• 제목/요약/키워드: B-spline surface

검색결과 188건 처리시간 0.02초

플라우 작업 곡면의 컴퓨터 원용 설계 (Computer-Aided Design of Plow Working Surfaces)

  • 정창주;박진식;우상하
    • Journal of Biosystems Engineering
    • /
    • 제17권1호
    • /
    • pp.37-44
    • /
    • 1992
  • This study was intended to develop the design program of the working surface of moldboard-plow by use of the computer-aided design. The mathematical model of the working surfaces of moldboard-plows by use of computer graphics was developed and plotted in two dimension on three major planes. The surfaces of moldboard-plows were represented with "B-spline surface fitting" by selecting the twenty-five three-dimensional data that could well describe the working surface of moldboard-plow. The shape of moldboard-plow on three major planes was drawn for varied design parameters. The representation of the mathematical model for the working surfaces of various types of moldboard-plows was manipulated by translation, rotation and scaling about arbitrary axes in space. By using three-dimensional graphics techique to describe moldboard-plows, it was capable of plotting the three-dimensional shape of moldboard-plow easily and quickly in comparison with the existing design methods that were difficult to grasp the shape of moldboard-plow as a whole. The design theories of moldboard plow and three-dimensional computer graphic technique were applied to find out the improved reversible Jaenggi bottom. It was resulted in the newly developed shape of Jaenggi which may be used for improving the performance compared to existing ones.

  • PDF

최적선형개발에 대한 기초연구 (Fundamental Study for the Development of an Optimum Hull Form)

  • 서광철;최희종;전호환;김문찬
    • 한국해양공학회:학술대회논문집
    • /
    • 한국해양공학회 2003년도 춘계학술대회 논문집
    • /
    • pp.37-42
    • /
    • 2003
  • Fundamental Study for optimizing ship hull form using SQP(sequential quadratic programming) method in a resistance point of view is presented. The Wigley hull is used as an initial hull and numerical calculations are carried out according to various froude numbers. To obtain the ship resistance the wave resistance is evaluated by a Rankine source panel method with nonlinear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of a hull surface is represented and modified by B-spline surface patch. The displacement and the waterplane transverse 2nd moment of inertia of the hull is fixed during the optimization process. And the shp design program called EzHULL is used to draw the lines of the optimized hull form to perform the model test.

  • PDF

A Generalized Scheme for Constructing Polyhedral Meshes of Catmull-Clark Subdivision Surfaces Interpolating Networks of Curves

  • Abbas, Abdulwahed;Nasri, Ahmad
    • International Journal of CAD/CAM
    • /
    • 제5권1호
    • /
    • pp.91-98
    • /
    • 2005
  • This paper presents a scheme for interpolating intersecting uniform cubic B-spline curves by Catmull-Clark subdivision surfaces. The curves are represented by polygonal complexes and the neighborhoods of intersection points are modeled by X-Configurations. When these structures are embedded within a control polyhedron, the corresponding curves will automatically be interpolated by the surface limit of subdivision of the polyhedron. The paper supplies a construction which clearly shows that interpolation can still be guaranteed even in the absence of symmetry at the X-configurations. In this sense, this scheme generalizes an already existing technique by the same authors, thereby allowing more freedom to designers.

MRI 데이터를 이용한 쥐의 경추와 인접한 조직의 유한요소 모델화 (Finite Element Modeling of the Rat Cervical Spine and Adjacent Tissues from MRI Data)

  • 정태은
    • 한국CDE학회논문집
    • /
    • 제17권6호
    • /
    • pp.436-442
    • /
    • 2012
  • Traumatic loading during car accidents or sports activities can lead to cervical spinal cord injury. Experiments in spinal cord injury research are mainly carried out on rabbit or rat. Finite element models that include the rat cervical spinal cord and adjacent soft tissues should be developed for efficient studies of mechanisms of spinal cord injury. Images of a rat were obtained from high resolution MRI scanner. Polygonal surfaces were extracted structure by structure from the MRI data using the ITK-SNAP volume segmentation software. These surfaces were converted to Non-uniform Rational B-spline surfaces by the INUS Rapidform rapid prototyping software. Rapidform was also used to generate a thin shell surface model for the dura mater which sheathes the spinal cord. Altair's Hypermesh pre-processor was used to generate finite element meshes for each structure. These processes in this study can be utilized in modeling of other biomedical tissues and can be one of examples for reverse engineering on biomechanics.

Defect Shape Recovering by Parameter Estimation Arising in Eddy Current Testing

  • Kojima, Fumio
    • 비파괴검사학회지
    • /
    • 제23권6호
    • /
    • pp.622-634
    • /
    • 2003
  • This paper is concerned with a computational method for recovering a crack shape of steam generator tubes of nuclear plants. Problems on the shape identification are discussed arising in the characterization of a structural defect in a conductor using data of eddy current inspection. A surface defect on the generator tube ran be detected as a probe impedance trajectory by scanning a pancake type coil. First, a mathematical model of the inspection process is derived from the Maxwell's equation. Second, the input and output relation is given by the approximate model by virtue of the hybrid use of the finite element and boundary element method. In that model, the crack shape is characterized by the unknown coefficients of the B-spline function which approximates the crack shape geometry. Finally, a parameter estimation technique is proposed for recovering the crack shape using data from the probe coil. The computational experiments were successfully tested with the laboratory data.

CNC 공작기계의 NURBS 보간 알고리즘에 관한 연구 (NURBS Interpolation Algorithm for CNC Machines)

  • 홍원표;양민양
    • 한국정밀공학회지
    • /
    • 제17권12호
    • /
    • pp.115-120
    • /
    • 2000
  • Increasing demands on precision machining of free-form surface have necessitated that the tool to move not only position error as small as possible, but also with smoothly varying feedrates. This paper presents new algorithm for high precision 3D(3-dimensional) NURBS(Non-Uniform Rational B-Spline) interpolation in the reference-pulse technique. Based o the minimum path error strategy, interpolation algorithm was designed to follow the NURBS curve. Using this algorithm a real-time 3D NURBS interpolator was developed in software. The algorithm implemented in a PC showed promising results in interpolation error and speed performance. It is expected that this can be applied to the CNC systems for the high precision machining of complex shapes.

  • PDF

IGES와 SRL format 사이의 3차원 정보교고한에 관한 연구 (A study on 3D data exchange between IGES and STL format)

  • 오도근;최홍태;이석희
    • 한국정밀공학회:학술대회논문집
    • /
    • 한국정밀공학회 1995년도 추계학술대회 논문집
    • /
    • pp.965-969
    • /
    • 1995
  • This paper deals with effective using the IGES file for flexible data exchange among the other CAD/CAM system. If a data exchange between STL file and the neutral IGES file in Stereolithography system is available, a product design becomes more flexible. THere can be many restrictions and difficulties intranslating these data. First, an STL file follows two rules, such as right-hand rule, and vertex-to-vertex rule, thus requires a structural verification. Second, translation should be performed with minmal errors. It becomes very important to translate IGES file of limited kinds of entities fot the purpose of geometric information into STL file with minor data manipulation. The developed system suggests a good approach of translating the sampled B-spline surface of IGES and shows a potential linkage between IGES and STL format file.

  • PDF

형상 역공학을 통한 공정중 금형 가공물의 자동인식 (Automatic Recognition of In-Process mold Dies Based on Reverse Engineering Technology)

  • 김정권;윤길상;최진화;김동우;조명우;박균명
    • 한국공작기계학회:학술대회논문집
    • /
    • 한국공작기계학회 2003년도 추계학술대회
    • /
    • pp.420-425
    • /
    • 2003
  • Generally, reverse engineering means getting CAD data from unidentified shape using vision or 3D laser scanner system. In this paper, we studied unidentified model by machine vision based reverse engineering system to get information about in-processing model. Recently, vision technology is widely used in current factories, because it could inspect the in-process object easily, quickly, accurately. The following tasks were mainly investigated and implemented. We obtained more precise data by corning camera's distortion, compensating slit-beam error and revising acquired image. Much more, we made similar curves or surface with B-spline approximation for precision. Until now, there have been many case study of shape recognition. But it was uncompatible to apply to the field, because it had taken too many processing time and has frequent recognition failure. This paper propose recognition algorithm that prevent such errors and give applications to the field.

  • PDF

그래픽 사용자 인터페이스(GUI)를 도입한 선형설계 기법에 관한 연구 (A Study on Hull Form Design Techniques Based on Graphical User Interface)

  • 신현경;박규원
    • 대한조선학회논문집
    • /
    • 제30권4호
    • /
    • pp.17-22
    • /
    • 1993
  • 3차원 자유곡면의 교차문제는 기하학적인 방법과 수치적인 방법으로 해결할 수 있으며, 지금까지는 일반적으로 선체형상의 단면을 얻기 위해서 기하학적인 방법인 곡면분할 기법을 사용하여 왔다. 본 논문에서는 할선법, 선형보간법 및 반분법 등 간단한 수치해석 방법들을 사용하여서, Bi-Cubic B-Spline Surface로 표현된 선체형상과 임의의 평면에 의해 교차된 선체 단면형상을 갖는 방법을 수행하여 비교 검토하고자 한다. 곡면간의 교체문제는 임의의 단면형상 파악, 선도작성 및 offset Table 구성에 직접 응용되어진다.

  • PDF

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

  • LEE, Sang Jin
    • Architectural research
    • /
    • 제18권2호
    • /
    • pp.65-74
    • /
    • 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.