209 research outputs found
Iterative surface warping to shape craters in micro-EDM simulation
This paper introduces a new method for simulating the micro-EDM process in order to predict both the toolâs wear and the workpieceâs roughness. The tool and workpiece are defined by NURBS patches whose shapes result from an iterative crater-by-crater deformation technique driven by physical parameters. Through hundreds of thousands of local surface warping, the method is able to compute the global as well as the local shapes of the tool and workpiece. At each step, the warping vector and function are computed so as to be able to generate a spherical crater whose volume is also controlled. While acting very locally to simulate the real physical phenomenon, not only the method can evaluate the toolâs wear from the overall final shape at a low resolution level, but it can also estimate the workpieceâs roughness from the high resolution level. The simulation method is validated through a comparison with experimental data. Different simulations are presented with an increase in computation accuracy in order to study its influence on the results and their deviation from expected values
Iterative surface warping to shape craters in microâEDM simulation
This paper introduces a new method for simulat- ing the micro-EDM process in order to predict both the toolâs wear and the workpieceâs roughness. The tool and workpiece are de ned by NURBS patches whose shapes result from an iterative crater-by-crater deformation technique driven by physical parameters. Through hundreds of thousands of local surface warping, the method is able to compute the global as well as the local shapes of the tool and workpiece. At each step, the warping vector and function are computed so as to be able to generate a spherical crater whose volume is also controlled. While acting very locally to simulate the real physical phenomenon, not only the method can evaluate the toolâs wear from the overall nal shape at a low resolu- tion level, but it can also estimate the workpieceâs roughness from the high resolution level. The simulation method is validated through a comparison with experimental data. Dif- ferent simulations are presented with an increase in compu- tation accuracy in order to study its in uence on the results and their deviation from expected values
Fast character modeling with sketch-based PDE surfaces
© 2020, The Author(s). Virtual characters are 3D geometric models of characters. They have a lot of applications in multimedia. In this paper, we propose a new physics-based deformation method and efficient character modelling framework for creation of detailed 3D virtual character models. Our proposed physics-based deformation method uses PDE surfaces. Here PDE is the abbreviation of Partial Differential Equation, and PDE surfaces are defined as sculpting force-driven shape representations of interpolation surfaces. Interpolation surfaces are obtained by interpolating key cross-section profile curves and the sculpting force-driven shape representation uses an analytical solution to a vector-valued partial differential equation involving sculpting forces to quickly obtain deformed shapes. Our proposed character modelling framework consists of global modeling and local modeling. The global modeling is also called model building, which is a process of creating a whole character model quickly with sketch-guided and template-based modeling techniques. The local modeling produces local details efficiently to improve the realism of the created character model with four shape manipulation techniques. The sketch-guided global modeling generates a character model from three different levels of sketched profile curves called primary, secondary and key cross-section curves in three orthographic views. The template-based global modeling obtains a new character model by deforming a template model to match the three different levels of profile curves. Four shape manipulation techniques for local modeling are investigated and integrated into the new modelling framework. They include: partial differential equation-based shape manipulation, generalized elliptic curve-driven shape manipulation, sketch assisted shape manipulation, and template-based shape manipulation. These new local modeling techniques have both global and local shape control functions and are efficient in local shape manipulation. The final character models are represented with a collection of surfaces, which are modeled with two types of geometric entities: generalized elliptic curves (GECs) and partial differential equation-based surfaces. Our experiments indicate that the proposed modeling approach can build detailed and realistic character models easily and quickly
Processing free form objects within a Product Development Process framework
The purpose of the chapter is then to review: (1) the stages of a product development pro- cess (PDP) where free-form shapes appear and are subjected to aesthetic and functional require- ments; (2) the modeling, sketching, and modification activities illustrating how free-form surfaces can be processed and what are the corresponding difficulties faced during these tasks; (3) the con- tributions of our community to solve some of these issues, and the problems which are still open
Adaptive parameterization for Aerodynamic Shape Optimization in Aeronautical Applications
CĂlem mĂ© disertaÄnĂ prĂĄce je analyzovat a vyvinout parametrizaÄnĂ metodu pro 2D a 3D tvarovĂ© optimalizace v kontextu prĆŻmyslovĂ©ho aerodynamickĂ©ho nĂĄvrhu letounu zaloĆŸenĂ©m na CFD simulacĂch. AerodynamickĂĄ tvarovĂĄ optimalizace je efektivnĂ nĂĄstroj, kterĂœ si klade za cĂl snĂĆŸenĂ nĂĄkladĆŻ na nĂĄvrh letounĆŻ. NĂĄstroj zaloĆŸenĂœ na automatickĂ©m hledĂĄnĂ optimĂĄlnĂho tvaru. KlĂÄovou ÄĂĄstĂ ĂșspÄĆĄnĂ©ho optimalizaÄnĂho procesu je pouĆŸitĂ vhodnĂ© parametrizaÄnĂ metody, metody schopnĂ© garantovat moĆŸnost dosaĆŸenĂ optimĂĄlnĂho tvaru. ParametrizaÄnĂ metody obecnÄ pouĆŸĂvanĂ© v oblasti aerodynamickĂ© tvarovĂ© optimalizace momentĂĄlnÄ nejsou pĆipravenĂœ na komplikovanĂ© prĆŻmyslovĂ© aplikace vyskytujĂcĂ se u modernĂch dopravnĂch letounĆŻ, kterĂ© majĂ ĆĄĂpovĂĄ zalomenĂĄ kĆĂdla s winglety a motorovĂœmi gondolami, pĆechodovĂ© prvky spojujĂcĂ napĆ. trup s kĆĂdlem atd.. Existuje tedy potĆeba nalezenĂ obecnĂ© parametrizaÄnĂ metody, kterĂĄ bude aplikovatelnĂĄ na ĆĄirokou ĆĄkĂĄlu rĆŻznĂœch geometrickĂœch tvarĆŻ. Free-Form Deformation (FFD[1]) parametrizace mĆŻĆŸe, vzhledem ke svĂœm schopnostem pĆi zachĂĄzenĂ s geometriĂ, bĂœt odpovÄdĂ na tuto potĆebu. AdaptivnĂ parametrizace by se mÄla bĂœt schopna automaticky pĆizpĆŻsobit danĂ©mu tvaru tak, aby byly jejĂ kontrolnĂ body vhodnÄ rozmĂstÄny. CoĆŸ umoĆŸnĂ dostateÄnou kontrolu deformacĂ objektu, kterĂĄ zaruÄĂ moĆŸnost vytvoĆenĂ optimĂĄlnĂho tvaru objektu a splnÄnĂ geometrickĂœch omezenĂ. PrimĂĄrnĂ aplikacĂ takovĂ© parametrizaÄnĂ metody je deformace tvaru objektu. DalĆĄĂm navrhovanĂœm cĂlem je modifikace FFD parametrizaÄnĂ metody pro souÄasnĂ© deformace tvaru objektu a CFD vĂœpoÄetnĂ sĂtÄ, umoĆŸnujĂcĂ velkĂ© deformace objektu pĆi zachovĂĄnĂ kvality vĂœpoÄetnĂ sĂtÄ.The goal of this doctoral thesis is to analyze and develop parameterization algorithms for 2D and 3D shape optimization in the context of industrial aircraft aerodynamic design based on simulations with CFD. Aerodynamic shape optimization is an efficient tool that aims at reducing the cost of the process of aircraft design. A tool that is based on automatization of the search for the optimum shape. Key part of successful aerodynamic shape optimization is the use of appropriate parameterization method, a method that should guarantee the possibility of reaching optimum shape. The parameterization methods used in aerodynamic shape optimizations are still not ready for complex industrial applications, which are present on modern passenger aircrafts with swept cranked wings with winglets and engine pylons, fuselage-wing interactions etc. So there is a need for general parameterization method that applies on wide variety of different geometries.The Free-Form Deformation (FFD[1]) parameterization can, thanks to its geometry handling qualities, be the answer to this need. Adaptive parameterization should automatically modify parameterization grid (lattice) to get appropriate lattice in regions of interest. Such that will allow sufficient control of deformations of the object with respect to reaching optimum shape and fulfilling optimization constraints. First application is in the surface deformation. The other proposed goal is development of the FFD parameterization that can do both surface deformations and CFD mesh deformations, while enabling large object deformations and preserving the level of mesh quality during the process.
êž°ííì ìŒëĄ ì ë°í ëčì í ê”ŹìĄ°ëŹŒì ììŽì-ì§ì€ë©ížëŠ íì ì€êł ëŻŒê°ë íŽì
íìë
ŒëŹž (ë°ìŹ)-- ììžëíê” ëíì : êł”êłŒëí ìĄ°ì íŽìêł”íêłŒ, 2019. 2. ìĄ°ì íž.In this thesis, a continuum-based analytical adjoint configuration design sensitivity analysis (DSA) method is developed for gradient-based optimal design of curved built-up structures undergoing finite deformations. First, we investigate basic invariance property of linearized strain measures of a planar Timoshenko beam model which is combined with the selective reduced integration and B-bar projection method to alleviate shear and membrane locking. For a nonlinear structural analysis, geometrically exact beam and shell structural models are basically employed. A planar Kirchhoff beam problem is solved using the rotation-free discretization capability of isogeometric analysis (IGA) due to higher order continuity of NURBS basis function whose superior per-DOF(degree-of-freedom) accuracy over the conventional finite element analysis using Hermite basis function is verified. Various inter-patch continuity conditions including rotation continuity are enforced using Lagrage multiplier and penalty methods. This formulation is combined with a phenomenological constitutive model of shape memory polymer (SMP), and shape programming and recovery processes of SMP structures are simulated. Furthermore, for shear-deformable structures, a multiplicative update of finite rotations by an exponential map of a skew-symmetric matrix is employed. A procedure of explicit parameterization of local orthonormal frames in a spatial curve is presented using the smallest rotation method within the IGA framework. In the configuration DSA, the material derivative is applied to a variational equation, and an orientation design variation of curved structure is identified as a change of embedded local orthonormal frames. In a shell model, we use a regularized variational equation with a drilling rotational DOF. The material derivative of the orthogonal transformation matrix can be evaluated at final equilibrium configuration, which enables to compute design sensitivity using the tangent stiffness at the equilibrium without further iterations. A design optimization method for a constrained structure in a curved domain is also developed, which focuses on a lattice structure design on a specified surface. We define a lattice structure and its design variables on a rectangular plane, and utilize a concept of free-form deformation and a global curve interpolation to obtain an analytical expression for the control net of the structure on curved surface. The material derivative of the analytical expression eventually leads to precise design velocity field. Using this method, the number of design variables is reduced and design parameterization becomes more straightforward. In demonstrative examples, we verify the developed analytical adjoint DSA method in beam and shell structural problems undergoing finite deformations with various kinematic and force boundary conditions. The method is also applied to practical optimal design problems of curved built-up structures. For example, we extremize auxeticity of lattice structures, and experimentally verify nearly constant negative Poisson's ratio during large tensile and compressive deformations by using the 3-D printing and optical deformation measurement technologies. Also, we architect phononic band gap structures having significantly large band gap for mitigating noise in low audible frequency ranges.ëłž ì°ê”Źììë ëëłíì êł ë €í íìŽì§ ìĄ°ëŠœ ê”ŹìĄ°ëŹŒì ì°ììČŽ êž°ë° íŽìì ì ìĄ°ìž íì ì€êł ëŻŒê°ë íŽì êž°ëČì ê°ë°íìë€. íë©Ž Timoshenko ëčì ì ííë ëłíë„ ì invariance íčì±ì êł ì°°íìêł invariant ì ìíë„Œ ì íì ì¶ìì ë¶(selective reduced integration) êž°ëČ ë° B-bar projection êž°ëČêłŒ êČ°í©íìŹ shear ë° membrane ì êč íìì íŽìíìë€. ëčì í ê”ŹìĄ° ëȘšëžëĄì êž°ííì ìŒëĄ ì ë°í ëč ë° ì ëȘšëžì íì©íìë€. íë©Ž Kirchhoff ëč ëȘšëžì NURBS êž°ì íšìì êł ì°š ì°ìì±ì ë°ë„ž ììŽì-ì§ì€ë©ížëŠ íŽì êž°ë° rotation-free ìŽì°íë„Œ íì©íìŹ ë€ëŁšììŒë©°, êž°ìĄŽì Hermite êž°ì íšì êž°ë°ì ì íììëČì ëčíŽ ìì ëëč íŽì ì íëê° ëìì êČìŠíìë€. ëŒê·žëì§ ìčìëČ ë° ëČìč êž°ëČì ëì
íìŹ íì ì ì°ìì±ì íŹíší ë€ìí ë€ì€íšìčê° ì°ì ìĄ°ê±Žì êł ë €íìë€. ìŽëŹí êž°ëČì íìíì (phenomenological) íìêž°ì”íŽëŠŹëšž (SMP) ìŹëŁ ê”Źì±ë°©ì ìêłŒ êČ°í©íìŹ íìì íëĄê·žëë°êłŒ íëł” êłŒì ì ì럏ë ìŽì
íìë€. ì ëšëłíì êČȘë (shear-deformable) ê”ŹìĄ° ëȘšëžì ëíìŹ ëíì ì ê°±ì ì ê”ë íë Źì exponential mapì ìí êł±ì ííëĄ ìííìë€. êł”ê°ìì êłĄì ëȘšëžìì ì”ìíì (smallest rotation) êž°ëČì í”íŽ ê”ì ì ê·ì§ê”ìąíêłì ëȘ
ìì 맀ê°íë„Œ ìííìë€. íì ì€êł ëŻŒê°ë íŽìì ìíìŹ ì 믞ë¶ì ëłë¶ ë°©ì ìì ì ì©íììŒë©° íìŽì§ ê”ŹìĄ°ëŹŒì ë°°í„ ì€êł ëłíë ê”ì ì ê·ì§ê”ìąíêłì íì ì ìíìŹ êž°ì ëë€. ì”ìą
ëłí íììì ì§ê” ëłí íë Źì ì 믞ë¶ì êłì°íšìŒëĄìš ëíì 돞ì ìì ì¶ê°ì ìž ë°ëł” êłì°ììŽ ëłí íŽìììì ì ì ê°ì±íë Źì ìíŽ íŽìì ì€êł ëŻŒê°ëë„Œ êłì°í ì ìë€. ì ê”ŹìĄ°ëŹŒì êČœì° ë©ŽëŽ íì ìì ë ë° ìì íë ëłë¶ ë°©ì ìì íì©íìŹ ëłŽê°ìŹ(stiffener)ì ëȘšëžë§ì ì©ìŽíêČ íìë€. ëí ëłž ì°ê”Źììë íìŽì§ ììì ê”ŹìëìŽìë ê”ŹìĄ°ëŹŒì ëí ì€êł ìëì„ êłì° ë° ì”ì ì€êłêž°ëČì ì ìíë©° íčí êłĄë©Žì ê”Źìë ëč ê”ŹìĄ°ëŹŒì ì€êłë„Œ ì§ì€ì ìŒëĄ ë€ëŁŹë€. ìì íìëłí(Free-form deformation)êž°ëČêłŒ ì ì êłĄì 볎ê°êž°ëČì íì©íìŹ ì§ìŹê° íë©Žìì íì ë° ì€êł ëłìë„Œ ì ìíêł êłĄë©Žìì êłĄì íìì ëíëŽë ìĄ°ì ì ììčë„Œ íŽìì ìŒëĄ ííí ì ììŒë©° ìŽì ì 믞ë¶ì í”íŽ ì íí ì€êłìëì„ì êłì°íë€. ìŽë„Œ í”íŽ ì€êł ëłìì ê°ìë„Œ ì€ìŒ ì ìêł ì€êłì 맀ê°íê° ê°ížíŽì§ë€. ê°ë°ë ë°©ëČëĄ ì ë€ìí íì€ ë° ìŽëíì êČœêłìĄ°ê±Žì ê°ë ëčêłŒ ìì ëëłí 돞ì ë„Œ í”íŽ êČìŠëë©° ìŹëŹê°ì§ íìŽì§ ìĄ°ëŠœ ê”ŹìĄ°ëŹŒì ì”ì ì€êłì ì ì©ëë€. ëíì ìŒëĄ, ì ëš ê°ì± ë° ì¶©êČ© íĄì íčì±êłŒ ê°ì êž°êłì ëŹŒì±ìčì ê°ì ì ìíŽ íì©ëë ì€ê·žì í± (auxetic) íčì±ìŽ ê·čëíë êČ©ì ê”ŹìĄ°ë„Œ ì€êłíë©° ìžì„ ë° ìì¶ ëëłí ëȘšëìì ìŒì í ìì íŹììĄëčë„Œ ëíëì 3ì°šì í늰í
êłŒ êŽíì ëłí ìžĄì êž°ì ì ìŽì©íìŹ ì€íì ìŒëĄ êČìŠíë€. ëí ì°ëŠŹë ììì ì ê°ì ìíŽ íì©ëë ê°ìČ ì ìŁŒíì ììëììì ë°Žëê°ìŽ ê·čëíë êČ©ì ê”ŹìĄ°ë„Œ ì ìíë€.Abstract
1. Introduction
2. Isogeometric analysis of geometrically exact nonlinear structures
3. Isogeometric confinguration DSA of geometrically exact nonlinear structures
4. Numerical examples
5. Conclusions and future works
A. Supplements to the geometrically exact Kirchhoff beam model
B. Supplements to the geometrically exact shear-deformable beam model
C. Supplements to the geometrically exact shear-deformable shell model
D. Supplements to the invariant formulations
E. Supplements to the geometric constraints in design optimization
F. Supplements to the design of auxetic structures
ìŽëĄDocto
Review of research in feature-based design
Research in feature-based design is reviewed. Feature-based design is regarded as a key factor towards CAD/CAPP integration from a process planning point of view. From a design point of view, feature-based design offers possibilities for supporting the design process better than current CAD systems do. The evolution of feature definitions is briefly discussed. Features and their role in the design process and as representatives of design-objects and design-object knowledge are discussed. The main research issues related to feature-based design are outlined. These are: feature representation, features and tolerances, feature validation, multiple viewpoints towards features, features and standardization, and features and languages. An overview of some academic feature-based design systems is provided. Future research issues in feature-based design are outlined. The conclusion is that feature-based design is still in its infancy, and that more research is needed for a better support of the design process and better integration with manufacturing, although major advances have already been made
Towards a better integration of modelers and black box constraint solvers within the Product Design Process
This paper presents a new way of interaction between modelers and solvers to support the Product Development Process (PDP). The proposed approach extends the functionalities and the power of the solvers by taking into account procedural constraints. A procedural constraint requires calling a procedure or a function of the modeler. This procedure performs a series of actions and geometric computations in a certain order. The modeler calls the solver for solving a main problem, the solver calls the modelerâs procedures, and similarly procedures of the modeler can call the solver for solving sub-problems. The features, specificities, advantages and drawbacks of the proposed approach are presented and discussed. Several examples are also provided to illustrate this approach
- âŠ