• Journal of Advanced Marine Engineering and Technology
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• 제18권5호
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• pp.56-67
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• 1994

The installation methods of diesel engines in ships would be largely classified into two groups : one is the direct mounting system fixing engine directly into double bottom of the hull, and the other is the resilient mounting system having vibration absorbers between engine and ship body such as rubber plate to prevent shocks or vibration transmission. The direct mounting system is generally used for large-sized low speed diesel engines, because the resilient mounting system has difficulties in reducing the natural frequency of engine itself under normal speed. On the contrary, the resilient mounting system is often used for medium or high speed engines for marine propulsion and generator that have light weight and high revolution speed. Recently, it is even applied to engines having relatively low speed(300-400rpm) for fishing boats. Although many researches for the resilient mounting system have been carried out, many problems in applying these results directly to marine vessels because most of these have been used for automobiles. Up to now we have had to depend on the professional foreign company in design and the supply of parts for the resilient mounting system of marinediesel engines utterly. In preseut study, the exciting forces of engines effecting to resilient mounting were examined, and patterns of vibration and evaluation procedure for force transmission from resilient mounting to the body of hull were established. Also, these results were applied to the analysis of free and forced vibration for the rubber-type resilient mounting systems of marine diesel engines. Besides, after changing the various design parameters, such as locations, angles, dynamic characteristics and the number of resilient mountings, the influences on resilient mounting system were also examined.

• 한국CDE학회논문집
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• 제17권5호
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• pp.324-332
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• 2012

In this paper, a method for calculating the contact force and the frictional force caused by contacts between the wire rope and the rigid body is introduced based on multibody dynamics. And the method is applied to a simulation of contacts between the wire rope and the shell plate of a block that can occur during shipbuilding. The wire rope is composed of a number of lumped masses and the wire rope segments that connect the masses. After calculating the position of interference, we inserted a contact node into the wire rope. We then derived the equations of motion of the wire rope and the rigid body using augmented formulation based on multibody dynamics taking into account the constraints between the contact node and the rigid body. Using the equations, we were able to obtain the constraint force between the contact node and the rigid body, and calculate the contact force and the frictional force, based on which the position of the contact node was corrected. Finally, we applied our results to perform simulation of contacts between the wire rope and the shell plate of a block in order to verify the efficacy of the method proposed in this paper.

• Journal of Advanced Marine Engineering and Technology
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• 제39권1호
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• pp.28-31
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• 2015

전기기기나 엔진의 축은 여러 가지 원인으로 축기전력이 발생한다. 이런 축과 베어링이 윤활유로 절연되어 있어 콘덴서를 이루고 있고, 콘덴서와 같은 역할로 기전력을 축적하고 있다. 이 축 기전력은 선체에 비해 극히 일부를 제외하고 +전압을 갖고 있다. 이 +전압이 축의 전기 스파크를 일으켜 부식을 야기 시킬 수 있다. 이 부식을 막기 위해 선박에서는 샤프트 그라운드 시스템을 설치하여 운용하고 있다. 이 축기전력을 측정은 프로펠러 축의 전압과 메인엔진의 회전수를 동시에 측정하였다. 측정장치는 내셔널인스트루먼트사의 24비트 A/D컨버터를 사용하여 측정하였고, 프로그램은 Lab View를 사용하였다. 본 논문은 축에 발생되는 기전력을 분석하였고, 분석결과를 이용하여 모델링을 하였다. 결과로 축기전력은 메인엔진의 회전수에 따라 비례하다가 일정회전수를 넘어가면 감소하는 경향을 보였다. 후진보다는 전진이 축기전력이 높은 결과를 얻었다. 전체기전력에 비하면 지구자기의 기전력은 미미하였다.

• 해양환경안전학회지
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• 제15권3호
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• pp.223-228
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• 2009

2003년 태풍 매미로 인하여 안전한 피항지로 여겨졌던 진해만에서도 강풍에 의한 주묘로 좌초, 충돌 등 많은 해양사고가 발생하였다. 투묘에 대한 사항이나 주묘를 예측하기 위해서는 외력과 대항력에 대한 비교 검토가 필요하다. 하지만 풍압력에 대한 부분에서 스윙현상으로 인한 풍압면적 적용에 대한 연구가 진행되고 있으나, 여전히 논란의 대상이 되고 있다. 따라서 실습선 한바다호를 대상으로 선체에 작용하는 외력과 외력에 대한 대항력을 수치적으로 계산하고, 이를 실제로 주묘가 발생했던 실선계측자료와 상호 비교 분석함으로써 묘박 중선박에 가해지는 풍압력에 대한 평가를 실시하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제34권7호
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• pp.963-970
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• 2010

This study makes an estimate of the laser-assisted machining (LAM) of an economically viable process for manufacturing precision silicon nitride ceramic parts using a high-power diode laser (HPDL). The surface is locally heated by an intense laser source prior to material removal, and the resulting softening and damage of the workpiece surface simplify the machining of the ceramics. The most important advantage of LAM is its ability to produce much better workpiece surface quality compared to conventional machining. Also important are its larger material removal rates and longer tool life. The cutting force and surface temperature were measured on-line using a pyrometer and a dynamometer, respectively. Tool wear, chips and the surface of the workpiece were measured using optical microscopy, and the surface and fractured cross-section of $Si_3N_4$ were measured by SEM. During the LAM process, the cutting force and tool wear were reduced and oxidation of the machined surface was increased according to the increase in the laser power. Moreover, the more the feed rate increased, the more the cutting force and tool wear increased.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.364-374
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• 2015

The purpose of this research is to compare and analyze the advanced speed of ships with different rudder controller in wavy condition by using a simulation. The commercial simulation tool named AQWA is used to develop the simulation of ship which has 3 degree of freedom. The nonlinear hydrodynamic force acting on hull, the propeller thrust and the rudder force are calculated by the additional subroutine which interlock with the commercial simulation tool, and the regular wave is used as the source of the external force for the simulation. Rudder rotational velocity and autopilot coefficients vary to make the different rudder controller. An advanced speed of ships depending on the rudder controller is analyzed after the autopilot simulations.

• 해양환경안전학회지
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• 제18권6호
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• pp.591-596
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• 2012

안전하며 친환경적인 근해운송시스템을 확보하기 위해서는 운송 수단인 선박의 안전한 운항 확보가 필수적이다. 특히 좌초, 충돌 등의 해난사고를 방지하기 위해서는 선박이 우수한 조종성능을 갖는 것이 요구되며 특히 조종성능 중에서 선회성능은 충돌 회피 등에 필수적인 성능이다. 본 연구에서는 선박에 부착된 조타기의 타력 증가가 선박의 선회성능에 미치는 영향을 모형선 실험을 통하여 고찰하였다. 먼저 Coanda 효과를 이용한 고 양력 타 장치 모형과 47 K PC의 모형선을 제작하였다. 또한 모형선의 선회 성능 실험을 위한 자유항주시스템을 구축하고 사각 수조에서의 타력 증가 값을 변화시켜가면서 모형선의 선회 성능을 계측하여 타력 증가에 따른 선회 성능의 변화를 평가하였다. 모형선의 선회성능 실험결과를 통해 타력 증가가 근해운송 선박의 선회 성능 향상에 효과적인 것을 확인하였다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제2권2호
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• pp.100-108
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• 2002

A fuzzy logic for collision avoiding navigation of marine vehicles is proposed in this paper. VFF(Virtual Force Field) method, which is used widely in the field of mobile robots, is modifiel to apply to marine vehicles. The method is named MVFF (Modified Virtual Force Field) mothod. The MVFF consists of the determination of the heading angles far track-keeping mode ($\psi_{ca}$)and collision avoidance mode ($\psi_{ca}$). The operator can choose the pattern of the track-keeping mode in the proposed algorithm. The collision avoidance algorithm can handle static and/or moving obstacles. These functons are implemented using fuzzy logic. Various simulation results verify the proposed alogorithm.

• Journal of Advanced Marine Engineering and Technology
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• 제22권3호
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• pp.328-336
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• 1998

Marine reduction gears are usually used to increase the propulsion efficiency of propellers for ships powered by medium and small sized high speed diesel engines. Most of shaft systems adopt flexible couplings to absorb the transmitted vibratory torque from the engines to the reduction gears and to prevent the chattering phenomenon of reduction gears. However some elastic couplings show non-linear characteristics due to the variable torque transmitted from the main engines and the change of ambient temperature. In this study dynamic characteristics of flexible couplings sare investigated and their effects upon various vibratory conditions of propulsion systems are clarified. A calculation program of torsional vibration for the propulsion systems are clarified. A calculation program of Results of the program developed are compared with ones of the existing linear method and propulsion systems with the elastic couplings the transfer matrix method is adopted which is found to give satisfied results.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2012년도 전기공동학술대회 논문집
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• pp.175-175
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• 2012

Proper shaft alignment is one of the most important actions during the design of the propulsion system. The stiffness of recently designed marine propulsion shafting has been increasing remarkably, whereas hull structures have become more likely to deform as a result of optimized design of the scantlings and the high tensile steel. Therefore, to obtain the optimum status in shafting alignment at the design stage, it is strongly recommended that the change of bearing reaction force depending on ballast/load condition, the bending moment force occurred by propeller thrust, elastic deformation of bearing occurred by vertical load of shaft mass and etc., should be considered. This paper dealing with introduction of shaft alignment concerning long shaft for high speed vessel and review its reliability evaluation theoretically.