GB1402495A - Method for measuring and evaluating ultrasonic test pulses - Google Patents

Abstract

1402495 Ultrasonic testing of materials THYSSEN NIEDERRHEIN AG HUTTEN. UND WALZWERKE 22 May 1973 [30 May 1972] 24464/73 Heading H4D In a method for processing ultrasonic test pulses using a plurality of transducer probes and wherein time gates are produced for the defect and bottom echoes, taking into account the time for the pulses to pass through the probe and a coupling medium, the defect and test sample bottom echo amplitudes being measured and their ratio taken, the amplitudes are corrected for depth, the path lengths of the probes and coupling medium being individually and successively determined and the ratio of the defect and bottom echo amplitudes being determined by obtaining their amplitudes logarithmically and then subtracting. In Fig. 3, the governing equipment provides all the necessary timing pulses for the transmitter and processing circuitry. In the gate control, the time gates, one enframing the expected time for defect echo arrival and one enframing that for bottom echo arrival, are generated. The time for the injected pulse to travel through the probe and coupling medium is gated out. In the echo level measurement section, the amplitudes of the defect and bottom echoes are measured. The depth of the defect is measured in the travel time measurement unit and from this measurement a compensation value is derived from the depth characteristic curve. In this way, the true defect size is obtained from the echo amplitude which has been compensated for its dependence on depth. Additionally, the bottom echo amplitude is compensated from a knowledge of the test sample thickness. The amplitudes are measured logarithmically, subtracted and the answer compensated. The resulting value is discriminated by a threshold detector before being passed as a detected defect to a computer or recording device. Detailed circuitry of the various units is given.