Studies On Fracture Mechanics Of Piezoelectric Materials Under Heat-mechanical-electric Loadings

Nowadays piezoelectric materials are widely used in electromechanical equipments, such astransducers, drivers, and sensors. However, due to their brittleness, piezoelectric materials easilycrack when subjected to combined electrical, mechanical, and thermal loads, which may lead to thefracture and failure of equipments or structures. Therefore, researches on the fracture of piezoelectricmaterials with cracks under combined loads are of great significance in theory and application.Based on the linear piezoelectric theory, and by means of complex variable method andintegration transform method, this dissertation studies the fracture problems of piezoelectric materials.The outlines are listed below:1) The problem of an infinite piezoelectric plate with a semi-permeable crack subjected to thermaland electrical loads has been studied. The stress intensity factor is solved by using the complexvariable method and the basic solution of a Hilbert problem. Numerical examples are then givento discuss the influence of thermal coefficients, electric coefficients and crack length on thestress intensity factors.2) The case of a half-infinite piezoelectric plate with an impermeable edge crack subjected tothermo-mechanical-electric loads has been studied. The electric potential, temperature filed, andstress fields are obtained, and then Numerical examples are also presented for discussion of theobtained results.3) The solution for a piezoelectric strip with a center and thermally semi-permeable crack underthermal and electric loading along the crack upper and lower surface has been presented. Basedon the basic piezoelectric equations, thermal governing equations and boundary condition,combined with Fourier transform and singular integral equation, the solution for thermal andstress in the strip are obtained.