| 摘要 |
PURPOSE:To defect a flaw of a high detection capacity by small number of sensors for all surfaces and sections of a plate to be inspected by receiving an incident ultrasonic wave and reflected waves from an internal flaw, and extracting only the reflected wave from the received wave. CONSTITUTION:An ultrasonic transmitting element 22 transmits an ultrasonic beam 23 perpendicularly to a plate 10 to be inspected, and propagates it in a thickness direction of the plate 10. When an internal flaw 28 exists in a propagating route, a received beam is reflected on an upper surface of the flaw 28. Further, a reflected wave 30 again reflected on a surface 10a and a reflected wave 31 again reflected on a lower surface of the flaw 28 after reflecting on a rear surface 10b are received by an ultrasonic receiver 25. The received waves are amplified by a receiving amplifiers 501-50N connected to respective ultrasonic vibrators, only reflected waves are extracted by gating means 521-52N, and presence or absence of the reflected waves of a predetermined amplitude or more is detected by comparators 541 54N. In this case, since reflected waves of the flaw 28 existing near the surfaces 10a, 10b are received by the receiver 25 by largely delaying from transmitted waves of the plate 10, these waves can be clearly identified and detected, thereby eliminating insensitive zones of the front and rear surfaces. |
