钢轨滚动接触疲劳裂纹形态参数的交流电磁场响应规律

Response Characteristics of Alternative Current Field to Morphological Parameters of Rail Rolling Contact Fatigue Crack

摘要:

为了探明交流电磁场检测中在钢轨表面形成的磁场响应与轨面滚动接触疲劳裂纹空间形态的关系，结合含滚动接触疲劳裂纹的钢轨现场观测和X射线断层扫描，确定了重载铁路不同通过总重下钢轨表面滚动接触疲劳裂纹的表面开口长度、内部倾角与椭圆比范围；建立钢轨裂纹交流电磁场仿真模型，分析不同裂纹形态参数的交流电磁场响应，并将电磁场响应拟合表达裂纹空间形态参数。结果表明：滚动接触疲劳裂纹的交流电磁场响应受裂纹各空间半椭圆参数综合影响并且可以通过函数模型进行描述，描述函数决定系数大于0.999 8，误差平方和小于1×10^-4，均方误差小于1.4×10^-3，函数模型计算结果与交流电磁场响应具有较好的一致性；整体上，交流电磁场响应特征受内部倾角影响较小，但随着内部倾角减小，影响逐渐增大；交流电磁场响应特征与裂纹表面开口长度近似呈线性变化规律，与椭圆比近似呈指数或高阶函数变化。

Abstract:

To investigate the relationship between the magnetic field response above the rail surface and the spatial morphology of rolling contact fatigue （RCF） crack on the rail surface in alternative current field measurement （ACFM）， the surface opening length， internal angle， and ellipse ratio range of RCF crack under different gross passing loads were determined by combining field visual observation， metallographic observation， and computer tomography（CT） scanning of rail with RCF crack. An ACFM simulation model for rail crack was developed to analyze the ACFM response of different crack morphology parameters， and the magnetic field response was fitted to express the crack spatial morphology parameters. The results show that the ACFM response of RCF crack is comprehensively affected by each semi-elliptic parameter of the crack and can be described by the function model. The determination coefficient of the description function is greater than 0.999 8， the sum of squares error is below 1×10^-4， and the mean square error is less than 1.4×10^-3. The calculated results of the function model are in good agreement with the ACFM response. Overall， the ACFM response characteristics are less affected by the internal angle， but the influence gradually increases as the internal angle decreases. The ACFM response characteristics vary linearly with the crack surface opening length， and exponentially or as a higher order multinomial function with the elliptic ratio.