【作者】 郭强；

【导师】 王平；

【作者基本信息】 西南交通大学 ， 建筑与土木工程（专业学位）， 2019， 硕士

【摘要】 磨耗是导致铁路小半径曲线钢轨更换的主要因素,减小钢轨磨耗能有效延长钢轨服役寿命、降低运营成本,本文基于国内外相关研究,对层流等离子强化材料的力学特性、损伤特性以及强化钢轨使用安全性做了一定研究,本文的主要研究内容如下:1.层流等离子强化试样力学特性研究基于拉伸试验,针对点状强化斑形式,研究了加载速率、加载历史、强化面数、以及打点个数对层流等离子强化试件拉伸性能的影响,并且和未强化U75V、未强化贝氏体钢试件进行了对比;针对条状强化斑形式,研究了不同强化斑方向、强化斑个数、强化斑长度、强化斑面数以及焊缝对层流等离子强化试件拉伸性能的影响;基于拉伸试样断口分析和应力-应变曲线,分析了强化材料的本构模型和破坏准则。针对条状纵向强化无焊缝钢轨、条状纵向强化有焊缝钢轨、条状横向强化无焊缝钢轨和条状横向有焊缝钢轨,进行了正压、反压和侧压试验,对强化钢轨的安全性进行了分析,确定了强化钢轨的破坏形式。2.层流等离子强化试样损伤特性研究对钢轨试样采取层流等离子强化,车轮试样均不强化,通过磨损与接触疲劳试验,分析了强化斑形状、强化斑长度、强化斑面积占比和强化斑方向对车轮、钢轨磨耗量的影响。使用光学显微镜对磨损后的车轮、钢轨试样纵向和横向剖面进行观察,使用电镜对磨损后的轮轨试样表面组织形貌进行观察,结合车轮、钢轨磨耗量,分析了不同强化方式下车轮、钢轨的损伤特性。3.层流等离子强化钢轨有限元模型的建立及安全性分析结合拉伸试样应力-应变曲线和有限元模型,分析了强化材料的本构模型。基于车辆-轨道耦合动力学理论,建立了小半径曲线动力学模型,结合赫兹理论,确定了接触应力函数。基于有限元理论,建立了条状横向、条状纵向、点状和普通钢轨三维弹塑性有限元模型,分析不同强化方式下钢轨的最大主应力和最大塑性应变,对钢轨的使用安全性进行了研究。4.强化钢轨现场服役磨耗量及伤损分析对现场服役的钢轨进行连续9个月的观测,针对未强化段钢轨和强化段钢轨,对比相同时间下钢轨的磨耗量及损伤情况,分析了层流等离子强化技术对钢轨耐磨性的影响;针对强化段钢轨,对比相同时间下点状强化、条状强化钢轨的磨耗量及伤损情况,结合磨损与接触疲劳试验,进一步分析了点、条状强化钢轨的抗疲劳和磨耗损伤特性。更多还原

【Abstract】 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.更多还原