JPS6469950A - Ultrasonic wave flaw detector - Google Patents

Abstract

PURPOSE:To make it possible to detect a flaw at the threaded part of a bolt, by providing a waveform memory device, an envelop forming device, a rate-of- change operator and the like. CONSTITUTION:A pulse generator 20 is connected to a probe 2 and generates a pulse signal. The probe 2 is excited with the pulse signal and transmits ultrasonic waves into a material under test 1. The probe 2 receives the reflected wave from a thread part 1A of the material under test 1A. The received ultrasonic wave is transduced into an electric signal. The probe 2 is connected to an amplifier 21. The signal is amplified, detected 22 and stored in a waveform memory 23. An envelop forming device 26 connects the peak points of the wave form of the electric signal, which is stored in the memory 23, and forms the envelop of the waveform. The forming device 24 is connected to a rate-of- change operator 25. The operator 25 obtains the rate of change of the envelop in a built-in differential circuit. Only when the magnitude of the result is larger than a specified value, a signal is outputted. A counter 26 counts the output signal from the operator 25. When the counted number becomes 2, a signal is outputted to a recorder 27 and an alarming device 28.