• 제목/요약/키워드: Non-uniform B-spline Surface

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Free Vibrations of Plates and Shells with an Isogeometric RM Shell Element

  • LEE, Sang Jin
    • Architectural research
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    • 제18권2호
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    • pp.65-74
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    • 2016
  • Free vibration analysis of plates and shells is carried out by using isogeometric approach. For this purpose, an isogeometric shell element based on Reissner-Mindlin (RM) shell theory is developed. Non-uniform rational B-spline surface (NURBS) definition is introduced to represent the geometry of shell and it is also used to derive all terms required in the isogeometric element formulation. New anchor positions are proposed to calculate the shell normal vector. Gauss integration rule is used for the formation of stiffness and mass matrices. The proposed shell element is then used to examine vibrational behaviours of plate and shell structures. From numerical results, it is found to be that reliable natural frequencies and associated mode shapes can be predicted by the present isogeometric RM shell element.

등기하해석법을 이용한 자유진동 평면구조물의 위상최적화 (Topology Optimization of Plane Structures under Free Vibration with Isogeometric Analysis)

  • 이상진;배정은
    • 대한건축학회논문집:구조계
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    • 제34권6호
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    • pp.11-18
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    • 2018
  • Isogeometric concept is introduced to find out the optimum layout of plane structure under free vibration. Eigenvalue problem is formulated and numerically solved in order to obtain natural frequencies and mode shapes of plane structures. For the exact geometric expression of the structure, the Non-Uniform Rational B-spline Surface (NURBS) basis functions is employed and it is also used to define the material density functions. A node-wise design variables is adopted to deal with the updating of material density in topology optimization (TO). The definition of modal strain energy is employed to achieve the maximization of fundamental frequency through its minimization. The verification of the proposed TO technique is performed by a series of benchmark test for plane structures.

등기하개념을 이용한 평면구조물의 자유진동해석 (Free Vibration Analysis of Plane Structures with Isogeometric Concept)

  • 이상진
    • 대한건축학회논문집:구조계
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    • 제35권9호
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    • pp.171-182
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    • 2019
  • Isogeometric concept is introduced to carry out free vibration analysis of plane structures. The geometry of structures is represented by using non-uniform rational B-spline surface (NURBS) and its basis function is consistently used in the formulation of plane stress element. In addition, multi-patch strategy is introduced to deal with the openings in building. The performance of the present isogeometric plane stress element is investigated by using five numerical examples. From numerical results, it is found to be that the isogeometric concept can successfully identify reliable natural frequencies and associated mode shapes of plane structures with/without openings in efficient way.

종모양 분포 변환함수를 이용한 선형최적화 기법에 관한 연구 (Hull Form Optimization by Modification Function of Bell-shaped Distribution)

  • 최희종;김희정;전호환;정광효
    • 대한조선학회논문집
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    • 제43권5호
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    • pp.550-559
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    • 2006
  • A design procedure for a ship with minimum total resistance was developed using a numerical optimization method called SQP(Sequential Quadratic Programming) and a CFD technique based on the Rankine source panel method with the nonlinear free surface boundary conditions. During the whole optimization process the geometry of the hull shape was represented based on the NURBS(Non-uniform rational B-spline) technique and the modification of the hull shape was controlled using the Bell-shaped distribution function to keep the fairness of the hull shape before and after the hull modification. The numerical analysis was carried out using 4000TEU container ship in the towing tank facility installed in the Pusan national university to know the validity of the developed algorithm for this study. As the results of the numerical analysis it proved that the resistance of the optimized hull is conspicuously reduced in comparison with the original hull in a wave-making resistance point of view.

NURB 곡선을 이용한 가스절연 원통형 관로 내에서의 전계 최적화 (Electric Field Optimization using the NURB curve in a Gas-Insulated Switchgear)

  • 한인수;김응식;민석원;이준호;박종근;이태형;박춘수
    • 전기학회논문지
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    • 제58권3호
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    • pp.548-558
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    • 2009
  • This paper attempts to develop an algorithm which optimizes the electric field through the so-called NURB(Non-Uniform Rational B-spline) curve in order to improve the insulation capacity. In particular, the NURB curve is a kind of interpolation curve that can be expressed by a few variables. The electric field of a conductor is computed by Charge Simulation Method(CSM) while that of a spacer by Surface Charge Method(SCM); this mixed calculation method is adopted for the electric field optimization. For calculation of the initial and optimal shapes, the Gauss-Newton method, which is quite easy to formulate and has slightly faster convergence rate than other optimization techniques, was used. The tangential electric field, the total electric field, and the product of the tangential electric field and area (Area Effect) were chosen as the optimization objective function by the average value of electric field for the determined initial shape.

형상모델 기반 선박계산 전산프로그램 개발 (Development of a Ship Calculation Program Based On the Geometric Model)

  • 박상수;이규열
    • 대한조선학회논문집
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    • 제36권2호
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    • pp.121-134
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    • 1999
  • 본 논문에서는 유체 정역학적 계산, 용적 계산, 비손상 및 손상시 복원성 그리고, 선형 변환을 수행할 수 있는 객체 지향적 선박계산 전산프로그램을 개발하였다. 선박 계산을 위한 선형과 구획 형상을 NURBS(Non-Uniform Rational B-Spline) curve wire-frame model로 표현하고, 선형과 구획 단면 형상을 직접 3차원 평면과의 교차 계산을 통해 유체 정역학적 계산과 용적 계산을 수행하였다. 선박의 3차원 정역학적 평형 상태 방정식을 정식화하고, 순차적으로 선형화하여 힘과 모멘트 평형상태의 자세를 구하였다. 상용 선박 계산 프로그램의 결과와 비교하여, 개발 프로그램을 쉽고, 편리하게 사용할 수 있고, 계산의 정확도가 높음을 확인할 수 있었다.

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파라메트릭 기법을 고속 단동선의 NURBS 모델링 (Construction of NURBS Model for Preliminary High-Speed Monohull Design Based on Parametric Approach)

  • 남종호
    • 한국해양공학회지
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    • 제20권3호
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    • pp.82-87
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    • 2006
  • An approach to model a high-speed monohull vessel is introduced. The high-speed monohull form belonging to the category of multihull is drawing new attention, due to the rapidly growing trend of fast passenger ships and military purpose. Multihull forms are much thinner in their overall shape, compared to those of the conventional commercial vessels. Moreover, the parent hull forms are not readily obtainable when a new design is intended, which makes it hard to perform various technical calculations in terms of hull optimization, hydrodynamic computation, structural design, and so forth. In this paper, a parametric technique is used to design a high-speed hull form. To model a hull form, NURBS (Non Uniform Rational B-Spline) representation is used. The goal of research is to provide a fast and convenient tool to design an initial hull form with fewer parameters available in the early design stage. The technique employed in this paper will be applied to the design of multihull forms, such as catamaran, trimaran, and semi-swath.

비정형 건축물의 외장 패널의 선제작과 시공을 위한 역설계 프로세스와 사례 분석을 통한 시사점 도출 (Implications Deduction through Analysis of Reverse Engineering Process and Case Study for Prefabrication and Construction of Freeform Envelop Panels)

  • 류한국;김성진
    • 한국건축시공학회지
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    • 제16권6호
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    • pp.579-585
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    • 2016
  • 3차원 이미지 스캐닝 기술은 복잡한 비정형 건축물의 외피의 정확한 형상과 위치 데이터를 확보하는데 효과적이다. 3차원 이미지 스캐닝 기술의 세부 과정인 점 군집화, 메쉬표면 분리, 넙스 표면 생성, 파라메트릭 솔리드 모델을 통하여 비정형 건축물의 형상을 구축할 수 있다. 이에 본 연구는 비정형 건축물의 외장재 제작과 시공을 위한 3차원 이미지 스캐닝에 의한 역설계 프로세스와 사례 분석을 통하여 시사점을 도출한다. 본 연구의 결과는 역설계 기술을 사용한 3차원 형상 기술과 설계 요소화 방법을 다양한 건설 프로젝트에 활용할 수 있을 것으로 판단된다.