铁路车轮对于确保铁路运输的安全起着重要作用。处于服役中的车轮如果出现损坏，可能会导致严重的经济损失以及人员伤亡。如今列车运行速度越来越快，因为车轮缺陷（扁疤，多边形化），轨道缺陷（波形磨耗）等原因，车轮发生冲击的可能性越来越大。为了更好地预测车轮在服役中的行为，要求我们对其材料的力学行为，特别是车轮钢在冲击载荷作用下的变形、损伤和破坏的机理进行深入的研究，建立车轮钢的动态本构模型。本文对现役的ER8车轮钢的轮辐钢和轮辋钢做了动态力学性能的研究。主要研究成果如下：

轮辐钢和轮辋钢的微结构存在差别，轮辐钢的先共析铁素体所占比例更大，珠光体的片层间距更大。在准静态加载下，轮辐钢和轮辋钢均具有较好的强度和塑性，但轮辋钢的强度明显比轮辐钢大，塑性略差。使用分离式霍普金森压杆（Split Hopkinson Pressure Bar, SHPB）对轮辐钢和轮辋钢在冲击载荷下的变形行为进行了研究，发现在动态压缩实验条件下，轮辐钢和轮辋钢都具有应变率强化效应。采用Johnson-Cook本构模型建立轮辐钢和轮辋钢的本构关系，发现拟合结果与轮辐钢较为吻合，而轮辋钢差别较大。轮辋钢具有较强的热软化效应，在高应变率下，变形产生的绝热温升会使得轮辋钢软化。因此，我们考虑了绝热温升对流动应力的影响，并采用改进的Johnson-Cook本构模型来拟合轮辋钢的本构关系，与实验结果进行比较后发现两者比较吻合。

利用分离式霍普金森压杆和帽型试样实验技术对ER8车轮钢的绝热剪切行为进行了研究。在强迫剪切的条件下，得到了相应的剪切应力-剪切应变曲线，并且在曲线中发现了标志着绝热剪切带（Adiabatic Shear Band, ASB）形成的“应力塌陷”现象。金相观察发现了ASB在帽形试样的端部形核，并且裂纹沿着ASB与过渡区的交界面扩展。观察变形不同阶段的微观结构，发现了在剪切变形的过程中，先共析铁素体先发生变形，珠光体后发生变形。在珠光体的剪切变形过程中，较宽片层间距的珠光体先发生变形。利用应变梯度效应解释了轮辐钢和轮辋钢绝热剪切敏感性的差异，轮辋钢更容易形成ASB，这与剪切应力应变曲线的结果相符合。对比充氢的帽型试样实验结果发现，氢能延缓车轮钢ASB的形成。

利用一级轻气炮实验装置和双靶板实验技术测试了车轮钢在10⁵s^-1应变率级别下的层裂强度。分别建立了轮辐钢和轮辋钢的高压状态方程。

Railway wheels play an important role in ensuring safety of railway transportation. Damage to these wheels can result in significant economic losses and casualties. As train speeds increase, the potential for impact forces on railway wheels also increases, which can be caused by defects in the wheel (flat, polygonization) or the rail (corrugation). Therefore, it is essential to conduct in-depth research on the material mechanical behavior of railway wheels to establish dynamic constitutive models for steel, especially in terms of deformation, damage, and failure mechanisms under impact loads. This paper focuses on studying the dynamic mechanical properties of ER8 wheel steel, specifically the web and the rim. The main research results are as follows:

The microstructure of the web and the rim is found to differ, with the web containing a higher proportion of proeutectoid ferrite and larger pearlite lamellar spacing. Under quasi-static loading, both the web and the rim demonstrate good strength and plasticity, with the rim showing significantly higher strength and slightly poorer plasticity than the web. The Split Hopkinson Pressure Bar (SHPB) is used to investigate the deformation behavior of the web and the rim under impact load, and it is found that both show strain rate strengthening effects. The Johnson-Cook constitutive model is used to establish the constitutive relationship of the web and the rim, with the fitting result being in good agreement with the web but quite different for the rim. It is suggested that the thermal softening effect of the rim is strong, causing the rim to soften due to adiabatic temperature rise caused by deformation under high strain rate. Thus, an improved Johnson-Cook constitutive model is used to fit the constitutive relationship of the rim, which yields good agreement with the experimental results.

The paper also examines the adiabatic shear behavior of ER8 wheel steel using SHPB and hat-shaped specimens test technology. The corresponding shear stress-shear strain curves were obtained, and the phenomenon of "stress collapse" marking the formation of adiabatic shear band (ASB) was observed. Metallographic observation shows that the ASB nucleates at the end of hat-shaped specimens, and the crack propagates along the interface between the ASB and the transition region. The microstructure at different stages of deformation was observed, and it was found that eutectoid ferrite deforms first, followed by pearlite deformation. The pearlite with wider lamellar spacing deforms first during the shear deformation of pearlite. The difference of adiabatic shear sensitivity between the web and the rim is explained by the strain gradient effect, with the rim being more prone to forming ASB than the web. Compared with the experimental results of hat-shaped specimens charged with hydrogen, it is found that hydrogen can delay the formation of ASB in wheel steel.

The spalling strength of wheel steel at around 10⁵ s^-1strain rate is tested using the first stage light gas gun and the double target plate experimental technology, and the high-pressure state equations of the web and the rim are established separately.