The Influence Of The Friction Heat On Wheel-Rail Contact Under Normal Operating Condition

With the rapid development of China's economy,the railway transportation system has also been developed rapidly.High-speed and heavy-loading are important trends in the development of railways.Under this development,the contact mechanism between wheel and rail becomes more and more complicated,and the contact conditions between wheel and rail are deteriorating.The wheel-rail has complex geometry and the contact problem between the wheel and rail is a highly nonlinear behavior.Previously,the contact problem between the wheel and the rail was based on the Hertz contact theory,but due to the limitations of the Hertz contact theory,it cannot be truely reveal the contact between the wheel and rail.With the development of large-scale finite element analysis,the use of finite element analysis software to calculate the contact stress between wheel and rail can obtain more reliable results of the wheel-rail contact stress under actual conditions,and can provide a reliable method for the study of wheel-rail problems.According to the contact relationship between wheel and rail,combined with the theory of wheel-rail tribology,wheel-rail contact theory,heat transfer,elastic mechanics,etc.,the three-dimensional wheel-rail contact finite element model is established using ANSYS.The elastic assumption is made for the contact of wheel and rail,and different wheel-to-shaft heavy loads are selected to simulate the shape,area,contact pressure and equivalent stress of the wheel-rail contact spot under the static load condition and pure rolling condition.And the influence of frictional heat on the shape,area,contact pressure and equivalent stress of wheel-rail contact spots under pure rolling conditions was analyzed.The following conclusions were drawn:(1)Under the static load condition,as the axle weight increases,the wheel-rail contact stress also increases,and the contact pressure of the wheel-rail is greater than the value calculated by Hertz theory.The shape of the wheel-rail contact spot is generally elliptical,but due to the influence of the wheel-rail profile,a smaller contact area is created near the elliptical contact spot.The area of the contact patch increases linearly with increasing axial weight.The equivalent stress of the wheel and the rail is irregularly distributed,and the maximum equivalent stress appears at a depth of about 2 mm on the contact surface.As the axle weight increases,the equivalent stress of the wheel and the rail increases,and the magnitude of the increase increases.Similarly,the maximum equivalent stress values of the wheel and rail are similar.(2)Under pure rolling conditions,as the wheel axle weight increases,the area and shape of the wheel-rail contact spot and the equivalent stress distribution on the wheel and rail aresimilar to those under static load conditions.Contact pressure at static state compared with that at the rolling condition,it increases,but the increase is small.(3)Under the action of frictional heat,when the wheel pair is purely rolling,the contact pressure on the wheel-rail contact spot is correspondingly reduced compared to that under the no action of frictional heat,and the maximum difference is 1.14%,and the reduction is small.The area of contact spots increased significantly,with a maximum increase of 7%.The shape of the contact spot is similar to that under the no action of the friction heat.(4)Under the action of frictional heat,the equivalent stress changes on the wheel and the rail are more obvious.The effective stress area is obviously larger than that without considering friction heat,and the influence depth is also increased.As the axle weight increases,the maximum equivalent stress increases,and is less than the equivalent stress of the wheel rail without friction heat acts.