The test block is designed according to the performance test requirements of the double crystal straight probe in Appendix C of the standard, and the performance of the double crystal straight probe is tested with the stepped flat bottom test block.

Test method:

(1) Measure the detection sensitivity: place the verified probe on the detection plane of the test block, move the probe back and forth so that the main sound beam is aligned with the φ5.6mm flat bottom hole of the test block, and find the strongest echo. The maximum echo height difference between the strongest echo and the characteristic curve of the twin probe should be within the range of -10dB±2dB.

(2) Effective beam width test: Place the verified probe on the detection plane of the test block, move the probe back and forth so that the main sound beam is aligned with the φ5.6mm flat bottom hole of the test block, find the strongest echo, move the probe parallel to the sound wave division plane, and test the beam width according to the 6dB method. For the steel plate used in pressure equipment, the effective value should be greater than 15mm.