Study On The Grinding Limit Of Typical Track Damage In Mountain City Metro

Due to the characteristics of high slope,small curve radius and overlapping of horizontal and vertical curves,the rail damage forms of metro lines in mountainous cities are various,especially typical rail damage such as rail corrugation,poor rail welded and poor rail joints.These track damages not only seriously affect the safety of train operation,but also become key factors restricting the high-quality sustainable development of rail transportation in mountainous cities.Generally,the rail grinding is the most effective way to control track damages,and determining the grinding limit of typical track damages is an important part of accurate rail maintenance.In this thesis,based on the field investigation of typical track damage in mountain city metro,the dynamic characteristics of vehicle-track system and the friction coupling vibration characteristics of wheel-rail system are studied,which are based on the vehicle-track system dynamic theory and the friction coupling vibration theory of wheel-rail system.The safety limits of the rail grinding for track damage are proposed from the perspective of vehicle operation safety to avoid vehicle operation safety problems.From the perspective of the development prediction of typical track damage,the optimal limits of the rail grinding are proposed to avoid the aggravation of track damage.The main work and conclusions of this thesis are as follows:(1)Based on the vehicle-track system dynamics model of rail corrugation and poor rail welding,combined with the evaluation index of vehicle service safety,the influence of rail corrugation and poor rail welding on the global dynamic characteristics of vehicle-track system is explored.The service safety index of the vehicle increases with the increase of the wave depth of rail corrugation and rail welding irregularity and the decrease of the wavelength,among which the wheel load reduction rate is the most obvious.(2)From the point of view of ensuring the safety of train operation,the grinding safety limits of rail corrugation and rail welding irregularity are proposed by taking the over-limit of wheel load reduction rate as the control index.The grinding safety limits of rail corrugation with wavelengths of 30 mm,40 mm,50 mm,60 mm and 70 mm are0.03 mm,0.04 mm,0.05 mm,0.08 mm and 0.15 mm,respectively.The grinding safety limits of welding irregularity with wavelengths of 100 mm,200 mm and 300 mm are0.3 mm,0.6 mm and 0.8 mm,respectively.(3)The finite element model of wheel-rail local system at typical track damage is used to study the influence of typical wavelength rail corrugation,poor welding wave depth,passing speed and rail gap on the frictional coupling vibration of wheel-rail local system.In the rail corrugation and poor welding section,as the rail corrugation and poor welding wave depth increase,the friction coupling vibration of the wheel-rail system increases,and the growth rate is the largest when the rail corrugation wave depth is0.02-0.03 mm and the poor welding wave depth is 0.25-0.30 mm.In the poor rail gap section,the friction coupling vibration of the wheel-rail system increases with the increase of the rail gap.When the rail gap is 8-10 mm,the growth rate reaches the maximum.(4)Based on the analysis of friction coupling vibration of wheel-rail system at typical track damage,the corresponding grinding optimization limit is proposed from the perspective of reducing the development trend of delaying track damage.In the rail corrugation with a wavelength of 50 mm and the poor welding section with a wavelength of 100 mm,the grinding optimization limits are 0.02 mm and 0.25 mm,respectively.In the section with poor rail gap,the optimization limit of rail gap is 8 mm.The friction coupling vibration of wheel-rail system can be effectively suppressed,and then the development trend of track diseases can be suppressed.