• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.1-5
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• 2018

Atomic force microscopy (AFM) simulation for Si (001) surface defects was conducted by using density functional theory (DFT). Three major defects on the Si (001) surface are difficult to analyze due to external noises that are always present in the images obtained by AFM. Noise-free surface defects obtained by simulation can help identify the real surface defects on AFM images. The surface defects were first optimized by using a DFT code. The AFM tip was designed by using five carbon atoms and positioned on the surface to calculate the system's energy. Forces between tip and surface were calculated from the energy data and converted into an AFM image. The simulated AFM images are noise-free and, therefore, can help evaluate the real surface defects present on the measured AFM images.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.1 no.1
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• pp.55-62
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• 2002

This investigation reports the grinding characteristics of titanium alloy(Ti-6AI-4V). Grinding experiments were performed at various grinding conditions. The grinding forces were measured to investigate the grindability of titanium alloy with the five different wheels including Green carbide, Alumina, Resin Diamond, Resin CBN and Vitrified CBN. To investigate the grinding characteristics of titanium alloy grinding force, force ratio, specific grinding energy and grinding-ratio were measured. Surface roughness was also measured with tracer and the ground surfaces were observed with SEM Residual stress measurement was conducted on the X-Ray Diffractometer. Force ratio of grinding of titanium alloy was very lower than that of grinding of SKD-11 Surface roughness with Resin Diamond wheel was a little larger and rougher surface than that with other wheels Grinding ratio of titanium alloy was a little lower than that of other materials. Grinding ratio of titanium alloy with Diamond wheel was almost six times larger than that With CBN wheel. As a result of five different wheels, the most excellent wheel in grinding of Titanium alloy was Resin Diamond wheel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.870-874
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• 2000

This investigation reports the grinding characteristics of titanium alloy(Ti-6Al-4V). Grinding experiments were performed at various grinding conditions and the grinding forces and specific grinding energies were measured to investigate the grindability of titanium alloy with the three different wheels including Diamond, Green carbide and Alumina. To investigate the grinding characteristics of titanium alloy grinding force, force-ratio, specific grinding energy and grinding -ratio, were measured. Surface roughness was also measured with tracer and the ground surfaces were observed with SEM. Force-ratio of grinding of titanium alloy was very lower than that of grinding of SKD-11. Specific grinding energy are almost five times larger and rougher surface was obtained in titanium grinding.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.5-14
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• 1999

The necessity of six axis force-torque sensors is well recognized in the fields of automatic fine assembly, deburring polishing, and automatic fish processing using robotic manipulators. The paper proposes a simple and compact elastic structure of the force-torque sensor which senses externally applied three force and three torque components. Rough surface strain distribution of the elastic structure is examined analytically, and then more accurate surface strain are obtained from finite element analysis. The compliance matrix which is a linear relationship between force components and strain measurements is obtained for the proposed sensor. Some basic principles of measuring 3 force and torque components are also presented.

• Journal of Institute of Convergence Technology
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• v.6 no.1
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• pp.37-41
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• 2016

The serpentine internal passage is located in turbine blade and it shows the variety heat transfer distribution. Especially, the Coriolis force, which is induced by blade rotation, makes different heat transfer distribution of the leading and trailing surfaces of serpentine internal passage. The different heat transfer is one of the reasons why the serpentine cooling passage shows low cooling performance in the rotating condition. So, this study tried to design the advanced the serpentine passage to consideration of the Coriolis force. The design concept of advanced serpentine cooling is maximizing cooling performance using the Coriolis force. So, the flow turns from leading surface to trailing surface in advanced serpentine passage to match the direction of Coriolis force and rotating force. We performed numerical analysis using CFX and compared the existing and advanced serpentine internal passage. This design change is induced the high heat transfer distribution of whole advanced serpentine internal passage surfaces.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.61-62
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• 2002

In order to clarify the contact mechanism between specimen surface and probe tip in the surface observation by the AFM (atomic force microscope) or the FFM (friction force microscope), several molecular dynamics simulations have been performed. In the simulation, a 3-dimensional simulation model is proposed where the specimen and the probe are assumed to consist of mono-crystal line copper and a carbon atom respectively and the effect of cantilever stiffness is also taken into considered. The surface observation process on a well-defined Cu{100} is simulated. The influences of cantilever stiffness on the reactive force images and the behavior of probe tip were evaluated. As a resuIt, several phenomena similar to those observed by the actual surface observation experiment, such as double-slip behavior and dispersion in the stick-slip wave period were observed.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.4
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• pp.49-58
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• 1998

The SPM could image the most detailed microstructure of a sample in a wet and dry state by measuring the interaction between the atoms on the sample surface and the extremely sharp probe tip. The refined fibre exhibited large wrinkles formed by fibrillar bundles, the disintegrated fibres extensively showed “scale-like features”. By using the Non-Contact Atomic Force Microscopy (NC-AFM) and Contact Atomic Force Microscopy (C-AFM) including Phase Detection Microscopy (PDM) and Force Modulation Microscopy (FMM), it was possible to investigate surface topography, surface roughness and mechanical property (hardness or visco-elasticity) of fibre surface in detail. The PDM and FMM images showed that the disintegrated only fibre displayed uniform mechanical properties, whereas the refined one did not. The surface roughness of pulp fibres was higher in refined fibres than in disintegrated fibres due to the presence of external fibrils. These SPM images would be used to provide visual evidence of morphological change of a single fibre created during mechanical treatments such as refining, drying, calendering and so on.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.8-18
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• 2002

Formulation of the far-field method for the prediction of time-mean hydrodynamic force and moment acting on a 3-D surface-piercing body in waves is reviewed. It is found that the inequality between the weight of the floating body and its buoyancy force permits the replacement of the fluid particles inside the control surface by the fluid particles outside the control surface. Under such circumstances, momentum exchanges across the control surface make the time-mean value of the time rate of the momentum of the fluid inside the control surface non-vanishing. It is a second-order quantity which is hard to calculate by the far-field method. The drift forces and moments on half-immersed ellipsoids are calculated by both the far-field method and the near-field method. The discrepancy between two numerical results is presented and discussed.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.723-730
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• 2017

This paper studies on dynamic and stability behavior of a clamped-elastically restrained nanobeam under the action of a nonconservative force with an emphasis on the influence of surface properties on divergence and flutter instability. Using the Euler-Bernoulli beam theory incorporating surface effects, a governing equation for a clamped-elastically restrained nanobeam is derived according to Hamilton's principle. The characteristic equation is obtained explicitly and the force-frequency interaction curves are displayed to show the influence of the surface effects, spring stiffness of the elastic restraint end on critical loads including divergence and flutter loads. Divergence and flutter instability transition is analyzed. Euler buckling and stability of Beck's column are some special cases of the present at macroscale.

• Korean Journal of Computational Design and Engineering
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• v.4 no.3
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• pp.247-258
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• 1999

With the contemporary CAD/CAM system, where the tool path is generated and verified purely based on the geometric operation, geometric accuracy of the machined surface cannot be guaranteed dut to the cutting mechanics, meaning that the cutting mechanics should be incorporated in some fashion. In this paper, we incorporate the instantaneous cutting force and the tool deflection phenomena in predicting the machined surface for the finish-cut and milling operation. For the given NC dat including cutting conditions, the developed algorithm computes cutting force and deflection amount along the tool trajectory, and outputs the 3D graphic model of the machined surface together with error analysis. The validity and accuracy of the presented method has been tested by the actual cutting experiments. Experimental results and accuracy enhancement method together with implementing architecture of the VMCS (Virtual Machining CAM System) are discussed in the paper.