Defect detector for underwater concrete structures - processes acoustic microscope output to produce video images of surface, showing cracks, pits, etc.

摘要

The acoustic microphone consists of a round transducer assembly (14) mounted on a carriage which is drawn across the surface under test (18). The assembly consists of a number of identical transmitting and receiving transducers mounted at such angles that the broad-band pulsed ultrasonic signals are reflected from the surface, received and processed to form an image on a VDU (15). Any pits or cracks in the surface cause a proportion of the longitudinal waves to travel along the surface as Rayleigh waves, following the profiles of the cracks. The angle between the transmitted wave and the surface is proportional to the ratio between the two wave propagation speeds.