• 대한조선학회논문집
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• 제49권3호
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• pp.227-231
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• 2012

In this study, a plastic hardening constitutive equation for steels of polar class vessels at low temperature is proposed. The equation was derived using the experimental data obtained from tensile tests at room and low temperatures. Tensile tests at low temperature are both costly and time consuming because an expensive cold chamber is necessary and it takes too much time to cool down a specimen to set temperature. Using the proposed plastic hardening constitutive equation the plastic hardening characteristics of steels for polar class vessels at low temperature can be easily predicted from the tensile test results at room temperature.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.463-468
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• 2011

The prospect of Arctic trade transportation opening on a year-round basis creates a vast opportunity of exploring untapped resources and shortened navigational routes. However, the environment's remoteness and lack of technical experiences remains a big challenge for the maritime industry. With this, engine designers and makers are continually investigating, specifically optimizing propulsion shafting system design, to meet the environmental and technical challenges of the region. Further, classification societies recognize the need to upgrade the Unified Rules concerning elements to meet current Polar requirements. Hence in this paper, excitation torque calculation on Polar class vessels propulsion shafting system will be reviewed. The propeller - ice interaction load effect, which is a main consideration of excitation source of Polar Class propulsion shafting system, on shaft design calculation will be analyzed.

• 대한조선학회논문집
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• 제49권3호
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• pp.232-238
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• 2012

The effects of temperature on the structural behavior of polar class vessels have been experimentally and numerically investigated. Experiments were carried out on single frame structures made of steel material, DH36, which is used for outer shell of the vessels making transit through the polar region. A knife edge type striker was dropped down onto single frame structures. The temperatures of the single frames were set to $-30^{\circ}C$, $-50^{\circ}C$ and room temperature. The deflection around the mid-point of the single frame was measured and numerically simulated using finite element model. Strain rate effect on the structural behavior has been investigated and turned out that the strain rate effect can be neglected. From the results of the experiment and numerical analyses, it has been noticed that the permanent deflection at lower temperature was reduced due to a temperature hardening of material as expected.

• 대한조선학회논문집
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• 제45권5호
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• pp.513-522
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• 2008

In this paper, one of the widely-used ice resistance prediction methods, introduced by Spencer(1992) of the Institute for Ocean Technology, Canada, is reviewed. Spencer's component-based scaling system for ship-ice model tests is analysed to estimate the ice resistance of various types of icebreaking vessels (Canadian MV Arctic, Terry Fox, R-Class icebreaker, US icebreakers Polar Star and Healy, Russian SA-15 cargo ships, Japanese PM Teshio and a model ship). The general form and the non-dimensional coefficients in ice resistance prediction formula are obtained using the published ice model test and full-scale sea trial data. The applicability of Spencer's method on R-Class icebreaker is discussed to estimate ice resistance for the larger icebreaking cargo vessels. Additional parameters to account for the difference in hull forms of icebreakers and cargo vessels are recommended to be included in the Spencer's original ice resistance prediction formula.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.376-384
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• 2018

Selection of suitable ice class for ships operation is an important but not simple task. The increased exploitation of the Polar waters, both seasonal periods and geographical areas, as well as the introduction of new international design standards such as Polar Code, reduces the relevancy of using existing experience as basis for the selection, and new methods and knowledge have to be developed. This paper will analyse what can be the limiting ice thickness for ships navigating in the Russian Arctic and designed according to the Finnish-Swedish ice class rules. The permanent deformations of ice-strengthened shell structures for various ice classes is determined using MT Uikku as the typical size of a vessel navigating in ice. The ice load in various conditions is determined using the ARCDEV data from the winter 1998 as the basic database. By comparing the measured load in various ice conditions with the serviceability limit state of the structures, the limiting ice thickness for various ice classes is determined. The database for maximum loads includes 3-weeks ice load measurements during April 1998 on the Kara Sea mainly by icebreaker assistance. Gumbel 1 distribution is fitted on the measured 20 min maximum values and the data is divided into various classes using ship speed, ice thickness and ice concentration as the main parameters. Results encouragingly show that present designs are safer than assumed in the Polar Code suggesting that assisted operation in Arctic conditions is feasible in rougher conditions than indicated in the Polar Code.

• 해양환경안전학회지
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• 제23권1호
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• pp.40-46
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• 2017

본 연구는 LS-DYNA 971 을 이용하여 내빙 구조 선박과 빙산 모형 간의 충돌 시험을 수행 후 북극해 운항 선박의 내빙 능력을 분석하였다. 국제선급연합회(IACS)의 Unified Requirements for Polar ship(URI) 규정을 바탕으로 FEM 선박 모형에 내빙 구조를 적용하였으며, 빙산 모형에는 Elastic-perfect plastic 물성과 Tsai-Wu 항복 곡면을 적용하였다. 또한 실험 결과 비교를 위하여 내빙 구조를 갖추지 않은 일반선박 모형과의 충돌 시험도 수행하였다. 실험 결과 일반 구조 선박의 구형 선수에 빙산 모형에 의해 움푹 들어간 약 1.8 미터 깊이의 선체 손상이 발생하였으나, 내빙 구조 선박의 충돌에서는 약 1.0 미터 깊이의 선체 손상만이 발생하였다. 또한 일반 구조 선박과 충돌한 빙산모형은 원형의 상태를 거의 유지한 반면, 내빙 구조 선박과 충돌한 빙산 모형은 내빙 구조의 구형 선수에 의해 빙산이 일부 파괴되는 현상이 발견되었다.

• 한국소음진동공학회논문집
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• 제21권12호
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• pp.1166-1176
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• 2011

연중 운항할 수 있는 북극 항로 개설에 따른 전망으로 미개발 천연자원의 탐사와 짧아진 항로로 많은 기회를 부여하고 있다. 이는 환경과 거리가 먼 그리고 기술적인 경험 부족으로 해사 분야에서 커다란 도전으로 남아 있다. 엔진 설계자와 제작자는 이 지역에서 환경적 그리고 기술적으로 적합한 최적화된 추진시스템을 위하여 계속적인 조사를 하고 있고, 국제선급연합과 선급에서 인정하고 있는 대빙 등급 선박의 추진축계 설계를 위하여 통일된 규격의 여러 가지 특성에 대하여 개선할 필요가 있다. 대빙 등급 선박의 추진축계 시스템에서 주 기진력은 프로펠러와 빙 하중의 상호작용으로 인식하고 있고 국제선급연합에서는 빙의 파쇄와 충격하중으로만 간주하고 있지만, 추진축계 설계에 있어 시스템에 대한 여러 가지 인자의 특징을 고려하여야 한다. 이 논문은 종류가 다른 추진 시스템의 동적 응답에 영향을 주는 인자들에 평가하고 있고, 추후 추진 시스템의 설계단계에서 이러한 인자들이 충분한 역할을 갖는 것을 감안 고려해줄 것을 기대하고 있다.

• 대한조선학회논문집
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• 제48권2호
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• pp.171-177
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• 2011

Tensile tests were conducted at low temperatures for the steel materials which are used for outer shell of the vessels making transit through the polar regions. The selected steel materials were GL-DH32, GL-DH36 and GL-EH36. In comparison with the results at room temperature, the yield stress increases approximately by 10 to 13 percent at $-30^{\circ}C$ and by 13 to 19 percent at $-50^{\circ}C$ while the tensile strength increases about by 9 percent at $-30^{\circ}C$ and 11 to 14 percent at $-50^{\circ}C$. To obtain true stress-true strain, i.e. correct plastic hardening characteristics, Bridgman's(1952) necking correction formula was introduced taking triaxial state of stresses after onset of diffuse necking into consideration. Photographs of fractured surfaces were taken by using Scanning Electron Microscope immedately after tensile tests completed and one for GL-EH36 has been presented in this paper.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.555-558
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• 2013

A type of electric propulsion employed by specialized purpose vessels or offshore is the azimuth thruster. Azimuth thruster application had been increasing recently and resulted to excellent vessel maneuverability. However, this system is very complex and some of its major component being exposed under the seawater level presents difficulty in sealing design. For Polar class icebreaker operating in extreme sea condition, this requires a high level of reliability and safety. In this study, the characteristics of lubricating orifice pipe structural vibration installed at the lower reduction gear were investigated and analyzed through beam analysis theory and comparison of experiments. Propeller excitation and the resonant modes of vibration causing excessive vibration and suitable countermeasures to prevent damage due to vibration fatigue on the pipe are presented.

• 대한조선학회논문집
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• 제54권1호
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• pp.43-48
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• 2017

In recent years, the demand for ships and offshore platforms that can navigate and operate through the Arctic Ocean has been rapidly increasing due to global warming and large reservoirs of oil and natural gas in the area. Winterization design is one of the key issues to consider in the robust structural safety design and building of ships that operate in the Arctic and Sub-Arctic regions. However, international regulations for winterization design in Arctic condition regulated that only those ships and offshore platforms with a Polar Class designation and/or an alternative standard. In order to cope with the rising demand for operating in the Arctic region, existing and new Arctic vessels with a Polar Class designation are lacking to cover for adequate winterization design with HSE philosophy. Existing ships and offshore platform was not designed based on reliable data based on numerical and experiment studies. There are only designed as a performance and functional purposes. It is very important to obtain of reliable data and provide of design guidance of the anti-icing structures by taking the effects of low temperature into consideration. Therefore, the main objective of this paper reconsiders anti-icing design of aluminum helideck using the heating cable. To evaluate of reliable data and recommend of anti-icing design method, various types of analysis and methods can be applied in general. In the present study, finite element method carried out the thermal analysis with cold chamber testing for performance and capacity of heating cables.