Reference blocks fabricated to this practice will exhibit specific area-amplitude and distance-amplitude relationships only with an immersion test at 5 MHz using the search unit, test instrument, and test parameters described in this practice. Comparison tests at other frequencies or with uncalibrated test systems will not necessarily give the same relationships shown in this practice.

Note 2—The 1964 and prior issues of this practice required a test frequency of 15 MHz. Blocks conforming to earlier issues of this practice may not produce ultrasonic responses that conform to this issue. See Section 13 regarding provision for recertification or correction curves and tables.

Although the primary ultrasonic evaluation of blocks is performed at a specified frequency, the blocks may be used to standardize ultrasonic tests at any frequency and with any pulse-echo ultrasonic test system. Establishment of distance-amplitude and area-amplitude characteristics is necessary for each application. This use may be inappropriate for other materials and curved surfaces without special compensation. Also see (3) for cautions regarding use of standard blocks for test standardization.

1.1 This practice covers a procedure for fabricating aluminum alloy 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 alloy products using pulsed longitudinal waves introduced into test material either by the direct-contact method or by the immersion method. A recommended procedure for checking blocks is described and calibration data for a number of reference blocks are tabulated. Statements concerning procedures are provided without a discussion of the technical background for the preference. The necessary technical background can be found in Refs. (1-16).

Note 1—Practice E 428 and Guide E 1158 also describe procedures for selecting material, fabricating blocks, and checking response. Unlike this practice, there is no requirement for evaluation relative to a specified standard target.

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.