Study On The Wheel Flange Crack Phenomenon Of HXN3 Highland-type Locomotive Form Dynamics View Point

With the rapid development of railway industry,gradually increasing axle load on vehicles and constantly improving running speed make the wheel-rail interaction force get more and more acute,therefore serious wear and tear has become the critical factor of operation safety and transport efficiency.In this thesis,in view of the wheel failure problem of the HXN3 highland-type locomotive used in the Golmud-Lhasa section of Qinghai-Tibet Railway,combined with the line conditions and locomotive operating procedures of the Golmud-Lhasa section,based on the consideration that the phenomenon of wheel edge cracking or even falling blocks is positively related to wheel-rail interaction,the study is carried out from the perspective of locomotive dynamics and relevant improvement measures are proposed,which are of great significance to improve the transportation efficiency and operational safety of the railway in highland and reduce operating costs,and provide references for the design and use of highland-type locomotives in the future.Firstly,this thesis analyzes the structure of the highland-type locomotive and constraints and degrees of freedom of all its parts and establishes the virtual prototype model of highland-type locomotive by dynamic analysis software.The wheel-rail interaction index of the wheel set when the curve is superimposed on a long uphill ramp is analyzed in combination with the actual line conditions of the Golmud-Lhasa section.Secondly,considering that the frictional heat when the locomotive passes through the curve may lead to higher wheel temperature,which in turn affects the wheel flange strength,a finite element thermal analysis model of the wheel is established,and the wheel temperature field distribution when the locomotive runs at low speed on the curve superimposed on a long uphill ramp,resulting in a larger wear index and the wheel flange closs to the rail is calculated.Finally,the dynamics optimization target of the locomotive wheel-rail contact is determined,and the influence of the change of the relevant dynamics parameters of the locomotive on the optimized target is analyzed.Through the research and analysis,the main conclusions obtained in this thesis are as follows:(1)Although the curve radius of Gera section line is large(not less than R600 m),but has the following significant features:the curve extension is large,and there are more curves superimposed on 20‰ large uphill ramp,Although the curve radius of Gera section line is large(not less than R600 m),but has the following significant features:curve extension is large,and there are more curves superimposed on 20‰ large uphill ramp,making the locomotive through this kind of curve traction force is large at a low speed,resulting in the guide wheel set attack angle is large,and then lead to one side of the wheel wear index is large,when the curve extension is large guide wheel pair through the curve friction work significantly increased,this means that the wheel-rail contact point is not only stable at the root of the wheel flange but also generates a lot of heat.Due to the large axle weight of the locomotive,the geometric force of the guide wheel on the outer wheel of the curve is about 40 kN when the through the curve,which makes the normal stress of the contact spot also very large,and this stress acts on the heated wheel flange for a long time,which may cause the local yield strength of the material to be reduced,and the long-term repeated action leads to the wheel flange failure specific to the HXN3 highland-type locomotive wheels used in the Golmud-Lhasa section.(2)By counting the frequency distribution of axle locations where wheel flange failures occurred in HXN3 highland-type locomotive,it is shown that the guide wheel set and intermediate wheel set are the majority,and the calculation results also show that the characteristics of wheel geometric force,lateral displacement of contact spot on the wheel and wear index are consistent with them,and these three indicators of the guide wheel set and intermediate wheel set are much larger than those of the rear wheel set,which indirectly proves that the wheel flange failures are related to the locomotive running for a long time on the curve with a large extension and superimposed on a long uphill ramp,and is related to the large amount of frictional heat generated by the wheel flange stably against the rail.(3)From the distribution of the transient temperature field of the wheels when the locomotive is running on a long ramp,the longer the guide wheel sets of the locomotive’s two bogies run on the curve,the higher the temperature at the wheel flange,the highest temperature rise can exceed 300℃,the wheel material is in the temperature of the yield strength is significantly reduced and the range of low stability of residual austenite,as the locomotive climbing speed the lower the guide wheel set attack angle and wear index is larger,so the wheel local temperature rise is very sensitive to the locomotive climbing speed.(4)The analysis of the adjustable parameters of the locomotive shows that by changing the values of the longitudinal positioning stiffness of a system,the lateral positioning stiffness of the wheel-rail after the end-axle free clearance is exhausted and the end-axle free clearance cannot effectively reduce the wear index,which means that the thermal effect between the wheel-rail cannot be significantly reduced;the thin wheel flange of JM3 will make the wheel-rail clearance widen and the lateral displacement of the guide wheel set to the outer rail larger,which leads to the increase of the attack angle in the low speed range,but the use of thin flange,the flange is not close to the rail,and the contact stress is reduced.(5)Studies have shown that the 3 main factors that can lead to wheel flange cracking are:low vehicle operating speed,long ramps,and superimposed long spreading curves.Of these 3 factors,speed is the only adjustable quantity.Calculations for R600 m,show that increasing the speed from 30 km/h to 35 km/h,the wear index of the guide wheel set will be significantly reduced.,but this will be at the expense of loss of traction force.Exhausting the allowance of traction capacity without raising the friction coefficient by sanding,the wheel heat generation will be significantly reduced with a slight increase in speed through the curve in the low speed range.