| 摘要 |
PURPOSE:To detect exactly a minute defect under the surface of a material to be inspected, by using each oscillator for transmission and reception as a focusing type oscillator, diffusing an ultrasonic wave by a delay line provided on a prescribed position, and erasing a surface echo by differentiating spatially an echo signal of the receiving oscillator. CONSTITUTION:Transmitting and receiving oscillators 1, 2 consist of a focusing type oscillator, and an ultrasonic beam is diffused large by making focusing areas 9, 10 of the ultrasonic beam coincide with the side end part of a material to be inspected of delay lines 7, 8. A flaw detecting area of the material to be inspected 11 is divided into four areas in the depth direction and a flaw detection is executed, and as for an echo signal detected by the oscillator 2, its amplitude is detected through an amplifier 29 and a peak holder 30, an echo amplitude of the present position and the position which is previous by one is stored in sample holders (SH) 32-35, and SH36-39 of the second stage, respectively, a difference between both stored amplitudes is taken by subtracters 40- 43 and sent to DC detectors 44-47, and a surface echo is erased. Accordingly, a minute defect under the surface is detected exactly. |
