• Journal of the Korean Society for Heat Treatment
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• v.31 no.2
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• pp.63-67
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• 2018

Recent mold industry uses many roll-to-roll processes that can produce high production speed and precision machining and automation process. In the circular cylinder mold, however, patterns of less than $10{\mu}m$ are difficult to manufacture and maintain. In this study, we fabricated a circular cylindrical mold with a DLC thin film which have high hardness, low coefficient of friction and high releasability by using lithography and lift-off process. The height, line width, and pitch of the fabricated DLC macro pattern are $3.1{\mu}m$, $9.1{\mu}m$ and $20.2{\mu}m$, respectively. The pattern size is finer than the current applied to the aluminum cylinder type, and this shows the possibility of practical use of DLC micro pattern roll mold.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.1
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• pp.1-7
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• 2003

The effect of the passive anti-rolling tanks(ART) decreases when the roll period of the vessel does not match the designed oscillating period of the fluid in the tank. In order to improve the effect of the passive ART, the damping plates are installed in the lower duct of the ART to adjust the oscillating period of the fluid. The effects of the damping plates on the oscillating period of the fluid and the changes of the stabilizing moments are examined through the series of bench tests. Acryl model tank larger than 1m breadth is made to minimize the viscous effect of the tank and the stabilizing moments of the tank are measured for various roll angles. Using the obtained tank damping coefficient, RAO(Response Amplitude Operator) value in the resonance range is computed and the stabilizing effect of a ART has been estimated.

• Journal of Navigation and Port Research
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• v.45 no.1
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• pp.16-25
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• 2021

Hydrodynamic coefficients should be accurately estimated to predict the maneuverability of underwater vehicles. Various captive model tests have been performed as part of estimation methods for these coefficients. Estimating hydrodynamic coefficients related to roll motion is important because underwater vehicles are sensitive to changes of roll moment. In this research, a pure roll motion equipment was newly designed to simply estimate hydrodynamic coefficients with respect to roll motion. Roll motion was implemented through a brief mechanical mechanism. The principle of operation, application process, and system identification of the equipment are described. An analysis method of the pure roll test is also suggested. Repeated tests of the newly equipment were carried out to check its reproducibility.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.538-542
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• 2015

The transverse moment of inertia is an indispensable factor in analyzing the roll motion characteristics of ships and the calculating method needs to be based on the more reasonable theories when deciding the value as the results and reliability of analysis could be much affected by the correctness. However, the mass distribution and shape of hulls are quite complicated and give much difficulties in case of calculating the value directly from the ship design data, furthermore even acquiring the detailed design data for calculation is almost impossible. Therefore some simpler ways are practically adopted in the assumption that the gyradius of roll moment can be decided by a given ratio and hull width. It is well known that the responses of the free roll decay are varied according to the value of roll moment in view of roll period and amplitude decay ratio, so that the general formula to get the moment value can be derived also from the observation of roll decay responses. This study presents how the roll period and decay ratio are interrelated each other from the roll motion characteristics with suggesting a general formula to be able to calculate roll moment from it. Finally, the obtained general formula has been applied to a ship data to check the resultant characteristics through analyzing graphs and showed that the roll moment becomes more accurate when rolling period and decay ratio are considered together in calculation.

• Transactions of Materials Processing
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• v.21 no.7
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• pp.420-425
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• 2012

A new model is suggested for the prediction of radial displacements of a roll in order to analyze multi-high rolling mills. The model was developed from predictions based on finite element simulations. This model utilizes the compliance coefficient, which is expressed as a function of three dimensionless parameters, and is approximated by using the same interpolation function as used in the finite element method. The prediction accuracy of the model is demonstrated through comparison with the predictions from the FE model.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.56-61
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• 2010

This paper presents dynamic clearance verification considering engine movement for vehicle engine room package and validates through physical vehicle test. Traditionally, static clearance guide has been used for engine room package, but it's only 2-dimension criteria that results in requiring unnecessary space and it's not possible to conduct engine movement with real driving conditions. Thus, the dynamic DMU considers engine movement based on 28 load cases that are Roll Data analyzed by CAE for maximum engine movement and visualizes part-to-part dynamic clearance into virtual space. The dynamic DMU enables to develop compact engine room package without unnecessary space. The result of comparison between simulation and physical test has 0.892 correlation coefficient.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.64-66
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• 2007

In this paper, a digital inclinometer to measure the angle and acceleration signals of subject laid on Roll was designed. The designed system consists of a tilt sensor, biaxial accelerometer, microcontroller and BlueTooth module. The designed digital inclinometer was easy to handle and easy to wear. To evaluate the performance of the system, we measured simultaneously the angle and acceleration signals from the 3 subjects on the Roll with two instruments which are ZEBRIS and our system. The measured signals were processed by statistical method and then the correlation coefficient of 0.93 was shown. From the results, the designed digital inclinometer is shown to be useful in assessment of body movement.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.145-151
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• 2012

In this study, finite element analysis is carried out to estimate horizontal forces needed for the required power calculation and vertical forces applied on the structural analysis model for the development of automatic serrated surface at metal gasket core machining system. By considering of elasto-plastic material characteristics, nonlinear contact analysis was conducted to compute these loads according to the change of roll reduction, frictional coefficient and core thickness. As the result, horizontal and vertical reaction force variations are found according to parameters and maximum reaction force is also confirmed to be most affected by roll reduction.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.6 s.150
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• pp.667-674
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• 2006

Accurate prediction of ship dynamics, particularly roll motion, is very important in ship safety. In the past, empirical or vortex based methods were commonly used for the hydrodynamic roll damping predictions but they could not be applied to practical ship roll motion cause of limitations about geometries ad design conditions. Recently RANS-based techniques are developed for the practical ship motion analysis. In this study, RANS based roil analysis about a rectangular cylinder with WAVIS developed by MOERI/KORDI are performed and compared with the experimental data and other RANS results.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.784-789
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• 2018

Accurate aerodynamic characterization of projectile is crucial for successful development of munition. The aerodynamic characterization of fin stabilized projectile is more difficult than characterization of traditional symmetric ballistic projectile. Instrumented free flight experiments were conducted to quantify rolling behavior of fin stabilized projectile. The instrumented projectiles were launched from a rifled tube and the onboard sensor data were acquired through a telemetry transmitter. Roll rate was measured for fin stabilized projectile by means of an angular rate sensor. And, roll damping coefficients were estimated from onboard sensor data acquired during gun firing and trajectory analysis of mathematical model.