Significance and Use The use of sound speed values to determine changes in the elastic constants due to applied or residual stress requires that such measurements be of high precision and low bias. For that reason, special evaluation tests to determine a representative precision and bias for the specific technique, method, and equipment setup used are given. Speed of sound is a measure that depends on the accurate measurements of length of path of travel and transit time or other related parameters such as frequency, etc. Both measurements are subject to certain interpretations and assumptions and are highly dependent on laboratory expertise. This practice provides a means of checking overall technique. This practice shall be used when it is necessary to assess the systematic and random errors associated with a particular speed of sound measurement in a solid medium. It can be used to check both equipment performance and measurement technique for these errors. It can also be used to study inherent errors in a particular method. It can also be used to assess proposed corrections to sound speed measurements such as the phase corrections of Papadakis (3, 4). The resultant precision and bias determined by the use of the described block represents a more ideal situation than the same measurement performed in practice, in the field. Thus, the error for the specific field measurement may be larger than indicated by this test. This test represents the best error condition for a given technique and practice. Scope1.1 This practice provides a means for evaluating both systematic and random errors for ultrasonic speed-of-sound measurement systems which are used for evaluating material characteristics associated with residual stress and which may also be used for nondestructive measurements of the dynamic elastic moduli of materials. Important features and construction details of a reference block crucial to these error evaluations are described. This practice can be used whenever the precision and bias of sound speed values are in question.1.2 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.
