Development of a Non-Local Damage Mechanics Model

Development of a Non-Local Damage Mechanics Model. The deformation and failure behaviour of metallic materials can be described by means of so-called damage models whereas the damage processes running on the micro-structure level are described with continuum mechanical approaches. In case of these classical damage models, damage directly depends on the local stress and strain conditions. If these models are used in finite element programs, the local approach leads to a localisation of damage and strain in one element layer and thus to a mesh dependency of the finite element solution. Good results can only be achieved if the element size is directly linked to the microstructure. This paper describes a new nonlocal formulation were the solution is mesh size independent. Hereby the width of the localisation zone is directly implemented into the constitutive equations as an additional material parameter. In this case, the Rousselier model is used as damage model. In the paper, derivation and implementation of this nonlocal Rousselier model into a finite element program are described. For verification of the derived model, differently sized flat tensile specimens, each with a hole, were used and simulated with different mesh sizes. It was proved that the influence of the specimens' sizes on the fracture behaviour can be predicted independently from mesh size.