3-DIMENSIONAL ANALYSIS OF DYNAMIC DUCTILE CRACK-GROWTH IN A THIN-PLATE

A three dimensional analysis of dynamic ductile crack growth in an edg e cracked plate is carried out, using a data parallel implementation i n a transient three dimensional finite element program. An elastic-vis coplastic constitutive relation for a porous plastic solid is used to model ductile fracture by the nucleation and subsequent growth of void s to coalescence. Two populations of second phase particles are repres ented, large inclusions with low strength, which result in large voids near the crack tip at an early stage, and small second phase particle s, which require large strains before cavities nucleate. Adiabatic hea ting owing to plastic dissipation and the resulting thermal softening are accounted for in the analyses. The crack speed and the crack path are based on the ductile failure predictions of the material model, so that the present study is free from ad hoc assumptions regarding appr opriate dynamic crack growth criteria. A convected coordinate Lagrangi an formulation is employed and the discretization is based on twenty-n ode brick elements with 2 x 2 x 2 Gauss points. The equations of motio n are integrated numerically by an explicit integration procedure usin g a lumped mass matrix. Crack growth occurs by tunneling in the centra l part of the plate and shear lip formation at the free surface. The e ffect of various material parameters and of plate thickness on this pr ocess is studied. For comparison purposes, a calculation with overall plane strain boundary conditions is carried out.