Study On The Fatigue Life Of Rail/wheel Rolling Contact Of Nonlinear Steady-state Curving

With the continuous improvement of train speed and axle load in our country,The wheel/rail interaction is becoming more intense. In recent years, a large number of literatures has studied the wheel/rail rolling contact relations deeply from two aspects of theory and experiment. And one of the most compelling causes is the wheel/rail rolling contact fatigue, which directly affect the operational safety and costs. Nonlinear steady-state curving as an important research field of locomotives and rolling stock research which is close to actual situation, is involving the geometric nonlinear, the creep characteristics and the nonlinear of spring component.Based on the explicit analysis platform ANSYS/LS-DYNA, focused the research object on wheel/rail contact problem of CRH2 EMUs, the finite element model of wheel/rail rolling contact of nonlinear steady-state curving is established. Through the dynamic simulation of wheel/rail rolling contact process, all time history stress data can be obtained, which is used to analyze the rail rolling contact fatigue life. Specific research contents and relevant conclusions are as follows:(1) On the basis of comprehensive exposition of the wheel/rail rolling contact fatigue research status at home and abroad, the research significance and direction of wheel/rail rolling contact fatigue is determined.(2) According to the actual stress state of wheelset, the simplified calculation formula of the initial lateral displacement and equivalent traction of wheelset of curved track is derived.Under considering the influence of the actual geometrical shapes of wheel/rail, the nonlinear of spring component, the train traction, initial lateral displacement of wheelset and the dynamic condition at the end of transition curve, the finite element model of wheel/rail rolling contact of nonlinear steady-state curving is established, which apply to the middle and low frequency rolling contact analysis, with the rail lateral and vertical vibration frequency are 0 ~ 400 Hz and 0 ~800 Hz respectively.(3) Through in-depth analysis of the features of implicit and explicit algorithm,the explicit-explicit order solution method is put forward. The calculation results of the explicit-explicit order solution method and the typical implicit-explicit order solution method o ANSYS are basically identical when solving the finite element model of wheel/rail rolling contact of nonlinear steady-state curving, but the CPU solution time of the explicit-explicit order solution method is only 1/3 of the implicit-explicit order solution method. Therefore, the explicit-explicit order solution method is more suitable for solving the model of wheel/rail rolling contact of nonlinear steady-state curving.(4) Import the initial residual stress of rail after straightening by the dynain file method, and apply the explicit-explicit order solution method to solve the wheel/rail rolling contact process to get the stress data of all time history, which is used topredict the wheel/rail rolling contact fatigue life by ncode DesignLife software according to the rain-flow counting method and the Palmgren-Miner linear cumulative rule. Results show that in the longitudinal direction of railhead tread, the rolling contact fatigue life presents obvious peaks and troughs phenomenon; and the olling contact fatigue life decreases gradually centered on wheel/rail contact area in the lateral direction of railhead tread; meanwhile there exist certain phase difference between the wheel/rail rolling contact fatigue life and the normal contact force.