Piezoelectric actuators are increasingly used in modern fuel injectors due to their quick response, high efficiency, and
excellent repeatability. Current understanding of the thermo-electro-mechanical performance of piezoelectric actuators
under dynamic driving fields is very limited. In this paper, the dynamic thermo-electro-mechanical performance of Lead
Titanate Zirconate (PZT) stack actuators is experimentally studied over the temperature range of -30 °C to 80 °C, under a
driving field of up to 2.4 kV/mm (with an AC drive method) and a constant preload of about 5MPa. Sinusoidal and
trapezoidal driving fields with rise times varying from 0.1 ms to 2 ms are applied. It is found that dynamic stroke
increases steadily with the temperature. Under driving frequencies lower than the resonance frequency of the testing
system ( ≈ 500Hz), the electric field-strain behavior under different temperatures is very similar to the quasi-static results
obtained previously. In the case of a trapezoidal pulse, decreasing the rise time is found to be equivalent to increasing the
frequency.
The governing equations of piezo-thermoelastic materials show full coupling between mechanical, electric, and
temperature fields. It is often assumed in the literature that in high-frequency oscillations, the coupling between the
temperature and mechanical displacement and electric field is small and, therefore, can be neglected. A solution for the
temperature field is then determined from an uncoupled equation. A finite element (FE) model that accounts for full
coupling between the mechanical, electric, and thermal fields, nonlinear constitutive behavior and heat generation
resulting from dielectric losses under alternating driving fields is under development. This paper presents a linear fully
coupled model as an early development of the fully coupled nonlinear FE model. In the linear model, a solution for all
field variables is obtained simultaneously and compared with the uncoupled solution. The finite element model is based
on the weighted-residual principle and uses 2-D four-node isoparametric finite elements with four degrees of freedom
per node. A thin piezoelectric square disk is modeled to obtain some preliminary understanding of the coupled fields in a
piezoelectric stack actuator.
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