GB1266342A - - Google Patents

Abstract

1,266,342. Ultrasonic inspection devices. BRITISH RAILWAYS BOARD. 5 June, 1969 [7 March, 1968], No. 11292/68. Heading H4D. In a pulse-echo ultrasonic flaw-detecting system using three transducers positioned rectilinearly a predetermined distance apart, at least one transducer has its beam axis at an acute angle to the line on which the transducers lie, a pair of transducers act as transmitters and one acts as a receiver or vice versa, and electronic or mechanical means enable two output signals derived from the use of said pair of transducers as transmitters or receivers and resulting from ultrasonic energy being transmitted into a test piece and reflected from a flaw therein to be made coincident on a common time-base. In the Fig. 1 embodiment, e.g. for testing railway track, clock pulse generator 1 periodically triggers pulsers 2, 3 for energizing probes B, C as transmitters. Probe A receives echoes of the two pulses reflected from flaw 10. The echoes are displayed as blips 8, 9 on a cathoderay tube. With the probes stationary, calibrated delay 4 is adjusted to delay the energization of probe B such that blips 8 and 9 coincide. The flaw position can then be deduced by triangulation. The roles of the probes as transmitters or receivers can be interchanged, with the delay 4 being inserted between a receiving probe and the cathode-ray tube. In the Fig. 2 system probes A, B, C are mechanically linked for movement together over the surface of rail 7, probe A being a transmitter and angle probes B, C being receivers. When path lengths a and b are equal the two echo blips will coincide and add in amplitude, and the flaw position can again be found by triangulation. An additional pair of angle probes may be added to the Fig. 1 or Fig. 2 system for inspecting regions at different depths in the rail, or one of the transducers in probes B and C may be combined with the transducer in probe A in a transmit/ receive probe.