Heat Generation, Temperature, and Thermal Stress of Structurally Integrated Piezo-Actuators

Abstract

While converting electrical energy into mechanical energy to actuate structures, piezoelectric (PZT) elements experience a temperature increase due to internal heat generation caused by their mechanical damping and dielectric loss. In practice, if the actuation is operated at system resonance or with a relatively high electrical field, the heat generation throughout PZT actuators may be significant. The temperature rise of PZT elements may result in the acceleration of material aging, even thermal damage. The situation becomes worse if the actuated host structures are made of thermalresistant materials, such as polymeric matrix composites and glass. In addition, the temperature distribution in PZT elements induces thermal stress that may increase the overall stress level and reduce the maximum safe stress. However, investigations done to date on these issues have been limited. This paper presents a simple analytical approach to estimate temperature rise and thermal stress in PZT patch actuators due to dynamic excition. A onedimensional heat transfer model is developed for integrated PZT/plate structures. The temperature field of the PZT actuators is analytically found and the corresponding thermal stress is predicted. To determine the internal heat dissipation in PZT actuators, an electromechanical impedance model developed by the authors is directly applied. The dissipative power in the systems, consumed by mechanical damping and dielectric loss of the PZT actuators, and structural damping of the host structure, is first determined. The dissipative power is then treated as the equivalent thermal dissipation to create a distributed heat source throughout the PZT actuators and host structures. In the case studies, the PZT patch elements were used to actuate a simplysupported plate. The impact of the thermal stress on the overall stress level is discussed in the paper. The effects of actuator thickness and material properties on the actuator temperature and the thermal stress level have also been investigated.