Most of the structures in service are subjected to cyclic loading of variable amplitude. The effect of load interaction is necessary to accurately predict the fatigue life of components in design phase. In the present paper, a fatigue damage methodology under complex loading history is proposed considering two stages of damage process and considering the effect of sequence of loading. This is further modified by considering opening stress in crack propagation stage. The proposed methodologies are compared with the linear damage rule by illustrating an example of dynamically induced stress in a slender bar under uniform axial time varying force. The effect of various influencing parameters on fatigue life of bar is also studied. The proposed methodologies are further validated using experimental fatigue test results. The comparison shows a good agreement between theoretical and experimental results. It is found that conventional Miner’s rule estimates higher damage index compared to the proposed methodology.

大多数使用中的结构都承受可变幅度的循环载荷。载荷相互作用的影响对于在设计阶段准确预测部件的疲劳寿命是必要的。本文提出了一种复杂加载历史下的疲劳损伤方法，考虑损伤过程的两个阶段并考虑加载顺序的影响。通过考虑裂纹扩展阶段的张开应力，可以进一步修改这一点。通过说明均匀轴向时变力下细长杆中动态诱发应力的示例，将所提出的方法与线性损伤规则进行比较。还研究了各种影响参数对杆件疲劳寿命的影响。使用实验疲劳测试结果进一步验证了所提出的方法。比较表明理论结果和实验结果具有良好的一致性。结果发现，与所提出的方法相比，传统的 Miner 规则估计了更高的损坏指数。