微动磨损与微动疲劳对无砟轨道扣件弹性下降的影响研究

Fastener technology was one of the key technologies of ballastless track structure. Fastener working principle was to use buckling pressure caused by their elastic deformation , then rail and track structure under rail was connected effectively into a whole for a long time.The fastener service life would be shortened if its elastic was reduced, and the operational cost and repair maintenance workload was increased. A tiny relative movement between the contact surface of each part of fastener, and the contact surface of fastener parts and other components was placed under train and temperature loads. Fastener was effected under the combination of fretting and load.Domestic and foreign research on fastener was often from stress and strain, while the actual fretting of fastener was ignored.An apparent fretting damage phenomenon was found in the position of fastener fracture during engineering practice and the scientific research work of applicant.In the project,the Influence of reduced elastic fastener caused by fretting wear and fretting fatigue would be researched,fretting model of ballastless track fastener would be established, the testing scheme of fastener fretting wear and fretting fatigue would be designed based on the theoretical analysis ,and the theory would be verified by test results.The decline law of fastener elastic caused by fretting wear and fretting fatigue would be revealed, the fastener elastic decreased value of allowable limit would be determined, improved design method of fastener would be proposed, the diagnosis and monitoring control measure of fastener fretting damage would also be proposed.The project has a good theory meaning and project application value.

扣件技术是无砟轨道结构的关键技术之一，其工作原理是利用自身弹性变形产生扣压力,将钢轨与轨下结构长期有效地联结成一个整体。扣件弹性下降会导致其使用寿命缩短,增加运营成本及维修养护工作量。在列车和温度荷载下,扣件各部分接触表面之间、扣件各部分与其它构件的接触表面之间均存在微小的相对移动,扣件工作时受微动和外荷载的联合作用。国内外对扣件的研究往往从应力、应变着手，而忽略了扣件"微动"的实际情况。在工程实践及申请人科研工作中,发现扣件断裂及产生裂痕的地方,有明显的微动损伤现象。项目针对微动磨损、微动疲劳对无砟轨道扣件弹性下降的影响进行研究，建立无砟轨道扣件的微动模型并进行数值计算，设计扣件微动磨损、微动疲劳的试验方案,用试验结果对理论进行验证,揭示微动损伤对扣件弹性下降的影响规律,确定扣件弹性下降的允许极限值,提出改进扣件的设计方法及微动损伤的诊断、监控措施。项目具有良好的理论意义和工程应用价值。

研究目的与背景：扣件技术是无砟轨道结构的关键技术之一，其工作原理是利用自身弹性变形产生扣压力,将钢轨与轨下结构长期有效地联结成一个整体。扣件弹性下降会导致其使用寿命缩短,增加运营成本及维修养护工作量,是亟需解决的科学与工程问题。无砟轨道扣件工作时，存在微动磨损和微动疲劳。在列车和温度荷载反复作用下，扣件各部分的接触表面之间、扣件各部分与其它构件的接触表面之间均存在微动磨损，微动磨损使扣件产生裂纹，降低扣件的弹性。在微动与外荷载反复作用下，裂纹进一步扩展甚至会导致扣件断裂。在工程实践及申请人科研工作中,发现扣件断裂及产生裂痕的地方,有明显的微动损伤现象，但国内外对扣件的研究往往从应力、应变着手，而忽略了扣件“微动”的实际情况。项目针对无砟轨道扣件微动磨损、疲劳对其弹性下降的影响机理进行研究。.研究内容与方法：项目采用模拟计算与实验相结合的方法，建立了无砟轨道扣件的微动模型，探讨了无砟轨道扣件的微动磨损、微动疲劳机理研究及其对扣件弹性下降的影响，在满足行车安全性及舒适性指标前提下，确定扣件弹性下降的允许极限值，对无砟轨道扣件微动磨损与疲劳的诊断及监控方法进行探讨。.研究结论及展望：扣件弹条在工作过程中，微动磨损对扣件弹性降低及裂纹生成、扩展及至断裂均起重要作用，微动磨损所起作用的大小与τ和τ·δ均相关，其疲劳断裂处在弹条尾部与轨距挡板表面接触处，位于弹条的τ最大处与τ·δ最大处之间。从行车安全性考虑，扣件扣压力允许下降极限值为初始扣压力的48%（初始扣压力为8kN)。项目具有良好的工程意义及进一步扩展研究的需求。