• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.497-498
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• 2012

• 한국공작기계학회논문집
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• 제16권5호
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• pp.115-121
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• 2007

Phase contrast imaging in atomic force microscopy showed a promise as an effective tool for better understanding of micromechanical properties of surfaces at nano scale. A qualitative estimation model for phase contrast images obtained with a tapping mode AFM was developed. This investigation demonstrated the high efficiency of combined analysis of topography and phase contrast images for characterizing nanosurfaces. Phase contrast images allowed estimation of relative stiffness(elastic modulus) of the sample surface. The phase contrast images revealed a significant inhomogeneity of the nano scale worn surfaces. Phase contrast images are also capable of revealing the formation of tribofilms.

• 한국생산제조학회지
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• 제22권4호
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• pp.735-739
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• 2013

The error motion of a machine tool spindle directly affects the surface errors of machined parts. Spindle motion errors such as three translational motions and two rotational motions are undesirable. These are usually due to the imperfectness of bearings, stiffness of spindle, assembly errors, and external force or unbalance of rotors. The error motions of the spindle need to be reduced for achieving the desired performance. Therefore, the level of error motion needs to be estimated during the design and assembly process of the spindle. In this study, an estimation method for five degree-of-freedom (5 DOF) error motions for a spindle with an angular contact ball bearing is suggested. To estimate the error motions of the spindle, the waviness of the inner-race of bearings and an external force model were used as input data. The estimation model considers the geometric relationship and force equilibrium of the five DOFs. To calculate the error motions of the spindle, not only the imperfections of the shaft and bearings but also driving elements such as belt pulley and direct driving motor systems are considered.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.63-64
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• 2002

In a micro-scale contact, surface forces such as capillary force and van der Waals Interaction significantly Influence the contact between asperities of rough surfaces. Little is, however, known about the variation of these surface forces as a function of chemical property of the surface (hydrophilicity), relative humidity and deformation of asperities In the real area of contact. A better understanding of these surface forces is of great necessity in order to find an optimal solution for reducing friction and adhesion of micro surfaces. We proposed an effective method to analyze capillary and van der Waals forces In nano-scale contact. In this method, Winklerian foundation model was employed to analyze the contact of rough surfaces that were obtained from atomic force microscopy (AFM) height Images. Self-mated contact of diamond-like-carbon (DLC) coatings was analyzed, as an example, by the proposed model. It was shown that the capillary force was significantly influenced by relative humidify and wet angle of the DLC surface. The deformation of asperities to a critical magnitude by external loading led to a considerable increase of both capillary and van der Waals forces.

• 한국정밀공학회지
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• 제28권3호
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• pp.285-291
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• 2011

The error motion of a machine tool spindle directly affects the surface errors of machined parts. The error motions of the spindle are not desired errors in the three linear direction motions and two rotating motions. Those are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle's performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions of the spindle is suggested. To estimate the error motions of the spindle, waviness of shaft and bearings, external force model was used as input data. And, the estimation models are considering geometric relationship and force equilibrium of the five degree of the freedom. To calculate error motions of the spindle, not only imperfection of the shaft, bearings, such as rolling element bearing, hydrostatic bearing, and aerostatic bearing, but also driving elements such as worm, pulley, and direct driving motor systems, were considered.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1806-1809
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• 2008

Study that form micro pattern by direct ink jet printing method is getting attention recently. Direct ink jet printing spout fine droplet including nano metal particle by force or air pressure. There is reason which ink jet printing method is profitable especially in a various micro-patterning technology. It can embody patterns directly without complex process such as mask manufacture or screen-printing for existent lithography. In this study, research of a technology that ejects fine droplet form of Pico liter and forms metal micro pattern was carried with inkjet head of piezoelectricity drive system. Droplet established pattern while ejecting consecutively and move on the surface at the fixed speed. Patterns formed in ink are mixed with organic solvent and polymer that act as binder. So added thermal hardening process after evaporate organic solvent at isothermal after printing. I executed high frequency special quality estimation of CPW transmission line to confirm electrical property of manufactured circuit board. We tried a large area printing to confirm application possibility of an ink jet technology.

• Elastomers and Composites
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• 제54권1호
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• pp.70-76
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• 2019

The function and purpose of the marine rubber fender, to prevent the damage of the ship and the mooring while the ship is being attached to the pier. However, maintenance of the fender after installation is not enough, because it is generally handled as an attachment facility. Estimation the life of a marine rubber fender is important in the maintenance of a port. When manufacturers design and produce marine rubber fenders, they do so according to various conditions such as the reaction force acting on the hull and docking vessel and deformation after absorbing the kinetic energy of the ship. In this study, a method for predicting and evaluating service life from the product design and development stage was established, in order to evaluate the durability of the marine rubber fenders. The SSp-300H and HSP-300H models were used to predict the service life. The method developed in this study, is expected to predict the service life of the marine rubber fender accurately and in a comparatively shorter time, thereby contributing to the evaluation standard and quality stability of the product.

• Tribology and Lubricants
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• 제35권6호
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• pp.343-349
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• 2019

According to a report in 2011, hexagonal boron nitride demonstrated good solubility in pure water, even without surfactants or organic functionalization. Hexagonal boron nitride nanosheets are an effective lubricant additive, and their solubility in pure water has motivated lubrication engineers to utilize aqueous solutions containing these nanosheets as water-based lubricants. In this study, we measure the width and height of the hexagonal boron nitride nanosheets dispersed in pure water by using the Zetasizer and atomic force microscopy. Without surfactants or functionalization, aqueous solutions containing 0.10, 0.07, 0.05, and 0.01 wt% of hexagonal boron nitride nanosheets are synthesized via sonication-assisted hydrolysis. The Zetasizer provides only a one-dimensional size of approximately 410 nm, regardless of the concentration of the solution. Thus, it does not allow the estimation of the shape of the nanosheet. To acquire the three-dimensional size of the nanosheets, atomic force microscopy is employed. The aqueous solutions containing 0.10, 0.07, 0.05, and 0.01 wt% of the hexagonal boron nitride nanosheets show average values of 740, 450, 700, and 610 nm in width, and 37, 26, 33, and 32 nm in thickness, respectively. No significant trend is observed between the concentration of the solution and size of the nanosheets. Therefore, when preparing a water-based lubricant, it may be appropriate to adjust conditions such as ultrasonication time rather than the concentration.

• Advances in nano research
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• 제12권4호
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• pp.405-414
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• 2022

In this study, the elastic plane problem of a layered composite containing an internal or edge crack perpendicular to its boundaries in its lower layer is examined using numerical analysis. The layered composite consists of two elastic layers having different elastic constants and heights. Two bonded layers rest on a homogeneous elastic half plane and are pressed by a rigid cylindrical stamp. In this context, the Finite Element Method (FEM) based software called ANSYS is used for numerical solutions. The problem is solved under the assumptions that the contacts are frictionless, and the effect of gravity force is neglected. A comparison is made with analytical results in the literature to verify the model created and the results obtained. It was found that the results obtained from analytical formulation were in perfect agreements with the FEM study. The numerical results for the stress-intensity factor (SIF) are obtained for various dimensionless quantities related to the geometric and material parameters. Consequently, the effects of these parameters on the stress-intensity factor are discussed. If the FEM analysis is used correctly, it can be an efficient alternative method to the analytical solutions that need time.