Increasing the speed and thoroughness and economy of ultrasonic and other non-destructive testing of materials for detecting flaws or variances therein

摘要

An ultrasonic flaw detection apparatus comprises a plurality of piezo-electric crystals such as I, II and III, disposed in spaced relationship to each other and relative to the surface of a material specimen, e.g. tube K, to be tested, means for moving said specimen lengthwise past the crystals, a flaw detection instrument adapted to transmit electrical pulses to the crystals and to receive flaw-revealing echoes from said crystals, and sequencing cyclical switching means connected between said crystals and the detection instrument in such a manner that each crystal is connected individually to the instrument in sequential and cyclically repeated order. By using a plurality of crystals instead of only one the necessity to rotate the specimen is removed, thus increasing the tube testing speed, and as the flaw detection instrument transmits to and receives from only one of the plurality of crystals at any given instant the ratio of " noise level " to the flaw signal is kept at a minimum. The crystals I, II and III are positioned around the circumference of the tube K at equal 120 degrees spacings and each is respectively connected to segments 1, 2 and 3 of switch S. The rotating blade 25 of switch S is connected to a flip-flop unit which forms part of the flaw detection instrument. The flaw detection instrument contains a synchronizer, working in conjunction with the flip-flop unit, which times the spacing of the pulses sent out over conductor T from generator 16 (whose output has been adjusted to match the natural frequency of the crystals), and also provides the receiver 18 with a time sense. The crystals are inclined away from the specimen radius so that the probing sound therefrom enters the specimen surface at an angle indicated by the dotted lines. The tube K is moved lengthwise past the crystals by means of rollers (Fig. 3a, not shown). The Specification describes arrangements of the crystals for testing solid cylindrical, solid and tubular multi-sided, and flat specimens.