JPS6426147A - Ultrasonic flaw detecting method - Google Patents

Abstract

PURPOSE:To increase the defect detecting capacity by setting an irradiation interval of a laser pulse to a time interval at which an ultrasonic wave is propagated through the distance of specific multiple of thickness of a body to be inspected, at the time of an ultrasonic flaw detection for using an ultrasonic wave generated by projecting a laser. CONSTITUTION:A pulse laser beam 2 is projected to the surface 4 of a body to be inspected 3 from a pulse laser 1. Subsequently, it is detected by a laser interferometer 10 that an ultrasonic wave generated thereby reaches the reverse side 5 of the body to be inspected 3 as a transmission wave 7, a defect reflected wave 8 and a first reflected wave 9 with a time difference, and displayed on an oscilloscope 12. Also, as for said laser beam, it is projected plural times, and also, its irradiation interval is set to a time interval at which a projected wave is propagated through the distance of two times of thickness of the body to be inspected 3. In this state, from the pulse laser 1, two pulse laser beams 2 are emitted at a time interval being equal to the time when the ultrasonic wave goes and returns in the body to be inspected 3. As a result, the first reflected wave by projecting a first pulse laser beam and the transmission wave by a second pulse laser beam are superposed, and the ultrasonic intensity can be increased without increasing a laser output.