This standard recommends two reference test blocks HS semi-circle step test block and SDH cross hole test block. This standard provides a method for determining the sound field generated in solids by probes used in contact testing. This standard is applicable to the probe determination of forged or rolled steel, aluminum alloy or titanium alloy products. This standard applies to the probe frequency range of 1MHz to 15MHz. 1MHz to 5MHz is most suitable for the detection of steel products, 5MHz to 15MHz is most suitable for the detection of fine grain structure products such as aluminum alloys.

Figure 2-6 shows the dimensions and shape of the SDH cross hole test block.

Use only when adjusting the sensitivity of the longitudinal wave probe with a test block. The longitudinal wave probe can use φ3, φ4, φ6 equivalent flat hole sensitivity.