Study On Wear Performance And Damage Behavior Of Wheel-Rail Materials Under Different Axle Load Conditions Of Heavy Haul Railway

It is an inevitable choice for modern freight heavy haul railway to develop towards heavy haul and intelligent road.The continuous increase of train axle load will lead to the increasing damage of railway materials.When the train usually has a small radius curve,the side wear will lead to abnormal wheel-rail wear,and the frequent elimination of old rails and the use of new rails will cause cost increase and economic loss.Therefore,it is of vital importance to promote the development of technology and materials of heavy haul railway in China by vigorously promoting the study of the influence of continuous axle load on the wear and damage behavior of wheel and rail materials.This paper focuses on the wear performance and damage mechanism of wheel-rail materials when the axle load of heavy haul railway is more than 30 t.The self-developed JD-DRCF/M test machine was used to simulate the wheel-rail rolling contact behavior under four different axle load conditions.Through experimental research and analysis,the following main results are obtained :(1)The adhesion coefficient under four axle load conditions decreases with the increase of axle load.At the same time,the four groups of adhesion coefficients have a continuous downward trend throughout the wear cycle,and the larger the axle load,the greater the decline.When the axle load is 40 t and 45 t,the minimum adhesion coefficient is less than0.2.(2)Axle load has a significant effect on the wear of wheel/rail materials.The wear of wheels and rails increases with the increase of axle load.In four different axle load conditions,the wear of wheel samples is 6-10 times that of rails.When the axle load increases from 30 t to 40 t,the wear surface of wheel materials increases greatly,and the wear increases by more than one time.Combined with the surface damage morphology of wheel and rail materials,there are many spalling pits,material peeling and fatigue cracks on the wear surface of wheel.The wear surface of the rail is relatively smooth,mainly dominated by delamination damage.Different damage mechanisms lead to significant differences in the wear of wheel and rail materials.(3)The near-surface fatigue crack propagation mechanism of wheel and rail is very different.The fatigue crack of wheel material propagates parallel to the surface direction,and the crack initiated from the surface will produce branch cracks when it extends to a certain depth.The crack of rail material expands towards the depth of the material,and the number of cracks is obviously more than that of wheel material.With the increase of axle load,there will be slender cracks initiated from the inside of the material when the axle load is more than 30 t.When the axle load is 45 t,due to the combined action of extreme normal stress and shear stress,there will be two parallel cracks in the surface layer of wheel material and rail material.The surface layer of the wheel is distributed with dense cracks,so that it is difficult to distinguish the main crack.(4)The morphology and size of wear debris are determined by the removal form of wheel/rail materials.The fatigue cracks of wheel materials mainly propagate parallel to the surface,resulting in a large peeling area and thickness of wheel materials.The fatigue crack of the rail material expands deep,and the connection between the crack and the crack leads to a smaller material fracture.Therefore,the small size wear debris mainly comes from the rail material,and the thick and large wear debris mainly comes from the wheel material.There is no linear correlation between the axle load and the characteristics of the wear debris.The size of the wear debris decreases first and then increases.When the axle load is above 40 t,cracks appear on the surface of the wear debris.