| 摘要 |
PROBLEM TO BE SOLVED: To discriminate the presence of crack of a work instrain-straightening with a high precision by arranging a displacement sensor, an AE sensor, a means to discriminate the presence of crack of the work, based on the detected value of the displacement sensor, detecting the work enters a plastic deformation region and conducting a prescribed processing to the output signal of the AE sensor. SOLUTION: A work W mounted to center pins 3 is rotated, the position, where the output of a displacement sensor 2 is max, is directed a punch 10 side, by retreating the center pins 3, the work W is loaded on an anvil 8 and is pressed by the punch 10. An AE sensor 5 for elastic wave detection is arranged to the side face of the punch 10. When an amplitude exceeds a reference value and its count number is a prescribed number or more in a fixed time, it is discriminated there is a crack. Counting of the out put signal of the AE sensor 5 is started after the work W enters an elastic deformation region so as not to count initial external disturbance vibration when the punch 10 is abutted on the work.
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