INFLUENCE OF GEOMETRY, CRACK-FACE CONDITIONS AND LOADING ON INTENSITY FACTORS OF CRACKS IN 3D LINEAR PIEZOELECTRIC MEDIA

Abstract

This thesis presents extensive results to demonstrate the influence of the crack geometry, crack-face boundary conditions, remote loading conditions and permittivity of a medium inside the crack gap on the intensity factors of cracks in linear piezoelectric media. A spherical cap crack, a cylindrical crack, a tunnel crack and a pair of identical penny-shaped cracks are chosen as representative cracks in the present study to fully explore the role of all parameters. In simulations, the weakly singular SGBEM is used to determine the unknown crack-face data and special local interpolations are employed along with the explicit formula to enhance the near-front approximation and directly extract intensity factors along the crack front. Results from a numerical study indicate that the curvature, the crack subtended angle and the crack aspect ratio significantly influence the value of the intensity factors. It is also observed that KI of impermeable, permeable and semi-permeable non-planar cracks exhibit completely different behavior from that of planar cracks when the mechanical load increases. Moreover, KI for both impermeable and semi-permeable non-planar cracks depends strongly on the applied electric field. These findings are in contrast with results in the case of planar cracks where KI of impermeable, permeable and semi-permeable cracks are identical and independent of the electric field. In addition, as the permittivity inside the crack gap increases, the stress intensity factors of impermeable, permeable and semi-permeable non-planar cracks are not identical and the semi-permeable solution strongly depends on the permittivity of a medium inside the crack gap.