JPS6438652A - Ultrasonic flaw detection method and apparatus - Google Patents

Abstract

PURPOSE:To always detect a flaw in a real time under the optimum receiving condition, by filtering a flaw detection signal by a filter group and selecting the signal having the highest S/N ratio in the flaw detection signal by a max. S/N signal selecting means. CONSTITUTION:The trigger signal TR outputted from a pulser 2 is sent out to a material 3 to be inspected through an ultrasonic probe 1 and, when there is a flaw in the material 3 to be inspected, the flaw detection signal F from the probe 1 is outputted to a wide band-pass filter BPF 7 and an optimum filtering circuit 42 through amplifying circuits 4, 6. The signal F inputted to the BPF 7 is detected by a detection circuit 8 to be outputted to a waveform display circuit 42. The flaw detection signal FMAX having the highest S/N ratio in the inputted signal F is selected in the filtering part 9 to be outputted to a non-linear amplifying circuit 32. The signal FMAX is non-linearily amplified by the circuit 32 to be outputted to a flaw judge circuit 11 as a flaw detection signal FNLA. The signal FNLA is made proportional to the threshold value TH of a threshold value setting circuit 31 in the circuit 11 and, when the signal FNLA is larger than the threshold value TH, the signal FNLA is outputted to a flaw display circuit 41.