The radial test block is designed according to the requirements of the standard NB/T47013-2015 nondestructive testing of pressure equipment for ultrasonic testing of steel bolt billets for pressure equipment. It is suitable for radial testing of steel bolt billets with radius of curvature less than 100mm by twin-crystal straight probe.

Test method: According to the thickness of the test specimen and the standard requirements, the appropriate test block is selected, and the verified twin-crystal straight probe is placed at the position a in the schematic diagram, and the probe is moved back and forth so that the direct sound beam can get the maximum reflection echo on the φ2 flat bottom hole. Adjust the echo amplitude to 80% of the height of the full screen, record the dB value at this time, which is the first point. The probe is placed at position b in the diagram, and the probe is moved back and forth so that the direct sound beam can get the maximum reflection echo on the φ2 flat bottom hole. Adjust the echo amplitude to 80% of the height of the full screen, record the dB value at this time, which is the second point. The probe is placed at position c in the diagram, and the probe is moved back and forth so that the direct sound beam can get the maximum reflection echo on the φ2 flat bottom hole. Adjust the echo amplitude to 80% of the height of the full screen, record the dB value at this time, which is the third point, and so on until the range can fully cover the detection thickness (at least three test points), and connect the above points into a curve, which is the twin-crystal straight probe distance-amplitude curve, and take this as the reference sensitivity. On this basis, a gain of 6dB is used as the scanning sensitivity.