Damage analysis for mixed mode crack initiation

The paper presents a numerical simulation for mixed mode crack initiation b ased on the concepts of damage mechanics. A model with two scalar damage va riables is introduced for characterization of damage in a material element. Then a tangent modulus tensor is derived for damage-coupled constitutive e quations. A failure criterion is developed with the concept of damage accum ulation not only to identify the location of damaged element where the crac k initiation angle but also to determine the critical load for mixed mode f racture. The damage model developed is incorporated in a general-purpose fi nite clement program ABAQUA through its UMAT subroutine. The finite element program is then used to perform numerical simulation for pre-cracked speci mens under monotonic tensile loading. The thin plates are made of aluminum alloy and particulate composite embedded with a crack of inclined angle bet a = 0 degrees, 30 degrees, 45 degrees and 60 degrees for mixed mode fractur e analysis. The predicted crack initiation loads and the angles of crack in itiation agree well with the test results.