• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1993년도 추계학술대회 논문집
• /
• pp.505-511
• /
• 1993

The results were obtained with changes according to the surface roughness of work roll and method to make the peak count on the roll in the temper rolling, and factors to affect to the work roll surface in actual rolling machine(ie. Temper mill). Conclusions are as follows. 1. E.D.T(Electro-discharge texturing)roll is more uniform roughness distribution than shot blasted roll and it's life time is two timees longer than that of shot blasted because it has more sine wave roughness. 2. The higher peak count of surface roughness, the more time is necessary to work roll texturing In shot blasting method, Surface roughness is relating to the grit size,impeller speed and hardness of roll material, But is can't control the peak count. 3. In shot blast texturing, Surface roughness of temper rolled strip which is transfered surface roughness of work roll is more ununiform than that of E.D.T roll 4. E.D.T roll has more uniform than the shot blasted roll and has more peak count than that of shot blasted roll. The surface of painted strip to image clarity is superior to that of shot blasted roll because E.D.T roll has more peak count and smooth surface.

• 대한조선학회지
• /
• 제20권1호
• /
• pp.47-58
• /
• 1983

A study is made, in the framework of linear potential theory, to investigate the hydrodynamic characteristics of two-dimensional wave-energy absorbers as like the Salter's duck and an oscillating cam with Lewis-form section, which undergo uncoupled heaving and rolling motions in an incident linear gravity wave in deep water. Wave energy is supposed to be extracted by a linearly damped generator with an spring. Some well-known formulae in ship hydrodynamics such as Haskind-Newman relation and Bessho-Newman relation are utilized in forms of Kochin functions to derived expressions for efficiency, breaking effect and drift force of the absorber. Maximum ideal efficiency of 100% can be arrived at an prescribed tuning frequency. Coupling effect is also examined to assess the detrimental effect of sway on efficiency. From numerical calculations for both types of two-dimensional devices it may be concluded that a wave-energy absorber functions at the same time as a wave breaker and that the drift force acting on the device becomes smaller when it absorbs wave energy than as it oscillates freely. Finally the study is extended to an infinite array system, equivalent to a body in a canal, to show that all incident wave energy can be absorbed regardless of the absorber's size, only if the optimum space and the optimum condition of control are realized.

• 해양환경안전학회지
• /
• 제11권1호
• /
• pp.23-28
• /
• 2005

선박 횡동요는 물적 손실을 초래할 뿐만 아니라, 승선자의 거주성, 안전성 및 작업능률을 저하시키는 가장 큰 요인이 된다. 횡동요억제를 위한 많은 연구는 다양한 형태의 장치개발이라는 결과를 가져왔으며 상당한 효과를 얻고 있다. 지금까지 개발 된 대부분의 장치는 그 성능을 고려하지 야더라도 특수한 목적의 선박을 대상으로 설치$\cdot$운영되고 있으며, 고가이고 복잡하여 설치 상에도 많은 문제점을 안고 있다. 따라서 본 논문에서는 선박의 선미측에 설치한 플랩을 이용하여 운항중인 선박의 횡동요 억제에 관해 고찰하고 있다. 본 장치는 중$\cdot$소형의 선박에도 쉽게 설치하여 운용이 용이할 뿐만 아니라, 적절한 제어시스템 구축으로 피칭운동도 제어할 수 있는 장점이 있다. 본 논문에서는 이러한 장치를 설치한 선박에 대해 실험적 기법을 이용하여 모델링을 행하고 시뮬레이션을 통해 장치의 횡동요 억제효과를 검증하고 있다.

• 한국해양공학회지
• /
• 제16권4호
• /
• pp.7-12
• /
• 2002

This study is aimed to find the scouring mechanism at the toe of rubble mound structures. To investigate the characteristics of scouring in front of the structure, experiments were performed with regular waves in a 2-D flume. The results of this study are as follows. 1) It can be said the characteristics of incident wave causes rolling and sliding of armour block. The difference of wave pressure on the slope, internal flow as well as settlement of armour block due to the weight cause scouring. 2) It is observed that scouring depth at the toe increased when wave height or period increased. The location of ultimate scouring and deposition depth moved seaward when wave period increased. 3) The failure of rubble mound structure was caused by waves or scouring. Failure by erosion increased with high waves and long waves. 4) Using surf-similarity parameter including characteristics of incident waves and structure, scouring and deposition pattern were found and their limit was formulated.

• 대한기계학회논문집A
• /
• 제20권9호
• /
• pp.2901-2907
• /
• 1996

Flatness of cold rolled strip is vital to the quality of the product and productivity of the mill. Therefore, in recent year requirement for flatness control in strip rolling have become increasingly severe. The necessity for more accurate automatic gauge control and automatic flatness control(AFC) has increased by customer's requirement for cold rolled steel sheets with thinner gauge and better flatness quality. In this paper, the performance and functions of AFC system installed on the 4 hi-reversing mill has been investigated under actual conditions. The test results are as follows : The more strip thickness is thick, the smaller the I-value. The I-value is a strain measured by stressometer. Complex distributions of strip tension are controlled to remove not only a quarter buckle but also a simple center wave and edge wave. The defects caused by poor flatness have been drastically decreased. And a proper coolant temperature for work roll cooling system on the AFC system is about $50~55^{\circ}C$.

• 해양환경안전학회지
• /
• 제23권7호
• /
• pp.956-964
• /
• 2017

본 연구는 어선전복경보시스템 개발을 위해 어선의 횡동요 특성을 파악하고 시간영역 횡동요 운동 시뮬레이션을 수행한다. 어선전복경보시스템의 검증을 위해서는 전복 상황을 가정하여 시험을 수행하고 실제 어선 계측을 수행해야 하지만, 상황의 위험성으로 인해 현실적으로 불가능하다. 또한 많은 전복사고의 경우 횡동요와 밀접한 연관이 있는 것으로 조사되었다. 이에 따라 어선전복경보시스템의 핵심인 어선의 횡동요특성을 정확히 파악하여 시간영역 기반 횡동요 시뮬레이션을 수행하고 해당 정보를 통해 시스템에 탑재된 경보시스템의 알고리즘을 검증한다. 주요내용으로 첫째, 횡동요 운동 특성을 운동 시험을 통해 계측하고 파악한다. 특히 어선과 같은 소형선박의 경우 CFD 및 포텐셜 코드를 포함한 해석적인 방법으로 점성과 관련된 횡동요 해석이 어렵다. 이에 따라 횡동요 운동 모드에 초점을 맞추어 운동 시험을 수행하고 횡동요 RAO를 도출한다. 둘째, 횡동요 RAO를 이용하여 Wave Spectrum과의 조합으로 시간영역 운동 시뮬레이션을 수행하고 전복 경보 알고리즘을 검증한다.

• 대한조선학회논문집
• /
• 제53권5호
• /
• pp.380-387
• /
• 2016

Present research target to develop the procedure of long-term fatigue analysis of the structural details near the upper rolling chock of IMO type B tank by using the time domain modal analysis technique where both the contact and friction behavior can be accurately simulated. In order to perform the time domain analysis focused on the contact and friction, the entire model of the hull and tank was condensed with DOF reduction technique, which is obtained by transforming the global finite element model into its quasi-static modal coordinate. Modal analysis using the quasi-static deformation modes is chosen as a cost effective time domain simulation method and this is based on the fact that the structural response of the tank is quasi-static. Based on the developed cost effective time domain simulation method, the long-term fatigue analysis procedure for the structural details near the rolling chock and key of independent type tank is targeted to be established. The developed fatigue assessment procedure takes into account, wave induced stress and both contact and friction induced stress without loss of accuracy.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2004년도 학술대회지
• /
• pp.30-35
• /
• 2004

Several roll motion reduction devices are reviewed and suggested for the application in FPSO. The firstly suggested solution is the shape of the bilge. The next is a bilge keel. The last suggestion is the ART (anti-rolling tank). Typical U-tube type ART is designed for a FPSO and examined extensively by model experiment. The model section was made of transparent acryl. Free decay test, forced oscillation test and wave test were carried out at a two-dimensional wave flume. U-tube type ART is effective only when the natural periods of ART and ship are same. Therefore, the divided U-tube type ART with split plate is suggested for the reduction of the roll motion of a FPSO over the wide range of the roll period.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
• /
• 제6권1호
• /
• pp.1-6
• /
• 2003

This study presents the results of series of studies, which are mainly devoted to the application of wavelet transforms to various problems in ocean engineering. Both continuous and discrete wavelet transforms were used. These studies attempted to solve detection of wave directionality, detection of wave profile, and decoupling of the rolling component from free roll decay tests. The results of these analysis, using wavelet transform, demonstrated that the wavelet transform can be a useful tool in analyzing many problems in the filed of ocean engineering.

• 대한기계학회논문집
• /
• 제17권2호
• /
• pp.257-266
• /
• 1993

본 연구에서는 보강롤의 굽힘변형을 고려한 젠지미어 압연기의 롤변형 해석을 통해, 궈터웨이브의 발생을 시뮬레이션하고, 형상제어 수단들의 궈터웨이브 억제에 미 치는 영향을 분석하여 궈터웨이브 감소 방안을 수립하였고, 실제 현장 압연실험을 통 해 그 제어효과를 확인하였다.