Strain energy density failure criterion

The initiation of macroscopic material failure is associated with the colle ctive disruption of atomic bonds, which is driven by the potential energy s tored in the atomic bonds. This potential energy, which is represented by s pecified elastic strain energy density in a mechanical system, is releasabl e. Thus, a universal macroscopic material failure criterion in a mechanical system can be defined by a specified elastic strain energy density togethe r with its critical value that is determined by preceding irreversible defo rmation process and current environmental state. A dissipative function bas ed on continuum mechanics and irreversible thermodynamics is proposed to re present the irreversible deformation process. The increase of this dissipat ive function due to material inelastic deformation, damage and other possib le intrinsic dissipative mechanisms in a mechanical system leads to the red uction of material strength. When the material failure is dominated by the dissipation, a dissipative energy density failure criterion can be defined by using the dissipative function. On the other hand when the intrinsic dis sipation is negligible during the deformation process before failure, the s pecified elastic strain energy density and its critical value, which is det ermined by the initial material bond strength, can be used to define materi al brittle failure. It also shows the possibility to set up a relationship between fracture mechanics and failure criterion. The proposed method to re present failure criteria is based on continuum mechanics and irreversible t hermodynamics and retrieves previously successful failure criteria. (C) 200 1 Elsevier Science Ltd. All rights reserved.