Abstract: On the basis of normal ultrasonic NDT (Non-Destructive Testing), the numerical signal analysis methods, the wavelet transformation, and the singularity analysis methods are used to characterize the weak signal reflected by friction welding defects from the large noise. The weak bonding defect, which can not be detected out using normal NDT methods, are detected out with the methods, and the precision of the detecting results to the other welding defects are increased with the methods. The characteristic analysis method as well as a fuzzy analysis method are carried out to classify the friction welding defects effectively.

Key words: Friction welding, NDT Ultrasonic wave, Welding defect Signal analysis