Defect Identification And Research Based On Ultrasonic TOFD-LWE Inspection

Ultrasonic TOFD-LWE (Locating With Ellipses of TOFD) method is an improved new detection method based on ultrasonic TOFD (Time Of Flight Diffraction) method. With the development of the non-destructive examination industry, ultrasonic TOFD method is getting more and more people's attention for its simple principle, easy operation, fast detection and high detection rate of weld cracks. Introduction of the TOFD-LWE method makes it possible to achieve high detection precision of inside defects using only one scanning mode and get very accurate measurements of defect geometric features. This paper shows realization principle of the TOFD-LWE method in details and presents its advantages comparing to the traditional TOFD method:higher quantitative accuracy of defect, much simpler in realization and broader application prospects.This paper focuses on the way of Hilbert-Huang Transform in processing ultrasonic testing signals. As a new method of processing non-linear and non-stationary signals, Hilbert-Huang Transform has been widely promoted and applied since proposed because of its simple theory and significant effect. The key problem of defect assessment is to determine the arriving time of echo signals. While using Hilbert-Huang Transform to process the echo signals can get the exact arriving time from the signals'envelopes. Combined with the TOFD-LWE method, we can point-device quantify and position the defects. The pivot way of predicating defects type is to observe the dynamic wave of defects'echo signal using kinds of scanning with ultrasonic detection related standards based. This predication requires great deal of detection experiences in practice.At last, a display-controlling platform of ultrasound TOFD-LWE detection system is designed and realized under Visual Studio 6.0. which is used to control the inferior machine of the system and for data communication. This platform receives data of detection signals and saves them. Signal processing part is realized by mixing programming with MATLAB. The major functions for processing detecting signals are explained in details.