GB1277065A - Device for measuring parameters of propagation of ultrasonic oscillations in material of article - Google Patents

Abstract

1277065 Ultrasonic inspection devices INSTITUT MEKHANIKI POLIMEROV AKADEMII NAUK LATVIISKOI SSR 22 Sept 1969 [20 Sept 1968 (2)] 46464/69 Heading H4D In a system for measuring the ultrasonic wave propagation characteristics in a specimen by comparing the waves received at one receiving transducer from two transmitting transducers or at two receiving transducers from one transmitting transducer after travelling two paths in the specimen of different length but having at least part thereof in common, the comparison is made on a cathode-ray tube (C.R.T.) with delayed sweep by superimposing the two displays of the waves received via the two paths, the two paths are travelled in respective half-cycles of a commutator cycle, and two delay generators are so controlled by the commutator that one provides the sweep delay and the other provides the differential delay #t needed to bring the two displays into coincidence on the C.R.T. time-base. In the Fig. 2 embodiment pulser 6 energizes transducer 7 once per half-cycle of commutator 5 and two-channel amplifier 9 is gated such that in alternate half-cycles the outputs of receiving transducers 8, 8<SP>1</SP> respectively are fed to the Y-plates of C.R.T. 10. Calibrated attenuators may be used for comparing the amplitudes of the two outputs. Sweep delay generator 13 enables a selected portion of the output to be displayed and calibrated delay generator 12 provides an additional sweep delay #t in those half-cycles where the longer path 7 to 8<SP>1</SP> is travelled in specimen 16. #t is thus a measure of the propagation characteristics over path l. Calibration markers 18, 20, may be used in calibrating the dial of delay generator 12. Transducer 7<SP>1</SP> may be used as transmitter for reversing the propagation direction so that measured values may be averaged to reduce acoustic coupling errors. In a second embodiment (Fig. 3, not shown) the delay #t is imparted to the transmission pulse in alternate half-cycles instead of to the sweep delay circuit. In third embodiment (Fig. 4, not shown), using two transmitters and one receiver, the transmitters are pulsed in respective half-cycles of the commutator, a single channel receiver amplifier is used, and the delay #t is imparted to the transmission pulse in alternate half-cycles. The invention enables propagation velocity, attenuation, wave dispersion and resonance oscillations to be studied.