2020 Volume 66A Pages 529-539
In the case that the fatigue crack face is contacted due to the stress condition, un-derestimation or overlook of the crack might happen in ultrasonic testing. To cope with such a crack closure problem, the nonlinear ultrasonic method is immensely promising. The contact and non-contact behaviors of crack faces generate super-and sub-harmonics arising from interactions with large amplitude incident waves. In this study, an attempt has been made to evaluate fatigue cracks in a structural components using ultrasonic waveforms traveling a long distance. Here, the ultra-sonic waves transmitted through the fatigue crack in a steel specimen were measured while changing the contact state of the crack face. The properties of the measured signals were investigated by comparing to numerical modeling results.
