Ultrasonic Signal and its Wavelet Package Analysis of Defects in a Coarse-grained Material

The ultrasonic defect echo of a austenite stainless steel with coarse grains was acqiuired and processed using a developed computerized ultrasonic signal analysis system. Its results indicate that the wavelet package technique is of high dependability to express the bine-frequency property of the ultrasonic signal for defects in the coarse-grained material so as to overcome the weakness of the split-spectrum processing technique. In the meantime it is found that the defect information is distributed at middle frequency band, while noise is distributod at high and low frequency bands. Based on mis feature the ultrasonic defect signal of coarse-grained material can be detected from the wavelet package decomposition, even the echo signal is rather weak.