ASTM B598-98 pdf free.Standard Practice for Determining Offset Yield Strength in Tension for Copper Alloys.
The definitions of terms relating to mechanical testing inTerminology E 6 apply.Summary of Practice.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 Use.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 diflicult 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.Standard testing machine of adequate capacity,con-forming to the requirements of Practices E 4 and E 74.Class B-l or more accurate Extensometers,conformingto the requirements of Practice E 83 and suitable to the tensiontest specimen required for the application.Extensometer Calibrator;or similar device accurate to0.00002 in. (0.0005 mm).Follow the accepted practices for preparation to performa tension test in accordance with Test Methods E8. Specialcare in the preparation of thin-gage samples, including contourand edge preparation should be used.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.
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 is attained.The rate of stress applicationshall not exceed 100 000 psi/min (12 MPa/s).Take care that therecording equipment is functioning correctly and indicating theload properly.Remove the extensometer when the curve indicatesadequate departure from linear behavior to reveal the desiredoffset,without stopping the test.Determine the offset yield strength from the stress-straindiagram as described in Test Methods E 8.ASTM B598 pdf download.