Applied Mechanics and Materials Vols. 479-480

Abstract: A simple yet comprehensive method is proposed for the design of a Geneva indexing mechanism with curved slots. In the proposed approach, conjugate surface theory is employed to derive an analytical description of the profile of the curved slots with and without an offset feature. The use of an appropriate offset angle to eliminate the singular points and double-points on the profile of the curved slots is then demonstrated. Finally, a mock-up Geneva mechanism is constructed to demonstrate the feasibility of the proposed approach. The results confirm that the methodology presented in this study enables the integration of the design, analysis and machining tasks for a Geneva indexing mechanism, and therefore makes possible a flexible and automatic production process.

Abstract: In this paper, a single silicon nanoemitter were investigated by means of experiments and simulation models andthe emitters array was fabricated by dry etching using an inductively coupled plasma (ICP) through a three-step process. Besides, in order to understand the field emission phenomenon in nano/micro scale, a novel experimental measurement technique by SEM with nanomotors including the constant voltage and the constant emission modes was developed to measure the accurate field emission properties.The results indicated that etching method is a good way to make the uniform field emitters and the electron field emission from a single nanoemitter is a barrier tunneling, quantum mechanicalprocess.

Abstract: Different inertia effect causes different control errors. To have an optimal control performance, the control parameters of a CNC machine tool should be adaptively tuned based on the variation of the weight of the workpiece in machining process. In this study, simulation based on a theoretical model was made to investigate the influence of inertial effect and friction force on the servo accuracy of a CNC machine tool’s. By using empirical method, an adaptive tuning system that can auto-tune the CNC control parameters based on the detected weight of workpiece was developed. An on-machine weight identification system that can on-machine identify the weight of the workpiece was developed. After integrating the two systems, a control parameter tuning system which can be implanted into CNC controller was developed with the macro executor. Experimental results have shown that the system can effectively improve the accuracy of a machine tool through adaptively tuning control parameters based on the current weight of the machined.

Abstract: This work experimentally investigated the effect of the oscillation move on the heat transfer enhancement of the pin-fin heat sinks with circular impinging jets. The forced convective cooling system usually applies the steady flow to pass through a stationary object. This work mounted the pin-fin heat sinks onto an oscillating platform with the impinging air jets. The experimental results indicate that strokes of the platform moving up and down as well as left and right are too long to enhance the overall heat transfer of the pin-fin heat sinks.

Abstract: A hidden ceiling-fan is the new design of embedding and hiding itself deeply into the ceiling floor. This design is different from conventional ceiling-fans or circulating fans that usually without an enclosing housing. The majority part of hidden ceiling-fan is embedded in the ceiling floor; hence the enclosing housing will be needed and be created to surround the axial-flow fan. The housing geometric is critical factor for hidden ceiling-fan because the air flow will pass though the horizontal plane of ceiling floor which the inlet and outlet are almost located at same plane. Consequently, the inappropriate design of enclosing housing will cause inhale-return phenomenon. It affects the induced flow performance of a hidden ceiling-fan. Few studies have investigated fan induced flow and its characteristics in a selected space. In this study, computational fluid dynamic (CFD) numerical simulation and experimental investigation were used to predict and valid the flow pattern with different geometric housing and operating conditions. The results showed that the flow pattern has different features as it leaves the fan downward the floor. The unique inhale-return phenomenon probably happens when inappropriate enclosing housing was designed such as high ring-plate and outlet-inlet ratio. Furthermore, the blockage effect will happen if the blockage distance is to short. In conclusion, thissystematic design investigation on hidden ceiling-fan not only provides the fan engineer’s design ability to avoid the inhale-return phenomenon, but also the predicting capability on the air flow induced characteristics and performance.

Abstract: The findings of new energy and energy harvester are the important issues for the lacking of fossil energy. For the purpose of the effective usage of supercritical CO₂ flowed from the product well of CO₂ EGS (Enhanced Geothermal System), an innovative heat pipe heat exchanger (Hx) is designed and practiced in this study. This study presents an innovative Hx of heat pipe for extracting the heat from CO₂ or warm gas. By using the heat pipe for cooling gas is the fundamental idea of this Hx. The experimental apparatus of Hx consists a heating blower to blow out hot gas, a circulating cool water device, and a set of heat pipes. The efficiency of Hx is approved as the increasing air velocity and the more fins gradually. This innovative heat pipe exchanger is proofed through our experiment. This heat pipe Hx is suitable for the application of enhanced geothermal system (EGS) and more energy harvesting application.

Abstract: Circular diamond saws rotating in high speed are widely used to cut hard materials, and narrow slots on saw blades are sometimes used to reduce the blades vibration and noise. Sizing optimization of the annular slots on saw blades is investigated in this paper. First, an accurate finite element model representing an actual saw blade is obtained by model updating. Then, sizing optimization on two types of annular slots is performed to maximize the frequency separation between the finite element analysis results and the saw blades operational speed, and to reduce the possibility of structural resonance. Optimization results demonstrate great improvements in frequency separation from the rotating speed of 500 Hz for the optimized models.

Abstract: This study analyzed and discussed the hydrogen storage reaction in the metal hydride hydrogen storage tank with internally fined heat tube. As the heat transfer and hydrogen storage efficiency of internal temperature control system are better than external temperature control, this study created a hydrogen storage simulation method to discuss the effect of thermistor fins on hydrogen storage. The results showed that the fins have significant effect on increasing the hydrogen storage efficiency, and the hydrogen storage time decreases as the thermistor fluid velocity increases, but the drawback is not apparent when the fluid velocity reaches a threshold.

Abstract: In this paper, feasibility of laser percussion drilling on highly reflective materials i.e., Al5052 using an assisting magnetic field was explored. During the laser percussion drilling, the Lorentz force generated by the assisting magnetic field affects the laser-induced plasma and results in significant influence of the laser percussion drilling. The magnetic field simulation was performed to investigate the field strength of the circular hollow permanent magnet. The influences of magnetic field and the laser radiation energy on the penetration depth and inlet diameter were examined.

Abstract: A new electric four-wheel wheelchair with function of climbing up and down a step is proposed. Each wheel has four telescopic rods driven by a ratchet mechanism which makes them stretchable. They retract into each wheel during the wheelchair moves on the flat roads. They stretch out of each wheel to overcome a step obstacle during the wheelchair encounters the steps and thresholds. The center of gravity and angular position of the seat relative to the horizontal axis can be adjusted simultaneously during climbing up and down a step or moving on the uphill or downhill road sections. The actual test of climbing up and down a height 15 cm step has been done successfully on condition of carrying a weight 85 kg person. This new electric wheelchair makes users more safe and scopes of activity of the elderly and those with disabilities wider.