The analysis of crack tip fields in ferroelastic materials

The stress and strain fields near a stationary crack in a ferroelastic material are analyzed. The constitutive response of the material is taken to be characteristic of a polycrystalline sample assembled from randomly oriented tetragonal single crystal grains. The constitutive law accounts for the strain saturation, asymmetry in tension versus compression, Bauschinger effects, reverse switching, and strain reorientation that can occur in these materials due to the non-proportional loading that can arise near a crack tip. Detailed finite element calculations are carried out to determine the stress and strain fields in the vicinity of the crack tip, and to compute values for the J-integral on various integration paths around the tip. The results of the calculations are discussed in relation to results for growing cracks and for stationary cracks in standard elastic–plastic materials