Research And Application Of Ultrasonic CT Technology On Non-destructive Testing Of Concrete

As one of the most economical methods of non-destructive test, ultrasonic computerized tomography (UCT) can reflect the quality of tested across section in an object precisely and integrally. So UCT have been a kind of efficient methods of non-destructive test method. Tomography including the calculation of two interrelated parts: forward and inversion. Forward is to strike a ray path, inversion is to strike a model of slow wave.Firstly, ultrasonic detection techlology and computerized tomography technology are introduced in the dissertation. Secondly, inversion algorithms and bend ray tracing are studied. A shortest path ray tracing (SPT) method is used during the iterations to get the real travel paths of rays. Based on the traditional image reconstruction arithmetic, the thesis presents two improved image reconstruction arithmetic, one is preconditioned conjugated gardient method (PCG) arithmetic; the other is damping least squares QR-factorization (DLSQR)arithmetic.The thesis uses the shortest path ray tracing (SPT) arithmetic to trace curve path caused by refraction and diffraction of ultrasonic. The algorithm for image reconstruction is one of the key techniques for computerized tomography (CT). The morbid state matrix convergence rate is slow, we use pretreatment method to improve its condition number and accelerate the convergence rate of iterative. The M combined with a general Conjugate Gradient Method, which lead to Preconditioned Conjugate Gradient Method (PCG). In view of the large date error, Least Squares QR-factorization algorithm will diverge. In order to improve the anti-noise capability of LSQR algorithm and inhibition iterative process of data error of divergence, iterative process can be imposed for certain damping. This is damping Least Squares QR-factorization algorithm.Numerical simulations and experiments show that the speed and quality of image reconstruction are improved due to the application of SPT. The PCG is more effective to improve the accuracy of computation and the quality of image reconstruction on concrete than the CG. DLSQR's healthy has good stability, the smaller storage capacity and calculation, the significant sense in assessing its safety, stability and administering diseases.