| Wear is the main factor leading to the replacement of rail in small radius curve of railway,reducing rail wear can effectively prolong rail service life and reduce operation cost.Based on the relevant research at home and abroad,this paper studies the mechanical properties,damage characteristics of laminar plasma-jet strengthening material and the use safety of strengthening rail.The main research contents of this paper are as follows:1.Study on mechanical properties of laminar plasma-jet strengthened specimensBased on the tensile test,the effects of the loading rate,loading history,the number of strengthened surfaces and the number of spots on the tensile properties of laminar plasma-jet strengthened specimens were studied,and compared with the unstrengthened U75 V and bainitic specimens.For strip-shaped strengthened area,the effects of different directions,number of spots,length of spots,number of surfaces and weld seams on the tensile properties of laminar plasma-jet strengthened specimens were studied.Based on fracture analysis and stress-strain curves of tensile specimens,constitutive models and failure criteria of strengthened materials are analyzed.In this paper,the positive pressure,negative pressure and side pressure tests were carried out for the longitudinal strip-shaped specimens without weld,the longitudinal strip-shaped specimens with weld,the transversal strip-shaped specimens without weld and the transversal strip-shaped specimens with weld.2.Study on damage characteristics of laminar plasma-jet strengthened specimensThe rail specimens were strengthened by laminar plasma-jet,and the wheel specimens were not strengthened.Through the rolling contact fatigue test,the effects of the shape,length,area and direction of the strengthened area on the wheel and rail wear were analyzed.The longitudinal and transverse sections of the worn wheel and rail specimens were observed with optical microscope,and the surface morphology of the worn wheel and rail samples was observed with electron microscope.The damage characteristics of the wheel and rail under different strengthening modes were analyzed in combination with the wear amount of the wheel and rail.3.Establishment of finite element model and safety analysis of laminar plasma-jet strengthened rail specimensCombined with the stress-strain curve and the finite element model of the tensile specimens,the constitutive model of the strengthened material is analyzed.Based on the vehicle-track coupling dynamics theory,the dynamic model of the small radius curve is established,and combined with Hertz theory,the contact stress function is determined.Based on the finite element theory,the three-dimensional elastic-plastic finite element models of the longitudinal strip-shaped,transversal strip-shaped,punctate and common rail are established.The maximum principal stress and plastic strain of rail under different strengthening modes are analyzed,and the safety of rail is studied.4.Analysis of wear and damage of strengthened rail in field serviceThe rail in service in the field has been observed for 9 consecutive months.The influence of laminar plasma-jet strengthening technology on the wear resistance of the rail is analyzed by comparing the wear and damage of the rail in the same time for the unreinforced rail and the strengthened rail.For the rail in the strengthened section,the wear and damage of punctate strengthening area and longitudinal strip-shaped strengthening area at the same time are compared.Combining the rolling contact fatigue test,the fatigue resistance and wear damage characteristics of punctate and longitudinal strip-shaped area are further analyzed. |
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