| 摘要 |
PURPOSE:To handily detect a defect due to decay by white ants or the like within a square pilar, by determining the center of an internal defect from the propagation time of ultrasonic waves to connecting with a smooth curve points of contact obtained by drawing a perpendicular line to each external tangent from the center of the defect. CONSTITUTION:An ultrasonic wave transmission element abuts at peripheral positions M1 and M1' of an internally decayed square pilar to measure ultrasonic propagation time and determine the propagation time sequentially between the positions M2-M2',...M7-M7'. Likewise, the propagation time between the positions N1-N1'...N7-N7' is measured and the intersection between measurement lines indicating the longest propagation time gives the center of the defect. Then, a transducer is fixed near the mid-point of one side is fixed and then, moved farther along the adjacent side to find an external tangent to an internal defect from the rapid increase point of the propagation time. Then, points of contact obtained by drawing a perpendicular line to each external tangent from the center of the defect are connected by a curve to present the shape of the defect thereby detecting the defect. |
