• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.217-217
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• 2009

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with 60 ~ 100 ${\mu}m$ lengths, $10\;{\mu}m$ width, and $0.4\;{\mu}m$ thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the 60 ~ 100 ${\mu}m$ long cantilevers, the fundamental frequency appeared at 373.4 ~ 908.1 kHz. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.17-24
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• 2003

A mathematical model of the hydrodynamic and heat transfer performances of two-phase flow (gas-liquid) in thin film region of micro channel is proposed. For the formulation of modeling, the flow of the vapor phase and the shear stress at the liquid-vapor interface are considered. In this work, disjoining pressure and capillary force which drive the liquid flow at the liquid-vapor interface in thin film region are adopted also. Using the model, the effects of the variations of channel height and heat flux on the flow and heat transfer characteristics are investigated. Results show that the influence of variation of vapor pressure on the liquid film flow is not negligible. The heat flux in thin-film region is the most important operation factor of micro cooler system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.856-860
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• 2002

The main objective of this study is to consider the effect of fatigue crack behavior on the variable depth of micro hole defects in SM20C at the symmetric position. The fatigue crack propagation test is performed by rotary bending fatigue test machine. The relationship between crack length(2a), cycles(N) and crack growth rate(da/dN) are investigated in this study. The result from the rotary bending fatigue test under the applied stress at 250MPa turned out that the fatigue life illustrated almost constant when the depth of symmetric micro hole deflects is both part A and B at the hope depth(h) = 0.5mm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.285-290
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• 2004

Electro-active polymer, one of smart materials, is a new alternative technology, which can get an ultra precision movements and bio-compatibilty. This paper presents the relationship between elastic modulus and maximum deflection as a key property of maxwell stress effects and also presents the relationship between dielectric constant and maximum deflection as a key property of electro-striction effects in disc-type actuators using segmented PU. To induce equation about distributed load of a disc, we use boundary condition of fully clamped circular plate and to obtain design parameters of a micro-fluidics system, CFD simulation is performed.

• Structural Engineering and Mechanics
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• v.18 no.5
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• pp.691-707
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• 2004

This paper presents the micro-mechanical modeling for predicting concrete behavior under compressive loading. The model is able to represent the heterogeneities in the microstructure up to three phases, i.e., aggregate particles, matrix and interfaces. The smeared crack concept based on non-linear fracture mechanics is implemented in order to formulate the constitutive relation for each component. The splitting tensile strength is considered as a fracture criterion for cracking in micro-level. The finite element method is employed to simulate the model based on plane stress condition by using quadratic triangular elements. The validation of the model is verified by comparing with the experimental results. The influence of tensile strength from both aggregate and matrix phases on the concrete compressive strength is demonstrated. In addition, a guideline on selecting appropriate tensile strength for each phase to obtain specified concrete compressive strength is also presented.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.303-306
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• 2009

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with $60{\sim}100{\mu}m$ lengths, $10{\mu}m$ width, and $0.4{\mu}m$ thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the $60{\sim}100{\mu}m$ long cantilevers, the fundamental frequency appeared at $373.4{\sim}908.1\;kHz$. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.207-210
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• 2003

Vacuum hot pressing has been used for the development of Ti-MMCs using foil-fiber-foil method, and subsequent micro-mechanical characteristics of the composites are evaluated by means of several experimental processes. As shown by the results, fiber strength degradation occurs during the consolidation, and particularly residual stresses results from the thermal expansion mismatch between fiber and matrix materials during cooling process are incorporated in the changes of mechanical properties of the composites. In industrial applications, the processing conditions avoiding micro-material failures are important together with the properties of finished products, and therefore should be included in the assesment of the material characterization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1088-1091
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• 1997

This paper describes the characteristic of hinges on which a lever pivots within a limited angle due to the torque. The hinges are exerted by the thermally expanded actuators connected with a level through hinges. To enhance the stroke of inchworm actuator, FEM(Finite Element Method) was utilized for the characterization in view of stress displacement according to the variation of notch radius and notch width. As a result, notch width of the hinges plays an important part in improvement of micro inchworm actuator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1059-1062
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• 2003

Micro-tensile testing system has been developed and micro-tensile tests for copper foil have been carried out. The system consisted of a micro tensile loading system and a micro-ESPI system for measuring strain. The loading system has a maximum loading capacity of 50N and a stroke resolution of 4.5nm. Stress-strain curves for the electro-deposited copper foil with the thickness of 18$\mu\textrm{m}$ were obtained, and tensile properties, including elastic modulus, yielding strength and tensile strength, were determined. The tensile properties obtained under three different conditions of testing speed showed a dependency on the speed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.127-132
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• 2014

Micro/nano-injection molding is one of the main processing techniques for polymer micro-fabrication. Most of the difficulties encountered in polymer micro-molding are caused by the demolding, rather than the filling of molds. Therefore, studying the demolding process is vitally important for manufacturing polymer replicas. The most important parameters are the thermal stress, friction and adhesion forces, and mechanical strength of the resist. In this research, we determinedthe effects of the processing conditions on the ejection force for cases involving two common thermoplastic polymers. The results showed that the processing conditions noticeably influenced the ejection force.