Analysis And Research On Fatigue Crack Initiation And Expansion Of Wheel/Rail Rolling Contact

With the rapid development of high-speed railway in China, the train speed and loadincrease gradually. A series of railway transportation challenges are put forward to scientificresearchers, some problems are also encountered. For example, how to solve the problem ofabrasion, elimination, thermal damage and thermal fatigue in wheel tread and rail surfacecaused by friction heat between wheel and rail has become a long-term study for manyexperts and scholars.Rail is one of the most important parts in the system of wheel rail contact. In theprocess of train operation, the complex vehicle loads directly load on the rail. The wheel isrunning parts of the high-speed train, and the contact mechanics behavior between rail andwheel relates to high speed train operation safety. In recent years, the train operationenvironment gets worse gradually. At the same time in order to ensure the safety, stability,long-term and comfort of train operation, the key parts of the wheel/rail contact has becomethe main object to be studied by researchers. Due to the changeable geometry, thecomplicated contact mode and the load transfer form of the wheel and rail, the test andnumerical simulation become very difficult. Furthermore, because of the highly nonlinearbehavior of wheel/rail, the real conditions of wheel rail rolling contact are difficult to bestudied in the experiment. The finite element method applied to computer simulation becomesthe main method to solve this problem.In this paper, the research results and the existing contact problems of wheel and railare summarized firstly. The research value of wheel rail rolling contact fatigue failure isillustrated. The fatigue crack initiation and propagation involve to the rail life and the safetyof the rain operation. Secondly, the Hertz contact theory is introduced. The theory providessolutions to simplify the wheel/rail contact problem, and lays the foundations for the furtheranalysis of wheel/rail contact. And some guiding significance conclusions are obtained. Withrapid development of the finite element method and the computer technology, numericalsimulation becomes the main analysis method. Again, the related theory of fracture mechanicsis introduced. It is pointed out that using the stress intensity factor establishes the fracturecriterion is reasonable. The exact solution of penny shaped crack front stress intensity factoris deduced under the surface normal uniform load. Finally, the finite element model of thewheel/rail contact is established with the finite element software ANSYS. The influence offoundation stiffness and thermal on the elastic-plastic stress field of the wheel/rail contactregion is analyzed. And the stress and displacement field near crack tip changing with thetrain speed are analyzed when the vertical cracks are in rail bottom. Finally, the variation of Mises and shear stress in crack tip is also analyzed when the wheel glides track with verticalcrack.