• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.136-138
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• 2005

The responses of nanocrystalline aluminum powder of different grain sizes, was modeled Using, Khan, Huang, and Liang (KHL) viscoplastic model including hi-linear Hall-Petch type, based on experimental measurements. Correlation of strain-rate-dependent stress responses for different grain sizes were in good agreement with the experimental results.

• Advances in nano research
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• 제4권4호
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• pp.265-279
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• 2016

Present study interests with the longitudinal forced vibration of nanorods. The nonlocal elasticity theory of Eringen is used in modeling of nanorods. Uniform, linear and sinusoidal axial loads are considered. Dynamic displacements are obtained for nanorods with different geometrical properties, boundary conditions and nonlocal parameters. The nonlocal effect increases dynamic displacement and frequency when compared with local elasticity theory. Present results can be useful for modeling of the axial nanomotors and nanoelectromechanical systems.

• 한국초전도ㆍ저온공학회논문지
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• 제26권2호
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• pp.19-23
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• 2024

3D printing has the advantage of being able to process various types of parts by layering materials. In addition to these advantages, 3D printing technology allows models to be processed quickly without any special work that can be used in different fields to produce workpieces for various purposes and shapes. This paper deals to not only increase the utilization of 3D printing technology, but also to revitalize 3D printing technology in applications that require similar cryogenic environments. The goal of this study is to identify the mechanical properties of polylactic acid and photopolymer resin processed by Fused Deposition Modeling (FDM) and Digital Light Processing (DLP) respectively. The entire process is meticulously examined, starting from getting the thermal contraction using an extensometer. A uniaxial tensile test is employed, which enables to obtain the mechanical properties of the samples at both room temperature (RT) and cryogenic temperature of 77 K. As the results, photopolymer resin exhibited higher tensile properties than polylactic acid at RT. However, at cryogenic temperatures (77 K), the photopolymer resin became brittle and failure occurred due to thermal contraction, while polylactic acid demonstrated superior tensile properties. Therefore, polylactic acid is more suitable for lower temperatures.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.67-70
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• 2003

To develop an effective geometric modeling is essential in order that precise mechanical properties and the geometrical properties of the 3-D braided composites can be estimated. RVE(representative volume element) was adopted fur geometrical modeling. RVE consisted of IC(inner unit cell), ISUC(interior surface unit cell) and ESUC(exterior surface unit cell). The whole geometrical model fur hybrid 3-D braided composites was developed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.485-485
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• 2009

Double side polishing process has been used for various industrial applications, such as polishing of semiconductor substrates and flat panel display glasses. In wafer manufacturing, double side polishing process is applied to improve wafer flatness and to minimize particle generation from wafers in device manufacturing processes, which is recognized as one of the most important processes. Whereas the kinematical modeling and analysis results of single side polishing, extensively used for chemical-mechanical polishing (CMP) in device manufacturing, are well investigated, the studies in conjunction with double side polishing are barely carried out, due to the complication of polishing system and the uncertainty of wafer motion in the carrier. This paper suggests the derivation of kinematical model with consideration of carrier and wafer motion in double side polishing, and then presents the effect of kinematical parameters on material removal amount and its non-uniformity. The kinematical analysis results help to understand the double side polishing process and to control the polishing results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.465-469
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• 2003

Microlens arrays were fabricated using a novel fabrication technology based on the exposure of a PMMA (Polymethylmethacrylate) sheet to deep X-rays and subsequent thermal treatment. X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. A new physical modeling and analyses for microlens formation were presented according to experimental procedure. A simple analysis based on the new model is found to be capable of predicting the shapes of microlens which depend on the thermal treatment. For the replication of microlens arrays having various diameters with different foci on the same surface, the hot embossing and the microinjection molding processes has been successfully utilized with a mold insert that is fabricated by Ni-electroplating based on a PMMA microstructure of microlenses. Fabricated microlenses showed good surface roughness with the order of 1 nm.

• Journal of Mechanical Science and Technology
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• 제17권3호
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• pp.380-390
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• 2003

This paper addresses the problem of the modeling and vibration control of tapered rotating blade modeled as thin-walled beams and incorporating damping capabilities. The blade model incorporates non-classical features such as anisotropy, transverse shear, secondary warping and includes the centrifugal and Coriolis force fields. For the rotating blade system, a thorough validation and assessment. of a number of non-classical features including the taper characteristics is accomplished. The damping capabilities are provided by a system of piezoactuators bonded or embedded into the structure and spread over the entire span of the beam. Based on the converse piezoelectric effect, the piezoactuators produce a localized strain field in response to a voltage and consequently, a change of the dynamic response characteristics is induced. A velocity feedback control law relating the piezoelectrically induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and thebeneficial effects upon the closed-loop dynamic characteristics of the blade are highlighted.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1264-1268
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• 2004

This paper presents a wafer motion modeling of the transfer unit and the control unit in the clean tube system, which was developed as a means for transferring the air-floated wafers inside the closed tube filled with the super clean airs. The motion in the transfer unit is modeled as a mass-spring-damper system where the recovering force by air jets issued from the perforated plate is modeled as a linear spring. The motion in the control unit is also modeled as another mass-spring-damper system, but in two dimensional systems. Experiments with a clean tube system built for 12-inch wafers show the validity of the presented force and motion models.

• International Journal of CAD/CAM
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• 제5권1호
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• pp.39-47
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• 2005

Different CAx systems are being utilized throughout the product lifecycle due to the practical reasons in the supply chain and design processes. One of the major problems facing enterprises of today is how to share and exchange data among heterogeneous applications. Since different software applications use different terminologies, it is difficult to share and exchange the product data with internal and external partners. This paper presents a method to enhance the CAD model interoperability based on feature ontology. The feature ontology has been constructed based on the feature definition of modeling commands of CAD systems. A method for integration of semantic data has been proposed, implemented, and tested with two commercial CAD systems.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1466-1474
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• 2003

This paper presents a system modeling, controller design and implementation for a rotational inverted pendulum system (RIPS), which is an under-actuated system and has the problem of unattainable velocity state. Two control strategies are applied to the RIPS. One is a sliding mode control method using the parameterization of both the hyperplane and the compensator for output feedback. The other is the disturbance observer which estimates disturbance and some modeling errors of RIPS with less computational effort. Some simulations and various kinds of experiments are performed in order to verify that the proposed controller has the ability to control RIPS whose velocity is assumed to be unavailable. The results of the simulations and experiments show that the proposed control system has superior performance for disturbance rejection and regulation at certain initial conditions as well as the robustness to model uncertainties.