Ultrasonic Testing for Thinkness of Thermal Barrier Coatings Based on Wavelet Analysis

Due to the singularity of the ultrasonic signals from the top and bottom surfaces of the coating, the ultrasonic signals can be analyzed through continuous wavelet transform. And the methods of the modulus maxima and Lipschitz exponential were exploited to determine the singularity of the ultrasonic signals. Therefore, the time difference of the reflected signals on the coating interface can be obtained and thickness of the coating can be calculated by using a known speed of sound of the coating. Finally, the results are compared with the coating thickness measured by the SEM to verify the feasibility of this method.