Study On The Effect Of Friction Modifier On Wheel-rail Adhesion And Damage Behaviors In Low Temperature Environment

Wheel-rail adhesion is an important parameter affecting train operation.Problems,such as abnormal wear and rolling contact fatigue damage,often occur after the service of the wheel and rail in the field.At present,the above problems are generally solved by methods such as rail grinding,laser strengthening,and wheel-rail adhesion regulation.The research shows that the use of friction modifiers to control the adhesion of the wheel-rail interface can effectively control the occurrence of abnormal wheel-rail wear,rail corrugation and squealing noise.As the railway system spread widely in different regions in China,the wheel-rail system often faces low temperature conditions.Many studies have found that the low temperature environment will significantly affect the wheel-rail adhesion,and at the same time aggravate the wear and damage of the wheel and rail.Therefore,it is hoped that friction modifiers can be used to control wheel-rail adhesion and to reduce wheel-rail wear and damage in low temperature environments.At present,there are few studies on the service performance of friction modifiers in low temperature environments.Therefore,it is necessary to study the effect of friction modifiers on wheel-rail adhesion and damage behaviors at low temperature.In this paper,the MJP-30 A wheel-rail rolling wear and contact fatigue testing machine was used to study the effect of friction modifier on wheel-rail adhesion under low temperature and water medium conditions.The influence of friction modifier on wheel-rail wear and damage behaviors under the low temperature.The influence mechanism of friction modifier on wheel-rail adhesion under different temperature and water medium conditions,and the influence mechanism of friction modifier on wheel-rail wear and damage were revealed.In addition,in view of the insufficient performance of existing friction modifiers under low temperature conditions,a new friction modifier which is suitable for the application under the low temperature condition was developed.The main conclusions of the paper are as follows:(1)Under low temperature conditions,as the temperature decreases,the adhesion coefficient of the friction modifier showed a law of increasing first and then decreasing,and the number of holding revolutions showed an opposite law to the adhesion coefficient,because the change of temperature affected the friction modifier viscosity and fluidity.(2)Under the water medium condition,when the water volume was small,the water-based friction modifier was prone to the occurrence of low adhesion,and the number of remaining revolutions increased to a certain extent.When the amount of water was large,the phenomenon of low adhesion would not occur,and the number of remaining revolutions would be significantly reduced.However,the oil-based friction modifier would show a serious low adhesion phenomenon in the water medium condition,and the number of maintained revolutions would increase significantly.The difference in the adhesion behavior of the two types of friction modifiers in aqueous media was caused by the difference in solubility between the friction modifiers and water.(3)With the decrease in temperature,the wheel-rail wear rate under the dry condition gradually increased,and the severer rolling contact fatigue damage occurred.The unoptimized friction modifiers showed good wear reduction performance under different temperature conditions.The wheel-rail rolling contact fatigue damage was significantly reduced under the condition of 25 °C.The rolling contact fatigue damage was slightly aggravated under the condition of 0 °C,and the serious rolling contact fatigue damage occurred under the condition of-40 °C.Therefore,unoptimized friction modifiers were not suitable for low temperature condition.(4)Compared with the unoptimized friction modifier,the optimized friction modifier could make the wheel-rail adhesion coefficient smaller and maintain more revolutions.Under various temperature conditions,the optimized friction modifier showed better wear reduction performance,and the fatigue damage of wheel-rail rolling contact was significantly reduced.Therefore,the optimized friction modifier was more suitable for low temperature conditions.