通过单轴拉伸试验、对称应变循环疲劳试验和非对称应力循环疲劳试验，研究了热处理U71Mn钢轨钢的循环特征和棘轮行为；基于试验结果，对Abdel-Karim-Ohno循环塑性本构模型进行修正，并将模拟结果与试验结果进行对比。结果表明：试验钢表现出初始循环软化特性；在非对称应力循环载荷下，试验钢产生了明显的棘轮行为，棘轮应变随应力幅、平均应力和峰值应力的增加而增加，棘轮应变率随峰值应力的增加而增加，当峰值应力不超过950 MPa时，棘轮应变率随循环周次的增加快速减小至稳定值，当峰值应力超过950 MPa时，棘轮应变率先减小后增大；大多数工况下采用所建立的修正Abdel-Karim-Ohno循环塑性本构模型得到的棘轮应变与试验值的平均相对误差约为9.8%，说明该模型能够较好地预测热处理U71Mn钢轨钢在应力循环工况下的棘轮行为。

Uniaxial tensile experiment, symmetry cyclic strain and asymmetric cyclic stress fatigue experiments were carried out to investigate the cyclic characteristic and ratcheting behavior of heat-treated U71Mn rail steel. Based on the experimental results, the Abdel-Karim-Ohno cyclic plastic constitutive model was modified. The simulation results were compared with the experimental results. The results show that the test steel exhibited a cyclic softening characteristic in the initial cycles. The obvious ratcheting behavior was observed under asymmetric cyclic stress loading, and the ratcheting strain increased with the increase of stress amplitude, mean stress and peak stress; the ratcheting strain rate increased with the increase of peak stress; when the peak stress was no more than 950 MPa, the ratcheting strain rate decreased rapidly and approached a stable state with the increase number of cycles; when the peak stress was more than 950 MPa, the ratcheting strain rate first decreased and then increased. The average relative error of ratcheting strain between experimental and simulated values obtained by the modified Abdel-Karim-Ohno cyclic constitutive model under most working conditions was about 9.8%, indicating that the model could reasonably predict ratcheting behaviors of heat-treated U71Mn rail steel in stress cyclic conditions.