Analysis Of Wheel-rail Rolling Contact Fatigue In Metro Track Curve

Rolling contact fatigue damage is one of the main damage which affects the life of wheel and rail.If it is not handled in time or properly,it will cause wheelset and rail failure at any time,which will endanger the safety of driving.In this paper,the causes of wheel-rail rolling contact fatigue of curve negotiating vehicle are studied from the point of view of track structure parameters.The main work and conclusions are as follows:(1)Firstly,the existing experimental and theoretical research on wheel-rail rolling contact fatigue were summarized and the research significance of wheel-rail rolling contact fatigue were clarified.And a suitable one for metro vehicle wheel and rail rolling contact fatigue was selected.(2)The influence of track structural parameters on the static matching performance and contact mechanical properties of subway vehicles was studied by establishing the wheel-rail contact geometric calculation model,creep rate calculation model and three-dimensional non-hertz rolling contact mechanical model.The results show that the decrease of the railcant of the inner and outer rails will worsen the wheel-rail contact relationship and cause greater wheel-rail contact stress.The widening of gauge can improve the wheel-rail matching relationship,significantly decrease the contact stress and reduce the sliding behavior of the wheel and rail.(3)Based on the model of subway vehicle-track coupling dynamics and the three-dimensional non-hertzian rolling contact mechanics model,according to the actual rolling contact state of wheel and rail,the influence of track structure parameters on the wheel-rail dynamic matching relationship and the contact mechanics characteristics was analyzed.The results show that the decrease of the curve radius will worsen the wheel-rail matching relationship and make the wheel-rail have a large creep rate and creep force.The reduction of the outer railcant has a greater impact on the contact geometry and contact stress of the outer rail,while the change of the inner railcant has a significant impact on the contact geometry and contact stress of the inner and outer rail.The widening of gauge can improve the wheel-rail relationship and facilitate curve negotiating,so that the contact between the flange and the outside of the rail is not easy to occur.The friction coefficient mainly affects the wheel-rail contact on the outer rail side,and the increase of friction coefficient can significantly reduce the shaking angle and creep rate,and reduce the contact stress between wheels and rails.(4)Based on three-dimensional non-hertz rolling contact theory,stability diagram and damage function,the influence of track structure parameters on wheel-rail rolling contact fatigue was further analyzed.When the vehicle passes through a small radius curve(especially when the radius is less than 500m),the track gauge angle contact will occur.At this time,the force on the contact spot is far greater than that on the non-rim contact.The material of the wheel-rail contact spot is in the ratchet effect zone,which is the main reason why the wheel rim and the inner side of the rail are prone to produce a large number of rolling contact fatigue damage.When the inner or outer rail appears a smaller rail cant,the contact stress of the surface and sub-surface layer of the wheel-rail will be significantly increased,the fatigue performance of the wheel surface will be deteriorated,and the probability of rolling contact fatigue will be increased.Appropriate widening of the gauge of the curve line is conducive to the matching of wheel-rail relationship and can alleviate the contact fatigue damage of the curve rail,and the effect is best when the gauge widening value is 2 mm.Too small friction coefficient will cause excessive wheel-rail contact stress on the outer rail side,and the fatigue damage of the wheel-rail materials will be accelerated with the cyclic loading.Increasing the wheel-rail adhesion can reduce the contact stress between wheels and rails,thus reducing the wheel-rail rolling contact fatigue and the effect is most significant when the friction coefficient is 0.3 and 0.4.