Vinh Tung Le

High actuation force of piezoelectric hybrid actuator with multiple piezoelectric pump design

The piezoelectric hybrid actuator is a new electro-hydrostatic actuator with broad prospects for development. Compared with the traditional hydraulic pump, the piezoelectric hybrid actuator is characterized by a simple structure, small size, lightweight, and low power. However, it has a well-known weakness: It produces only a small actuation force and then cannot be used in real applications. Because the maximum force produced by a one-piezoelectric pump design cannot be increased much due to limitations in the power supply and piezoelectric materials, researchers have moved to the use of multiple piezoelectric pumps. In this research, a double-piezoelectric pump-hydraulic cylinder hybrid actuator was designed, manufactured, and tested in order to increase the actuation force. Key design factors such as the connection method and driving method were investigated to realize the double-piezoelectric pump design and achieve a high level of performance. A total of three kinds of double-piezoelectric pump-hydraulic cylinder hybrid actuator designs were selected by a theoretical approach and implemented using two identical piezoelectric pumps. A manual valve system was installed for switching the connection method (series and parallel modes). The driving method, phase, or voltage was controlled by a LabVIEW program. The maximum blocking force of 4615 N was measured at 250 Hz for cross driving, series connection and φ30-mm cylinder. The maximum velocity of 68.3 mm/s was measured at 300 Hz for cross driving, series connection and φ21-mm cylinder. Fluid structural interaction analysis using ANSYS software confirmed the experimental results. The performance of double-piezoelectric pump-hydraulic hybrid actuator meets the minimum requirements for mechanical and aerospace actuator applications.

Thermal Protective Properties of the Allomyrina dichotoma Beetle Forewing for Thermal Protection Systems

ABSTRACT This paper studies the heat-shielding performance of a beetle forewing to explore how it has excellent thermal protective properties. With an experimental setup of a self-developed heating environment, the heat transfer characteristics of the beetle forewing were tested at 50°C under steady state conditions. Two types of the forewings are considered: cut wing and live wing. The heat transfer results show that the live forewing provides a good heat-shielding performance with the heat-shielding index stabilizing at around 22.1%, which is 60% higher than that of the cut wing. Based on scanning electron microscope images of the microstructure of the cross section of the beetle forewing, a simplified finite element analysis is performed to numerically calculate the heat transfer properties of the forewing. The numerical simulations reveal that the proposed structure of the forewing is good for the design of an effective thermal protection system. In addition, the uncertainty analysis is performed to evaluate the quality of experimental data. These results provide a foundational understanding of the heat transfer characteristics of beetle forewing, which will inspire a promising candidate for an actively cooled thermal protection systems.

Insulation system using high-temperature fibrous insulation materials

ABSTRACT In this study, we performed a preliminary research on an insulated sandwich structure using high-temperature fibrous insulation materials. Two types of fibrous materials, Saffil alumina and KCC cerakwool insulation materials, were selected. A sandwich specimen was invented to test the heat-shielding performance of the fibrous materials which were sandwiched by an Inconel plate and a titanium plate. The insulated sandwich structure was heated to 800°C for 2,000 seconds. The temperature profiles of the back side of the titanium plate were measured to compare the heat-shielding performance of the fibrous insulation materials. The microstructure of insulation materials, such as the fiber diameter, fiber orientation, and the parent materials of the fiber, was studied to understand how those characteristics influence the radiative properties of the fiber. The difference in microstructural parameters caused a difference in thermal resistance in the fibrous materials. The Saffil alumina insulation had a better performance than KCC cerakwool insulation because of its small fiber diameter and in-plane fiber orientation. The experimental results confirmed the heat transfer simulation results for fibrous materials done by other researchers. In addition, the reusability of high-temperature fibrous insulation, one of the important issues in real applications, was tested.