Rolling Wear Of Rail And The Safety Assessment Of Surface Crack

Under the conditions of manufacture,welding and wheel rolling,rail is easy to produce cracks,crushing,depression and other damage on the rail surface,resulting in huge safety accidents and economic losses every year.Therefore,in this paper,the wheel-rail rolling wear and rail surface crack are taken as the research objects,and the rail rolling wear law,the influence of inclusions on rail fatigue life and the safety assessment of crack cracking on rail surface are studied by the test,finite element simulation and structural safety assessment methods.Firstly,tensile test,three-point bending test and wheel-rail rolling friction test are carried out on wheel and rail materials,respectively.The wear morphology,plastic flow and fatigue phenomena of wheel-rail rolling contact are studied and the effects of different axle loads and rotating speeds on wear rate and friction coefficient are explored.The wear morphology and the plastic deformation layer of rail specimens are observed,and the effects of axle loads and rotating speed on rail surface wear are analyzed,as well as the accumulation of plastic deformation layer on rail surface.This provides basic data and boundary conditions for subsequent research.Secondly,the finite element method is used to simulate the wheel-rail contact.Considering the different characteristics of inclusions(hardness,size and distance from the rail surface,etc.),the influence of different axle loads and inclusion conditions on the stress and strain fields of rail cross-section is analyzed comparing with rail containing no inclusion.The fatigue life of rail matrix near inclusions is calculated.The influence of different axle loads and inclusion conditions on fatigue life is analyzed and the influence of inclusions near rail surface on fatigue crack ignition is studied.Finally,the concept of structural integrity assessment method and failure assessment diagram is introduced.Based on criterion of fracture mechanics and structural integrity assessment method,the unstable cracking of rail surface cracks is judged.The influence of train load on cracking at different crack angles is discussed and it is concluded that the larger the axle load and crack angle,the easier the cracking will be unstable.Taking the most dangerous vertical crack as the calculation condition,the influence of axle load on the evaluation results of different crack lengths is studied and the results show that the increase of axle load and crack length will lead to the development of evaluation points towards unsafe direction.Taking the driving speed into account,the evaluation results show that the larger the speed,the more vulnerable the crack to instability and cracking.The research work provide an effective method for determining the cracking of rail cracks,which has certain theoretical significance and value.