Effect of electromechanical loadings on fracture strength of piezoelectric ceramics

The effect of electromechanical loadings including their sequence, which was motivated by the property of crack energy density for piezoelectric material, was experimentally investigated. Three-point bending fracture test was performed for two piezoelectric ceramics under different electromechanical loading conditions. It was found that the fracture loads under closed circuit condition are greater than those under open circuit condition. Effect of applied electric field on fracture load in the test varied with materials. Applied electric field always enhanced crack extension in C-21 ceramics regardless of their directions, while it produced very little effect on crack extension under negative electric fields in C-2 ceramics. It was also found that electromechanical loading sequence clearly affects fracture strength, although its effect varies also with materials.