Continuum Damage Mechanics
1. We use a state variable D to represent the effects of damage on stiffness etc.
We use the second law of thermodynamics to develop the theory 
2. Insights from experiments help us simplify the model, e.g. we see only traverse and parallel cracks, even under shear, so we make D a diagnol second order tensor We derive explicit equations relating the thermodynamic forces to stress, thus greatly simplifying the theory and computations.

3. Material Behaviours is predicted upto initiation of a micro crack

4. The model is incorporated in ANSYS

References