Theoretical investigations on the cracking of ferroelectric ceramics

摘要

One of the most essential problems with ferroelectric ceramics is the low srength and durability of the brittle material, which prevents many most promising technical applications in mechatronics and adaptronics. In order to supply knowledge about design features and strength criteria and to improve the safety of components with smart ceramics, a more fundamental understnaidng about hte process of fracture udner combined mechanical and electrical loading is required. Therefore, numerical tools are developed permitting the stress analysis of arbitrarily shaped smart ceramics with a given crack under combined electromechanical loading boundary conditions. To solve the coupled electromechanical field problem, the Finite Element Method is used taking account of linear constitutive equations for an anisotropic piezoelectric continuum. Stress intensity factors and energy release rates are subsequently calculated inserting near tip node values fro mechanical displacements and forces as well as electrical potnetials and charges. In connection with experiemtns on the cracking of Duble Cantilever Deam (DCB) sepcimens, the influence of electrical and mechanical loading conditions on the crack propagation is investigated. On the basis of calcualted energy release rates and intensity factors as functions of the crack length, possible fracture criteria are discussed.