Dynamic Coupling Electromechanical Responses Of Piezoelectric Materials With Electrodes

Piezoelectric ceramics have the advantages of light weight, high sensitivity,and constitutive property. They are widely used in the piezoelectric sensors,piezoelectric actuators. However, these advantage materials are of fragile in natureand low strength. In practical applications, an electrode is attached to piezoelectricmaterials surface, in order to enhance their strength and realize theelectromechanical coupling function of piezoelectric materials. The stronginteraction between electrode and piezoelectric material can lead to the failure of thestystem. Therefore, stydy of dynamic coupling electromechanical responses ofpiezoelectric materials with electrodes is useful for effectively preventing the failureof piezoelectric materials and structures subjected to transient electrical pulses. Thisarticle focuses on some typical electrode-piezoelectric material interactions under aninstantaneous electrical impulse. These include a half space/finite piezoelectricceramic with a circular surface electrode and a double piezlelectric medium with acircular interface electrode. With the graphics of electric displacement intensityfactor, discussions of dynamic coupling electromechanical behavior ofelectrode-piezoelectric ceramic interations are made. Laplace transform, singularintegral equation, double integral equation are applied to explore the exact solutionsof electric displacements and stresses. Major results of the thesis are outlined below:It is found that the stress and electric fields around the vicinity of the electrodeedge are singular, under the transient electrical pulses, either for the piezoelectricceramic half space/finite medium or for the double piezoelectric medium. Theelectric displacement intensity factors increase with the response time, and tend to afixed value, which depend on the medium geometry and material type. The resultsshow that as the response time continuously increase, the electromechanicalconcentration phenomenon becomes increasely aggravated.The influence of the ratio of piezoelectric medium layer thickness to electroderadius on the singular of the electrode edge is obvious. Electric displacementintensity factor decreases with the decreasing ratio of piezoelectric medium layerthickness to electrode radius. The reduction of the thickness of the piezoelectriclayer or increase of the electrode radius could properly offer the protection of crackoccurrence.The results suggest that the most likely cracking direction is the verticaldirection of the electrode edge. The tangential stress at the electrode edge candecrease or increase with the tangential angle and show a maximum value near thevertical direction. Naturally, attention should be paid to the vertical direction of the electrode edge, which prones to cracking under dynamic electromechanical loading.