Study On The Parallel Computation Of The Dynamic Analyse Of The Wheel/Rail System

Many mechanics analysis computational problems of large-scale complicated structures arise with the development of science research and engineering technology.The dynamics theory of wheel/rail system based on the finite element principle is a complicated numerical solution. In the complex system, the number of freedom degree is very large and many numerical computations are needed with the running of the train. While the theory of wheel/rail system dynamics is applied in the points(switch) dynamics, the system is more complicated and computation time is longer, therefore the parallel computing technology is an effective method to increase computation speed.In this dissertation, the series program structure of wheel/rail system dynamics is analyzed to search the solutions to parallel processing. First, the serial number of freedom degree is arranged according to the sleeper number in the finite element model. So the nonzero elements in the coefficient matrix can be arranged according to approximate belt-style in order that the method is favorable to parallel computation. Then the vibration equations in the wheel/rail system dynamics are constituted again and the rigidity matrix, the damping matrix and the load matrix can be formed by different computer processor for the sake of increasing parallel computation efficiency.The analysis of computation time of different subroutines shows that the solution of linear equations account for 75 percent of total workload and it is also the main work in the study. The characteristics of different parallel algorithms are compared in accordance with the specialty of coefficient matrix of vibration equations of wheel/rail system. Then, four parallel algorithms are used to solve the linear equations, such as Gaussian elimination, LU decomposition, LDR decomposition and WZ decomposition. With the method of cyclic distribution, all rows of the coefficient matrix is allotted into different processes, then eliminated and decomposed by relevant processors. The computation result is identical to that of series program, and the correctness of the parallel program is verified.Some methods are used to increase the parallel computation efficiency, such as the data cyclic distribution, overlapping of communication and computation, load-balancing in accordance with the computation ability of the Dawn-2000 node, communication mergence and so on. Compared with the complexity of different algorithms, the numerical test shows that the LU decomposition has the largest speedup and WZ decomposition has the fastest computation speed.This dissertation lays a foundation for the study of more complicated wheel/rail system dynamics and its development direction is proposed in the thesis.