Scattering Of SH Waves By Mode-? Crack In Layered Piezoelectric-piezomagnetic Structures

Layered structures are important forms of piezoelectric(PE)-piezomagetic(PM)composites.They are readily fabricated and have higher magnetoelectric coefficients,and electricity conversion into magnetism vice versa are easily controlled when electric field or magnetic field is applied.These advantages make layered PE-PM composites have potential applications in sensing,controlling,information technology,emerging smart materials and structures as well as micro-electromechanical systems.Most of both PE and PM materials are very brittle.This results in PE-PM composites or related devices being susceptible to fracture or failure.Therefore,it is important to study the fracture behaviors of layered PE-PM composites.This results from two main aspects: one being to reveal new fracture phenomena due to magnetoelectric coupling,the other being to provide a theoretical support for applications of layered PE-PM composites.The conversion between electric energy and magnetic energy come from the deformation transfer between PE phase and PM phase.So in investigating the magnetoelectric effect,the researches in the condensed matter physics and material science did not consider the magnetic field in PE materials and the electric field in PM materials.Based on such physics background,this dissertation studies the dynamic fracture of the PM-PE-PM sandwich structure and PE-PM layered half-space with mode-? crack under SH waves.The Fourier transform is used to reduce the mixed boundary value problems to the Cauchy singular integral equation of the first kind.The Cauchy singular integral equation is solved by employing the Gauss-Chebyshev polynomials.Numerical calculations are carried out to shown the effects of material properties,incident wave frequency,crack length and PE layer thickness on the dynamic stress intensity factor(DSIF).The main results are as follows.(1)For the PM-PE-PM sandwich structure,the DSIF first increases with increasing incident wave frequency,reaches a peak value and then decreases.The larger the ratio of PE layer thickness to crack length is,the larger the DSIF is.(2)For PE-PM layered half-space structure,the DSIF reaches its maximum peak value and then decrease oscillatorily with the increase of incident wave frequency.The smaller the ratio of PE layer thickness to crack length is,the larger the maximum peak value of the DSIF is,which is different from the result of the PM-PE-PM sandwich structure.The peak values of the DSIF under the electrically-shorted condition are larger than those under the electrically-open condition.(3)For two kinds of structures considered,the larger the velocity of the shear bulk wave of a PE layer,the larger the maximum peak value of the DSIF for the corresponding structure.