• 한국해안·해양공학회논문집
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• 제26권2호
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• pp.103-111
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• 2014

크기가 작은 다수의 부이들이 원형으로 배열되어 있을 때 부이를 통한 추출 파워를 포텐셜이론 통하여 살펴보았다. 부이의 크기와 배열 간격이 수심과 파장 그리고 설치면적의 반경에 비하여 작다는 가정 아래에서 다수부이로 채워진 수면에서의 경계조건식을 유도하고 이를 포함한 경계치문제를 고유함수전개법을 이용하여 해석하였다. 추출 파워와 입사파 에너지의 비인 취득 폭을 packing ratio, 배열 반경, 그리고 PTO 감쇠계수를 바꿔가면서 살펴보았다. 또한 다수의 소형 부이를 원형 배열하였을 때 추출된 파력이 같은 잠긴 체적을 갖는 대형 단일 부이보다 효율적임을 계산을 통하여 밝혔다.

• 한국전산구조공학회논문집
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• 제15권4호
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• pp.639-647
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• 2002

본 연구에서는 원주형 절취 독본(dogbonc) 내진 접합부 도입에 따른 철골모멘트골조의 횡강성 감소 정도를 용이하게 산정할 수 있는 실용적 해석기법을 제안하였다. 된 연구의 방안은 원래의 원주형 절취 형상의 독본에서 발생하는 신장량과 동일한 크기의 신장량이 유발되도록 등가의 균등한 유효폭을 갖는 독본 형상으로 치환하는 것에 근거하고 있다. 등가 유효폭을 도입하는 목적은 공액보법을 적용하여 보의 휨변형에 의한 골조의 횡변위 성분을 유도할 때 수행되는 전분을 해석적으로 하기 위함이다. 이러한 접근법의 타당성을 먼저 검증된 유한요소해석모델에 의해 확인한 후, 기둥, 패널존 그리고 보의 변형에서 기인하는 골조의 횡변위 성분을 독본의 존재를 고려하여 해석적으로 유도하였다. 이 유도결과를 이용한 사례분석에 의할 때, 독본의 도입에 따른 횡변위 증가율은 2%∼3%(횡강성 감소율로는 1%∼2%) 정도로서 실무적으로 무시할 수 있는 크기로 나타났다.

• 융합정보논문지
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• 제9권7호
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• pp.33-40
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• 2019

최근 항공 관련 산업이 활성화됨에 따라 복합재 해석 소프트웨어의 범용화가 요구되고 있다. 지금까지는 복합재 해석에 상용 소프트웨어를 주로 사용해 왔으나 고가의 가격과 제한적인 기능으로 인해 사용에 어려움을 겪어왔다. 이런 문제를 해결하기 위해 해석 절차를 모두 온라인화하고 범용화한 면내 및 코너 부외 파손 자동 해석 소프트웨어가 최근에 개발되었다. 그러나 이들은 다중의 파손 기준으로 동시에 해석할 수 없는 단점이 있었다. 본 논문에서는 CUDA 코어를 장착한 GPU에서만 동작하는 병렬 처리 플랫폼을 이용하여 다중의 파손 기준에 대한 해석을 동시에 처리하면서 처리 속도를 획기적으로 향상시키는 방법을 제안한다. 방대한 구조물 데이터에 대해서 해석 처리 속도를 실험하였을 때 만족할 만한 결과를 얻었다.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1773-1785
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• 1997

The cooling stage is the very critical and most time consuming stage of the injection molding process, thus it cleary affects both the productivity and the part quality. Even through there are several commercialized package programs available in the injection molding industry to analyze the cooling performance of the injection molding coling stage, optimization of the cooling system has npt yet been accomplished in the literature due to the difficulty in the sensitivity analysis. However, it would be greatly desirable for the mold cooling system designers to have a computer aided design system for the cooling stage. With this in mind, the present study has successfully developed an interated computer aided design system for the injection molding cooling system. The CAD system utilizes the sensitivity analysis via a Boundary Element Method, which we recently developed, and the well-known CONMIN alforuthm as an optimization technique to minimize a weighted combination (objective function) of the temperature non-uniformity over the part surface and the cooling time related to the productivity with side constranits for the design reality. In the proposed objective function , the weighting parameter between the temperature non-uniiformity abd the cooling time can be adjusted according to user's interest. In this cooling system optimization, various design variable are considered as follows : (i) (design variables related to processing conditions) inlet coolant bulk temperature and volumetric flow rate of each cooling channel, and (ii) (design variables related to mold cooling system design) radius and location of each cooling channel. For this optimum design problem, three different radius and location of each cooling channel. For this optimum design problem, three different strategies are suffested based upon the nature of design variables. Three sample problems were successfully solved to demonstrated the efficiency and the usefulness of the CAD system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.185-190
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• 2001

Rotating disks are used in various machines such as floppy disks, hard disk, turbines and circular sawblades. The problems of vibrations of rotating disks are important in improving these machines. Many investigators have dealt with these problem. Specially, vibrations of a rotating flexible disk taking into account the effect of air is difficult problem in simulation. The governing equation of a rotating flexible disk coupled to the surrounding fluid is investigated by a simple mathematical model. And several important parameters concerned with the stability of a rotating flexible disk are defined. Coupling strength between air and rotating flexible disk is proportional to square of disk radius directly and square root of the all of bending rigidity, disk density and thickness inversely. Lift-to-damping coefficient has relation to the onset of disk flutter.

• Structural Engineering and Mechanics
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• 제45권1호
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• pp.69-93
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• 2013

The present study deals with the dynamics of the flapwise (out-of-plane) vibrations of a rotating, internally damped (Kelvin-Voigt model) tapered Bernoulli-Euler beam carrying a heavy tip mass. The centroid of the tip mass is offset from the free end of the beam and is located along its extended axis. The equation of motion and the corresponding boundary conditions are derived via the Hamilton's Principle, leading to a differential eigenvalue problem. Afterwards, this eigenvalue problem is solved by using Frobenius Method of solution in power series. The resulting characteristic equation is then solved numerically. The numerical results are tabulated for a variety of nondimensional rotational speed, tip mass, tip mass offset, mass moment of inertia, internal damping parameter, hub radius and taper ratio. These are compared with the results of a conventional finite element modeling as well, and excellent agreement is obtained.

• 전기전자학회논문지
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• 제2권1호
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• pp.160-165
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• 1998

본 연구에서는 2차원 자계 해석 프로그램을 이용하여 평판형 브러시레스 직류 전동기의 자계 해석을 위한 방법을 제시하였다. 정확한 자계 해석을 위해서는 3차원 자계 해석이 필요하지만 많은 시간 및 비용이 요구되는 단점이 있다. 따라서 본 연구에서는 자계 해석을 위하여 3차원 문제를 해당 자석의 평균 반지름에 대한 원통방향의 단면으로 해석하여 2차원 경계치 문제로 축소시켰다. 본 방법을 이용할 경우 시스템의 크기 및 형태에 관계없이 정확한 2차원 자계해석 결과가 합리적으로 얻어지게 된다.

• 한국자동차공학회논문집
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• 제21권5호
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• pp.25-33
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• 2013

All-wheel steering (AWS) system is applied to articulated vehicles to reduce turning radius. The swing-out suppression algorithm is applied to AWS ECU, a key component of AWS system. The swing-out suppression algorithm applied to AWS ECU has a problem when velocity of vehicle is changed. In this paper, new algorithm based on moving distance that solve velocity problem is proposed. The HILS simulation and the test articulated bus is used to validate algorithm.

• Structural Engineering and Mechanics
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• 제58권4호
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• pp.719-729
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• 2016

The main objective of the present paper is to study the effect of the yield criterion on the magnitude of the strain rate and plastic work rate intensity factors in axisymmetric flow of isotropic incompressible rigid perfectly plastic material by means of a problem permitting a closed-form solution. The boundary value problem consisting of the axisymmetric deformation of a plastic tube is solved. The outer surface of the tube contracts. The radius of the inner surface does not change. The material of the tube obeys quite a general yield criterion and its associated flow rule. The maximum friction law is assumed at the inner surface of the tube. Therefore, the velocity field is singular near this surface. In particular, the strain rate and plastic work rate intensity factors are derived from the solution. It is shown that the strain rate intensity factor does not depend on the yield criterion but the plastic work rate intensity factor does.

• Structural Engineering and Mechanics
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• 제45권2호
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• pp.259-275
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• 2013

Free vibration of symmetric angle-ply layered conical shell frusta of variable thickness is analyzed under shear deformation theory with different boundary conditions by applying collocation with spline approximation. Linear and exponential variation in thickness of layers are assumed in axial direction. Displacements and rotational functions are approximated by Bickley-type splines of order three and obtained a generalized eigenvalue problem. This problem is solved numerically for an eigenfrequency parameter and an associated eigenvector of spline coefficients. The vibration of three and five-layered conical shells, made up of two different type of materials are considered. Parametric studies are made for analysing the frequencies of the shell with respect to the coefficients of thickness variations, length-to-radius ratio, length-to-thickness ratio and ply angles with different combination of the materials. The results are compared with the available data and new results are presented in terms of tables and graphs.