| 摘要 |
PURPOSE:To improve detection accuracy of a surface defect by allowing a supersonic wave to impinge on from a probe at an incidence angle so that a reflection echo from a corner of the surface defect can be received. CONSTITUTION:A probe 2 is laid out so that the incidence angle alpha of an ultrasonic wave ranges from 5 to 20 degrees and then the ultrasonic wave is applied to the surface of a steel pipe 1 from the probe 2 through an acoustic lens 20. Then, when the reflection echo is received by the probe 2, a flaw-detection signal representing the received reflection echo is fed to a sate circuit 6 through an amplifier 4 and a detector 5, and then the flaw-detection signal of reflection echo which is equal to or higher than a specified threshold level is discriminated, an alarm indicating the presence of the surface defect is output. Then, when the surface defect exists in the steel pipe 1, the reflection echo at the corner of the surface defect can be received by the probe 2, thus detecting the surface defect including a crack flaw which is narrow, a blush flaw, etc. |
