室温蠕变与疲劳对无砟轨道扣件扣压力下降的影响研究

Fastener technology was one of the key technologies of ballastless track structure, fastener pressure drop had been an urgent scientific and engineering problem.Pressure of ballastless track fastening was produced mainly by its deformation and requried to maintained a long time, micro deformation of fastener would be increased with time gradually even in normal temperature, it was also found in the engineering practice and scientific research work that the decreased fastener pressure resulted by room temperature creep couldn't be ignored even under no train loads. Wave loads and constant loads were longly and alternately effected on fastener in the complex working conditions, fastener was not only beared the pure creep damage and pure fatigue damage,but also suffered the effect of fatigue damage and creep damage interactly.But the domestic and foreign research on fastener was often from the traditional fatigue, and room temperature creep was ignored. The project is to aime at the research of room temperature creep and fatigue on ballastless track fastener decreased pressure, a model of room temperature creep,fatigue and the loss of fastener pressure will be established, theoretical analysis and experimental study will be carried out, the room temperature creep and fatigue damage mechanism of fastener is to be revealed out, the allowable limit of pressure drop of fastener is to be determined. The project has a good theory meaning and engineering application value.

扣件技术是无砟轨道结构关键技术之一,扣件扣压力下降是目前亟待解决的科研与工程问题。无砟轨道扣件扣压力主要由其自身变形产生且要求保持较长时间,即使在常温下扣件也会随着时间的推移逐渐发生微量变形- - 室温蠕变。在工程实践及申请人科研工作中,发现扣件即使在无列车荷载作用下其室温蠕变导致的扣压力下降也是不可忽略的。扣件长期处于波动荷载与恒定荷载交替作用的复杂服役条件下,不仅承受着纯蠕变与纯疲劳损伤,而且承受着疲劳损伤与蠕变损伤交互作用的影响。但国内外对扣件的研究往往从传统疲劳着手，忽略了室温蠕变现象。项目拟针对室温蠕变、疲劳对无砟轨道扣件扣压力下降的影响进行研究,建立室温蠕变、疲劳与扣件扣压力损失模型并开展理论计算分析与试验研究，揭示室温蠕变与疲劳对扣件的损伤机理,确定扣件扣压力下降的允许极限值。项目具有良好的理论意义与工程应用前景。

扣件技术是无砟轨道结构关键技术之一,扣件扣压力下降是目前亟待解决的科研与工程问题。无砟轨道扣件扣压力主要由其自身变形产生且要求保持较长时间,即使在常温下扣件也会随着时间的推移逐渐发生微量变形——室温蠕变。在工程实践及申请人科研工作中,发现扣件即使在无列车荷载作用下其室温蠕变导致的扣压力下降也是不可忽略的。扣件长期处于波动荷载与恒定荷载交替作用的复杂服役条件下,不仅承受着纯蠕变与纯疲劳损伤,而且承受着疲劳损伤与蠕变损伤交互作用的影响。但国内外对扣件的研究往往从传统疲劳着手，忽略了室温蠕变现象。项目针对室温蠕变、疲劳对无砟轨道扣件扣压力下降的影响进行理论与试验研究,发现：(1)蠕变对扣件扣压力的损失在工程中不应忽视，在分别保持扣件弹条变形不变和保持扣件扣压力不变情况下测试弹条的蠕变试验中，即使没有列车与温度荷载作用，由于扣件弹条的蠕变也会使得扣压力减小10%以上;(2) WJ-7型扣件都是前期蠕变大，后期蠕变小，在一定时间后，蠕变趋于微小，但二者的时间节点不同：在保持扣件变形不变的蠕变试验中，从第８个月开始扣件蠕变量很少；在保持扣压力不变的蠕变试验中，要从第11个月开始扣件弹条蠕变才会明显比之前减小。（3）两种加载（加载幅值分别为25±5kN、25±7.5kN、25±10kN和25±12.5kN）方式下，荷载大小对疲劳寿命影响显著，荷载越大，疲劳寿命显著降低。两种载荷控制方式下，弹条的扣压力及位移曲线都有“阶梯状递增”和“阶梯状递减”的特征，压力控制下疲劳试验始终弹条扣压力衰减量为22%~33%，中圈位移增加量为18%~25%；位移控制下疲劳试验始终弹条扣压力衰减量为26%~38%，中圈位移增加量为15%~29%。项目具有良好的理论意义与工程应用前景。