Mesh size effects in simulating ductile fracture of metals

Physical scale and size effects influence the failure of structures and structural components. This can be especially true when failure is due to brittle, quasibrittle, or ductile fracture. When simulating ductile fracture using the finite element method, mesh size effects are also encountered. A common approach for analyzing the response of hull structures due to grounding and impact, for example, is to eliminate elements or to allow elements to split when a critical strain to failure is achieved. However, an important complication arises because of the observed mesh size sensitivity whereby strain to failure generally increases with finer finite element meshes. In this paper we explore the relation between the critical strain to failure, f e , and the size of the “unit cell” or finite element. Our study focuses on applications for marine structures involving fracture of metals including, for example, aluminum, magnesium, and steel alloys. Extensions to two and three dimensional stress states are also discussed.

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