Edge-to-edge Cohesive Shell Elements in LS-DYNA

This paper presents a new cohesive element in LS-DYNA for edge-to-edge connection of quadrilateral thin shells. Cohesive elements are an important tool for simulating the propagation of cracks in materials. For example, to describe failure propagation in a thinwalled sheet metal structure along an a priori known crack path, e.g. along a weld line, through-the-thickness crack propagation has in the literature been modeled by embedding interface cohesive zone elements in between shells elements, see e.g. References. By connecting faces and edges of neighboring elements, the cohesive elements are used to describe the degrading load carrying capacity of the material in the evolving fracture process zone. The elements do not, however, model a physical material in a continuum mechanics sense; instead they model a (non-linear dissipative) spring based force response depending on the separation of the neighboring faces and edges through a cohesive law. Hence, they can remain stable under zero or negative volume. LS-DYNA has a variety of solid cohesive elements to simulate cracks between solids (element type 19 and 21) and delamination of shells (type 20 and 22). As of Revision 8.0 a new cohesive shell element is now available for edge-to-edge connection of quadrilateral thin shells. The new cohesive element (type 29) accounts for in-plane and out-of-plane separation as well as hinge bending and works with existing cohesive material models. This paper presents the new element type 29 in detail and shows some relevant benchmark simulations.