Electrical permeability and domain switching effect on fracture behavior of piezoelectric material

Sureshkumar Kalyanam, Purdue University

Abstract

The crystal structure and domain microstructure within each grain of a piezoelectric material and 90°, 180° polarization switch observed experimentally are discussed. The work and internal energy density domain switching criteria are used to predict domain switch zones near crack tip of CT fracture specimen. Constitutive relations are modified to reflect changes in material properties and strains arising from domain switch. An incremental finite element solution procedure using UNIX program was developed to use ABAQUS piezoelectric FEA software along with FORTRAN codes for prediction and modeling of domain switching in piezoelectric material. Insulating materials like silicone oil are used by researchers to prevent electric arcing between crack faces during fracture tests with piezoelectric material. A finite element (UEL) was developed to model dielectric medium filling crack cavity of piezoelectric fracture test specimens. An iterative procedure was adopted to solve geometrically nonlinear crack opening using an UNIX program. The effect of permeability of crack cavity medium on near tip electric fields in CT fracture specimen was investigated. A CT fracture specimen was modeled using incremental domain switch finite element solution procedure. Domain switch zones in the vicinity of the crack tip were obtained for various electrical and mechanical fracture loads applied. The effect of actual crack profile on near tip domain switch zones, opening stress, stress intensity is discussed. A gradual polarization switch model which considers the gradual change in the average polarization direction from the original poling direction was developed. Fracture load predictions using stress intensity factor obtained from assuming linear material behavior, nonlinear behavior using the instantaneous and gradual polarization switch model are compared. Gradual polarization switch model was used to model a SENB fracture specimen to obtain the near tip strain field and compare it to the strain field obtained using Moire technique. Large intensification of electric field near crack tip leads to possibility of electric displacement saturation zone. FORTRAN codes are used along with ABAQUS FEA software to modify dielectric property of saturated elements to model electric displacement saturation. The effect of the electric displacement saturation on stress intensity near crack tip of a CT specimen was investigated.

Degree

Ph.D.

Advisors

Sun, Purdue University.

Subject Area

Aerospace materials|Materials science|Mechanical engineering

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