| 摘要 |
PURPOSE: To enhance the efficiency for determining defects by comparing the signal level of an image located within a set testing range with a specific threshold, and selecting an image which has exceeded the threshold. CONSTITUTION: If a plate ultrasonic wave is made to propagate from an ultrasonic probe placed near one of the edges of a material for flaw detection to the other edge, since an indefinite image resulting from irregular reflections caused near the ultrasonic probe is formed on one side of a two-dimensional flaw detection image, and a beltlike image caused by the other edge is formed on the other side in accordance with the dimension of the material for flaw detection, by setting a flaw detection range from an image of the other edge in the two-dimensional flaw detection image according to the size of the material for flaw detection, meandering of the material for flaw detecting, if any, can be followed. In this flaw detection range, since the images related to the edges and the image caused by the irregular reflections exist near both ends, by setting a threshold that gets larger toward near both ends and that gets smaller at the portion halfway between the ends and by selecting an image of a signal level exceeding the threshold, images produced by defects are selected at a high rate even near both ends. |
