Thermodynamic Entropy for Improved LCF Prediction Method of Metal Materials Considering Heat Conduction

From the thermodynamic perspective, metal fatigue involves energy transfer and transformation. During each fatigue cycle, a portion of the energy dissipates as heat into the environment, accompanied by changes in entropy. Most existing studies focus only on the relationship between plastic deformation energy and entropy production, while neglecting the effects of energy dissipation caused by thermal conduction. To address this issue, low-cycle fatigue (LCF) experiments were conducted under different loading amplitudes, and infrared thermography was used to record the surface temperature fields during uniaxial tension-compression fatigue. Based on the experimental data, the entropy generation and accumulation resulting from both thermal conduction and plastic deformation were quantified. A real-time fatigue life prediction model was then established using thermodynamic entropy. The results show that incorporating energy dissipation due to thermal conduction effectively reduces prediction errors in the fatigue life model.