• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.118-124
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• 2017

To investigate and analyze the cause of the failure of the connecting rod bolt and the crank pin bearing bolt of the diesel engine of this study, the following results were obtained through site surveying, the investigation of literature referring to similar failures, testing and inspection of the fracture surface, and the experience of the researchers. The fractured crank pin bearing bolt of the diesel engine is estimated to be damaged later than the connecting rod bolt. From the shape of fracture surface, it is evident that the failed connecting rod bolt is fractured by fatigue failure due to abnormally repeated loads (e.g. loosening of the connecting bolt, etc.), and is not failed by brittle fractures due to the impact load. The surface of the U-nut on the fractured connecting rod bolt has been worsening due to the improper use of lubricant (agent for prevention of thread fixing) and no usage of separating the each connecting rod on each cylinder. Moreover, there is the possibility that those poor surface conditions of the fractured connecting rod bolt have affected the failure of the connecting rod bolt of the main engine. And it could be assumed that the mechanical characteristic and manufacturing process of the failed connecting rod bolt and crank pin bearing bolt, which were made by a domestic company, conform to the design requirements for those bolts.

• Journal of Navigation and Port Research
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• v.41 no.3
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• pp.119-126
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• 2017

As container vessels get larger, container terminals are also likely to grow. The problem that arises is that the growing volume should be handled in the same amount of time as before. Container terminals are introducing an automation system in order to overcome the limitations of existing manual methods and to continuously reduce operating expenses. Because, Manual handling of carrying containers gate in and out of terminals causes inaccurate data, which results in confusion. An alternative is for containers to be labeled with barcodes that can be scanned into a system with a scanner, but this takes quite a long time and is inconvenient. A RFID system, also known as a gate automation system, can solve these problems by reducing the time of gate management with a technology that detects number identification plates, helping operators more efficiently perform gate management work. Having said that, with this system, when container damage is detected, gate operators make and keep documents manually. These documents, which are insufficient evidence in proving container damage, result in customer claims. In addition, it is difficult for gate operators and other workers to manage containers, exposing them to danger and accidents. This study suggests that if an automation system is introduced at gates, containers can be managed by a video storage system in order to better document damage The video system maintains information on container damage, allowing operators the ability to search for videos they need upon customer request, also allowing them to be better prepared for customer claims. In addition, this system reduces necessary personnel and risk of accidents near gates by integrating a wide range of work.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.120-129
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• 2023

Marine structures are subject to damage not only from sea salt but also from the adhesion of marine microorganisms and suspended particles, which cause additional damages. In order to prevent this, periodic coating is employed in the case of vessels to maintain the necessary performance. However, it is true that periodic coating is difficult for concrete or steel support structures, and there is a risk of marine environmental pollution. In this study, authors developed an anti-fouling coating agent using eco-friendly materials that possess hydrophilic cellulose nanofibers and AKD(alkyl ketene dimer). To achieve a homogeneous mixture, the content of cellulose nanofibers was fixed at 1 %, and AKD, distilled water, and waste glass were mixed using a digital mixer and homogenizer. The contact angle of the prepared coated surface was observed to be over 130°, indicating sufficient performance even in a water droplet flow test with a 15° slope, suggesting self-cleaning capability. Furthermore, through the analysis of viscosity characteristics at different temperatures, it was confirmed that the application is feasible at room temperature. Microstructure analysis also verified that the coating agent is uniformly applied to the concrete surface.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.83-93
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• 1998

The twin aims of the present study are to develop a PC program for the statistical analysis of the measured cohesion data and to suggest a probabilistic corrosion rate estimation model for longitudinal members of tanker structures. A data analysis for the corrosion rate statistics(i.e., mean, standard deviation) as a function of the corrosion parameters is established for various structural member categories/locations of interest. Development of the computer program is focused on possible operation together with future addition of more corrosion data as they become available. To investigate the influence of the corrosion protection scheme a series of the corrosion analysis varying the life of coating are carried out and several different corrosion models as a function of time are suggested depending on the coating life.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.92-92
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• 2011

최근 건설기술의 발전과 함께 강재 케이블을 이용하는 시설물의 시공이 점점 증가하는 추세이다. 특히 현수교, 사장교와 같은 초장대 교량에 사용되는 케이블은 주거더 및 상판에 의한 하중의 대부분을 지지하는 핵심부재이다. 하지만 이러한 케이블 부재는 부식, 파단 등으로 인한 단면손실이 발생할 수 있고, 이로 인한 손상부의 응력집중으로 인해 시설물 전체의 붕괴로 이어질 수 있는 위험성을 가진다. 따라서 조기에 단면손실을 찾아 사고를 미연에 방지할 수 있는 강재 케이블 비파괴 검사 기술기반의 건전성 모니터링이 필수적이다. 이러한 효율적인 건전성 모니터링을 위해 스마트 센서를 활용한 연구가 활발히 이루어지고 있는데, 그중 대표적인 스마트 센서중 하나인 마그네틱 센서는 높은 신뢰도와 어디에나 적용 가능한 재현성 때문에 구조물 건전성 평가에 적용하기 유용한 기술로 그 적용범위가 선박, 항공등으로 점점 넓어지고 있는 추세이다. 마그네틱 센서는 그 적용대상에 따라 다양한 마그네틱 특성을 활용할 수 있는데, 최근에는 투자율 계측을 통해 케이블의 장력 측정이 가능한 Elasto-Magnetic 센서(E/M 센서)가 개발되었고 그 활용성에 대한 연구가 이뤄지고 있다. 이에 본 연구에서는 E/M 센서를 이용한 강재 케이블 모니터링 기술을 제안하고자 한다. E/M 센서는 본래 케이블의 장력측정을 위해 개발되었지만 본 연구에서는 강재 케이블 부재의 단면손실 검색을 위해 적용하였다. 제안된 기술의 실험적 검증을 위해 E/M 센서를 이용하여 4가지의 다른 직경을 가지는 강봉시편을 E/M 센서헤드의 1차 코일을 통해 자화시키고, 각각의 직경에서 출력전압을 2차 코일을 이용하여 계측하였다. 그 결과 강봉의 직경이 감소함에 따라 출력 전압이 감소함을 보였다. 반복실험을 통해 해상도 및 선형성이 확보되는 최적의 입력전압과 출력전압의 워킹포인트를 선정하였고, 선정된 조건에서 강봉시편을 일정 간격으로 스캔한 결과 단면감소에 따른 선형적인 출력전압 감소와 동시에 단면 변화 지점에서는 추세선에서 크게 벗어난 출력전압 계측값을 나타내었다. 본 실험을 통해 제안된 E/M 센서를 이용한 강재 케이블 모니터링 기술의 유용성 및 적용가능성을 확인할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6440-6445
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• 2014

In steel structures, including ships and offshore structures, defects induced during construction or in use causes cracks and damages. Calculation of the stress intensity factor (SIF) K is one method for crack analysis by fracture mechanics approach. In this paper, an evaluation of K was carried out using the J integral. In particular, in this study, a CT specimen was used to calculate the J integral. In the evaluation, 859 nodes and 1618 elements were used for the J integral calculation of the CT specimen by the in-house FEM program. A comparison of the result with the ASTM formula showed that the results from the current research of the J integral was in the 99% coincidence interval. Overall, cracks in this study can be studied satisfactorily by the J integral from the above mesh size.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1074-1083
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• 2010

Recently sloshing that fluid in fuel tank is undulating by the external force during motion of automobile, ship and aircraft is greatly affecting by damaging the inside of structure. It's most important to precisely analyze the behavior of fluid by computational fluid dynamics for minimizing the effect of sloshing for the loaded fuel. This study characterized volume of fluid and pressure according to the length and number of vertical baffle and horizontal baffle in fuel tank for Kia Frontier cargo and analyzed for reduction of sloshing during driving on corner and hill by using ADINA-CFD. As a result of analysis, the optimum length for sloshing reduction shows 0.19 m for vertical baffle and 0.08 m for horizontal baffle. And it shows that vertical baffle is better for the reduction effect of sloshing during driving on corners, on the other hand, horizontal baffle is effective and stable during driving on hills.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.946-952
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• 2013

Large scale fire tests were conducted to develop water mist nozzles as a component of fixed water- based fire fighting systems for Ro-Ro spaces and special category spaces. Fire scenarios for this system consist of two cases which are for cargo fire in a simulated truck and for passenger vehicle fire, and each case has 3 different tests according to the position between fixed water mist nozzles and fire source. Every experiment proceeded for 30 minutes and acceptance criteria were based on gas temperature, fuel package's damage and ignition of targets. This study primarily dealt with the experimental results of cargo fire and focused on fire suppression capability in accordance with discharge pressure, flow rate and flow characteristics like swirl and penetration of the developed water mist nozzles. It appeared that low pressure water mist nozzles with about 40 L/min were able to control fire occurred in Ro-Ro spaces.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.3
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• pp.281-287
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• 2011

This paper explains the basic theory and a new development of for the residual strength prediction program of the asymmetrically damaged ships, being capable of searching moment-curvature relations considering neutral axis mobility. It is noted that moment plane and neutral axis plane should be separately defined for asymmetric sections. The validity of the new program is verified by comparing moment-curvature curves of 1/3 scaled frigate model where the results from new algorithm well coincide with experimental and nonlinear FEA results for intact condition and with nonlinear FEA results for damaged condition. Applicability of new algorithm is also verified by applying VLCC model to the newly developed program. It is proved that reduction of residual strengths is visually presented using the new algorithm when damage specifications of ABS, DNV and IMO are applied. It is concluded that the new algorithm shows very good performance to produce moment-curvature relations with neutral axis mobility on the asymmetrically damaged ships. It is expected that the new program based on the developed algorithm can largely reduce design period of FE modeling and increase user conveniences.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.6
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• pp.710-718
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• 2008

This paper presents a simple and fast approach to plan the arrangement of supports and to do a ship docking analysis. The unpredicted structural damages often happen from a docking works as the size of ships are getting larger and larger. In docking a ship, excessive reaction forces from supports are primary causes of the structural damage. The grillage analysis method is employed to simply calculate only the reaction forces at supports. The grillage modeling strategies are proposed to improve the accuracy. In this paper, the results obtained by the proposed approach are compared with those of the current whole-ship FEA for typical types of ships. Comparison shows that the results from the present grillage approaches are reasonably in a good agreement with the 3-D full F.E one. Finally, an integrated program developed for the ship docking analysis is described.