Dual-Scale Porosity Effects on Crack Growth in Additively Manufactured Metals: 3D Ductile Fracture Models
Dual-Scale Porosity Effects on Crack Growth in Additively Manufactured Metals: 3D Ductile Fracture Models
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DOI：
10.1016/j.jmps.2021.104727
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发表时间：
2021-11
影响因子：
5.3
通讯作者：
R. Muro-Barrios;Y. Cui;J. Lambros;H. Chew
中科院分区：
文献类型：
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作者：
R. Muro-Barrios;Y. Cui;J. Lambros;H. Chew
导致不可预测的失效行为的微观结构缺陷的存在限制了增材制造（AM）金属在结构应用中的使用。除了导致常规金属中的延性断裂的分布孔隙之外，在增材制造期间可以引入较大的缺陷（20-50 μm），从而导致AM金属中的双尺度孔隙失效过程。在这里，我们提出了一个三维的，小规模的屈服边界层模型，包含一个中心线裂纹远程模式IK场加载，以研究这种双尺度孔隙率对裂纹缺陷的相互作用在AM Ti-6Al-4V合金的影响。我们模型的背景孔隙度隐含在断裂过程区，即几行含空隙的计算单元格的Gurson多孔材料关系，而较大的AM空隙缺陷离散表示的基础上的实际AM Ti-6Al-4V试样的尺寸和孔隙度分布，其特征在于使用光学和电子显微镜。结果表明，AM缺陷可以通过激活裂纹周围的孤立和/或聚集的损伤区，从而屏蔽和钝化裂纹尖端并促进裂纹曲折度，来增加AM金属的表观韧性。然而，AM缺陷的平面簇的存在也可以加速裂纹生长，并通过形成优先裂纹路径而导致过早失效。
The presence of microstructural defects resulting in unpredictable failure behavior has limited the use of additively manufactured (AM) metals in structural applications. In addition to the distributed porosity responsible for ductile fracture in conventional metals, larger defects (20–50 μm) can be introduced during additive manufacturing resulting in a dual-scale porosity failure process in AM metals. Here, we subject a three-dimensional, small-scale yielding boundary layer model containing a centerline crack to remote mode IK-field loading to study the effects of such dual-scale porosity on crack-defect interactions in an AM Ti-6Al-4V alloy. We model the background porosity implicitly within the fracture process zone viz. several rows of void-containing computational cell elements governed by the Gurson porous material relation, while the larger AM void defects are discretely represented based on size and porosity distributions of actual AM Ti-6Al-4V specimens characterized using optical and electron microscopy. Results show that AM defects can contribute to an increased apparent toughness of the AM metal over its conventional counterpart by activating isolated and/or clustered damage zones surrounding the crack, which shields and blunts the crack-tip and promotes crack tortuosity. However, the presence of planar clusters of AM defects can also accelerate crack growth and cause premature failure by forming preferential crack paths.