| There are many factors involved in the operation safety of urban rail transit,which results in that many potential conditions will trigger safety accidents no matter what stage including the design stage,construction stage and operation stage.Therefore,higher safety requirements are also put forward.The rail's bear performance will decline a lot after a long period of service than its initial period.However,the fatigue crack in welded joints of subway rails is one of the key factors in the research on rail fracture.To analyze the mechanical field of rail fatigue around crack tip in detail,a combined method of theoretical research and elastic-plastic finite element analysis was adopted in this paper.Mechanical properties of subway rails fatigue crack under different working conditions have been studied and its remaining life was also predicted by establishing a wheel-rail contact model.The main tasks completed are as follows:(1)The wheel and rail of the subway was taken as an research object.Stress variation law in the contact position between the rail and the wheel was studied based on its finite element contact model.The crack location was analyzed according to the stress variation,and thus the FEM model with a elliptical shaped crack was established,the tensile stress distribution and the stress intensity factor at the crack tip was also obtained;(2)To accurately analyze the impact of load changes on the fatigue crack field of wheel-rail during the driving process,sub-model technology in ABAQUS software was adopted to analyze the influence of wheel-rail friction coefficient and overload on the stress strain field at the fatigue crack front;(3)Based on the U71Mn stress-strain curve relationship,an elastic-plastic material model of the rail was established.The effect of the variation of the yield strength and the... |
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