• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1044-1053
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• 2003

There are two major differences between the centerless infeed grinding process and the centerless through-feed grinding process. One is an axial movement of workpieces, and the other is that several workpieces are ground simultaneously and continuously by through-feeding. Because of these differences, through-feed ground parts inherently possess not only the roundness error but also the tapering error. The aims of the research reported in this paper are to examine this inherent tapering characteristic and to find the effects of grinding variables (center height angle, regulating wheel tilt angle, and shape of grinding wheel surface). To accomplish the objectives, experiments were carried out using two types of cylindrical workpiece shapes. Also, computer simulations were performed using the 3-D through-feed grinding model.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.115-118
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• 2001

An image processing method was applied to characterize a shape of the flexible grinding disk. A disk surface image was taken by CCD camera. Depth of cut was changed to be 2 and 4mm. Circles marked on the disk were captured to extract the key features of the deflection. Notable correlation has been observed between the intervals and the process conditions. Same methodology has been applied to check the symmetry of the human face. Tentative results revealed that symmetry could be checked using the filtered face image.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.39-42
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• 2000

Cutrent technological development toward miniaturization requires smaller components. These components usually generate complex multi-DOF motions other than simple 1-DOF motlon. Therefore it is essential to develop measurement methodology for 6-DOF motions. In this paper, a new 6-DOF measurement system for milli-struchlre is presented. This methodology basically employs the Optical Beam Deflection Method (OBDM) with a diffraction grating. A laser beam is emitted toward the difliaction grating which could be attached on the surface of a milli-structue and the incident ray is dif'||'&'||'acted in several directions. Among these difliacted beams, $0^{th}$ and $\pm$ $1^{th}4" order difkicted rays are detected by 4 Quadrant Photodiodes. From coordinate values fram each detector, we can get information for 6-DOF motions with lineariration method, Required resolutions for milli-struchue measurement are suh-micrometer in translation and arcsec in rotation. Experimental results indicate that proposed system has possibility to satisfy this requirement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.1
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• pp.64-71
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• 2009

In this paper, a study on low-velocity impact response of honeycomb sandwich panels was done for the changes of impact location and core fabrication angles. The test specimens were made of glass/epoxy laminate facesheet and aluminum honeycomb core. Square samples of 100mm and 100mm sides were subjected under low-velocity impact loading using instrumented testing machine at three energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for the changes of impact location and core fabrication angle. The impact damage size were measured at facesheet surface by 3-Dimensional scanner. Also, sandwich specimens after impact test were cut to analyse the failure mode.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.2
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• pp.192-197
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• 2015

In many fields, the importance of reducing weight is increasing. A product should be designed such that it is profitable, by lowering costs and exhibiting better performance than other similar products. In this study, the mass and deflection of steel structures have to be reduced as objective functions under constraint conditions. To reduce computational analysis time, central composite design(CCD) and D-Optimal are used in design of experiments(DOE). The accuracy of approximate models is evaluated using the $R^2$ value. In this study, the objective functions are multiple, so the non-dominant sorting genetic algorithm(NSGA-II), which is highly efficient, is used for such a problem. In order to verify the validity of Pareto solutions, CAE results and Pareto solutions are compared.

• Proceedings of the KSR Conference
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• 2006.11a
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• pp.239-252
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• 2006

The existing track structure for urban Maglev system is designed for the Maglev vehicles of HSST in Japan and UTM in Korea. The tracks hvaing cross beams for supporting rails are located on bridge girders and have several draw backs. Linimo in Nagoya, Japan, the first commercial urban Maglev line, has separated tracks from a bridge to overcome the previous track structure. However, the Linimo just put the existing track on bridge deck. This study suggests a improved track structure for urban Maglev system and compares the behavior of the new and existing track through static structural analyses. In the improved track, the power collector of a Maglew vehicle is installed parallel to the bridge deck surface, and, thus, the bottom width of the track structure is not limited by the vehicle's width. Therefore, the live load is distributed more effectively by the wide bottom of the track. Also, steel plates instead of steel cross beams are used to support rails, and, thus, the rail's deflection is improved.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.291-295
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• 2007

The irregularities in the guideways used in the Maglev transportation system that result from surface roughness and deflection of guideway have strong effects on the dynamic characteristics of Maglev vehicles, because the electromagnetic suspension of Maglev vehicles strongly interacts with the guideway. For this reason, a numerical prediction of air gap responses to these irregularities is desirable to improve aspects of running performance, such as stability and passenger comfort, while minimizing aesthetic impact and construction cost. This paper presents a procedure to predict the air gap response which is a criteria for stability, and investigates the responses with the goal of attaining higher travel speeds in the urban Maglev vehicle UTM-01 utilizing electromagnetic suspension.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.40-45
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• 2003

The high-speed rotating arc process forms a flat bead surface with decreased penetration depth because the molten droplets are deflected by centrifugal force. Therefore the rotating arc welding for horizontal fillet welding increases the leg length with the increase of rotation frequency and prevents the deflection of weld bead and overlap. In this study, the relationship between the welding parameters and the weld bead shape - leg length and undercut - are investigated experimentally. Consequently, the weld quality could be improved by rotating arc welding, and sound weld bead was achieved when applied to horizontal fillet welding with 4mm gap by avoiding the undercut which is inevitable for the conventional GMA welding methods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1483-1491
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• 2001

Enhancement of pulsed-laser ablation by an artificially deposited liquid film is presented. Measurements of ablation rate, ablation threshold, and surface topography arc performed. Correlation between material ablation and photoacoustic effect is examined by the optical beam deflection method. The dependence of ablation rate on liquid-film thickness and chemical composition is also examined. The results indicate that photomechanical effect in the phase explosion of liquid is responsible for the enhanced ablation. The low critical temperature of liquid induces explosive vaporization with localized photoacoustic excitation in the superheat limit and increases the ablation efficiency. Experiments were carried out utilizing a Q-swiched Nd:YAG laser at near-threshold laser fluences with negligible plasma effect (up to ∼100 MW/cm$^2$).

• Laser Solutions
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• v.7 no.1
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• pp.29-36
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• 2004

The dynamics of laser-induced plasma/shock wave and the interaction with a surface in the laser shock cleaning process are analyzed by optical diagnostics. Shock wave is generated by a Q-switched Nd:YAG laser in air or with N$_2$, Ar, and He injection into the focal spot. The shock speed is measured by monitoring the photoacoustic probe-beam deflection signal under different conditions. In addition, nanosecond time-resolved images of shock wave propagation and interaction with the substrate are obtained by the laser-flash shadowgraphy. The results reveal the effect of various operation parameters of the laser shock cleaning process on shock wave intensity, energy-conversion efficiency, and flow characteristics. Discussions are made on the cleaning mechanisms based on the experimental observations.