Study on crack detection in cast iron plates using the acousto-ultrasonic technique

Crack detection in cast iron has always been an important and difficult problem in the field of non-destructive testing. The traditional ultrasonic testing technique is time-consuming and is far from perfect because of coarse grains. The acousto-ultrasonic (AU) method, which was proposed in the 1980s, propagates externally-generated kilohertz frequency vibrations. In the current study, receiver arrays were used to measure the amplitude attenuation caused by slots on grey cast iron plates and to investigate the feasibility of the AU technique for inspecting cracks in cast iron. Moreover, different types of sensors were tested to optimise the testing frequency. The results indicate that the slots interact with one another when the wave frequency is higher than 480 kHz. The amplitudes of the signals around the slots are dramatically reduced. However, the decay effect of the cracks is observed in the near, rather than the far, field. A comparison method based on normalised amplitude curves is proposed to identify slots with depths greater than 2 mm.