高铁齿轮钢18CrNiMo7-6循环变形行为实验和本构模型

Cyclic Deformation Experiment and Constitutive Model of High-speed Railway Gear Steel 18CrNiMo7-6

采用RPL100电子式蠕变疲劳试验机,对高铁齿轮钢18CrNiMo7-6开展了不同应变幅值下的对称应变循环实验,研究了齿轮钢在对称应变循环下的循环软硬化行为;对齿轮钢18CrNiMo7-6在不同应力工况下开展了非对称应力循环下单轴棘轮行为实验,研究了齿轮钢棘轮变形的演化规律.结果显示,在实验研究循环周次内齿轮钢18CrNiMo7-6在对称应变控制循环下表现出循环软化的特征,在非对称应力控制循环下呈现出衰减的棘轮应变率和常棘轮应变率两阶段.通过在Ohno-Abdel-Karim非线性随动硬化律中引入与累积塑性应变相关的棘轮参数的演化方程,建立了修正的循环弹塑性本构模型.模拟结果显示,该模型能够合理预测齿轮钢18CrNiMo7-6的循环软化特征和棘轮行为的演化规律.

To study the cyclic softening/hardening behavior of high-speed railway gear steel 18CrNiMo7-6,RPL 100 electronic creep fatigue tester was used to carry out the uniaxial symmetrical strain cycling experiments on the gear steel under different strain amplitudes.Then,the ratchetting behaviour of gear steel 18CrNiMo7-6 under different stress conditions was tested to study the ratchetting evolution of gear steel under asymmetric stress cycling.The results show that the gear steel(18CrNiMo7-6)exhibits the cyclic softening characteristics under strain cycling and exhibits two stages of decaying ratcheting strain rate and constant ratcheting strain rate under asymmetric stress cycling.Then,a modified elasto-plastic cyclic constitutive model was established by introducing the evolution equation of ratchetting parameters related to the cumulative plastic strain into the Ohno-Abdel-Karim nonlinear kinematic hard ening rule.The simulated results show that the model can reasonably predict the cyclic softening characteristics and the ratchetting evolution of gear steel(18CrNiMo7-6).