| Summary: | 碩士 === 中原大學 === 土木工程研究所 === 96 === Tomography has applied in testing in many domains. In the medicine and geoscience both has quite mature application and development, but actually not yet develops practical pattern in the non-destructive testing for structural elements. Because the structure element cross section belongs to highly non-isotropic cross section, and the size of flaw is smaller. Therefore the ray path is more complex.
This article use seismic tomography method proceed to the non-destructive testing for the structural elements, and use pseudo-bending ray tracing method to be the forward modeling of seismic tomography. Discuss the effect of tomography of structural element by pseudo-bending ray tracing method.
The seismic tomography contains two important procedures. The first one is the forward modeling for given ray path and travel time. The second is the inversion for updating the model of wave velocity. In forward modeling, this article use pseudo-bending ray tracing method. The principle of this algorithm is assumed an initial ray path. The initial guess of the ray path is iteratively perturbed by known model of wave velocity until the travel time along the path is minimized. Calculates ray path by forward modeling, then reconstructs the model of wave velocity by SIRT inversion technique and LSQ inversion technique. Finally, process the result by image replot technique, and then output it by gray scale chart. By the gray scale chart can ascertain the components of the structural elements.
Besides discusses the effect of tomography of structural elements by
pseudo-bending ray tracing method, also compares the effect of reconstruct the model of wave velocity by SIRT inversion technique and LSQ inversion
technique. The result demonstrates that to display the damage region and
position of steel bar in concrete by SIRT inversion technique, both has good
effect. Otherwise, LSQ inversion technique is unable the effective to display
position of steel bar in concrete.
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