Nonlinear fracture mechanics for ferroelastic materials

Nonlinear fracture mechanics concepts for ferroelastic materials are presented. A phenomenological constitutive law for ferroelastic domain switching is implemented within a steady state finite element formulation to determine the stress and strain fields near growing cracks in ferroelastic materials. Hutchinson's I-integral is applied to determine the relationship between the far field applied energy release rate and the local crack tip energy release rate. Computations are performed on both unpoled and "mechanically poled" materials with and without T-stress to quantitatively determine the toughening due to domain switching in these situations. Results are discussed in comparison to "transformations toughening" type analytical models.