| 摘要 |
PURPOSE:To detect even a small defect with high accuracy by compensating the detected signal of a bottom face echo by the detected signal of a surface echo, and deciding the state of a defect, based on the compensated detecting signal of the bottom face echo. CONSTITUTION:An ultrasonic pulse is made incident on an object material to be inspected 12, an echo which is generated by its reflection is detected, and the detected height S of a surface echo 20, and the detected height B of bottom face echoes 21-33 are detected. In this state, in order to compensate the detecting signal of the bottom face echo by the detecting signal of the surface echo, the S/B or B/S of each signal height S, B is calculated. In this case, the compensation can be executed by only taking the ratio, therefore, a bottom face echo signal can be compensated by a comparatively simple procedure. A threshold level is provided against the variation quantity of a value of a compensated bottom face echo signal B/S or S/B, and when a variation exceeding its threshold level is generated, it is decided that an internal defect exists in the object material to be inspected. Also, when the threshold level is not provided, the value itself of the calculated S/B or B/S is used as an index for deciding the state of the internal defect of the object material to be inspected.
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