Study On Mechanism And Countermeasure Of Rolling Contact Fatigue Of Metro Tread

With the vigorous development of China's railway industry,high-speed railway runs throughout countries,subway winds in the underground of the major cities.Rapid development is also accompanied with a large number of problems and wheel-rail rolling contact fatigue is one of urgent problems to be solved.Wheel-rail rolling contact fatigue not only greatly increases operating costs,but also brings security risks to the vehicle operation.In this paper,there are a lot of rolling contact fatigue creaks and a large amount of peelings occur in wheel rim root and outer area of tread of subway vehicles.Rolling contact fatigue causes running noise and makes the comfort lower.In this paper,wheel-rail relationship is used to study the rolling contact fatigue mechanism in wheel tread of the subway vehicle.The main work and conclusions are as follows:(1)First of all,methods to study wheel rolling fatigue used by domestic and foreign scholars wear summarized and a suitable one for subway vehicle wheel rolling contact fatigue is selected.(2)A single-layer vehicle-track coupling dynamic model with elastic rails and fastenings was established,shakedown map and damage function were used as the numerical analysis model to study wheel rolling contact fatigue.The corresponding program is compiled according to the numerical analysis model.(3)This paper makes a field investigation on the profile of the wheel,rail profile,rail cant and corrugation of track,and records the position and angle of the rolling contact crack.Field survey found that the wheel rolling contact fatigue cracks appear in the-20?-10 mm(the rim root zone)and 20?30 mm(the area outside nominal rolling circle);rail cant in tracks with different curve radius are basically changed,especially the inner track cant increases more,so that the rail contact position is biased to the gauge angle side.(4)The model established in(2),with standard wheel profiles and wear rail profile,is used to study wheel rolling fatigue.The analyses cover the wheel-rail contact force,the contact point of the wheel,responses character of material and the magnitude and distribution of wheel damage.The results show that the rolling contact fatigue in the zone of-20?-10 mm(the root of the rim)is formed mainly on the high-side wheel of the driven shaft,and the rolling contact fatigue in the 20?30 mm area(outside the nominal rolling circle)is formed mainly on the low-side wheel of the guide shaft,and the small radius curve(especially R?550 m)is the main cause of the rolling contact fatigue of vehicles.(5)Further,the influence of parameters such as friction coefficient,wear surface of wheel,rail cant and lateral stiffness of fastenings on wheel rolling contact fatigue is studied.The results show that the friction coefficient has a great influence on the rolling contact fatigue at-20?-10 mm.The expansion of the rolling contact fatigue crack can turn slowly by appropriately reducing the rim lubrication.The main reason is that reducing the rim lubrication can increase the friction coefficient of the material at the rim and also can increase the wear of the rim root.The wear of wheel has little effect on the rolling contact fatigue,and main reason is that the rail wears wear surface and rail cant is not set for the standard and wheel abrasive wear rarely exists.The impact of the rail cant on the wheel rolling contact fatigue is more obvious.When the cant of low rail changes from 1/20 to 1/40?1/50,the rolling contact fatigue in the rim side has rarely increased,while the rolling contact fatigue in the nominal rolling circle outside has significantly reduced.So regular maintenance for track cant can slow down the rolling contact fatigue development in the area outside nominal rolling circle and the rolling contact fatigue at the rim can be reduced by appropriate increasing the friction coefficient at the rim.Rolling contact fatigue state can be improved by increasing the lateral stiffness of fastenings,but the effect is not obvious.