MESH INDEPENDENT CELL MODELS FOR CONTINUUM DAMAGE THEORY

The conventional use of continuum ductile damage mechanics in finite element analyses identifies the ''cell'' in which damage occurs with the finite elements in which the distribution of stress and strain is modelled. Since the cell size is a fixed, metallurgically-defined, property of the material being analysed, this methodology forces a minimum size for the finite element mesh. Mesh refinement is thereby disallowed. This paper presents one way of avoiding the problem by developing a mesh-independent cell model which, with a fixed cell size, allows the finite element mesh to be refined to any degree within the cells. Procedures which average some state variables within the cells are introduced to prevent the localisation of damage after a certain critical stage is reached. The method has been tested in numerical simulations of (a) the deformation of a notched tensile bar, (b) a 35 mm compact tension specimen and (c) the first of the AEA spinning cylinder tests. There is a reasonable agreement between the results of the computer simulations and those of the experiments.