Soft adhesives exhibit nonlinear viscoelastic behavior during cyclic loading, suggesting that their cycle-dependent fatigue behavior can be significantly affected by the time-dependent deformation behavior. Soft adhesives are frequently subject to various cyclic conditions in practical applications, presenting potential safety risks. This paper has proposed a fractional cyclic cohesive zone model (CZM) to characterize the time-dependent fatigue behavior of soft adhesives. To capture the nonlinear evolution of fatigue damage under asymmetric stress-controlled cyclic loading, a fatigue damage model that considers the contribution of in-situ stress/strain was incorporated into fractional-order viscoelastic model. The proposed CZM was validated through single-lap shear creep tests at various stress levels and fatigue tests at various stress amplitudes and loading periods. Furthermore, the impacts of stress ratio and peak stress level on fatigue failure under different loading periods were investigated using the proposed CZM. The results indicate that under a short loading period, the failure of the soft adhesives is primarily influenced by cycle-dependent fatigue damage, while under a long loading period, it is primarily affected by time-dependent creep deformation. Overall, this work offers a numerical strategy to describe the fatigue failure of nonlinear viscoelastic soft adhesives and to understand their time-dependent fatigue failure mechanism, with implications for product design and optimization.

中文翻译：

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II 型加载下软粘合剂随时间疲劳行为的分数循环内聚区模型

软粘合剂在循环加载过程中表现出非线性粘弹性行为，这表明它们的循环疲劳行为可能会受到时间相关变形行为的显着影响。软胶在实际应用中经常受到各种循环条件的影响，存在潜在的安全风险。本文提出了一种分数循环内聚区模型（CZM）来表征软粘合剂随时间变化的疲劳行为。为了捕获非对称应力控制循环载荷下疲劳损伤的非线性演化，将考虑原位应力/应变贡献的疲劳损伤模型纳入分数阶粘弹性模型。所提出的 CZM 通过各种应力水平下的单搭接剪切蠕变试验以及各种应力幅度和加载周期下的疲劳试验进行了验证。此外，使用所提出的 CZM 研究了不同载荷周期下应力比和峰值应力水平对疲劳失效的影响。结果表明，在短加载周期下，软粘合剂的失效主要受到循环疲劳损伤的影响，而在长加载周期下，软粘合剂的失效主要受时间依赖蠕变变形的影响。总的来说，这项工作提供了一种数值策略来描述非线性粘弹性软粘合剂的疲劳失效，并了解其随时间变化的疲劳失效机制，对产品设计和优化具有影响。