Surface crack detection by using vibrothermography technique

ABSTRACT This paper aims to optimise the vibration frequency that produces the highest temperature difference between crack location and non-defect location. The optimisation was based on thermoelastic damping analysis, and the analytical frequencies were varied between 10 Hz and 100 kHz. The result of optimisation was frequency 20 kHz for this study. In experiments, the effects of vibration frequency and vibration amplitude were studied. The experimental frequencies were 4.7, 20, 24 and 28 kHz. The piezoelectric disc was used as a sensor to measure the vibration amplitude on crack location. Then, the measured amplitudes were read in terms of the output voltage from the piezoelectric disc as 2, 4, 6 and 10 Vrms. The maximum difference in temperature between crack and non-defect locations was 0.33°C, which was obtained from vibration frequency of 20 kHz. Using high vibration amplitude did not significantly increase the temperature difference between crack and non-defect locations.