This work introduces a new methodology to predict the fatigue life of viscoelastic materials by considering the creep effect on fatigue behavior under the concurrent effects of stress level, stress ratio, and temperature. The model established based on the total amount of energy dissipated during fatigue loading. To estimate the amount of dissipated energy under varying stress ratios and temperatures, two shift factors, and , were derived, attributed to the cyclic and creep parts of fatigue loading. These shift factors were subsequently incorporated into defined equilibrium equations to create the relationship between estimated dissipated energy and fatigue life. The input data for the model consisted of the dissipated energy and cyclic creep values obtained from experiments conducted at a reference stress ratio of 0.5 and reference temperature of 20 °C, together with the storage and loss moduli measured from one dynamic mechanical analysis () experiment in the temperature range of 15 °C–60 °C on a fully-cured epoxy adhesive. To validate the accuracy of the results, the predicted fatigue life at three temperatures of 20 °C, 40 °C and 55 °C, each loaded under three stress ratios of 0.1, 0.5, and 0.9 were compared with the experiments conducted under the same conditions. Almost all predicted results were in good agreement with the experiments, nevertheless; at the stress ratio of 0.9 at 20 °C, due to the significant change in the cyclic creep behavior, the accuracy of the prediction was lower. The developed model was used as a new constant life diagram () formulation, which afterwards was further developed to plot three-dimensional constant life diagrams (3-D ) in which the constant life surfaces were a synergistic function of stress ratio and temperature.

中文翻译：

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基于粘弹性材料能量耗散、应力水平、应力比和温度协同效应的新型疲劳寿命预测方法

这项工作引入了一种新的方法来预测粘弹性材料的疲劳寿命，该方法考虑了在应力水平、应力比和温度的同时影响下蠕变对疲劳行为的影响。该模型是根据疲劳加载期间耗散的能量总量建立的。为了估计不同应力比和温度下的耗散能量，导出了两个位移因子 和 ，归因于疲劳载荷的循环和蠕变部分。随后将这些偏移因子纳入定义的平衡方程中，以创建估计耗散能量和疲劳寿命之间的关系。该模型的输入数据包括在 0.5 的参考应力比和 20 °C 的参考温度下进行的实验获得的耗散能和循环蠕变值，以及从一项动态力学分析 () 实验中测量的储能模量和损耗模量。在完全固化的环氧粘合剂上的温度范围为 15 °C–60 °C。为了验证结果的准确性，将在20℃、40℃和55℃三个温度下分别在0.1、0.5和0.9三种应力比下加载的预测疲劳寿命与相同条件下进行的实验进行比较。状况。尽管如此，几乎所有的预测结果都与实验非常吻合。在20℃应力比为0.9时，由于循环蠕变行为发生显着变化，预测精度较低。所开发的模型被用作新的恒定寿命图 () 公式，随后进一步发展为绘制三维恒定寿命图 (3-D)，其中恒定寿命表面是应力比和温度的协同函数。