Transient Response Of Mode-Ⅲ Crack In The Orthotropic Piezoelectric Materials

Due to being able to transform mechanical energy into electric energy and vice versa, piezoelectric materials have been widely used in technology such as sensors, transducers, filters, actuators, resonators, energy harvesters as well as sensing and actuating components in smart structures. The brittle behavior and low fracture toughness of most piezoelectric materials make them be susceptible to fracture during service. The reliability and integrity of piezoelectric devices or structures demand a comprehensive understanding of fracture behaviors of piezoelectric materials. Based on the electrical contact mode-III crack, integral transforms and dislocation density functions are employed to reduce the problem to Cauchy singular equations. Numerical results for the time-dependent stress intensity factors are obtained. The main objective of this thesis is to show the influence of material parameters, geometry parameters, piezoelectric coupling and crack orientation on dynamic fracture behaviors.Firstly, the fracture analysis for the mode-III crack in the infinite orthotropic material is investigated. Numerical calculations are carried out to show the influence of the material parameters on the normalized dynamic stress intensity factors. The results show that the elastic constants and piezoelectric constants have a great impact on the peak of the normalized DSIF. However, the effect of the dielectric constants of piezoelectric materials on the normalized DSIF can be neglected.Secondly, the dynamic response of a piezoelectric strip with a central/eccentric crack parallel to the boundary is investigated. The curves of normalized DSIF with the various geometry parameters are described. This leads one to the conclusion that we can restrict the propagation of crack through increasing the thickness of the piezoelectric materials.Thirdly, the emphasis is placed on the effect of material anisotropy and crack orientation on the dynamic fracture behaviors. The numerical results from the proposed method show that the peak values of normalized stress intensity factor are increased from β=0oto β=45oand then they decreased from β=45oto β=90o.