Investigation of Generalized SIFs of cracks in 3D piezoelectric media under various crack-face conditions

This paper investigates the influence of crack geometry,crack-face and loading conditions,and the permittivity of a medium inside the crack gap on intensity factors of planar and non-planar cracks in linear piezoelectric media.A weakly singular boundary integral equation method together with the near-front approximation is adopted to accurately determine the intensity factors.Obtained results indicate that the non-flat crack surface,the electric field,and the permittivity of a medium inside the crack gap play a crucial role on the behavior of intensity factors.The mode-I stress intensity factors(K1)for two representative non-planar cracks under different crack-face conditions are found significantly different and they possess both upper and lower bounds.In addition,K1 for impermeable and semi-permeable non-planar cracks treated depends strongly on the electric field whereas those of impermeable,permeable,and semi-permeable penny-shaped cracks are identical and independent of the electric field.The stress/electric intensity factors predicted by permeable and energetically consistent models are,respectively,independent of and dependent on the electric field for the penny-shaped crack and the two representative non-planar cracks.Also,the permittivity of a medium inside the crack gap strongly affects the intensity factors for all crack configurations considered except for K1 of the semi-permeable pennyshaped crack.