Using geometrically, topologically and materially unstructured methods to reduce mesh dependency in dynamic cohesive fracture simulations

We present a method to reduce mesh bias in dynamic fracture simulations using the fi nite element method withadaptive insertion of extrinsic cohesive zone elements along element boundaries. The geometry of the domaindiscretization is important in this setting because cracks are only allowed to propagate along element facets andcan potentially bias the crack paths. To reduce mesh bias, we consider geometrically unstructured polygonal fi niteelements in this study. To overcome the problem of limited crack paths, and to signifi cantly improve crack patterns,we propose adaptive refi nement [1] and adaptive element splitting [2], increasing the number of potential crackdirections at each crack tip. As an additional means of reducing mesh dependency, microstructural randomness isincorporated into the method by means of statistically distributing material properties [3]. Numerical examples arepresented which demonstrate improved agreement with experimental results in the literature. REFERENCES[1] Spring, D.W., Leon, S.E., Paulino, G.H. Unstructured adaptive refi nement on polygonal meshes for the numerical simula-tion of dynamic cohesive fracture. International Journal of Fracture (submitted)[2] Leon, S.E., Spring, D.W., Paulino, G.H. Reduction in mesh bias for dynamic fracture using adaptive splitting of polygonalfi nite elements. International Journal for Numerical Methods in Engineering (accepted).[3] Zhou, F. Molinari, J.F. Dynamic crack propagation with cohesive elements: a method to address mesh dependency. Inter-national Journal for Numerical Methods in Engineering. 2004, 59, 1–24.