Research On The Influence Of Medium On Thermal Damage During Wheel-rail Sliding Contact

With the development of high-speed and heavy-duty railways,the problem of railway wheel/rail damage has become increasingly prominent.Wheel-rail sliding contact is one of the most common contact methods in the process of starting and braking heavy-duty railways,and it is also the main way to cause wheel-rail damage.When the wheel and rail are in sliding contact,there are different contact media between the wheel and rail,such as leaves,sand,ballast powder,water,snow,and oil.The existence of these contact substances will accelerate or slow down the development of contact damage between the wheel and rail to a certain extent.At the same time,when the wheel and rail are in sliding contact,the mechanical action between the wheel and the rail will cause the temperature of the wheel and rail material to rise.When the contact medium acts together,It can further trigger complex physical and chemical reactions.The study of the relationship between the occurrence of wheel-rail sliding contact damage and thermal damage by different contact media is a supplement to the research on wheel-rail contact and has important guiding significance for the determination of the railway maintenance period.In this paper,the wheel-rail sliding friction tester is used to study the temperature rise and contact surface damage of the wheel-rail under different test media and simulated different axle loads.At the same time,the conditions of different media and axles are studied.The dynamic coefficient and sliding friction coefficient under heavy working conditions are analyzed and calculated.According to the results of wheel-rail sliding friction test,the article analyzes the various temperature change stages,and compares the node temperature and the temperature development trend under different medium conditions and axle load conditions.Finally,based on image analysis,the article analyzes the microscopic mechanism of wheel-rail damage under different contact media.The research in this article was funded by the National Natural Science Foundation of China "Research on Key Thermophysical Issues of High-speed Trains(51236003)".The main research carried out in the article are as follows:(1)Based on the application theory of rolling contact theory and lubrication mechanics in wheel-rail friction,design experiments through literature investigation and theoretical calculations,and carry out wheel-rail sliding friction tests with wheelrail sliding friction testing machine as the test platform.(2)Based on the strain data collected by the testing machine,the dynamic coefficient and sliding friction coefficient of the testing machine under different axle loads and contact media during wheel-rail sliding friction are studied,and the corresponding numerical value change interval is obtained.(3)The test uses FLEX-4015 thermal resistance temperature module to collect the temperature during the wheel-rail sliding friction process,and the research discusses the temperature change trend and obvious change stages during the wheel-rail sliding friction process.At the same time,on the basis of the above research results,further refinement and research on the rapid heating stage of wheel-rail sliding friction have been done,and the influence of the medium on the temperature rise of wheel-rail sliding friction under different contact media has been analyzed and studied.The test also collected the temperature changes of the wheel-rail specimens at different contact depths,and compared the temperature attenuation trend along the normal direction of the contact spot during the sliding friction of the wheel-rail under different media.(4)On the basis of the test,the damage images of the wheel-rail sliding contact surface under different media and axle loads were compared and analyzed,and the thermal fatigue damage under different axle loads and different test media was obtained.The thermal fatigue damage behavior is further analyzed and explained.The conclusion shows that the liquid medium causes more serious damage to the wheel and rail than the solid medium and non-medium conditions,and the damage mechanism is obviously different.Finally,based on thermal damage images,the article analyzes and supplements the microscopic mechanism of wheel-rail sliding thermal fatigue damage.At the same time,it proposes that the proportion of fatigue damage,thermal effects and mechanical friction caused by different test media is affected by the type and quantity of contact media.Double influence,and clarify the crack initiation and development mechanism under different media working conditions from a microscopic point of view.This paper analyzes the wheel-rail surface temperature changes and interface damage during wheel-rail sliding friction through experimental methods,and studies the wheel-rail temperature rise changes during the wheel-rail sliding friction process and the influence of different media on the temperature rise process in detail.Finally,the microscopic mechanism of damage caused by different media conditions is analyzed from a microscopic perspective.The test design and method in this paper are reasonable,and the test results are true and reliable,which can provide references for theoretical analysis and numerical analysis of wheel-rail sliding friction under different contact media.