Ultrasonic Infrared Thermal Wave Nondestructive Evaluation For Crack Detection

The ultrasonic infrared thermal wave technique is a new method for crack detection in which a short pulse of ultrasonic is introduced to materials to produce frictional heating at defects. It is difficult to test cracks interfacial or vertical with structure's surface by the traditional nondestructive testing methods. Ultrasonic infrared thermal wave nondestructive testing technology uses high-power and low-frequency ultrasonic as heat source to excite the sample and an infrared video camera as detector to detect the surface temperature. The ultrasonic emitter launch pulses of ultrasonic into the skin of sample, which causes the crack interfaces to rub and dissipate energy as heat, and then caused local increase in temperature at one of the specimen surfaces. The infrared camera images the returning thermal wave reflections from subsurface cracks. A computer collects and processes thermal images according to different properties of samples to get satisfied effect. The ultrasonic infrared thermal wave technique has advantages of ultrasonic and infrared thermal wave technology. It is promised that ultrasonic infrared thermal wave method is a sensitive, fast, wide-area, nondestructive evaluation technique. The ultrasonic infrared thermal wave nondestructive detection is fast, sensitive for cracks, especially cracks that vertical with structure's surface. It is significant for nondestructive testing in manufacture produce and application of aviation, cosmography and optoelectronics.In attempting to implement an inspection using ultrasonic infrared thermal wave, the ultrasonic energy should be coupled to the defects as efficiently as possible. For this purpose, the sample and the ultrasonic device should be mounted rigidly. Moreover, it is important to control the pressure between the surface of the sample and the horn tip to insure effective defects excitation.The work in this paper analyses the influence of the force between sample and ultrasonic emitter, ultrasonic swing, and ultrasonic pulse width in ultrasonic infrared thermal wave nondestructive evaluation, design devices to control and measure the pressure between sample and horn tip which could make ultrasonic infrared thermal wave technique quantitative. In addition, ultrasonic infrared thermal wave inspection has been carried on to a laser welding stainless steel plate and a carbon fiber juncture, and then extraction and processing of the raw data are realized in MATLAB.