Abstract: Using Stroh's formalism the simple explicit expressions of Green's functions for a 2D piezoelectric body with two semi-infinite fixed conductor cracks subjected to a generalized line force were given. The Coulomb force acting on the free line charge aroused by the piezoelectricity and the distributed boundary polarization charges was discussed at first. Interactions between two singularities with free charge(s) located in a region with external cracks were studied, too. The numerical results show that the Coulomb force for two or more singularities with one free charge at least will have much influence on the electromechanical fields in piezoelectric media when these singularities move closely with each other and therefore cannot be overlooked again. The solutions obtained are valid not only for plane and anti-plane problems but also for coupled problems between in-plane and out-of-plane deformations.

Key words: external crack, intensity factor, Green's function, Coulomb force