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Full-Text Articles in Mechanical Engineering
A Bubble-Powered Micro-Rotor: Conception, Manufacturing, Assembly And Characterization, Jonathan Kao, Xiaolin Wang, John Warren, Jie Xu, Daniel Attinger
A Bubble-Powered Micro-Rotor: Conception, Manufacturing, Assembly And Characterization, Jonathan Kao, Xiaolin Wang, John Warren, Jie Xu, Daniel Attinger
Daniel Attinger
A steady fluid flow, called microstreaming, can be generated in the vicinity of a micro-bubble excited by ultrasound. In this paper, we use this phenomenon to assemble and power a microfabricated rotor at rotation speeds as high as 625 rpm. The extractible power is estimated to be of the order of a few femtowatts. A first series of experiments with uncontrolled rotor shapes is presented, demonstrating the possibility of this novel actuation scheme. A second series of experiments with 65 µm rotors micromanufactured in SU-8 resin is then presented. Variables controlling the rotation speed and rotor stability are investigated, such …
Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Gap-Yong Kim
For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/mesoscale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the feature/specimen size effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with three separate experiments obtained from previous research: a simple compression with a round specimen, a simple tension with a round specimen, and a simple tension in …
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
Gap-Yong Kim
The potentials of semi-solid forming technology have generated much interest regarding its application in micromanufacturing. This study investigates the feasibility of using semi-solid forming technology to produce parts with micro/meso features. An experimental setup has been developed to study the effects of die/punch temperature, initial solid fraction, punch speed, and workpiece shape on the semi-solid forming process. A part has been produced for a microreactor application and has been analyzed with an optical measurement system for feature formation. The results indicated complex interaction among the process parameters and the material flow, which affected the final pin formation. The punch temperature …
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Gap-Yong Kim
One of the major challenges in simulation of semi-solid forming is characterizing the complex behavior of a material that consists of both solid and liquid phases. In this study, a material model for an A356 alloy in a semi-solid state has been developed for high solid fractions (>0.6) and implemented into a finite element simulation tool to investigate the micro-/mesoscale feature formation during the forming process. Compared to previous stress models, which are limited to expressing the stress dependency on only the strain rate and the temperature (or the solid fraction), the proposed stress model adds the capability of …
Control And Ultrasonic Actuation Of A Gas–Liquid Interface In A Microfluidic Chip, Jie Xu, Daniel Attinger
Control And Ultrasonic Actuation Of A Gas–Liquid Interface In A Microfluidic Chip, Jie Xu, Daniel Attinger
Daniel Attinger
This paper describes the design and manufacturing of a microfluidic chip, allowing for the actuation of a gas–liquid interface and of the neighboring fluid. The first way to control the interface motion is to apply a pressure difference across it. In this case, the efficiency of three different micro-geometries at anchoring the interface is compared. Also, the critical pressures needed to move the interface are measured and compared to a theoretical result. The second way to control the interface motion is by ultrasonic excitation. When the excitation is weak, the interface exhibits traveling waves, which follow a dispersion equation. At …