• Title/Summary/Keyword: Parametric Surface

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Modeling of Blend Surfaces by Bezier Surface Patches (비지어곡면에 의한 블렌드곡면의 모델링)

  • 주상윤
    • Korean Journal of Computational Design and Engineering
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    • v.2 no.2
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    • pp.122-129
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    • 1997
  • Ball rolling blending is a popular technique for blending between parametric surfaces. The ball rolling blend surface is conceptually a trajectory of a ball rolling between two base sufaces. It is constructed by sweeping a circular arc along a ball contact curve pair. Since a ball rolling blend surfaces does not have a polynomial form like a Bezier surface patch, it is impossible to apply this method directly to a commercial CAD/CAM system. In this paper an algorithm is developed to approximate a ball rolling blend surface into Bezier surface patches. Least square method is applied to obtain proper Bezier surface patches under a given tolerance. The Bezier surface patches have degree three or more and guarantee VC1-continuity.

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Computing Planar Curve Offset Based on Surface/Surface Intersection (교차곡선 연산을 이용한 평면 곡선의 오프셋 계산)

  • 최정주
    • Korean Journal of Computational Design and Engineering
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    • v.3 no.2
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    • pp.127-134
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    • 1998
  • This paper presents d new algorithm to compute the offlet curve of a given planar parametric curve. We reduce the problem of computing an offset curve to that of intersecting a surface to a paraboloid. Given an input curve C(t)=(x(t), y(t))∈R², the corresponding surface D/sub c(t)/ is constructed symbolically as the envelope surface of a one-parameter family of tangent planes of the paraboloid Q:z=x²+y²along a lifted curve C(t)=(x(t), y(t), x(t)²+y(t)²∈Q. Given an offset distance d∈R, the offset curve C/sub d/(t) is obtained by the projection of the intersection curve of D/sub c(t)/ and a paraboloid Q:z=x²+y²-d² into the xy-plane.

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Addendum Surface Modeling in Draw Die Design for Stamping Automotive Panels (자동차 프레스 패널 성형을 위한 드로 금형의 어덴덤 곡면 모델링)

  • Chung, Yunchan
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.6
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    • pp.1018-1024
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    • 2013
  • In the process of draw die design for stamping automotive press panels, the addendum surfaces generated in metal forming simulation software cannot be used in downstream processes such as machining and making draw dies because simulation tools use simple discrete models for the surface geometry. The downstream processes require more precise and continuous geometric models such as NURBS surfaces. Generally, automotive die engineers manually regenerate the addendum surface geometry using the discrete model. This paper presents an automated geometric modeling process for generating addendum surfaces using draft surface models. The design parameters of the section curve for the addendum surfaces are extracted automatically from the draft geometry. Using the extracted design parameters, smooth addendum surfaces are generated automatically as NURBS surfaces. The generated surfaces are $G^1$ continuous with the part surface and the binder surface, and can be used in downstream processes.

An Accuracy Analysis of Run-test and RA(Reverse Arrangement)-test for Assessing Surface EMG Signal Stationarity (표면근전도 신호의 정상성 검사를 위한 Run-검증과 RA-검증의 정확도 분석)

  • Lee, Jin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.2
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    • pp.291-296
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    • 2014
  • Most of the statistical signal analysis processed in the time domain and the frequency domain are based on the assumption that the signal is weakly stationary(wide sense stationary). Therefore, it is necessary to know whether the surface EMG signals processed in the statistical basis satisfy the condition of weak stationarity. The purpose of this study is to analyze the accuracy of the Run-test, modified Run-test, RA(reverse arrangement)-test, and modified RA-test for assessing surface EMG signal stationarity. Six stationary and three non-stationary signals were simulated by using sine wave, AR(autoregressive) modeling, and real surface EMG. The simulated signals were tested for stationarity using nine different methods of Run-test and RA-test. The results showed that the modified Run-test method2 (mRT2) classified exactly the surface EMG signals by stationarity with 100% accuracy. This finding indicates that the mRT2 may be the best way for assessing stationarity in surface EMG signals.

A Study on the Impact and Solidification of the Liquid Metal Droplet in the Thermal Spray Deposition onto the Substrate with Surface Defects (표면 결함이 있는 모재에 대한 용사 공정에서 용응 금속 액적의 충돌현상과 응고 과정 해석)

  • Ha, Eung-Ji;Kim, Woo-Seung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.11
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    • pp.1597-1604
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    • 2002
  • In this study, numerical investigation has been performed on the impingement, spreading and solidification of a coating material droplet impacting onto a solid substrate in the thermal spray process. The numerical model is validated through the comparison of the present numerical result with experimental data fer the flat substrate without surface defects. An analysis of deposition formation on the non-polished substrate with surface defects is also performed. The parametric study is conducted with various surface defect sizes and shapes to examine the effect of surface defects on the impact and solidification of the liquid droplet on the substrate.

Parametric Modelling of Cutter Swept Surface for Z-Map Based Cutting Simulation (Z-Map기반 모의가공을 위한 공구 이동 궤적면의 매개변수형 모델링)

  • Park, Bae-Yong;An, Jeong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.9
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    • pp.1814-1821
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    • 2002
  • NC cutting simulation is an important factor in the development of products. The geometric modelling of cutter swept surface should be done in NC cutting simulation. A part of cutter swept surface is a ruled surface blended with silhouette curve and cutter path. Finding an intersection point between cutter swept surface and a line is one of major problems in Z-map based cutting simulation. In this paper, cutter swept surface is defined parametrically and it's intersection point with Z-map is found in an exact form. Triangular grid Z-map based 3-axis NC cutting simulation is performed.

A New Method of the Global Interpolation in NURBS Surface: II (NURBS Surface Global Interpolation에 대한 한 방법: II)

  • 정형배
    • Korean Journal of Computational Design and Engineering
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    • v.3 no.4
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    • pp.243-250
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    • 1998
  • In parametric surface interpolation, the choice of the parameter values to the set of scattered points makes a great deal of difference in the resulting surface. A new method is developed and tested for the parametrization in NURBS surface global interpolation. This method uses the parameter value at the maximal value of relevant rational basis function, to assign the parameter values to the arbitrary set of design data. This method gives us several important advantages in geometric modeling, the freedom of the selection of knot values, the feasible transformation of the data set to the matrix, the possibility of affinite transformation between the design data and generated surface, etc.

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A Method of Surface Mapping for Deep Drawing Process (Deep Drawing 공정을 위한 곡면 매핑 방법)

  • 임용현;박준영
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 2000.04a
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    • pp.721-723
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    • 2000
  • Deep Drawing공정은 2차원 박판(Sheet Metal)에 그림이나 글자를 인쇄한 다음, 박판을 다이에 고정하고 펀치로 눌러서 3차원의 제품을 생산하는 소성가공의 한 방법이다. 그러므로, 2차원 평면인 박판에 어떻게 적절히 인쇄하여, 가공 후의 3차원 제품에 원하는 그림과 글자가 나타나게 할 수 있는지가 문제가 되고 있다. 본 논문에서는 Deep Drawing공정을 거쳐 완성된 제품을 측정한 후, 형상 역공학(Reverse Engineering) 기술을 이용하여 측정 데이터(Measured Points Data)를 입력으로 하는 매개변수 곡면 (Parametric Surface)을 만들고, Deep Drawing공정 전의 박판에 대한 매개변수 곡면을 만든 다음 두 곡면간의 매핑을 통해 위의 문제점을 해결하고자 한다.

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Oscillatory Thermocapillary Flow in Cylindrical Columns of High Prand시 Number Fluids

  • Lee, Kyu-Jung;Yasuhiro Kamotani;Simon Ostrach
    • Journal of Mechanical Science and Technology
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    • v.15 no.6
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    • pp.764-775
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    • 2001
  • Oscillartory thermocapillary flow of high Prandtl number fluids in the half-zone configuration is investigated. Based on experimental observations, one oscillation cycle consists of an active period where the surface flow is strong and the hot corner region is extended and a slow period where the opposite occurs. It is found that during oscillations the deformation of free surface plays an important role and a surface deformation parameter S correlates the experimental data well on the onset of oscillations. A scaling analysis is performed to analyze the basic steady flow in the parametric ranges of previous ground-based experiments and shows that the flow is viscous dominant and is mainly driven in the hot corner. The predicted scaling laws agree well with the numerical results. It is postulated that the oscillations are caused by a time lag between the surface and return flows. A deformation parameter S represents the response time of the return flow to the surface flow.

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Automatic Mesh Generation in the General Three-Dimensional Trimmed Surface using Qua (쿼드트리를 이용한 일반적인 3차원 트림곡면에서의 유한요소 자동생성)

  • 유동진;윤정환
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.3
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    • pp.136-148
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    • 2000
  • In this work, a general method for the mathematical description of three-dimensional trimmed surface is proposed by introducing the base parametric surface and boundary curves. Since mesh density distribution for the analysis may vary by cases, a grid-based mesh generation algorithm using quadtree is proposed in the present work. For the assurance of connectivity of generated meshes among surfaces, a method for the pre-cleaning of boundary curves has been developed to be used in the automatic generation of the finite elements. In addition, mesh-smoothing algorithm is suggested which can be used in the general trimmed surface. In this algorithm nodes are moved on the original surface by the normal projection in each iterative smoothing procedure.

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