Anti-Plane Moving Crack In The Orthotropic Piezoelectric Materials And Piezoelectric/Elastic Layered Structures

Fracture mechanics of piezoelectric materials plays an important role in analyzing the failure mechanism and reliability of piezoelectric devices or structures. Since the early 1990 s, a lot of investigations on this topic have been carried out, and some important process has been made. However, almost all of them have been focused on transversely isotropic piezoelectric solids. In this thesis, the permeable moving cracks in orthotropic piezoelectric materials and orthotropic piezoelectric/elastic bilayers are studied. The main aim is to reveal the influences of material anisotropy and inertia effect on fracture behaviors of moving cracks. The research work and obtained results are as follows.Moving cracks in an infinite orthotropic piezoelectric media. The electro-elastic fields are derived in explicit closed-form, and the hoop shear stresses are calculated. The results shows that:(1) the stress intensity factor(SIF) does not depend on the material constants and crack moving velocity;(2) the material constants and crack moving velocity have the obvious influence on hoop shear stresses;(3) When crack moving velocity exceeds certain value, the crack may deviate from its original path.Moving cracks in an orthotropic piezoelectric strip. The mixed boundary value problem is reduced to solve a Cauchy singular integral equation numerically. The numerical examples demonstrate that:(1) for a given strip thickness, SIF increase with increasing the crack velocity;(2) when the crack length is unchanged, the thinner the strip thickness, the larger the value of SIF;(3) the applied electric displacement can either promote or retard the crack growth, depending on its amplitude and direction.Moving cracks in a piezoelectric /elastic bilayer. The used methods and solution procedure are same for the piezoelectric strip. The obtained results indicate that:(1) the effects of crack length and applied electric displacement on SIF are similar to the piezoelectric strip;(2) for given crack length and bilayer thickness, the thicker piezoelectric layer result in the larger SIF;(3) the elastic modulus has a significant influence on SIF.