Research And Application On Key Technology Of Metal Materials Ultrasonic Flaw Detection

Ultrasonic testing is used and studied in industrial nondestructive testing widely. Ultrasonic phased array technology is developed on the basis of ultrasonic testing. The beam is controlled well to the desired directions by controlling the time delay to realize the multi-directional scanning for the metal materials, to identify defect compared with traditional ultrasonic testing. The goal of this paper is to research the method of ultrasonic signal processing and to identify the defect in metal materials by phased array technology.The main works done in this paper include:(1)The theories of ultrasonic defect detection in metal materials were researched, including ultrasonic testing, phased array technology and Hilbert-Huang transform which was used in ultrasonic signal processing.(2)The improved Hilbert-Huang transform (HHT) was proposed and applied to ultrasonic signal de-noising. Improved algorithm put forward wavelet packet which doing pretreatment for signal firstly. The log-likelihood test was proposed which was with the log-likelihood value of each intrinsic mode function component and the original signal as the judgment basis to identify and remove illusive components. Then useful defection signal was reconstructed. Finally, by de-noising the ultrasonic signal, the result demonstrated feasibility and effectiveness of the improved HHT.(3)Phased array technology based metal materials for defect recognition and imaging method is researched. The directivity and beam scanning of ultrasonic were analyzed. The time delay of sensor in transmitting and receiving ultrasonic was controlled in MATLAB to realize the multi-directional scanning for metal materials. The beam of defect was focused on by phased array theory. Then defect image based on signal energy was produced. Finally, the experiment based on without direction data collection was designed to identify the defect in metal materials accurately.(4)The application of ultrasonic phased array technology to defect detecting in metal materials is researched. The advantage of phased array technology was took to implement the nondestructive testing, which contained test for a calibration block and test for butt weld in aspect of scanning mode and focusing algorithm of the probe. The result of the experiment confirmed that the ultrasonic phased array technology is better than the traditional ultrasonic testing ones.