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In this study, the most part is acquainted with the effect of elbow pipe to the guided wave. Elbow pipes were most seen feature in work environment. It was difficult for inspection that the anti-symmetric of signal increased when it passed the elbow pipe by happening mode conversion. The study content includes the using modal solution of the finite element method to solve the dispersion curve of four different bend radius of elbow pipe, they were : 1.0 m, 0.6 m, 0.4 m and 0.2 m. Therefore, by using simulation of wave propagation and experiment to verify dispersion curve of bend pipe were accuracy. This study reveals that, the dispersion curve of elbow pipe is similar to that of straight pipe, and T(0,1) mode in the elbow pipe is most similar with it in straight pipe. Thus, the dispersion curve in elbow pipe and straight pipe were similar, but the effect of geometry of elbow pipe will make the symmetrical incident signal time delay and wave front will distortion, and then it will cause mode conversion. According to the experiment of this study, although the signal of feature behind the elbow pipe caused by mode conversion will make anti-symmetry of reflection signal increase, it still won¡¦t make shift between reflection signal location and real feature location. It is very difficult and complex for inspecting the particular geometry pipe. If we can use the modal analysis of finite element method to solve the dispersion curve of particular geometry pipe, the inspection can be improve.

The work presented in this thesis concerns the development of vision based systems for two hardness (destructive) tests, namely; the Shore and Vickers and a quality assurance non-destructive test. In each case the vision system is based on an IBM PC compatible computer fitted with a commercially available frame store. Bespoke image analysis software was written using the C language for each system. In the Shore test, hardness is judged by the maximum rebound height attained by an indenter incident on a test sample. The purpose of the vision system is to measure the rebound height automatically. Laser light is used to illuminate the indenter and a vidicon vision camera is used to view its motion. Two approaches to the problem are considered; one in which image data is analysed in real time and one in which image·data is merely stored in real time and analysed a posteriori. Non-real time analysis is shown to be superior to real time analysis in terms of accuracy and reliablity and its software implementation is discussed in detail. The Vickers test uses the size of the permanent impression left by an indenter forced into the test material under a known load as a hardness index. In this case the purpose of the vision system is to measure the size of the indentation automatically. The original image analysis algorithms are shown to be capable of analysing good quality samples but are unreliable when applied to poor quality specimens. Further, fault-tolerant, algorithms are described to provide reliable and accurate results over wide variations in sample quality.The quality assurance application involves automated visual inspection of novel ferrite components for defects. Each component is approximately 8 mm in diameter, annular in shape, and coated with aluminium. Laser light is used to illuminate individual components which arc viewed using a charge-coupled device (CCD) video camera. Image analysis algorithms for characterising defects in component geometry and surface finish arc discussed. The system is shown to capable of measuring component edge eccentricity and hole offset as well as providing a quantitative description of surface chips and cracks. The system is further shown to be capable of separately classifying surface defects extending to the edge of a component. Calculation of shape parameters for surface defects also provides a means of distinguishing cracks from surface chips.

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