GB1341005A - Method of and apparatus for testing a workpiece for disconformities of dimensions or shape - Google Patents

Abstract

1341005 Measuring strip material BRITISH STEEL CORP 17 Dec 1970 [17 Dec 1969] 61544/69 Heading G1M [Also in Divisions B2 H4] Disconformities of the dimensions or shape of a workpiece are detected by directing a stream of liquid on to a surface of the workpiece, transmitting ultrasonic energy along the stream and utilizing the energy reflected back from the surface through the stream to provide an indication of any such disconformities. In an embodiment for detecting buckling of hot or cold metal strip issuing from a rolling mill the strip profile is sensed by pulse-echo measurement of the distances between the strip surface and several test heads arranged above or below the strip at points spaced across the strip width. Each test head comprises Fig. 2 a Piezo-electric transmit/receive transducer 7 in a housing 6 into which water is fed at 9 as that it passes via apertures 17 into tube 15 and emerges from nozzle 10. Laminar flow is induced by a member 19 having bores 20, and is maintained by annular flange groove 21 which produces a toroidal air motion around a stream at the nozzle exit. Each test head is connected to a respective signal processing channel in which a bi-stable is set just before the expected arrival of the echo pulse, is reset by the echo pulse, and the reset pulse is displayed on an oscilloscope common to all channels and whose time-base sawtooth sweep is synchronized with the acoustic pulse transmission. The sawtooth amplitude is also sampled at the echo arrival instant and the sampled values for the different channels are recorded and may be used for automatic control of the rolling operation or strip feed rate. A single test head scanned across the width of the strip may be used instead of the several heads.