热载荷工况下的车轮裂纹周边应力分析及拓展评估

Stress Analysis and Expansion Evaluation Around Wheel Crack under Thermal Load

利用有限元法建立轮轨瞬态热载荷三维弹塑性接触计算模型,从实际角度出发,分析列车制动时产生高热条件下的车轮内部裂纹处的应力场与温度场。系统地分析了多种裂纹参数对裂纹周边应力场的影响规律。基于实测,建立了两种类型的裂纹,其中直裂纹长度和深度分别取10~20mm和2~4mm(长深比固定为5)。作为对比的斜裂纹特征参数:长为6~30mm,深为10~20mm,裂纹角度为15°~40°热载荷工况下计算结果表明:热应力对裂纹尖端应力场的增强效应不可忽略,某些工况下热应力对合成应力的贡献率可达24.8%;各工况下,直裂纹裂尖应力场普遍高于斜裂纹,说明该型裂纹更危险,更易拓展;裂纹位置越靠近车轮表面,裂尖应力越高,越易拓展并发展至表层,进而引起车轮踏面剥离掉块。

Finite element method is used to establish a three-dimensional elastic-plastic contact calculation model for transient thermal load on wheels and rails.From a practical perspective,the stress and temperature fields are analyze at the internal cracks of the wheels under high thermal conditions generated by train braking when there are internal cracks.The influence of various crack parameters on the stress field around the crack was systematically analyzed.Based on actual measurements,two types of cracks were established,with straight crack lengths and depths of 10-20 mm and 2-4 mm respectively(with a fixed aspect ratio of 5).As a comparison,the characteristic parameters of oblique cracks are 6-30 mm in length,10-20 mm in depth,and a crack angle of 15°to 40°.The calculation results under thermal load conditions indicate that the enhancement effect of thermal stress on the stress field at the crack tip cannot be ignored,and the contribution rate of thermal stress to the composite stress can reach 24.8%under certain conditions.Under various working conditions,the stress field at the crack tip of the straight cracks is generally higher than that of the oblique cracks,indicating that this type of crack is more dangerous and easier to expand.The closer the crack location is to the surface of the wheel,the higher the stress at the crack tip,which is more likely to expand and develop to the surface,causing the wheel tread to peel off blocks.