A study of the effect of the electro-mechanical loading history on the fracture strength of piezoelectric material

Many studies to grasp and describe the fracture behavior of piezoelectric materials under electro-mechanical loading have been done. Although the crack energy density (CED) theory predicts that the mechanical and electrical CEDs can depend on the loading history, the effect of electro-mechanical loading history on the fracture strength of piezoelectric materials has not been studied. Therefore, in this paper, a fracture criterion based on the mechanical contribution of CED (CEDM) is introduced. Its applicability is studied by analyzing the results of three-point bending test regarding the loading path dependence of the fracture strength of piezoelectric ceramic. From the results of (E → M) and (M → E) tests for a C-21 piezoelectric ceramic specimen, it was found that the fracture behavior of piezoelectric ceramics depend on the loading history. The results further showed that the effect of the electric field on the fracture strength of piezoelectric ceramic in the (M → E) test was larger than that in the (E → M) test. Results from linear FE analyses, which assumed that the fracture-initiating load was the same, indicated that the CEDM values increased linearly from negative to positive, and the slopes of CEDM in descending order were: linear (M → E) analysis > linear (M, E) analysis > linear (E → M) analysis.