金属低周疲劳过程热力学熵特征分析及寿命预测模型

选取Q235钢试样开展低周疲劳试验，通过改变加载幅值、加载频率等条件，研究分析了低周疲劳过程热力学熵产率与累积熵产变化特征。结果表明，熵产率随加载幅值的增大而升高且在同一载荷下熵产率近似恒定。低周疲劳过程中热力学熵的累积是一个准线性累加过程。试样最终疲劳断裂熵随加载幅值的增大而减小，与加载频率无明显关系。在此基础上建立了基于热力学熵的金属低周疲劳寿命预测模型，该模型可用于金属构件疲劳损伤的实时评估。

Thermodynamic Entropy Characteristics Analysis and Life Prediction Model of Metal Low Cycle Fatigue Processes

Q235 steel samples were selected to carry out low-cycle fatigue tests.The thermodynamic entropy generation rate and cumulative entropy production characteristics of low-cycle fatigue processes  were analyzed under different loading conditions such as loading amplitude and loading frequency.Results show that the entropy generation rate increases with the increase of the loads and it is approximately constant under the same loads.The accumulation of thermodynamic entropy during low cycle fatigue is a quasi-linear accumulation process.The final FFE value of the material increases with the decrease of the load amplitudes,but has no obvious relationship with the loading frequency. Then,a low-cycle fatigue life prediction model was established based on thermodynamic entropy,which may be used in real-time evaluation of fatigue damages of metal component.