• 대한조선학회논문집
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• 제46권1호
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• pp.69-77
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• 2009

Loss of human lives and properties including environmental damage due to large scale accidents requires change of our perception to marine safety. IMO is trying to re-establish overall marine safety system through long term plan such as GBS. Along this line, current regulation based safety evaluation is in process of changing into performance based methods, and for this transition, simulation based safety evaluation during design stage considering damage is highly necessary. In this paper, first, damage scenario is developed from IMO regulations and accident case studies. Then an integrated and simulation based safety evaluation prototype system considering both damage stability and structural safety is developed for the use during ship design process.

• 한국해양공학회지
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• 제22권3호
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• pp.47-57
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• 2008

Many accidents occur on the oceans. Accidents involving ships can cause enormous damage. When an accident occurs, the cost of environmental restoration can bankrupt even a top-ranked international company. The potential damages resulting from ship accidents have resulted in many international agreements such as MARPOL, SOLAS, ISM Code, etc. The viability of damaged ships has become more and more important. A damaged ship's viability and cargo safety can be improved by a safety assessment design procedure. We consider th￡ shipbuilding industry's distributed characteristics to define a safety assessment system with software engineering-based requirements analysis. We used a distributed network-based simulation method (HLA - High level architecture), because of ease of reuse and expansion of existing components to other situations, and because it is a military standard. HLA is the standard for distributed network-based simulation in many countries including the United States, Canada, Israel, and Korea. The paper describes research to develop a prototype of a network-based safety assessment simulation system by software engineering based analysis.

• 한국기계가공학회지
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• 제20권9호
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• pp.1-10
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• 2021

Recently, the repair and recycling of damaged mechanical parts via metal additive manufacturing processes have been industrial points of interest. This is because the repair and recycling of damaged mechanical parts can reduce energy and resource consumption. The directed energy deposition(DED) process has various advantages such as the possibility of selective deposition, large building space, and a small heat-affected zone. Hence, it is a suitable process for repairing damaged mechanical parts. The shaft is a core component of various mechanical systems. Although there is a high demand for the repair of the shaft, it is difficult to repair with traditional welding processes because of the thermal deformation problem. The objective of this study is to propose a repair procedure for a damaged shaft using the DED process and discuss its applications. Three types of cases, including a small shaft with a damaged surface, a medium-size shaft with a worn bearing joint, and a large shaft with serious damage, were repaired using the proposed procedure. The microstructure and hardness were examined to discuss the characteristics of the repaired component. The efficiency of the repair of the damaged shaft is also discussed.

• 한국구조물진단유지관리공학회 논문집
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• 제1권1호
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• pp.75-87
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• 1997

To study the behavior a deck when it was collide with the ship approaching to the deck to berth, it was analyzed the effect zone by the ship collision which consists of deck slab and PC piles of the quay. The numerical technique is used to simulate the behavior of the deck when the ship hit the expansion joint of deck between the deck slabs. The failure behavior and zone of the deck are determinated by the comprehensive numerical study. The impact energy by the ship is also evaluated. It is concluded that these numerical analysis gave a reasonable estimation of the remedial area of the deck damaged by ship collision.

• 해양환경안전학회지
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• 제28권4호
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• pp.620-631
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• 2022

본 논문은 CFD 해석법을 이용하여 사고 선박의 손상부 형상에 따른 기름 유출량 변화를 예측하고, 이론 추정식에서 이를 고려할 수 있는 방출계수 도출 결과를 소개한다. Froude수와 Reynolds수 상사를 만족하는 조건에서 다상유동 해석법을 사용하여 모형선 크기의 기름 유출 문제를 다루었다. 수치해석 결과는 알려진 실험 결과와 비교하여 검증하였다. 수학적 형상들로 정의한 손상부 형상의 변화와 함께 손상부 가로세로비와 기름탱크 두께의 변화가 기름 유출 유동에 미치는 영향을 조사하였다. 보다 현실적인 상황을 고려하기 위해 손상부의 찧어진 철판의 영향에 대한 해석도 포함하였다. 수치해석 결과를 통해 사고 선박의 손상부 형상에 따른 기름 유출량의 변화를 확인하였으며, 다양한 손상부 형상이 가지는 점성 영향을 방출계수로 정량화하여 추출하였다. 본 논문에서 제시하는 방출계수에 대한 검증을 위하여 알려진 기름 유출량 주정식에게 적용하였으며, CFD 해석과 좋은 일치를 얻었다.

• 선박안전
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• 통권24호
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• pp.4-20
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• 2008

Stainless steel 304 or stainless steel 630 types using propeller shaft of a small ship or a FRP fishing boat generally restrain localization corrosion and abrasion damage occurrence to shaft bearing or grand packing contact. In general, the residual stress which remains after welding or heat treatment in material can cause the stress concentration or localization corrosion. In case of small ship, stainless steel such as STS304 has long been used for propeller shaft. Meanwhile, crew of small ship tend to reuse damaged propeller shaft after repair by welding and performing heat treatment to save cost. However, it was found that reused propeller shaft by repair often caused troubles in ship's operation. In this study, the basic guideline for maintenance and treatment of propeller shaft are investigated. From the results of investigation, remarkable deterioration of the material properties and corrosion resistance on the welded work part was observed.

• Corrosion Science and Technology
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• 제19권5호
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• pp.239-249
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• 2020

The characteristics of cavitation-erosion damage with changes in the amplitude of 5052-O aluminum alloy for ships were investigated in a seawater environment. In the cavitation-erosion experiment, the cavitation environment was created using a vibration-generating device with a piezo-electric effect. The amplitudes of 5 ㎛, 10 ㎛, and 30 ㎛ were created by changing the geometric shape of the cavitation horn. The resistance characteristics of cavitation-erosion damage were evaluated by weight loss and pitting area. The damaged surface was analyzed using scanning electron microscopy (SEM) and 3D optical microscopy. As the amplitude increased, the amount of damage and the area of the damaged surface increased, and the damage was concentrated at the center and edge of the specimen. The pit was created after the initial incubation period with increasing experimental time, and then the pits were merged to grow and propagate into craters, and eventually, the surface was detached and damaged. The cavitation-erosion damage after 30 minutes with amplitude of 10 ㎛ and 30 ㎛ was 1.48 and 2.21 times compared to 5 ㎛, respectively.

• 대한조선학회논문집
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• 제44권5호
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• pp.526-533
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• 2007

It should be primarily aimed to increase survivability consisting of susceptibility, vulnerability and recoverability of naval vessels including ship hull, armament system as well as crews from the design stage to practical operations. With this in mind, swift and efficient actions should be executed on the basis of accurate calculations for the recoverability of damaged vessels. In this paper, it is established how the damage control system of naval vessels is embodied through step-by-step processes intending to cope with various damaged situations that may possibly occur during real operations. It is validated that this system has the applicability to naval vessels through the case study of the battle ship which has been damaged during the operation.

• 한국해양공학회지
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• 제33권1호
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• pp.1-9
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• 2019

This paper considers a numerical assessment of the self-propulsion performance of a damaged ferry carrying cars in irregular waves. Computational fluid dynamics(CFD) simulations were performed to see whether the ferry complied with the Safe Return to Port (SRtP) regulations of Lloyd's register, which require that damaged passenger ships should be able to return to port with a speed of 6 knots (3.09 m/s) in Beaufort 8 sea conditions. Two situations were considered for the damaged conditions, i.e., 1) the portside propeller was blocked but the engine room was not flooded and 2) the portside propeller was blocked and one engine room was flooded. The self-propulsion results for the car ferry in intact condition and in the damaged conditions were assessed as follows. First, we validated that the portside propeller was blocked in calm water based on the available experimental results provided by KRISO. The active thrust of starboard propeller with the portside propeller blocked was calculated in Beaufort 8 sea conditions, and the results were compared with the experimental results provided by MARIN, and there was reasonable agreement. The thrust provided by the propeller and the brake horsepower (BHP) with one engine room flooded were compared with the values when the engine room was not flooded. The numerical results were compared with the maximum thrust of the propeller and the maximum brake horse power of the engine to determine whether the damaged car ferry could attain a speed of 6 knots(3.09 m/s).

• 한국해양공학회지
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• 제20권3호
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• pp.24-36
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• 2006

This paper investigates wave loads of ships that suffer sinkage due to flood in a compartment caused by damage on the side of the hull. By analyzing ships with various sizesof damage opening, the influence of opening size on ship response is investigated. The motion of the damaged ship is analyzed by using the boundary element method, based on three-dimensional potential theory, considering hydrodynamic pressure in the flooded compartments. The shear forces, bending moments and torsional moments are calculated by the direct integration of the three dimensional hydrodynamic pressure on the outer and inner hulls. A RORO passenger ship with length of 174.8 m is considered in the numerical example, and results for wave loads are discussed.