESThis section identifies the principle changes to this practice that have b
24、een incorporated since the 1992 issueas follows.(1) The practice has been extensively, editorially revised. Notechnical changes have been made.(2) Section 1.1.1 was added for amplification.(3) Sections 1.2, 4, 5, and 7 were reworded for clarification.ASTM International takes no position respecting t
25、he validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard
26、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 addressed to ASTM International H
27、eadquarters. 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, at the address shown below.This
28、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).B 598 98 (2004)2
