GB1422441A - Ultrasonic testing - Google Patents

Abstract

1422441 Ultrasonic testing MATERIALS & METHODS Ltd 31 Dec 1973 [12 Jan 1973] 1792/73 Heading H4D The velocity of sound in a solid specimen is measured, e.g. to test the quality of a metal casting subject to thickness variation, by comparing the time taken for an ultrasonic signal to pass through the thickness of the specimen with a standard time value which is varied in proportion to the local thickness as measured in the path of the ultrasonic signal. In the Fig. 1 embodiment the specimen is supported by table 2 and an echo pulse from its back wall, obtained from probe 1, is displayed within a time gate marker on a CRO time-base. A sensor 5 incorporating a rotary or slider potentiometer is brought down on to the specimen to gauge its thickness. The sensor output positions the time gate at a point corresponding to an acceptable reference sound velocity. The echo from an acceptable test specimen should thus be within the gate, irrespective of specimen thickness. Lamps may also give a "go-no go" indication of the test result, In the Fig. 2 embodiment the specimen is held in a sliding caliper, one arm of which includes an ultrasonic probe 25. A grip 24 to to close the caliper also operates a potentiometer to control the time gate position as above.