基于实测动应力分析的车轴台架试验谱编制

Compilation of Axle Bench Test Spectrum Based on Measured Dynamic Stress Analysis

通过长距离线路动应力测试,编制适用于车轴磁粉探伤周期优化研究的台架试验谱。首先,分析测试结果中车辆载重、线路工况、运行交路对车轴动应力的影响,并考虑车轮失圆的影响,确定不同影响因素的灵敏度;然后,进行应力谱极值推断,得到车轴外推应力谱;最后,得到台架试验谱,并开展台架疲劳试验。结果表明:车轴最大应力截面上的最高频次应力,在动车组满载运行时增大至空载运行时的1.2倍,在曲线和道岔工况下相较于直线工况分别增大了15.6%和13.0%;车轴动应力极值在动车组运行于不同交路时约有16 MPa的波动,随着外推里程的增加,极值逐渐趋于稳定;外推应力谱可划分为极值应力区、高频次应力区、过渡应力区3个区域,在应力分区的基础上等损伤建立了3级台架试验谱;在完成含表面2 mm深弦形缺陷车轴的108周次疲劳加载台架试验后,缺陷表面和根部未萌生微裂纹,车轴磁粉探伤周期延长具有较强的可行性。

Through the dynamic stress test of long-distance line,the bench test spectrum suitable for the optimization research of flaw detection period of axle using magnetic particle was compiled.Firstly,the influence of vehicle load,line condition and running route on the dynamic stress of axle in the test results was analyzed,and the sensitivity of different influencing factors was determined by considering the influence of wheel out-of-roundness.Then,the extreme value of stress spectrum was inferred to obtain the extrapolated stress spectrum of the axle.Finally,the bench test spectrum was obtained and the bench fatigue test was carried out.The results show that the maximum frequency stress on the maximum stress section of axle increases to 1.2 times of that in no-load operation when the EMU is running at full load.Compared with the condition of straight line,the maximum frequency stress for the conditions of curve and turnout increases by 15.6%and 13.0%respectively.When running on different routes,the dynamic stress extreme value of the axle fluctuates about16 MPa.With the increase of extrapolated mileage,the extreme value gradually tends to be stable.The extrapolated stress spectrum can be divided into three area:extreme value stress,high frequency stress and transition stress.Based on the stress zoning,a three-level bench test spectrum is established with equal damage.After 108 cycles of fatigue loading bench test of axle with 2 mm deep chord defect on the surface,no microcracks were initiated on the surface and root of the defect.It is feasible to prolong the flaw detection period of magnetic particle for axle.