高速滚滑下轮轨表层材料的应变率水平估计

基于显式有限元法建立了三维轮轨高速瞬态滚动接触模型，详细分析了车轮以300 km/h速度滚过平顺钢轨表面、钢轨波磨（波长30 mm~170 mm）和宏观粗糙度（波长4 mm~30 mm）时钢轨表层0.25 mm~0.5 mm厚材料的平均应变率水平。结果显示：1）空间上，表层单元的应变率最大，时间上，表层材料的最高应变率发生于其进出接触斑的加、减载过程，且法向应变分量的应变率最大，其最值是Von Mises（V-M）等效应变率最值的1.50倍~1.86倍；2）网格大小和时间步长对应变率估计有不可忽略的影响；3）采用0.5 mm网格和0.32 μs步长，平顺轮轨表层单元的最大V-M等效应变率为64.1 s^-1，材料弹塑性无影响，波磨和宏观粗糙度使弹性下的最大V-M等效应变率分别增至92.5 s^-1和79.4 s^-1；采用0.25 mm网格和0.042 μs步长的结果约为上述值的1.65倍~1.88倍；4）最大V-M等效应变率随速度线性增加，随摩擦系数的增加而单调递增，牵引系数的影响可忽略。

ESTIMATION OF STRAIN RATES FOR WHEEL-RAIL SURFACE MATERIALS UNDER HIGH-SPEED ROLLING-SLIDING CONTACT

A 3D wheel-rail transient rolling contact model has been developed using the explicit finite element method to calculate the average strain rates of rail surface material of 0.25 mm^0.5 mm deep at 300 km/h, for which smooth rail, rail corrugation (wavelength of 30 mm^170 mm) and macro-roughness (wavelength of 4 mm^30 mm) are considered. Obtained results have shown: 1) the highest strain rate occurs on the surface layer spatially, and during the loading or unloading processes of a material particle passing the contact patch;the rate of the normal strain is the largest among all strain components, being 1.50~1.86 times of Von Mises (V-M) strain rate;2) element size and time step have important effects on strain rate results;3) the V-M strain rate of smooth surfaces reaches the maximum of 64.1 s^-1 when the element size is 0.5 mm and the time step is 0.32 μs, the material elasto-plasticity has no effects, the rail corrugation and macro-roughness result in the maximum V-M strain rate of 92.5 s^-1 and 79.4 s^-1 in elasticity respectively;the results are 1.65~1.88 times higher when an element size of 0.25 mm and a time step of 0.042 μs are used;4) the maximum strain rate increases linearly with speed, monotonically with increasing friction coefficient, while the influence of traction coefficient is negligible.