| 摘要 |
PURPOSE:To provide a crack detection device having the capability of properly detecting a crack occurring in a workpiece under application to an induction hardening device of travel hardening type. CONSTITUTION:A digital filter 11 adjustable in passband is laid between an acoustic emission (AE) detecting means 8 for detecting acoustic emission from a workpiece 1 and outputting a signal after the conversion of the emission into a digital AE signal, and a periodic degree calculation means 9 for calculating the degree of the periodicity of the acoustic emission on the basis of the AE signal. In this case, the passband of the filter 11 is set so as to exclude a band containing the frequency of a heating noise signal due to a heating process, thereby allowing the passage of only an AE signal excluding the heating noise signal for output to the means 9. As a result, even if the workpiece 1 is subjected to heating and cooling treatment concurrently and a crack occurs therein, the periodicity of the acoustic emission can be detected with high accuracy for the proper detection of the crack. |
