【作者】 周素霞；

【导师】 谢基龙；

【作者基本信息】 北京交通大学 ， 载运工具运用工程， 2010， 博士

【摘要】 高速列车的运行环境比较恶劣,车轴可能受到道砟等硬物的高速冲击,极端情况下,这种尖锐硬物冲击可能造成车轴表面一定深度的锋利角缺口。虽然这是一种小概率事件,但是一旦发生,这种缺口在车轴随机载荷下可能会很快萌生裂纹,并逐渐扩展到临界尺寸,给高速列车运行安全带来很大隐患。本论文在国家973项目《高速列车安全服役关键基础问题研究》支持下,研究高速列车空心轴表面在硬物冲击损伤下裂纹的形成寿命和裂纹扩展规律及其剩余寿命问题,为科学地制定车轴检修周期与管理方法提供依据。主要工作如下:1、制作模拟车轴表面尖锐硬物冲击缺口试样,采用四点支撑旋转弯曲试验,研究车轴钢在含不同缺口条件下的S-N曲线,分析了缺口应力集中系数及其相应的S-N曲线参数变化规律。2、线路实测高速列车在既有线路和京津城际铁路上的车轴应力-时间历程,利用雨流循环计数方法得到车轴的实测弯曲应力谱,通过统计推断发现应力谱符合三参数威布尔分布,并编制相应的程序应力谱。运用等效损伤原则比较不同线路运行时车轴的损伤,发现既有线路上运行时对车轴的损伤大于京津城际铁路。3、根据异物冲击造成的缺口类型和方位,提出用于缺口疲劳损伤分析的物理模型及形状参数。通过有限元分析,得到空心车轴表面不同缺口构型根部的应力集中系数。运用Miner法则及缺口试样S-N曲线,估算实测载荷谱下车轴表面缺口处裂纹的萌生寿命,并分析出不同缺口构型对萌生寿命的影响。4、提出空心轴表面裂纹的几何模型。考虑到空心轴内孔的影响,对实心圆柱表面裂纹应力强度因子解析式进行修正,得出空心轴表面裂纹应力强度因子的解析式。全面分析了旋转弯曲载荷下车轴表面裂纹前缘应力强度因子变化情况以及裂纹前缘最深点处的应力强度因子变化规律。5、采用EI Handdad短裂纹应力强度因子模型,根据实测应力谱研究空心轴表面不同应力集中系数缺口下的短裂纹扩展特性和扩展寿命,发现当缺口系数比较大时,车轴表面短裂纹扩展速率高,几千公里的运行就会进入长裂纹扩展阶段。6、采用NASGRO方程建立了疲劳裂纹扩展模型,根据空心轴表面裂纹的形状因子随深度和形状变化的特性,确定出裂纹扩展的门槛条件和临界尺寸和形状比的函数关系,运用实测载荷谱模拟出空心轴表面裂纹的扩展规律和剩余寿命,并探讨了车轴异物冲击缺口损伤容限及其安全性。更多还原

【Abstract】 The train works in a complex system and its running condition may become more sever with the speed increasing, and edge hard object impacts can occur on high speed tracks. Such events can leave sharp angled notches at the surface of axles. Under this condition cracks can initiate and grow to the critical size, which will bring great hide safe trouble.This paper is supported by the national basic research and develop project, the fatigue life and crack propagation life of the surface crack of hollow axles of the high speed train which is very important for the axles examine and repair management. The mainly work are as follows:1. Notched samples are made to simulate the impact damage from hard objects on the surface of axles. Using four-point rotary bending test, the S-N curves of different notched samples of axle steel were studied. The parameters change of S-N curves with different stress concentration factors were analysed.2. The stress spectrum under bending load was got on the basis of stress-time data of hollow axles using the rain-flow cyclic counter method. Using the statistic method we find that the stress spectrum accords with three-parameters Weibull distribution and the procedure stress spectrum was got. The effects of different railway line levels and the running conditions on the dynamic stress of axles by the equal stress are researched. The results indicate that the values of the rebuilt railway line are higher than that of the special railway line. On the basis of the researches above the service and design load spectrum are proposed for establishing the design standard of high speed train axles. At the same time the general dynamic load factors on the rebuilt railway line and the special railway line are evaluated comparing with that of the JIS standard and the EN standard. It is concluded that the JIS standard and the EN standard can not satisfied the damage tolerance limit design.3. The types and position from the foreign object damages and the physical model and the shape parameters of the notches are analyzed. The Finite Element model of the railway axle is built with which we can get the stress concentrator factors at the base of the notches. The Miner rule is used to calculate the fatigue life of the axle with a notch under the variable amplitude loading and the effect of the notch shape on the fatigue life is evaluated. 4. The geometry model of surface crack of a hollow axle is built, and the analytic formula of the stress intensity factor of the hollow axle surface crack is obtained by modifying that of the solid cylinder surface crack. The modified model considered the effect of inner surface of the hollow axle on the stress intensity factors. The stress intensity factor at the crack center point of different aspect ratios and depths are calculated using the analytic formula under the rotary bending load.5. The propagation characteristic and life of the short crack from different notches are estimated using the service loading and the EN13103 standard, it is indicated that the values under the service loading are higher than the design loading.6. The NASGRO equation is used to build the propagation model of fatigue crack and the propagation condition of the crack is analyzed. Because the shape of the surface crack changes with the crack depths and aspect ratios, the critical crack size are different under the given crack aspect ratios, so the relationship between the critical crack size and the crack aspect ratios is given. The propagation rules and residual lives of long cracks under service loading are executed更多还原