• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.22-27
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• 2018

One problem of the Discrete Element Method is the assumption of a spherical particle shape, which reduces the computing time but significantly limits the application of the DEM to analysis. This limitation can be overcome by a recently developed rigid-rod model. However, the rigid-rod model has an essential problem related with friction: it always contains friction error because of the bumpy surface. To overcome this issue, we suggest a superposed rigid-rod model in this paper. The superposed rigid-rod model is notably consistent with the theoretical value in terms of the velocity and angular velocity after the collision. The estimated error is negligible(less than 2%). Then, the developed model is applied to hopper discharging. The developed model shows no problem in the discharging flow from the hopper.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.180.1-180.1
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• 2010

This paper introduces a 3MW embedded Permanent Magnet Synchronous Generator(PMSG) for wind turbine. The generator features 313mm stator inner radius and 974mm stator length. The blade rotor angular velocity is 15.7 rpm and the gear ratio is set to be 92.93. The nominal generator rpm at rated load is about 1459. The number of poles is six and embedded in the generator rotor. Embedded permanent magnet excitation shows higher reliability, and better efficiency. Using the finite element method, electromagnetic and thermal results are simulated by ANSYS and the results are summarized in this report.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.643-648
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• 2004

This paper is dedicated to the thermoelastic modeling and dynamic response of the rotating blades made of functionally graded ceramic-metal based materials. The blades modeled as non-uniform thin walled beams fixed at the hub with various selected values of setting angles and pre-twisted angles. In this study, the blade is rotating with a constant angular velocity and exposed to a steady temperature field as well as external excitation. Moreover, the effect of the temperature gradient through the blade thickness is considered. Material properties are graded in the thickness direction of the blade according to the volume fraction power law distribution. The numerical results highlight the effects of the volume fraction, temperature gradient, taper ratio, setting angle and pre-twisted angle on the dynamic response of bending-bending coupled beam characteristics are provided for the case of a biconvex cross section and pertinent conclusions are outlined.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.8
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• pp.203-211
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• 2002

ABS (Anti-lock Braking System) is a safety device for preventing wheel locking in a sudden braking. It consists of hydraulic modulator, ECU(Electronic Control Unit) and angular velocity sensors. Its control methods are classified into three types; deceleration control, slip ratio control and deceleration/acceleration control. In this paper, ABS mounted vehicle is mathematically modeled and the proposed model is verified by actual cars experiments, and the braking characteristics of the control methods with pulse width modulation are compared and analyzed through computer simulations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.976-982
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• 2005

This paper is dedicated to the thermoelastic modeling and dynamic response of the rotating blades made of functionally graded ceramic-metal based materials. The blades are modeled as non-uniform thin walled beams fixed at the hub with various selected values of setting angles and pre-twisted angles. In this study, the blade is rotating with a constant angular velocity and exposed to a steady temperature field as well as external excitation. Moreover, the effect of the temperature gradient through the blade thickness is considered. Material properties are graded in the thickness direction of the blade according to the volume fraction power law distribution. The numerical results highlight the effects of the volume fraction, temperature gradient, taper ratio, setting angle and pre-twisted angle on the dynamic response of bending-bending coupled beam characteristics and pertinent conclusions are outlined.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.9-16
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• 1997

A numerical method based on the spectral collocation method is developed for the steady rotating flows in eccentric annulus. Steady flows between rotating cylinders are of interest on lubrication in large rotating machinery. Steady rotating flow is generated by the rotating inner cylinder with constant angular velocity. The governing equations for laminar flow are simplified from Navier-Stokes equations by neglecting the non-linear convection terms. Integrating the pressure round the rotating cylinder based on the half Sommerfeld method, the load on the cylinder is evaluated with eccentricity. The attitude angle and Sommerfeld variable are calculated from the load. It is found that those values are influenced by the eccentricity. The attitude and Sommerfeld reciprocal are decreased with eccentricity. As expected, the effect of the annular gap ratio on them is negligible.

• Tribology and Lubricants
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• v.24 no.6
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• pp.355-361
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• 2008

In highly stressed machine elements such as angular contact ball bearings and toroidal type traction drives, the elastohydrodynamic lubrication of elliptical contacts with both rolling and spinning motion are occur. In this paper, a finite difference method with non-uniform grid systems and the Newton-Raphson method are applied to solve the problems. Pressure distributions, film contours and variations of the minimum and central film thicknesses are compared with various ellipticity parameter, dimensionless speed and load parameter. The results showed that the spinning motion has significant influence especially on the film shapes. Reduction of the minimum film thickness under spinning is remarkable whereas the central film thickness is relatively less. Especially variations of the minimum film thicknesses with rolling velocity, load and ellipticity ratio are a great different from those of pure rolling. Therefore present numerical scheme can be used in the analysis of general elliptical contact EHL problems and further studies are required.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1067-1072
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• 1996

Sensitivity analysis of the cylindrical zigzag cams under acceleration and centrifugal forces is performed. A Lagrangian method is used to determine the mechanism constant of zigzag track, And the equation of motion for cylindrical zigzag cam under rectangular pulse is derived by the governing equations of a single spring mass system. The ratio of the drive force tn resisting force is derived by angular acceleration, centrifugal force and setback force on the operation of the munition. The theoretical sensitivity curves for 3 models are analyzed. And experiments for 3 models are conducted to check safe and functional zone. Zigzag cam types can be satisfied all major design requirements for switch system of munition.

• Journal of the Korean Society of Visualization
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• v.5 no.2
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• pp.26-32
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• 2007

Stereoscopic PTV and Stereoscopic-PIV measurements have been carried out for the studies of the wake of a ship's propeller. Stereoscopic photogrammetry based on a 3D-PTV principle was introduced using two high-definition cameras(1k x 1k, 30Hz). The arrangement of the two cameras was based on angular position. The pair-matching of the three-dimensional velocity vectors were based on Genetic Algorithm based 3D-PTV technique. The results obtained by both measurement systems have been compared at the advance ratio J=0.88(290 rpm, d=54 mm). Turbulent properties have also been compared each other at the same condition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.725-730
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• 2012

In this paper, flow noise characteristics of Savonius-type vertical-axis wind turbines are numerically investigated using hybrid CAA techniques. High frequency harmonics as well as BPF components are identified in the predicted noise spectra from a Savonius wind turbine. As the BPF components belong to infrasound, the higher harmonic components affects human response dominantly. Further analysis is performed to investigate the reason causing the higher frequency harmonic noise by changing operational conditions of a Savonius wind turbine. Based on this result, it is revealed that the frequency of higher harmonic components is determined by the radius of blades and angular velocity of Savonius wind turbine.