• 대한조선학회논문집
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• 제44권4호
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• pp.439-444
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• 2007

A damage analysis simulator, which is applicable for evaluating the residual strength of damaged ship, was developed in this paper. For this process, CDM (Continuum Damage Mechanics) approach has been implemented to the simulator by virtue of the numerical technique for evaluation of crack initiation and/or enlargement. A damage calculation program has been linked with a commercial finite element analysis code (NASTRAN) and a ultimate strength evaluation program (LSAP) in order to assess residual strength of damaged ship. As a results of series calculation for the frigate model, giving the quantitative structural damage to the ultimate strength evaluation, a residual strength with damage is predicted to be at least 70 percentage lower than the case of intact condition. It was found that the proposed technique can be used as a design support tool in the field of simulation based ship design.

• 한국구조물진단유지관리공학회 논문집
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• 제15권1호
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• pp.77-84
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• 2011

연속보를 대상으로 한 재료비선형 전달행렬법을 제시하였으며, Gauss-Lobatto 적분법을 사용하여 보의 강성행렬로부터 전달행렬을 도출한다. 전달행렬법에서는 유한요소해석법과는 달리 각 절점의 자유도 수에 상관없이 일정한 미지값만을 가지게 되므로 선형해석뿐만 아니라 비선형해석에서도 빠른 연산속도를 보인다. 연속보에 대한 비선형 해석의 적용 예를 통한 비교 결과, 재료비선형 전달행렬법이 변위-모멘트, 변위-하중, 곡률-모멘트의 관계에서 유한요소해석법에 비해 효율적인 것으로 평가되었다.

• 한국군사과학기술학회지
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• 제11권4호
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• pp.83-91
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• 2008

The development of the equal channel angular pressing(ECAP) process in metals has recently provided a feasible solution to produce ultra-fine or nano-grained bulk materials with tailored material properties. However, ECAP process is difficult to scale up commercially due to requirements of an excessive load. In this paper, a new Hybrid-ECAP process with torsional die is considered to obtain materials of ultra-fine grain structure under low forming load. An upper bound analysis and numerical simulation (DEFORM 3D, a commercial FEM code) are carried out on the torsional die. By the upper bound analysis, analytical expression for the compression force and rotation speed are obtained. By the FEM analysis, the distribution of strain, stress and deformation are obtained. These results show that the Hybrid-ECAP is a useful process because this process can obtain the homogeneous deformations with relatively low forming load. Additionally, due to decreased forming load, die life can be improve.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.1059-1063
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• 2005

Development of a feed drive-system with high speed, positioning accuracy and thrust has been an important issue in modern automation systems and machine tools. Linear motors can be used as an efficient system to achieve such technical demands. By eliminating mechanical transmission mechanisms such as ball screw or rack-pinion, much higher speeds and greater acceleration can be achieved without backlash or excessive friction. However, due to great power loss and magnetic attraction of the linear motors heating and deflection problems occur. Therefore, it is necessary to design strong structure, cooling device with high efficiency and light weight construction in designing stage of linear motors. This paper presents an investigation into a structural design of linear motor system. In this research, a new concept of moving table with high stiffness and of cooling plate is also introduced. Structure analyses are performed by using a commercial code ANSYS in order to evaluate the design safety.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.810-812
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• 2008

Previously study on structural design of the main wing of the twenty-seat class WIG(Wing in Ground Effect) craft. In the final design, three spars construction was selected for safety in the critical flight load, and the Carbon-Epoxy material was selected for lightness and structural stability. In this study, the forced vibration analysis was performed on the composite main wing structure of the twenty-seat class WIG craft with two-stroke pusher type reciprocating engine. The vibration analysis based on the finite element method was performed using a commercial FEM code, MSC/NASTRAN. Excitations for the frequency response analysis were assumed as the H-mode(horizontal mode), the V-mode(vertical mode) and the X-mode(twisted mode) which are typical main vibration modes of engine. And excitations for the transient response analysis were assumed as the L-mode(longitudinal mode) with the oscillating propeller thrust which occurs in operation. According to the result of forced vibration analysis, structural design was modified to reduce the vibrations.

• 한국해양공학회지
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• 제33권5호
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• pp.411-420
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• 2019

It is essential to design crashworthy marine structures for operations in Arctic regions, especially ice-covered waters, where the structures must have sufficient capacity to resist iceberg impact. In this study, a numerical analysis of a colliding accident between an iceberg and stiffened plates was carried out employing the commercial finite element code ABAQUS/Explicit. The ice material model developed by Liu et al. (2011) was implemented in the simulations, and its availability was verified by performing some numerical simulations. The influence of the ambient temperature on the structural resistance was evaluated while the local stress, plastic strain, and strain energy density in the structure members were addressed. The present study revealed the risk of fracture in terms of steel embrittlement induced by ambient temperature. As a result, the need to consider the possibility of brittle failure in a plate-stiffener junction during operations in Arctic regions is acknowledged. Further experimental work to understand the structural behavior in a plate-stiffener junction and HAZ is required.

• 한국해양공학회지
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• 제37권3호
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• pp.111-121
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• 2023

This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

• 한국전산구조공학회논문집
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• 제21권5호
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• pp.493-504
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• 2008

본 논문은 유한요소법을 이용하여 Edwards MIRA 기계식인공심장판막에 높은 혈압이 작용할 때 발생하는 비선형 탄성 변형률을 계산하였다. 상용 유한요소해석 코드인 MISA의 수치해석기법을 채택하여 Edwards MIRA 기계식인공심장판막에 대하여 판첨의 두께를 조금씩 변화시키면서 구조해석을 수행하여 판첨내에 발생하는 최대응력이 판첨재질(Si-Alloyed PyC)의 항복응력보다 작도록 판첨 표면에 혈압이 작용할 시에 판첨에 발생하는 탄성변형률을 계산하였다. 따라서 높은 혈압 작용 시에 판첨의 재질에 따른 물질비선형변형률 보다는 구조적인 기하학적 형강비선형변형률만이 예상되기 때문에 오직 기하학적 형상비선형성만 가정되었다. 계산된 선형, 비선형 변형률들은 발생한 탄성변형률의 비선형성을 확인하기 위하여 비교검토 되었다 비교검토 결과는 비교적 매우 얇은 판첨에서 혈압이 높게 작용할 때에 높은 탄성변형률이 발생하는 것을 보여주고 있다. 그렇지만 동시에 해석결과는 매우 낮은 혈압이나 매우 두꺼운 두께의 판첨에서는 높은 혈압이 작용하더라도 매우 작은 탄성변형률이 발생함을 보여주고 있다. 따라서 기계식인공심장판막의 구조설계 시 비선형 구조해석은 꼭 필요함을 알 수 있다.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.672-679
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• 2018

본 논문은 최적설계 시스템을 이용한 형상설계 방법론에 대해 설명하고 있으며, 일반적으로 3차원 해석은 설계를 위해 반드시 필요하다. 퍼지지식처리 수법과 계산기하학적 기법에 바탕을 둔 자동화된 유한요소 메쉬 생성 기법은 상용화된 유한요소해석코드와 솔리드모델러와 함께 시스템에 결합되어 있다. 또한, 다층형 신경망의 도움과 함께 개발된 시스템은 다차원 설계변수 공간에 존재하는 여러 만족하는 설계해인 디자인윈도우를 얻을 수 있게 해준다. 개발된 최적화 설계 시스템 사용된 부품을 평가하는데 성공적으로 적용하였다. 사이드 하우징 브라켓을 현장에서 사용되어지는 굴삭기의 힘과 유압브레이커의 작용하는 응력을 응력 게이지로 사이드 하우징 브라켓의 크랙 발생부위에 부착하여 최대응력이 얼마나 걸리는지를 측정하였다. 적용하는 대상을 현장에서와 동일한 조건하에서 최대응력이 허용응력보다 같거나 적게 하고, 기존형상 유지, 재질은 SM490, 중량 최소화 안전계수는 3으로 하여, 최대응력 값에 대한 해석을 수행하였다. 구조가 비교적 간단한 36톤용 사이드 하우징 브라켓을 최적화하였지만, 다른 클래스의(톤수 별) 사이드 하우징 브라켓 적용 시 품질향상에 크게 기여하리라 생각된다.

• Structural Engineering and Mechanics
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• 제52권3호
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• pp.613-632
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• 2014

In the early design stage of ships, the two most important structural analyses are performed to identify the structural capacity and safety. The first step is called global strength analysis (longitudinal strength analysis or hull girder strength analysis) and the second step is local buckling analysis (stiffened panel strength analysis). This paper deals with the ultimate strength performance of Arctic Sea Route-going commercial ships considering the effect of low temperature. In this study, two types of structural analyses are performed in Arctic sea conditions. Three types of ship namely oil tanker, bulk carrier and container ship with four different sizes (in total 12 vessels) are tested in four low temperatures (-20, -40, -60 and $-800^{\circ}C$), which are based on the Arctic environment and room temperature ($20^{\circ}C$). The ultimate strength performance is analysed with ALPS/HULL progressive hull collapse analysis code for ship hulls, then ALPS/ULSAP supersize finite element method for stiffened panels. The obtained results are summarised in terms of temperature, vessel type, vessel size, loading type and other effects. The important insights and outcomes are documented.