Estimation of toughening produced by ferroelectric/ferroelastic domain switching

An estimate is made of the upper limit of the toughening that might be expe cted by the crack tip stress induced reorientation of domains in ferroelect ric ceramics. The calculation is based on obtaining the shielding stress in tensity factor produced by the shear transformation of a zone surrounding t he crack tip and extending over the crack surfaces. The estimate suggests t hat the toughening that might be expected is less than 10% even in the most ideal conditions. This case is contrasted with the much greater toughening which is expected from the crack tip stress induced phase transformations which are largely driven by the chemical, or bulk, free energy change of th e transformation. (C) 2001 Elsevier Science Ltd. All rights reserved.