Affecting Factors of Ultrasonic Vibrothermography

Vibrothermography is one of the most important techniques in infrared thermographic NDT, and it has a special advantage in close crack-type defect detection. In order to find the suitable vibration excitation conditions, the influence of material thermal properties(conductivity and diffusivity) and defect depth on the surface temperature rise was solved with analytical method, and the influence of the support condition and geometric dimension of a specimen on its resonance frequencies was also studied. The results show that composite materials are easier to be detected than metals. A short duration excitation is appropriate for metal specimens, while a long duration excitation is preferred for composite parts. From the resonance point of view, the combination of simple support and ultrasonic excitation is a better choice.