• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.918-921
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• 2001

In grinding process, the heat of $1200^{\circ}$~$1500^{\circ}$ on the grinding area between grinding wheel and workpiece is generated. It decreases the surface integrity of workpiece and causes the thermal damages such as the deformed layer, residual stress and grinding burn. Generally coolant is widely used for preventing the heat generation on the grinding area, but it deteriorates the working condition by polluting the atmosphere of workplace and in the end pollutes the environment. The grinding methods using the compressed cold air and mist are the cooling methods to substitute conventional coolant. They can decrease the environmental pollution through not using coolant any more or minimizing it. In this study, the cooling effects of grinding methods using the compressed cold air and mist have been investigated. The grinding system equipped with the water bathe and mist spray nozzle was developed. The energy partition to workpiece through measuring the temperature on the workpiece surface was calculated. The surface integrity of workpiece and thermal damage like the deformed layer were analyzed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.1
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• pp.80-85
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• 2007

High speed cutting is a machining process which cuts materials with the fast movement and rotation of a spindle in a machine tool. High speed cutting leaves a plastically deformed layer on the machined surface. This deformed layer affects in various forms to the surface roughness of machined parts such as the dimensional instability, the micro crack. The surface roughness is called surface integrity which is very important in precision cutting. This paper aims to study on the machined surfaces characteristics of aluminum alloy and brass by AFM(Atomic force microscope) measurement. The objective is contribution to ultra- precision cutting by exhibit foundation data of surface roughness and tool wear when parts are cutting with diamond tool at the factory.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.135-140
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• 2004

Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. With our experiences of experimental investigations on nasal airflows in normal and abnormal nasal cavity models, we are going to deal with the topic that may contribute to the diagnosis and treatment of nasal diseases. In this paper, airflows in the normal and artificially deformed models, which simulate surgical treatment, are investigated experimentally by PIV. High-resolution CT data and careful surface rendering of computational model with the help of the ENT doctor provide more sophisticated nasal cavity models. The CBC PIV (Correlation Based Correction PIV) algorithm with window offset is used for PIV flow analysis. Average and RMS distributions in sagittal and coronal sections are obtained for inspiratory and expiratory nasal airflows. Comparisons in nasal airflows for both normal and deformed cases are also appreciated. In case of simulations of surgical operations, velocity and RMS distributions in coronal section changes locally, this may cause some difficulties in physiologic functions of noses and may hurt mucosal surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.54-58
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• 1991

It is well known that metal cutting leaves a plastically deformed layer in the machined surface. This residual phenomenon affects in various forms the physical properties of machined components such as the fatigue strength, the dimensional instability, microcracks, and the stress corrosion cracking. These physical properties, so called surface integrity, are very important for designing highly stressed and critically loaded components. Typical plastic strains in the machined surface are very difficult to measure, since they are located within a very short distance from the surface and they change very rapidly. There is an alternative way to determine the residual strain in plastically deformed materials by measuring the grain size after a subsequent recrystallization process. Although, this technique has been successfully applied by several researchers to find the plastic zone around notches and cracks in various materials and welding beads, few works have been reported using the recrystallization method to determine the residual strains in machined surface. Therefore, the purpose of this investigation Is to explore the effectiveness of the recrystallization technique in machining applications, and in particular, to find the effect of cutting parameters, i.e., depth of cut and rake angle on the plastic strains.

• Tribology and Lubricants
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• v.16 no.5
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• pp.389-394
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• 2000

Scanning Probe Microscope (SPM) such as Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AEM) was shown to be the powerful tool for nano-scale characterization of material surfaces. Using this technique, surface morphology of the cyclically deformed Cu or Cu-Al single crystal was observed. The surface became proportionately rough as the number of cycles increased, but after some number of cycles no further change was observed. Slip steps with the heights of 100 to 200 nm and the widths of 1000 to 2000 nm were prevailing at the stage. The slipped distance of one slip system at the surface was not uniform, and formation of the extrusions or intrusions was assumed to occur such place. By comparing the morphological change caused by crystallographic orientation, strain amplitude, number of cycles or stacking fault energy, some interesting results which help to clarify the basic mechanism of fatigue damage were obtained. Furthermore, applicability of the scanning tunneling microscopy to fatigue damage is discussed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.20 no.1
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• pp.16-24
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• 2024

Denting of steam generator (SG) tube is defined as the reduction in tube diameter due to the stresses exerted by the corrosion products formed on the outer diameter surface. This phenomenon is mostly observed in the crevices between SG tube and the top-of tubesheet or tube support plate. Despite the replacement of SG tube with Alloy 690, which has better corrosion resistance than Alloy 600, the denting of SG tube still remains a potential problem that could decrease the SG integrity. Deformation of SG tube by denting phenomenon can affect the surface properties and microstructure of SG tube. In this study, the effects of plastic deformation on surface properties and microstructure of Alloy 690 thermally treated (TT) tube was investigated by using the various analysis techniques. The plastic deformation of Alloy 690 increased the surface roughness and area. Many surface defects such as ripped surface and micro-cracks were observed on the deformed Alloy 690TT specimen. Based on the electron backscatter diffraction analysis, the dislocation density of deformed SG tube increased compared to non-deformed SG tube. In addition, the effects of changes in surface properties and microstructure of SG tube on general corrosion behavior were discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.141-150
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• 1998

The measurement of strains in stamped sheet metal is essential to the design and manufacture of sound sheet metal products. The measured strains can also be used in verifying the reliability of the computer analysis such as finite element analysis. In most engineering applications, strains are measured from the deformed square grids or deformed circular grids in comparison with the initial undeformed grids. In such a case, however, strains are averaged in each grid and the localized strain in a region smaller than a grid size can not be measured. In the present study, the B-spline surface interpolation technique is introduced in order to measure the strains more exactly and effectively. The strains calculated by using the surface interpolation technique are compared with the strains calculated from the three-noded grids as well as with the finite element analysis.

• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.38-50
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• 1998

Laser cutting tests were conducted to investigate the laser cutting characteristics of solid woods such as 25mm-thick white oak(Quercus acutissima) and maple(Acer mono), and wood-based panels such as 15mm-thick medium density fiberboard and particleboard. Test variables were laser power, cutting speed, grain direction, and moisture content. Specific cutting energy was measured and the qualities of cut surface were estimated in constant laser power. Specific cutting energy of white oak was larger than that of maple, and specific cutting energy of medium density fiberboard was smaller than that of particleboard. For both white oak and maple, specific cutting energy of green wood was smaller than that of air-dried wood because weight loss of moisture evaporation in green wood was larger than that in air-dried wood. In laser-cut surface, wood cells were not deformed and damaged, but in circular saw-cut surface fibers were pushed out and cut, and wood cells were deformed severely. However, mechanical surface roughness of saw-cut surface was smoother than that of laser-cut surface because of the existence of undeformed cell cavity in laser-cut surface.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1107-1112
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• 2009

To design and build a deformed building, new approaches and technologies are required, in which a design approach with parametric and generative technology is used for design and for building it, computer based fabrication technology. Even if parametric design technology is not a state of the art thing, the technology is still used widely, in order to effect the efficiency and furthermore it will continue to be innovated upon continuously. To cope with the limitation of it, the generative design system is developed. Deformed building design requires new methodology to overcome the limitations of conventional ways, which have difficulties to create enough design alternatives to explore satisfied design solutions order to deformed design have geometrical complexity and dramatically increased amount of data. Hence the generative design system can be a cutting edge methodology to solve it. However we should consider how to build the design in the real world. For this, the computer based fabrication technology which is used in mechanical industry is required to introduce to architecture and construction domain for efficiency. In this research, the methodology is modeled and tested with Bezier surface based shell structure.

• Transactions of Materials Processing
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• v.32 no.6
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• pp.360-366
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• 2023

This study is concerned with the surface quality of products according to the material and coating condition of the forming tool in incremental sheet forming. Three forming tools, SKD11 with and without diamond-like-coating (DLC) and polymer tool tip, were used to form conical and pyramidal geometries to take into account the influence of friction between the forming tool and the sheet on the surface quality including geometric accuracy of deformed samples. Each test was performed using SUS304 with a thickness of 0.4 mm according to different incremental depths per lap of 0.5 mm, 1.0 mm, and 1.5 mm for the contour tool path, considering the increase in normal force which is associated with the frictional behavior during local deformation. The surface quality was then investigated through surface roughness measured with KEYENCE VR-6000 and relative strain distribution including deformed shape analyzed with ARGUS which is a non-contact optical strain measurement system. Differences between 3D CAD surfaces and captured geometry from experiments were evaluated to compare the effect of friction on geometric accuracy. From comparisons of experimental results, it was revealed that the polymer-based tool tip can improve surface quality and geometric accuracy by reducing the undesired material flow due to local friction in the increment sheet forming process.