Method of and apparatus for ultrasonic non-destructive testing

Abstract

Abstract 716,687. Testing materials by ultrasonic vibrations. KRAUTKRAMER, J., and KRAUTKRAMER, H. Aug. 11, 1952, No. 20208/52. Class 118 (2). Relates to ultrasonic pulse-echo systems for detecting flaws in thin sheets of materials of the type in which an electro-acoustic transceiver transducer is coupled to a surface of the sheet by a wedge such that a beam of shear waves is propagated through the sheet by multiple reflections between the two surfaces of the sheet, the echoes produced by reflected waves travelling back over a similar path being displayed on a cathode-ray oscilloscope. In such systems a reference echo from a boundary may not be produced and since such an echo is useful for testing the coupling efficiency between the transducer and the sheet, for detecting the absorption or scattering effect of flaws incapable of producing echo indications and for estimating the size of flaws which do, a reference echo is produced according to the present invention by employing two spaced transceiver transducers connected in parallel and mounted on opposed wedges c and e so that the cathoderay display comprises a response p representing the pulses transmitted simultaneously by each transducer, a response t representing the signal received by each transducer from the other after at least one reflection at a surface, a response r representing the echo received by each transducer due to reflection at the other wedge and reponses s and q representing the echoes produced by a flaw b as received by the left and right-hand transducers respectively. When testing a pipe, the two transducers are adjacent and the two wedges are arranged to transmit waves travelling in opposite directions round the pipe, Fig. 2 (not shown).

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