Finite Element Analysis On Damage Mechanism Of Rails In Sharp Curved Subway

With the increased pressure of urban traffic,the development of the subway becomes more and more rapid,and the damage of rails in the subway lines,especially in the sharp curved section,becomes more and more serious.With the evolution of profile of rails in service,a three-dimensional finite element model of wheel-rail contact was established.The improved Abdel-Karim-Ohno model,which was implemented into finite element code ABAQUS by using a user material subroutine(UMAT),was applied for the simulation of the stress field,plastic strain and contact pressure of rails.Finally,the fatigue life contours of rails were calculated,and the damage mechanism of rails in sharp curved subway was revealed,which is helpful for the online evaluation of rails in the subway lines.The main work of this thesis is listed as follows:(1)The improved Abdel-Karim-Ohno model,which was implemented into finite element code ABAQUS by using the UMAT,was applied for the simulation of the responses of U75 V under the monotonic tension and cyclic loadings.Numerical results show that the improved the revised Abdel-Karim-Ohno model can reasonably predict the cyclic characteristic and ratcheting behavior of the U75 V rail steel.(2)The three-dimensional wheel/rail rolling contact finite element model was established and the influences of axle load,friction coefficient and offset of wheel on the stress field,equivalent plastic strain and contact pressure of rails were discussed.Numerical results show that the maximum equivalent stress and equivalent plastic strain of rails are not in the same location.The maximum contact area is not a linear relation with axle load.The plastic accumulation of rails makes the distribution of contact pressure more homogeneous.The offset of wheel increases,the wheel/rail contact point approaches the rail gauge corner,the contact pressure of rails increases with the increase of number of cycles,which results in a serious side wearing.(3)The finite element models with different rail's profiles were established,and the influences of profiles on the stress field,equivalent plastic strain and contact pressure of rails were discussed.Numerical results show that a serious side wearing appears in the rail gauge corner after different mileages in sharp curved subway.The increased side wearing can reduce the maximum contact pressure of rails and reduce the wear of rails in turn.Therefore,the profile of rails should be regularly measured in service,and the profile of rails should be polished to optimize the contact state according to the actual wear,which can reduce the wear of rails.