• Title, Summary, Keyword: initial shape analysis

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A Controllable Ternary Interpolatory Subdivision Scheme

  • Zheng, Hongchan;Ye, Zhenglin;Chen, Zuoping;Zhao, Hongxing
    • International Journal of CAD/CAM
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    • v.5 no.1
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    • pp.29-38
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    • 2005
  • A non-uniform 3-point ternary interpolatory subdivision scheme with variable subdivision weights is introduced. Its support is computed. The $C^0$ and $C^1$ convergence analysis are presented. To elevate its controllability, a modified edition is proposed. For every initial control point on the initial control polygon a shape weight is introduced. These weights can be used to control the shape of the corresponding subdivision curve easily and purposefully. The role of the initial shape weight is analyzed theoretically. The application of the presented schemes in designing smooth interpolatory curves and surfaces is discussed. In contrast to most conventional interpolatory subdivision scheme, the presented subdivision schemes have better locality. They can be used to generate $C^0$ or $C^1$ interpolatory subdivision curves or surfaces and control their shapes wholly or locally.

Initial Blank Design Considering Springback Reduction (스프링백 저감을 고려한 초기블랭크 설계)

  • 양우열;이승열;금영탁
    • Transactions of Materials Processing
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    • v.12 no.3
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    • pp.208-213
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    • 2003
  • The methodology to design initial blanks considering the reduction of both springback and flange trimming amounts is studied. Three dimensional forming analysis of a trial blank Is first carried out using FEM and the tentative Initial blank shape is then determined by cutting the outer edge of the trial blank whose shape is nearly matched with the trimming line. During the shaping the blank edge, tile movement of blank outer line is described with random variables to reduce the sensitivity of initial blank geometry. After performing 2-D FEM forming and springback simulations for selected sections and optimizing the trimming and springback amounts in terms of section length of the blank, the initial blank is finally determined. In order to see tile springback reduction in the initial blank determined by the proposed method, a stepped s-rail is stamped and the sppingback is measured. The springback of newly designed initial blank of stopped s-tail is tremendously reduced.

Optimum Blank Design of Automobile Sub-Frame (우물정(井)자형 Sub-frame의 블랭크 설계)

  • Kim, Jong-Yop;Kim, Nak-Soo;Heo, Man-Seong
    • Transactions of Materials Processing
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    • v.7 no.3
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    • pp.260-273
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    • 1998
  • A new blank design method is proposed to predict the optimum initial blank shape in the sheet metal forming process. The rollback method for blank shape design takes the difference between final deformed shaped and target contour shape into account. Based on the method a computer program composed of blank design module FE-analysis program and mesh generation module is developed. The rollback method is applied to square cup drawing process with the flange of unifiorm size around its periphery to confirm its validity. The optimum initial blank shape is obtained from an arbitrary square blank after three modification. Good agreements are recognized between the numerical results and the published results for initial blank shape and thickness strain distribution. The optimum blank shape for two parts of automobile sub-frame is designed, The thickness distribution and the level of punch load is improved. Also the method is applied to design the weld line in the tailor-welded blank. It is concluded that the rollback method is an effective and convenient method for an optimum blank shape design.

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A Shape Finding and Cutting Pattern Determination for Membrane Structures (막 구조물에 관한 형상 탐색과 재단도 결정법)

  • Choi, Ho;Lee, Jang-Bog;Kim, Jae-Yeol;Sur, Sam-Uel;Kwon, Taek-Jin
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.175-182
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    • 1998
  • The object of this study is shape finding and cutting pattern generation of membrane structures under the following assumptions : (1) material is linearly elastic (2) stress state is plane stress. Cable and membrane structures should introduce the nonlinear analysis considering geometric nonlinearity because these structures deform largely under the external loads. The analysis procedure is consisted of three steps considering geometric nonlinearity unlike any other structures. First step is the shape finding analysis to determine the initial equilibrium shape. Second step is the stress-deformation analysis to investigate the behaviors of structures under various external loads. Once a satisfactory shape has been found, a cutting pattern based on the shape finding analysis may be generated from the view point of construction. In this paper, (1) shape finding analysis formulation and an example, (2) cutting pattern determination procedure using weighted least-square minimization flattening method and some results are presented.

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A Study on Structural Analysis and Optimum Shape Design of Tilting Index Table (틸팅 인덱스 테이블 구조해석 및 최적형상 설계에 관한 연구)

  • Lee, Mun-Jae;Lee, Choon-Man
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.2
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    • pp.86-93
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    • 2010
  • The tilting index table has attached to CNC machining center with 3axes, it can be improvement of its performance and its machining efficiency. The tilting index table is a key unit in order to manufacture some non-rotational and 3-dimensional parts, using the conventional machining center. In this study, structural analysis is carried out by FEM simulation using the commercial software ANSYS Workbench 11 to develop tilting index table using direct drive motor. The shape of the tilting index table obtained from the optimization was analyzed and compared with the initial model. Also, the initial model was modified based on the optimization model and the result was verified to have the acceptable improvement.

Sensitivity Analysis of Initial Pressure and Upper Control Limit on the Pressure Decay Test for Membrane Integrity Evaluation (압력손실시험을 이용한 막 완결성 평가에서 초기압력 및 UCL 도출인자 민감도 분석)

  • Lee, Joohee;Hong, Seungkwan;Hur, Hyunchul;Lee, Kwangjae;Choi, Youngjune
    • Journal of Korean Society on Water Environment
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    • v.24 no.6
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    • pp.793-800
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    • 2008
  • Recently domestic drinking water industry has recognized membrane-based technology as a promising alternative for water treatment. To ensure successful application of membrane processes, the integrity of membrane systems should be maintained. According to US EPA guidance, the pressure decay test based on the bubble point theory is recommended to detect any membrane defection of which size is close to the smallest diameter of Cryptosporidium oocysts, $3{\mu}m$. Proper implementation of the pressure decay test is greatly affected by initial test pressure, and the interpretation of the test results is associated with upper control limit. This study is conducted to investigate various factors affecting determination of initial test prtessure and upper control limit, including membrane-based parameters such as pore shape correction factor, surface tension and contact angle, and system-based parameters, such as volumetric concentration factor and total volume of system. In this paper, three different hollow fibers were used to perform the pressure decay test. With identical initial test pressure applied, their pressure decay tendency were different from each other. This finding can be explained by the micro-structure disparity of those membranes which is verified by FESEM images of those membranes. More specifically, FESEM images revealed that three hollow fibers have asymmetry, deep finger, shallow finger pore shape, respectively. In addition, sensitivity analysis was conducted on five parameters mentioned above to elucidate their relation to determination of initial test pressure and upper control limit. In case of initial pressure calculation, the pore shape correction factor has the highest value of sensitivity. For upper control limit determination, system factors have greater impact compared to membrane-based parameters.

A Study on the Shape Analysis of Membrane Structures Using Line Elements (선재 요소를 이용한 막 구조물의 형상해석에 관한 연구)

  • Kim, Seung-Deog;Lee, Shin-Woo
    • Journal of the Korean Association for Spatial Structures
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    • v.10 no.2
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    • pp.45-60
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    • 2010
  • Nonlinear problems for membrane structures are very sensitive in convergence procedure in nonlinear iterations. Therefore many researchers have suggested a lot of ideas in published papers. In this study, authors are trying to get easier solution for taking membrane shape by initial stresses from substitution of the membrane to line elements. To obtain nonlinear stiffness, the nonlinear finite element method is used for both membrane and cable elements, and only geometric nonlinear terms are taken for shape analysis. By some examined models, we can find that the substituted models show better results to get, initial shape in which the concentrating phenomenon is removed at edge parts.

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Efficient Numerical Analysis for Shape Design of Turbine Seal (효율적인 수치해석에 의한 터빈 시일의 형상설계)

  • Han, Kyu-Taek
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.15 no.4
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    • pp.118-124
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    • 2016
  • In this paper, the model to develop the forming process for turbine seal is suggested. And numerical approach for the shape design of the turbine seal is examined. Because of the thin thickness of the turbine seal, the seal is easily fractured in the manufacturing process. The main factors of the seal manufacturing consist of addendum angle and dedendum angle, fillet on the addendum face, number of the gear teeth, sheet initial location and gear initial location, rake and vertical clearance. The structure and shape of seal are modeled using the commercial 3D mechanical design program, CATIA(V5/R20). Also, rolling process to manufacture the turbine seal is analyzed using DEFORM$^{TM}$-3D(V11), commercial forming analysis software and runs under PC workstation. This study focused on the shape design of turbine seal. Through this research, the main factors to make the turbine seal for airplane turbine engine can be obtained. This study results are reflected to the shape design for turbine seal.

A CAE Approach for Net-Shape Automobile Stamping Components of Aluminum Alloy (자동차용 알루미늄 합금 정형의 스탬핑 부품 성형을 위한 CAE 기법 개발)

  • Choi, Han-Ho;Ku, Tae-Wan;Hwang, Sang-Moon;Kang, Beom-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.10
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    • pp.164-171
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    • 1999
  • An optimum blank design technology is required for near-net of net-shape cold forming using sheets. Originally, the backward tracing scheme has been developed for preform design in bulk forming, and applied to several forming processes successfully. Its key concept is to trace backward from the final desirable configuration to an intermediate preform of initial blocker. A program for initial blank design in sheet forming which contains the capabilities of forward loading simulation by the finite element method and backward tracing simulation, has been developed and proved the effectiveness by applying to a square cup stamping process. In the blank design of square cup stamping, the backward tracing program can produce an optimum blank configuration which forms a sound net-shape cup product without machining after forming. Another general application appears in the blank design of a cup stamping with protruding flanges, one of typical automobile components. The blank configurations derived by backward tracing simulation have been confirmed by a series of loading simulations. The approach or decision of an initial blank configuration presented in this study will be a milestone in fields of sheet forming process design.

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Forward Projection Using Fuzzy Logic in Axisymmetric Finite Element Simulation for Cold Forging (축대칭 냉간단조의 유한요소해석에서 퍼지로직을 이용한 전방투사법)

  • 정낙면;이낙규;양동열
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.8
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    • pp.1468-1484
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    • 1992
  • In the present paper forward projection is proposed as a new approach to determine the preform shape in rib-web type forging. In the forward projection technique an optimal billet is determined by applying some mathematical relationship between geometrical trials in the initial billet shape and the final products. In forward projection a volume difference between the desired product shape and the final computed shape obtained by the rigid-plastic finite element method is used as a measure of incomplete filling of working material in the die. At first linear inter-/extrapolation is employed to find a proper trial shape for the initial billet and the method is successfully applied to some cases of different aspect ratios of the initial billet. However, when the initial guesses are not sufficiently near the optimal value linear inter-/extrapolation does not render complete die filling. For more general application, a fuzzy system is used in the forward projection technique in order to determine the initial billet shape for rib-web type forging. It has been thus shown that the fuzzy system is more reliable for the preform design in the rib-web type forging process.