A finite element model of ferroelastic polycrystals

A _nite element model of switching in polycrystalline ferroelastic ceramics is developed[ It is assumed that a crystallite switches if the reduction in mechanically driven potential energy of the system exceeds a critical value per unit volume of switching material[ Stress induced "i[e[ ferroelastic# switching is a change of permanent strain in characteristic crystallographic directions[ Martensitic twinning is one example\ but the strain response of ferroelectric materials has the same characteristics[ The model is suitable for representing ferroelastic systems such as shape memory alloys and as a preliminary model for ferroelectric:ferroelastic materials such as perovskite piezoelectrics[ In the simulations\ each crystallite is represented by a _nite element and the crystallographic principal direction for each crystallite is assigned randomly[ Di}erent critical values for the energy barrier to switching are selected to simulate stress vs strain hysteresis loops of a ceramic lead lanthanum zirconate titanate "PLZT# at room temperature[ The measured stress versus strain curves of polycrystalline ceramics designated PZT!A and PZT!B are also reproduced by the model