The last decade has seen a lot of two-dimensional studies of cracks in piezoelectric materials
(Suo et al., 1992; Park and Sun, 1995; Zhang and Tong, 1996; Zhang andMeguid, 1997), however,
there are comparatively few works of three dimensional analysis. Sosa and Pak (1990)
considered a three-dimensional eigenfunction analysis of a semi-infinite crack. Wang (1992)
obtained expressions for stress and electric displacement intensity factors for a flat elliptical
crack embedded in a piezoelectric material with arbitrary anisotropy. For penny-shaped crack
in a transversely isotropic piezoelectric medium, Huang (1997) obtained a complicated form
of expressions for stress and electric displacement intensity factors, in which material constants
are involved. That remains questionable as one can see in Pak (1992) whose solution
was based on the method of distributed dislocations. A little earlier, Kogan et al. (1996) also
derived the mode I intensity factors of a penny shaped crack as a limiting case of a spheroidal
inclusion.
The potential theory method has been developed by Fabrikant (1989) as an efficient method
to analyze various mixed boundary value problems in pure elasticity. It will be shown here
that the method can be further generalized to analyze corresponding mixed boundary value
problems in three-dimensional piezoelasticity, by reconsidering the mode I problem of a
penny-shaped crack in piezoelectrics.