Based on strain-controlled thermomechanical fatigue (TMF) experiments, this study conducts a comprehensive analysis of the TMF behavior of AISI H13 hot work die steel. Moreover, a life prediction model for the TMF behavior of AISI H13 steel has been developed and validated. The experimental results reveal that, under the in-phase (IP) and out-of-phase (OP) TMF conditions, the stress–strain response curves of AISI H13 steel under different mechanical strain amplitudes exhibits the similar evolution tendency. However, it is worth noting that in the stable TMF cycle, the hysteresis loop area is enlarged with the increase of the number of cycles, which can be attributed to the cyclic softening characteristics of the AISI H13 steel under cyclic thermomechanical loading. When examining different TMF conditions, it is found that at higher strain amplitudes and under OP TMF conditions, the hysteresis loop area significantly expands, leading to a substantial reduction in the TMF life of AISI H13 steel. From a microstructural perspective, the thermal–mechanical coupling effect makes the recovery of martensitic matrix and the coarsening of carbide precipitation, which substantiates the deterioration of mechanical properties of AISI H13 steel. Finally, a modified Ostergren model by integrating the hysteresis loop area has been developed to assess the TMF life of AISI H13 steel under complex thermomechanical loading conditions, and this refined model exhibits strong agreement with experimental data. An evaluation using scatter band shows that the predicted TMF life of AISI H13 steel are within 1.2 times the experimental values, which illustrates a high reliability and validity.

中文翻译：

---

AISI H13钢在循环热机械载荷作用下的疲劳损伤及寿命预测


基于应变控制热机械疲劳 （TMF） 实验，本研究对 AISI H13 热作模具钢的 TMF 行为进行了综合分析。此外，已经开发并验证了 AISI H13 钢 TMF 行为的寿命预测模型。实验结果表明，在同相 （IP） 和异相 （OP） TMF 条件下，AISI H13 钢在不同机械应变幅值下的应力-应变响应曲线表现出相似的演化趋势。然而，值得注意的是，在稳定的 TMF 循环中，磁滞回线面积随着循环次数的增加而增大，这可归因于 AISI H13 钢在循环热机械载荷下的循环软化特性。在检查不同的 TMF 条件时，发现在较高的应变幅值和 OP TMF 条件下，磁滞回线面积显着扩大，导致 AISI H13 钢的 TMF 寿命大幅缩短。从微观结构的角度来看，热-机械耦合效应使马氏体基体的恢复和碳化物沉淀的粗化，这证实了 AISI H13 钢机械性能的恶化。最后，通过整合磁滞回流区域，开发了一种改进的 Ostergren 模型，用于评估 AISI H13 钢在复杂热机械载荷条件下的 TMF 寿命，该改进模型与实验数据表现出很强的一致性。使用散射带的评估表明，AISI H13 钢的预测 TMF 寿命在实验值的 1.2 倍以内，这说明了高可靠性和有效性。