Influence of applied electric field and mechanical boundary condition on the stress distribution at the crack tip in piezoelectric materials

A finite element technique is used to study the stress distributions at the crack tip of a piezoelectric ceramic subject to the applied electric fields. Under a negative applied electric field (electric field opposite to the direction of poling), the assumption of crack surfaces to be free of surface traction as the mechanical boundary condition is found to be invalid. It is shown that the stress distributions at the crack tip under the negative applied electric field are different for the closed crack mechanical boundary condition than those for the traction-free crack surface mechanical boundary condition.