• 열처리공학회지
• /
• 제31권2호
• /
• pp.63-67
• /
• 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.

• 대한조선학회논문집
• /
• 제40권1호
• /
• pp.1-7
• /
• 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.

• 한국항해항만학회지
• /
• 제45권1호
• /
• pp.16-25
• /
• 2021

동유체력 미계수는 수중운동체의 조종성능을 예측하기 위해 정확히 추정되어져야 하며 추정 방법의 일환으로 다양한 모형시험이 수행되어오고 있다. 수중운동체는 횡동요 모멘트 변화에 민감하므로 관련 동유체력 미계수를 추정하는 작업은 정확히 수행되어져야 한다. 본 연구에서는 횡동요 운동과 관련한 동유체력 미계수를 간단하게 추정할 수 있는 순수 횡동요 장비를 새롭게 설계하였다. 횡동요 운동은 간단한 기계적 메커니즘을 통하여 구현하였으며, 메커니즘의 원리와 적용과정 그리고 설계한 장비의 system identification에 대해 기술하였다. 또한 순수 횡동요 시험의 해석방법을 제시하고 설계한 장비에 대해 반복시험을 거쳐 결과의 재현성을 확인하였다.

• 해양환경안전학회지
• /
• 제21권5호
• /
• pp.538-542
• /
• 2015

선체의 횡관성모멘트는 선박의 횡운동 특성을 다루는 경우 제외될 수 없는 요소로서 그 크기의 적정성은 선체 동특성 해석의 결과와 신뢰성에 큰 영향을 미친다. 그러나 선박은 질량분포와 형상이 복잡하므로 이를 직접적인 계산을 통해 값을 구하기에는 과정이 매우 복잡하고 대상 선박의 구체적인 관련 자료를 얻기도 어렵다는 점에서 실용적으로는 선체 질량의 등가적 관성반경을 선체폭의 일정비율로 계산하는 간접적인 방법이 통용되고 있다. 한편, 어느 선체의 자유 횡운동이 나타내는 횡요 주기와 감쇠형태는 관성모멘트에 의해 영향을 받기 마련이고 따라서 이러한 응답의 결과적인 모양으로부터 역으로 해당 선박의 관성모멘트를 구하는 일반식의 도출이 가능할 것으로 유추될 수 있다. 본 연구에서는 관찰에 의한 선체의 횡요 주기는 경사각의 진폭 감쇠비에 의해서도 달라지는 관계를 해석하여 횡요 주기와 경사각 진폭 감쇠비 모두를 함수 인자로 포함하는 일반식에 의해 횡관성모멘트 크기가 구해질 수 있음을 나타내었다. 또한 이러한 일반식에 횡요 관찰 선박의 주요 제원을 적용하였을 때 나타나는 특성 그래프들을 분석한 결과 횡요주기뿐 아니라 진폭감쇠비가 함께 검토될 때 얻어지는 관성모멘트 값이 보다 정확해진다는 것을 확인하였다.

• 소성∙가공
• /
• 제21권7호
• /
• pp.420-425
• /
• 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.

• 한국자동차공학회논문집
• /
• 제18권5호
• /
• pp.56-61
• /
• 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.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.64-66
• /
• 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.

• 한국기계가공학회지
• /
• 제11권6호
• /
• pp.145-151
• /
• 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.

• 대한조선학회논문집
• /
• 제43권6호
• /
• pp.667-674
• /
• 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.

• 한국군사과학기술학회지
• /
• 제21권6호
• /
• pp.784-789
• /
• 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.