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3D predictions of the local effective stress intensity factor as the fatigue crack propagation driving force
International Journal of Fatigue ( IF 6 ) Pub Date : 2021-06-03 , DOI: 10.1016/j.ijfatigue.2021.106365
W. Taleb , C. Gardin , C. Sarrazin-Baudoux

The objective of this study is to develop a numerical tool using the commercial software, Abaqus and Python, to predict the fatigue crack front shape while taking into account the influence of plasticity induced crack closure on crack propagation in three Dimensional (3D) structures. In this aim, a 3D model of a compact tension specimen made out of stainless steel 304L, and subjected to a constant loading scheme, is proposed. The crack propagation is considered to be driven by the stress fields developed in the vicinity of the crack tip and thus by the stress intensity factor K. Two parallel simulations are used: an elastic simulation intends to calculate the local maximum stress intensity factor while the other, an elasto-plastic one, aims at obtaining the plastic wake and the resulting crack closure load. The results of both simulations are combined in order to constitute the effective stress intensity factor range, which is in turn used, along with Paris law, to calculate the crack propagation along the thickness. The local crack advancements obtained allow to construct the new crack front. Finally, a node release technique is used with geometry remeshing to issue new iterations with new boundary conditions that respond to the changes in the crack front. The procedure is repeated until the stabilization of the effective stress intensity factor values all along the specimen thickness is reached. The results obtained are compared with previously issued experimental results, showing very good results in small scale yielding and beyond that a large dependency on the plastic zone size developed in the neighborhood of the crack front.



中文翻译:

作为疲劳裂纹扩展驱动力的局部有效应力强度因子的 3D 预测

本研究的目的是使用商业软件 Abaqus 和 Python 开发一种数值工具,以预测疲劳裂纹前沿形状,同时考虑塑性诱导裂纹闭合对三维 (3D) 结构中裂纹扩展的影响。为此,提出了一个由 304L 不锈钢制成的紧凑拉伸试样的 3D 模型,并受到恒定载荷方案的影响。裂纹扩展被认为是由裂纹尖端附近形成的应力场驱动的,因此由应力强度因子 K 驱动。使用了两个并行模拟:弹性模拟旨在计算局部最大应力强度因子,而另一个,一种弹塑性的,旨在获得塑性尾流和由此产生的裂纹闭合载荷。两种模拟的结果相结合以构成有效应力强度因子范围,该范围又与巴黎定律一起用于计算沿厚度的裂纹扩展。获得的局部裂纹进展允许构建新的裂纹前沿。最后,节点释放技术与几何重新划分网格一起使用,以响应裂纹前沿的变化,以新的边界条件发出新的迭代。重复该过程,直到达到沿试样厚度的有效应力强度因子值的稳定为止。将获得的结果与先前发布的实验结果进行比较,显示出在小规模屈服方面的非常好的结果,并且在很大程度上依赖于裂纹前沿附近发展的塑性区尺寸。

更新日期:2021-06-18
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