Papers by Author: Dong Teak Chung

Abstract: A micro ball supersonic impact test system was developed for the study of dynamic fracture of ceramic materials. This system consists of (1) low pressure gas gun, (2) sabot assembly and stopper block for velocity multiplication system, (3) velocity measurement device for sabot and ball, and (4) enclosed target box for final impact test. The principle of velocity multiplication system is similar to two stage gun. The plastic sabot assembly houses steel plunger and the void filled with silicone rubber. The sabot is stopped by the stopper block then the steel plunger inside the sabot compress the silicon rubber to high pressure to rupture the plastic membrane. Then the compressive energy of the silicon rubber is transferred to the ball. More than ten times of initial speed was attained. Non-contact velocity measurement system uses two set of ribbon laser with optical array sensor to measure the supersonic speed of the micro ball. Maximum speed up to 1200m/s for plastic and 600m/s for steel ball was attained. Perforation test of plastic film laminated glass window was successfully done by the developed impact system.

Abstract: Flying robots with flapping wings are preferred over conventionally fixed or rotational wings in terms of hovering capability for a simple mechanical configuration. Until recently, available actuators for such a robot are limited to (1) a conventional motor with four-bar linkage mechanism or (2) a piezo electric actuator, but none of them could provide enough lift because of low flapping frequency, small stroke angles, and/or frequent mechanical failure. A new actuator capable of generating large stroke angles with high frequency is developed. It consists of an out-runner brushless motor with a modified motor driver attached to a torsion spring. The wing is attached directly on the cap of the motor. A prototype is built and preliminary thrust force measurements are performed. Properties of wing materials suitable for powerful and robust actuators will be discussed. The actuator employed in the present study utilizes resonance oscillation, which leads to high energy efficiency. Further study of wing shape and directional stiffness is needed for generating higher lift capability.