Nonlinear behavior of polycrystalline piezoceramics

Piezoelectric materials exhibit nonlinear behavior when subjected to large electric or mechanical loads. This strong nonlinear material behavior is induced by localized polarization switching at the domain level. In this paper, a finite element code in conjunction with a polarization switching criterion is described to model the nonlinear behavior in piezoceramics. Each element represents a single domain with a tetragonal structure. The nonlinearity is introduced in the behavior of each element by allowing it to undergo 180 degrees and 90 degrees polarization switchings. In order to simulate the real piezoceramic, which possesses a polycrystalline nature, material is modeled as a mixture of crystallites each oriented in some random direction. The model is used to generate the dielectric and strain response of the material, i.e. hysteresis and butterfly loop. The model output is compared with experimental data, and reasonable agreement is achieved. Behavior of the material under compressive stress, which doesn't cause full polarization switching, is studied to investigate the influence of compressive stress on the strain output. It is observed that strain output of a preloaded block of piezoceramic increases for moderate electric fields but decreases for small and large electric fields.