基于非线性超声的CL60车轮和U75V钢轨磨损检测方法

针对早期轮轨滚动磨损变化过程难以通过无损手段进行表征的问题，提出了非线性超声技术对不同磨损程度的CL60车轮与U75V钢轨试样进行检测评估；建立了基于轮轨试样表面磨损特征的Murnaghan模型，并利用非线性超声有限元仿真，通过塑性变形层厚度变化情况模拟不同程度的摩擦损伤，分析了其相对非线性系数变化规律及其产生原因。试验结果表明:轮轨的早期磨损会导致材料表面产生塑性变形层，随着塑性变形的加剧，材料损伤将以微裂纹为主，车轮角加速度越大，轮轨间相对滑动作用时间越短，塑性变形层越薄，且CL60车轮较U75V钢轨磨损程度更为严重；CL60车轮试样在车轮角加速度分别为10、250、1 500 r·min-2时，对应的相对非线性系数分别为12.19、8.43、5.68，U75V钢轨试样在车轮角加速度分别为10、250、1 500 r·min-2时，对应的相对非线性系数分别为7.57、6.09、5.04，与CL60车轮试样相比，U75V钢轨试样的相对非线性系数变化缓慢。可知，相对非线性系数与塑性变形层厚度呈正相关，微裂纹产生的非线性效应比塑性变形层更强，相对非线性系数增幅更大，因此，可通过材料的相对非线性系数变化判断材料的磨损阶段。 

Wear detection method of CL60 railway wheel and U75V rail steel based on nonlinear ultrasound

With an aim to resolve the difficulty of the characterization of the change process of early wheel/rail rolling wear by non-destructive measurement, a nonlinear ultrasonic technology was proposed to detect and evaluate CL60 wheel and U75V rail specimens with different wear degrees. The Murnaghan model was established based on the surface wear characteristics of wheel/rail specimens. A finite element simulation of nonlinear ultrasonic was used to simulate different degrees of friction damage based on the plastic deformation layer thickness. The change law of the relative nonlinear coefficient and its causes in the process of wheel/rail friction damage, were analyzed. Experimental results indicate that the early wear of wheel/rail can result in the formation of a plastic deformation layer on the material surface, and with the aggravation of plastic deformation, the material damage appears mainly through microcracks. With an increase in the wheel angular acceleration, the relative sliding time between wheel and rail is shorter, the plastic deformation layer is thinner, and the CL60 wheel wear is more serious than the U75V rail wear. When the wheel angular accelerations for the CL60 wheel specimens are 10, 250, and 1 500 r·min-2, respectively, the corresponding relative nonlinear coefficients are 12.19, 8.43, and 5.68, respectively. When the wheel angular accelerations for the U75V rail specimens are 10, 250, and 1 500 r·min-2, respectively, the corresponding relative nonlinear coefficients are 7.57, 6.09, and 5.04, respectively. Compared with the CL60 wheel specimens, the nonlinear coefficient of the U75V rail specimens changes more slowly. Therefore, the relative nonlinear coefficient and plastic deformation layer thickness are positively correlated, and the nonlinear effect caused by microcracks is stronger than that of the plastic deformation layer, resulting in a high increase in the relative nonlinear coefficient. Thus, the wear stage of a material can be determined by the change in the relative nonlinear coefficient of the material. 2 tabs, 15 figs, 30 refs.