MULTIPLE FREQUENCY ULTRASONIC AUTOMATIC FLAW DETECTION OF WELDED STEEL PIPE MADE OF AUSTENITE ALLOYED STEEL

摘要

PURPOSE:To make it possible to enhance S/N by improving energy efficiency, by performing flaw detection by allowing a finite number of ultrasonic pulses narrow in a frequency band width having mutually different center frequencies to be incident so as not to interfere the same to each other. CONSTITUTION:A wide band high damping type probe having an excessive frequency band width is connected to a narrow frequency band electric pulse oscillator for continuously chaning both of oscillation frequency and oscillation pulse amplitude in an excessive range and capable of adjusting both of them and a finite number of mutually different frequency values are successively and cyclically set to a tolerant frequency range inherent to each flaw to be inspected so that either one of said frequency values is certainly fallen in said range to allow an ultrasonic pulse to be incident to a steel pipe. The incident acoustic pulse reaching a flaw position is reacted with the flaw and the reflected pulse beam generated as the result of the mutual action thereof is reflected and propagated in the body to be tested and received by a receiving probe through a coupling.