GB1207385A

GB1207385A - Improvements in or relating to flaw detection

Info

Publication number: GB1207385A
Application number: GB4842867A
Authority: GB
Inventors: Jaroslav Obraz
Original assignee: SVU PRO STAVBU STROJU
Current assignee: SVU PRO STAVBU STROJU
Priority date: 1966-11-01
Filing date: 1967-10-25
Publication date: 1970-09-30
Also published as: AT288740B; DE1648739A1

Abstract

1,207,385. Ultrasonic inspection devices. STATNI VYZKUMNY USTAV PRO STAVBU STROJU. 25 Oct., 1967 [1 Nov., 1966], No. 48428/67. Heading H4D. In an ultrasonic pulse-echo system for inspecting a rod moved axially relative to several probes disposed in a plane normal to the rod axis, three-dimensional flaws (e.g. cavities and occlusions) and two-dimensional flaws (e.g. cracks) are distinguished on the basis that the three-dimensional flaws return echoes to more probes than do the two-dimensional flaws. In the Fig. 4 embodiment an m-phase synchronizer 10 controls m circuits 6 to 9 for pulsing m probes 1 to 4 sequentially in m respective periods which together make up an operating cycle. Echo signals returned to the probes are applied to gating circuits 11 to 18 which are opened by synchronizer 10 for times such that in the nth period echoes received by the nth probe and the (n+1)th probe are passed via lines 25, 26 to amplifiers 27, 32 respectively. The amplifier outputs are applied via flaw echo-gating circuits 28, 33 to staircase waveform generators 29, 34 whose outputs comprise as many steps as there are echoes from a flaw in one cycle, the generators being reset to zero at the end of each cycle. It is argued that an ultrasonic pulse from the nth probe is likely to be reflected to both the nth and (n+ 1)th probes if the flaw is three-dimensional, but to one probe only if the flaw is two-dimensional. Hence, at the end of each cycle the waveforms of both generators 29 and 34 will have m steps if the flaw is three-dimensional: this condition is detected by lower level limiters 30, 35 and coincidence circuit 37. The presence of fewer than m steps in either or both waveforms is detected by upper level limiters 31, 36 and a crack indicator 38. Output signals from circuit 37 and indicator 38 are applied to a recording device, an evaluating computer, or to an audible or visual signalling device. Indicator 38 is inhibited if circuit 37 is actuated.