Analysis On Wheel/rail Profiles Matching And Experimental Research Of Locomotives' Wheels Spalling

With the high-speed and heavy-haul development of railway,wheel-rail wear and spalling have resulted in a serious decrease in its service life,and the destruction is becoming increasingly prominent,which not only greatly increases the railway operating costs,but also directly endangers traffic safety,so it is of great significance to make an intensive study of wheel-rail wear and spalling.The research methods of some specific wheel-rail damage have reference significance for the comprehensive and in-depth analysis of other kinds of damage.The contact performance of the standard and worn wheel-rail profile is calculated and analyzed by the method of numerical calculation and test,in order to study the effect of the third medium on the wheel-rail contact performance.In this paper,the wheel-rail contact test platform is used to study the spalling problem of locomotive wheel tread,and the forming mechanism of spalling is analyzed,and some improvement suggestions are put forward for the problem of wheel spalling on the spot.Then the wheel service performance after the corresponding improvement measures are tracked and tested to verify the correctness of the research conclusions.The main contents and achievements of this paper are as follows:(1)The wheel-rail profile was measured on the spot,and the standard and worn wheel-rail profile was obtained.The 3D wheel-rail elastic-plastic contact calculation model was established by using the finite element parameter quadratic programming method,and the wheel-rail contact problem was simulated and calculated.The contact performance of wheel-rail profiles with axle load and wheel lateral displacement is compared and analyzed,The wheel-rail contact test platform was built,and the wheel-rail specimen was cut from the real wheel and rail in the field,and the wheel-rail contact test was carried out under multiple working conditions.The experimental results are in agreement with the numerical results.The contact patch area of the wheel-rail contact surface is larger than that of the standard surface,and the contact stress and deformation of the wheel are smaller after wear.(2)The wheel-rail contact test is carried out in the presence of the third medium for water,oil,sand and other media,and the influence of the third medium on the maximum static friction coefficient and tread damage of the wheel-rail is analyzed.It is found that the maximum static friction coefficient of wheel-rail is greatly reduced when there is water and oil on the contact surface,and the maximum static friction coefficient of wheel-rail is greatly reduced compared with the dry and clean condition of wheel-rail surface in the case of dry,wet and oil.Sand spraying can significantly increase the maximum static friction coefficient of wheel-rail,and the viscosity increasing effect of river sand is better than that of quartz sand,but the abrasion degree of wheel tread caused by river sand is much higher than that of quartz sand.(3)Taking the wheel and sand sampled in the field as samples,the sand spraying test was carried out to analyze the influence of wheel hardness and sand on tread spalling.The results show that quartz sand will not cause the wheel tread to form pitting and fish scale spalling,but when some kinds of river sand are used as viscosity increasing medium,the phenomenon will appear.By comparing and analyzing the properties and parameters of various kinds of sticky sand,it is concluded that the relationship between the hardness of sand and the degree of pitting damage of wheel is not obvious.The friction coefficient,shape size and grain size uniformity of sand have important influence on the pitting damage,and the shape of sand after compaction is the dominant factor.(4)On the test platform,the pitting and fish scale cracks of wheel tread were reproduced.The microstructure of the specimens with cracks was analyzed.It was found that there was serious plastic deformation and fold phenomenon in the crack root.The crack is formed by fold nucleation,and the mechanism of wheel tread spalling is as follows:due to bad shape of river sand after compaction,there are thick sand cakes between wheel and rail,which leads to serious plastic deformation on the wheel surface.After repeated action of river sand,plastic deformation accumulative effect of wheel surface material occurred,and finally fish scale spalling was formed.That is,the river sand is the main cause of the pitting and fish scale spalling of wheel tread.(5)This paper investigates and tests the spalling problem of locomotives' wheel tread on the spot,and finds that the field situation is in good agreement with the test results.According to the research results,the suggestion of using quartz sand to increase viscosity is put forward,and according to this,the sticky sand is replaced by the application department.Then the wheels' service performance is tracked and tested,and it is found that the spalling problem has been solved fundamentally,which shows the correctness of the research conclusions and the engineering practicability of this paper.