Reduction of dead space in ultrasonic fault detection - involves shaped transmitter to separate surface and fault echoes

摘要

Detection of faults in products by means of echos from ultrasonic beams results in a dead space which reduces the efficiency of fault detection. The dead space is reduced by separating in space the echo signal from the surface from that of the fault. A spherical shaped ultrasonic transmitter (1) has a radius of curvature equal to the distance from the surface of the sample (2) added to the distance of the receiver (3) from the surface. The transmitted rays are focussed in the receiver plane after reflection. Rays from the surface are focussed at a point (4) separated from the focal point (6) of the rays from a fault (5). A screen (7) may be used to prevent the surface reflected rays from reaching the receiver.