The Improvement Of Ray Tracing In Heterogeneous Medium And Finite Element Numerical Simulation

The computerized tomography (CT) technology with the genetic engineering, the new granule discovery and the astronavigation technology compound was the four international biggest science and technology achievement in 1970. As an across discipline, it involves knowledge of mathematics, physics, computer and so on ,so it has developped vigorously in the past several decades.Thus it will have a widespread application value in the future.Both at home and abroad,it has succeeded in appling to the medical diagnosis, geophysics, radio astronomy etc.In the water resources & hydropower engineering and the civil engineering, the CT technology also has the broad application prospect.In order to enable the computerized tomography technology to have a better application in the non-uniform medium field, this thesis improves one kind of ray tracing algorithm-two step synthesis method depending on the original algorithm.This algorithm has the characteristic of the simpler programme,the quicker tracing speed and also the higher precision.The result from the three simulation model continues that two step synthesis method is one effective ray tracing method.Because it can accurately persue the least travel time of ray fast and have very strong antinoise nature, so it can be used to the complex medium tomography analysis.This thesis simulates the transmittance of the ultrasonic and seismoscope in the two structure models with the transient dynamic analysis module of Ansys finite element method procedure under the sine load function of displacement.Through various particles'displacement, speed and acceleration curves of time history ,we may obtain the law of motion of each particle, hereby we can simulate the travel of wave.This thesis conductes the experimental study to be aimed at the ultrasonic speed inversion,then does the CT experiments in two circumstances of the arch dam model in good condition and having crack after loading. Whereafter,the rusult indicates this improved CT software could accurately reflect the position and depth of the crack inthe arch dam body.At the same time,we also realize the CT result couldn't reflect the width of the crack very well,explaines the software also has many bugs,we should take further improvement.In sum,the improved algorithm indicates in this thesis has good effect when using formation of image,especially suitable for heterogeneous medium and has very important application value in the concrete non-destructive testing.