Abstract

Nonlinear ultrasonic waves, including higher -harmonic (HH)-waves, are likely to be applied in non-destructive evaluations of power plants. We first constructed a system to measure the frequency response characteristic of ultrasonic waves and experimentally investigated the mechanism of second HH generation caused by fatigue cracks. The system comprised of three-dimensional laser Doppler vibrometer (3D-LDV) to obtain contactless and local measurements. The features of 3DLDV are suitable for crack-induced scattered ultrasonic vibration measurements. Subsequently, by sweeping the input frequency, we measured the frequency response characteristic caused by fatigue cracks using the system and consequently obtained a natural frequency from the characteristic. Further, we measured the frequency response characteristic of the second HH using the same system and consequently, confirmed that the second HH resonated when its frequency corresponded to the natural frequency caused by the cracks. Additionally, we analytically revealed that the resonant second HH was generated from natural vibration and nonlinearity.

How to Cite:

Kanda, K. . & Lin, S. ., (2019) “Study of second higher -harmonic waves generation caused by fatigue cracks”, Review of Progress in Quantitative Nondestructive Evaluation .