The Laser Ultrasonic Flaw Signal Processing Method Based On Wavelet Analysis

Since the metal member (such as, aluminum) will affect the life of the aging or damaged parts, more likely lead to other serious harm, surface damage is important cause of aging and damage to the metal parts, so the metal surface dent or damage detection is necessary. Ultrasonic testing is one of the most commonly used non-destructive testing techniques, the use of laser ultrasonic technology has many advantages:It can achieve excitation and non-contact measurement, frequency bandwidth, a wide range of suitable materials, measurement precision, it also can be detected on the surface of the dent and positioning.This paper studies the laser ultrasonic surface defect detection principles and built laser ultrasonic surface defect detection system. Analysis of the laser ultrasonic surface wave propagation characteristics and applications of laser ultrasonic surface wave wavelet sym8defect signal decomposition and reconstruction of its7layers noise reduction, and achieved good results, while providing for Signal Processing foundation. The surface acoustic wave signal propagation methods were studied, but also for the laser to the sample surface acoustic wave velocity was measured. By comparing three different experiments summarized the characteristics of the excitation wave signal source location changes and when the presence of a defect wave signal characteristics, and with the use of finite element simulation of the experimental results agree. This paper realized by "scanning" to accurately determine whether a sample contains a metal plate defects, and can determine the precise location of the dent, but to further determine the extent of the surface of a dent the size of the echo signal by comparing the peak to peak.