Numerical modelling of piezoelectric actuators exposed to hydrogen

Abstract

Modern fuel injectors have been developed based on piezoelectric stack actuators. Performance and durability of actuators in a hydrogen environment are important considerations in the development of hydrogen injectors. 2D plane stress and 3D models for analysis of coupled diffusion and thermo-electromechanical response of actuators are presented. Chemical potential, electric field and temperature gradients are taken as driving forces for hydrogen transport. The explicit Euler finite difference method is used to solve the nonlinear diffusion governing equation. The finite element method is used for time-dependent analysis of fully coupled mechanical, electric and thermal fields. The diffusion process and thermo-electromechanical deformations are coupled through the dependence of piezoelectric properties on hydrogen concentration. Experimental results for the piezoelectric coefficient d 33 of PZT ceramics exposed to different hydrogen concentrations are used. A comparison of a fully coupled 2D model with 2D and 3D models with reduced coupling is made to examine the significance of coupling and computational efficiency. Selected numerical results are presented for time histories of hydrogen concentration, temperature and stroke of an idealized actuator unit cell to obtain a preliminary understanding of the performance of actuators exposed to hydrogen.

Performance of piezoelectric actuators in a hydrogen environment: Experimental study and finite element modelling

“…Conceptually, the model integrates three physical phenomena, viz., (a) thermo-electro-mechanical coupling in a piezoelectric material [26], (b) diffusion of hydrogen [27] and (c) hydrogen-induced variations in the piezoelectric properties as reported by Wu et al [11]. It also extends the previously developed, independent models [26,27] to fully coupled 3-D cases.…”

“…It has also been reported earlier [27] that the temperature gradient has a minor influence on the diffusion of H-atoms inside the PZT. The diffusion process is, therefore, primarily controlled by the gradient of H-atoms concentration based on Fickian diffusion.…”

“…Senousy et al [26] developed a 2-D fully coupled thermo-electro-mechanical finite element (FE) model of a piezoelectric actuator based on the weighted-residual principle and using linear constitutive relations. Sapsathiarn et al [27] developed a 2-D finite difference (FD) model to simulate the non-linear diffusion process of hydrogen in a PZT material, including the thermotransport effect. They also sequentially combined the FE model of [26] with their FD model for a 2-D plane stress case.…”

Creep Effect Analysis at the Friction Interface of a Rotary Ultrasonic Motor

“…Based on piezoelectric composite structure, traveling wave type rotary ultrasonic motor (TRUM) shows a wide application prospect in the field of micro-actuators, precision driving stage and electro-optic modulators, and has gained increasing attention from many researchers [Ueha, 1988;Parashar et al, 2005;Sapsathiarn et al, 2014]. Depending on the piezoelectrically induced vibration in composite structure and contact mechanism, TRUM has a high ratio of torque to weight, excellent electromagnetic compatibility, compact size and fast response while the rotor is pressed on the piezoelectric composite structure (usually called stator), so that it has many advantages over the conventional actuator in some applications such as auto focus camera lenses, precise positioning and robot actuation [Zhao, 2009;Jeon et al, 2014].…”

Electro-Mechanical Response and Engineering Properties of Piezocomposite with Imperfect Interface

“…The response of piezoelectric composite materials is governed by several parameters, such as the fiber-to-matrix volume ratio, the properties of the fiber, the surrounding matrix material, and the interphase layer between piezoelectric fibers and the matrix [3][4][5]. Properties of piezocomposites can be globally represented by a homogeneous medium with anisotropic properties.Micromechanics model can provide the relations between the microstructure and the overall or effective properties of composites based on the known properties of each material phases in the composites.…”