Calculation And Study On The Press Straightening Technology Of Rail End Bending

Rail straightness directly influences on the running speed of train, the comfort of passengers and even the running safety. In production process of rail, rail is straightened by roller-straightening machine generally. However, rail ends will be formed non-straightening area after roller straightening, the rail end bending brings difficulty to rails joint, and then it will debase the running quality of train, so rail end bending still need be straightened by press straightener. Above all, the method to attain high straightness of rail end has become one of important research subjects. On the basis of current theoretical model of press straightening process, the calculation of press straightening technology of rail end bending is studied by the method of combination of theory analysis-finite element simulation-experiment research in this paper. Main research work is as follows:From the viewpoint of elasto-plastic mechanics theory, the deformation process of press straightening is analyzed, and the main technological parameters in press straightening technology flow are also expounded. The current calculating methods for straightening parameters are described and compared. Aiming at the disadvantage of current theoretical methods, the calculation of straightening parameters is developed on the basis of straightening process model in this paper. Then, the straightening process model is expatiated systematically.Considering the successful application of finite element method in press straightening, the finite element analysis software ANSYS is used to simulate the process of rail press straightening. By means of ANSYS, the load-deflection curve of press straightening process is obtained, and the relationship between straightening pressure and residual stress is analyzed. Meanwhile, the simplification of rail cross-section and its rationality are analyzed, in order to give facilities for the theoretical calculation of rail press straightening.Based on the mathematical load-deflection model of straightening process for rectangular section parts and shafts, the load-deflection model of straightening process for I-shaped section parts is established. The method for calculating straightening pressure and stroke based on straightening process model is obtained. Examples are calculated by theoretical model, and also analyzed by finite element method. Comparison shows that theoretical calculation results are in good agreement with the simulating results by ANSYS, the error is smaller, so it is proved that the theoretical model and calculation method of parameters are correct.The analogy experiments of I-shaped section parts are carried out. Experiments indicate that straightening process curves by the model are closed to experimental curves, correctness of the method based on straightening process model is further verified, and the applicability of the process model in calculating the straightening parameters is confirmed. The theoretical model can be effectively used for the studying on press straightening technology of rail end bending. So it will be meaningful and helpful for the design of auto straightening machine.