Transient thermal fracture analysis of ferroelectric ceramics under electromechanical loading

Abstract

During their applications, ferroelectric devices are subjected not only to electromechanical loading but also to thermal fields, inducing additional stresses and impairing their functionality. Additionally, internal heat generation can occur by the dissipation of the inelastic work resulting from ferroelectric hysteresis. Moreover, at extreme electromechanical field concentrations like cracks, ferroelectric devices may fail by brittle fracture or fatigue. In the present study, the thermal effects on the fracture behavior of ferroelectric ceramics are investigated. The well-established micromechanical material model for ferroelectric domain switching is enhanced to represent the fully coupled thermo-electro-mechanical behavior. The coupling considers the pyroelectric and thermal strains effects. The internal heat production, which leads to transient temperature fields, is taken into account, as well as the temperature dependency of material parameters. The thermo-electro-mechanical fields at the crack tip are analyzed using a boundary layer approach for small-scale switching conditions. A fully transient heat conduction problem is considered, emphasizing the effect of the driving frequencies on heat generation. The configurational forces concept combined with the thermo-electro-mechanical extension of the J-integral are used to analyze the impact of the different factors on the crack driving energy.