This practice may be used for approximating a limiting design stress at room temperature and, in some cases, for approximating the range of elastic behavior. Elastic limit, or the greatest stress that a material is capable of sustaining without any permanent strain remaining upon complete release of the stress, is a more technically accurate design parameter; however, the elastic limit is extremely difficult to measure in routine testing. Caution should be used in applying such values to predict the behavior of flat or wire springs in bending, torsion or other stress modes, or at temperatures other than that at which the determination is made.

1.1 This practice establishes the requirements for determining offset yield strength (0.01 %, 0.02 %, and 0.05 % offset) at room temperature. It is intended for copper alloys in tempers commonly used for spring applications, and materials thicker than 0.010 in. (0.25 mm).

1.1.1 The primary application of this practice is intended for flat strip materials that are used for springs; however, this practice can be used for other product forms, such as wire, rod, and bar.

1.2 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.