Piezoelectric materials are excellent actuator candidates due to their high frequency bandwidth. However, hysteresis and nonlinear material effects can reduce their overall performance, particularly when driven at high amplitudes and high frequencies. Of interest here is an application for high-frequency actuation. The demand for actuation authority requires careful characterization and accurate modeling of the piezoelectric actuator dynamics to ensure the intended performance. This paper presents such a characterization of a ring-shaped piezoelectric stack actuator. A series of experiments is presented to explore the ring stack actuator's response both under free boundary conditions and with spring-applied preloads. Fixed voltage tests conducted confirm the expected quasi-static response, while oscillatory tests exhibit dynamics that impact response at higher frequencies. Preload stiffnesses appear to minimally change the nominal displacement observed compared to the baseline, no-load case. While the preloads were small, the actuator showed qualitatively similar performance for the unloaded and several loaded cases.

This paper presents a fundamental non-contact valve design developed by integrating a ring-stack piezoelectric actuator into a converging nozzle design to impart harmonic flow. The paper also outlines the governing equations as well as limiting factors that constrain the design and operating performance. The converging nozzle design achieves choked flow at the valve exit when the nozzle is fully open. Valve actuation centers around piezoelectric ring stacks: the piezoelectric stack is fixed within the valve on one end to the base plate and has a conical nozzle tip attached to the opposite end of the stack. When the stack fully displaces to its maximum length, the nozzle tip is in the closed position where minimal flow passes through the valve exit. The flow area between the nozzle tip and casing wall achieves maximum mass flow rate when the piezoelectric stack is at minimum length. The change in flow cross-sectional area due to the piezoelectric stack displacement generates a change in mass flow rate through the valve. Due to the small-scale displacement of piezoelectric stacks, different angles of the nozzle cone and casing are required to achieve a greater desired mass flow rate. This model is adjustable to accommodate various piezoelectric stack sizes and displacements or to alter the exit mass flow rate to best suit a particular application.