Effects of Contact Interface Roughness and Sample Mass on Vibration Characteristics in Ultrasonic Infrared Thermography

Nonlinear vibration plays a vital role in ultrasonic infrared thermography testing due to contact-collision effect between a horn and sample, and the effects of contact roughness and sample mass on vibration characteristics of a horn-sample system are deeply investigated in this paper. A two-degree-of-freedom dynamic model based on GW contact model is proposed for exploring the vibration characteristics of a horn-sample system. Then, the vibration characteristics of the horn and sample are calculated under different contact roughness and different sample mass. The results demonstrate that the contact roughness does not influence vibration characteristic of horn, but there are mainly $2f$ and $3f$ except the first harmonic $f$ in velocity responses of the sample. Besides, the amplitude of sample velocity increases with the increase of real contact area as the contact interface is smoother, and there is a 1.8-fold approximate relation in the three amplitude of harmonic $f$ under different contact roughness. On the other hand, with the increase of sample mass, the harmonic $f$ becomes the main component and higher harmonics decreases little by little. This work will be extraordinarily meaningful to optimize testing parameters and evaluate surface quality of sample in ultrasonic infrared thermography testing.