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

Abstract

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 characteristic of a horn-sample system are deeply investigated in this paper. A two-degree-offreedom dynamic model based on GW contact model is proposed for exploring the vibration characteristic 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.

Analysis on high-frequency vibration characteristics of complex blades under ultrasonic excitation

“…Due to the complex shape of the blade structure and the existence of energy dissipation under ultrasonic excitation, the blade vibration waveform is not as regular as the metal plate vibration waveform in the literature [19], and the blade amplitude is much smaller than the amplitude of the horn. It can be seen from Figure . 7(a) and Figure . 8(a) that the displacement amplitude of blade A is about 10.1 μm, and the displacement amplitude of blade B is about 6.7 μm, with a difference of 33.7%, while the mass of blade A and B differs by 35.7%, indicating that mass is the main factor affecting the amplitud [15] . Blade A has a smaller mass than blade B, and under the same power ultrasonic excitation, the high-frequency vibration is more severe, the vibration waveform is more complex, and there are more high-order harmonics in the frequency domain response.…”