| 摘要 |
PURPOSE:To detect a micro defect in the surface of a thin piece with high precision and high efficiency by arranging plural ultrasonic probes so that the angle between projection ultrasonic beams is <=90 deg. and the angle of ultrasonic beam incidence of the same point is larger than a critical angle. CONSTITUTION:Plural ultrasonic probes 1a, 1b... are arranged radially so that the projection ultrasonic wave beams OE, OD, OF... are at an angle of 60 deg., etc., smaller than 90 deg. and the angle of ultrasonic wave beam incidence on the same point O of the thin piece 2 to be tested is larger than the critical angle. When the angles between those projection ultrasonic wave beams and the lengthwise direction of the defect 15 are 90 deg., the detection output of the corresponding probe 1a, etc., for ultrasonic wave received and scattered light is maximum and when the beams coincide with the lengthwise direction, the output is minimum, so that the micro defect in the surface of the thin piece is detected by plural ultrasonic wave probes in a specific array regardless of the influence of the defect direction with high precision and high performance. |
