1.1 This practice covers a procedure for fabricating alumi-num aloy ultrasonic standard reference blocks that can be used for checking performance of ultrasonic testing equipment and for standardization and control of ultrasonic tests of aluminum aloy prodlucts using pulsed longitudinal waves introduced into test material either by the direct-conact method or by the immersion method A recommended procedure for checking blocks is deseribed and cealibration data for a number of reference blocks are tuabulated. Statements concerning proce-dures are provided without a discussion of the technical background for the preference. The necessary technical back-ground can be found in Refs. (1-15).2
