The fatigue crack growth (FCG) process is usually accessed through the stress intensity factor range, ΔK, which has some limitations. The cumulative plastic strain at the crack tip has provided results in good agreement with the experimental observations. Also, it allows understanding the crack tip phenomena leading to FCG. Plastic deformation inevitably leads to micro-porosity occurrence and damage accumulation, which can be evaluated with a damage model, such as Gurson–Tvergaard–Needleman (GTN). This study aims to access the influence of the GTN parameters, related to growth and nucleation of micro-voids, on the predicted crack growth rate. The results show the connection between the porosity values and the crack closure level. Although the effect of the porosity on the plastic strain, the predicted effect of the initial porosity on the predicted crack growth rate is small. The sensitivity analysis identified the nucleation amplitude and Tvergaard’s loss of strength parameter as the main factors, whose variation leads to larger changes in the crack growth rate.

中文翻译：

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Gurson-Tvergaard-Needleman损伤模型对疲劳裂纹增长率影响的研究

疲劳裂纹扩展 (FCG) 过程通常通过应力强度因子范围 Δ K，这有一些限制。裂纹尖端的累积塑性应变提供的结果与实验观察结果非常吻合。此外，它允许了解导致 FCG 的裂纹尖端现象。塑性变形不可避免地导致微孔隙的出现和损伤积累，这可以用损伤模型进行评估，例如 Gurson-Tvergaard-Needleman (GTN)。本研究旨在了解与微孔洞的生长和成核相关的 GTN 参数对预测裂纹扩展速率的影响。结果显示了孔隙率值与裂纹闭合水平之间的联系。虽然孔隙率对塑性应变的影响，但初始孔隙率对预测裂纹扩展速率的预测影响很小。