Dissertations / Theses on the topic 'Computer-aided modeling (CAD)'

The scope of this study is to illustrate the relationship between computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, and to show how architectural modeling should be positioned in the process of computer-aided design/computer-aided manufacturing (CAD/CAM) systems. The integration of computer aided technologies with architectural design is investigated in terms of design-production/fabrication interaction. The research has been based on a case study in which the CAD/CAM process from the initial design phase to the actual manufacturing of the design object has been explored. A design object is modeled using CAD and the model is manufactured using CAM in order to illustrate the process of CAD/CAM and its potentials related to architectural design and the construction/manufacturing/fabrication process of building. Thus, the study tries to demonstrate what digital tools can provide to the field of architecture, and lists the requirements for architectural modeling to acquire compatibility among the parts of the building process.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Schaefer, Dirk; Committee Member: Panchal, Jitesh; Committee Member: Paredis, Chris; Committee Member: Rosen, David; Committee Member: Yoder, Douglas. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Les transistors rapides actuels présentent un retard lorsqu’ils fonctionnent à très hautes fréquences ou en régime transitoire rapide. Cet effet est appelé effet non quasi-statique (NQS). Dans cette thèse, l’effet NQS est analysé de manière concise de façon à être directement implanté dans les modèles de composant pour les bibliothèques de circuit en utilisant le langage standard VerilogA. Les mécanismes physiques à la base de l’effet NQS sont évalués dans le domaine de fonctionnement petit signal et les résultats sont comparés aux travaux déjà publiés. S’agissant du modèle standard bipolaire HICUM, les effets NQS latéraux et verticaux sont examinés séparément à partir du même modèle, en régime de fonctionnement transitoire et fréquentiel grâce à un sous-circuit dédié au calcul de la phase du signal. A partir de ce sous-circuit, la modélisation compacte avec HICUM est comparée aux données issues de mesures et issues de simulation amont. Enfin, un nouveau sous-circuit calculant l’excès de phase est proposé pour prendre mieux en compte les effets non quasi-statiques dans les transistors bipolaires<br>Modern high speed (RF) transistors encounter certain delay while operated at high frequency or under fast transient condition. This effect is named as Non Quasi Static (NQS) effect. In the current work, NQS effect is analyzed in a concise manner so that it can be readily implemented in a compact model using the VerilogA description language. The basic physics behind this effect is investigated in small signal domain and the results are compared with the published work. In popular bipolar model HICUM lateral and vertical NQS are examined separately and uses the same model for both transient and AC operation which requires an additional minimum phase type sub circuit. Compact modeling with HICUM model is performed in both measurement and device simulated data. At last, an improved excess phase circuit is proposed to model the NQS effect

Saab Aeronautics’ section Overall Design and Survivability develops early aircraft concepts and utilizes Computer Aided Design (CAD) to ensure the feasibility of principal- and critical characteristics. Saab has over the years developed several start models of aircrafts in CAD from pre-defined aircraft configurations, which are to some extent non-generic. When new configurations are to be explored, manual- and repetitive work is required if the new configuration cannot be attained solely through parametric modifications of a start model. The complexity of these CAD models also demands great knowledge of how aircraft components interact with each other to ensure compatibility. The project covered in this thesis was thus carried out to develop a more effective way for Saab to create and explore a larger design space. This by creating a framework that consists of a product configurator coupled with a library of generic CAD models. The product configurator that was created is the Saab Tradespace Analyzer &amp; Reconfigurator (STAR), which takes compatibility relationships into consideration to facilitate concept selection. The STAR also provides a dynamic design space calculation to indicate how close the user is to a final concept selection. Two generic CAD models were created, a fuselage model and an air inlet model. A skeleton model was also created in order to reduce model dependencies and to control the main geometry of the aircraft product. In addition to these, an already existing wing model was implemented to form the library of generic CAD models. The framework coupling the STAR with the CAD library utilizes design automation to allow automatic CAD model generation of a concept that has been selected within the STAR. It was concluded through extrapolation that the created framework would allow Saab to create and explore a larger design space in a more effective way than what is done today, provided the library of CAD models were to contain the same number of components as today’s start models.

Computer Aided Design (CAD) is a tremendously powerful tool within the design industry, yet when used inappropriately, can be a hindrance to product designers. Employing ineffective CAD modelling strategies (CMS) can lead to increased project costs as a result of an unnecessary amount of time being spent making design changes to the product. However, when CMS are implemented effectively, it has been shown that novice CAD users can not only create an accurate three-dimensional (3D) representation of a product, but are able to make key design changes quickly and effectively (a skill often associated with practiced CAD users). The submission detailed herein documents the development of 3D CAD modelling strategies and the investigation into their impact on novice users. The submission has been split into eleven chapters. The subject is introduced in Chapter One, where the background and structure of the research is considered, as well as the implications of lack of CAD experience for novice CAD users. Some initial research aims were generated, which are examined in the Exploratory Study detailed in Chapter Two. This includes an exploratory review of literature together with details of the initial studies involving CAD users, where it was found that there were potential benefits of communicating CMS to novice CAD users. Having examined the prior art in the field, a theme emerges regarding the benefits of communicating CMS to product designers and focused research aims are presented. The research methodology is considered in Chapter Three, which outlines the databases built to manage the periodic review of literature, to ensure that methodologies were in place to draw meaningful results from the data, both qualitative and quantitative. The pilot study, used to understand how designers implemented strategies when modelling on CAD is discussed in Chapter Four, which lead to the definition of the content of the CAD Modelling Strategies Support (CMSS) material in Chapter Five. Following this, a systematic review of literature on the subject of teaching and learning is discussed in Chapter Six, including pedagogical issues such as the Experiential Learning Theory and visualisation, where a blended learning approach was identified as being the most appropriate method with which to present the CMSS material. The CMSS material was then piloted a number of times within the Pilot Study Two phase detailed in Chapter Seven. The final CMSS material is then outlined in Chapter Eight, which was later evaluated against the emergent theme, as documented in Chapter Nine. The discussion continues in Chapter Ten where it was found that the participants exposed to the CMSS material had used a more effective strategy to model a product on CAD than those who did not use the material (the Control Group). This resulted in them being able to make key design changes to their models in approximately half the time of the Control Group. It was found that the CMSS material produced competent CAD users who could easily make design changes to their models, which inferred implications on the teaching and learning of CAD. Overall conclusions and recommendations relating to the research are drawn in Chapter Eleven that, again, bear direct relevance to how product designers learn to use CAD.

Ingeniero Civil Mecánico<br>Tanto los software de Diseño Asistido por Computadora (CAD) como las herramientas de análisis por medio del Método de Elementos Finitos (FEM) han tenido un enorme impacto en la actividad ingenieril en las últimas décadas. Aun así, tienen la desventaja de que las geometrías CAD no son directamente compatibles con las geometrías utilizas en FEM, lo cual resulta en la necesidad de re-mallar la geometría varias veces durante un ciclo de soluciones FEM. Para solucionar esto, IGA ha sido propuesto como una metodología capaz de generar un vínculo directo entre el diseño mediante CAD y el análisis FEM. La principal idea dentro de IGA es sustituir las funciones de forma utilizadas en FEM por las funciones de base que utiliza el software CAD, conocidas como NURBS. Por otro lado, los problemas de mecánica de fractura presentan dificultades extras para los métodos numéricos debido a las irregularidades que presenta la geometría de la grieta y el campo de esfuerzos singular que se origina alrededor de la punta de la grieta. Para solucionar esto, una nueva generación de métodos numéricos ha sido desarrollada, la cual incluye el renombrado XFEM. La misma idea del XFEM ha sido formulada dentro del contexto de IGA, conocido como Análisis Isogeométrico Extendido (XIGA) y ha sido aplicado exitosamente en grietas rectas y curvas en problemas de elasticidad 2-D. Sin embargo, los trabajos publicados en este tema se han limitado a problemas simples. El objetivo de este trabajo es aplicar el XIGA en problemas de mecánica de fractura con grietas en geometrías complejas dadas por curvas CAD. El trabajo consiste en implementar la metodología de enriquecimiento del XFEM dentro de un código IGA para solucionar problemas de mecánica de fractura 2D. La primera simulación consiste en el problema de una placa infinita con una grieta recta. Esta es resuelta utilizando enriquecimiento Heaviside y Heaviside con punta de grieta. La segunda simulación consiste en emplear NURBS cuadráticos y cúbicos para resolver el problema de un agujero circular con una grieta. En ambas simulaciones se calculan las normas de error $L^{2}$, $H^{1}$ y energética, y el factor de intensidad de esfuerzos (SIF) $K_{I}$ para evaluar los resultados. Ambos problemas exhiben convergencia sub-óptima al momento de refinar la malla y el $K_{I}$ está en concordancia con la solución analítica. ---- Both the CAD software and FEM software have a huge impact on engineering nowadays. Even though both are powerful tools for design and analysis, the main drawback is that CAD geometries and Finite Element models do not completely match, which results in the necessity to re-parametrize the geometry many times during the solution cycle in FEM. Isogeometric Analysis (IGA) was proposed to fulfill this gap and create the direct link between the CAD design and FEM analysis. The main idea of IGA is to substitute the shape functions used in FEM by the shape functions used in the CAD software. Nevertheless, fracture mechanics problems present difficulty for any numerical method due to the irregularity in the crack domain and the singularity of the stress field in the vicinity of the crack tip. To overcome this difficulty, a new generation of numerical methods has been developed, which includes the so-called Extended Finite Element Method (XFEM). The same idea was implemented within the IGA (XIGA) and applied successfully for straight and curved cracks in two-dimensional elasticity. However, the published work is limited to simple crack configurations. The objective of this work is to investigate the applicability and efficiency of the XIGA for cracks of complex geometries given by CAD curves. The work consists in implementing the enrichment method of the XFEM into the in-house IGA code and in verifying the approach on a number of benchmark problems. Heaviside and Heaviside $+$ crack tip enrichment has been implemented for a benchmark problem of an edge crack and the results are shown to be in excellent agreement with the analytic solution. The comparison of the results is done in $L^{2}$, $H^{1}$ and Energy norm of the error, which exhibit the sub-optimal convergence rates, when the mesh size tends to zero. Quadratic and Cubic NURBS were employed to solve the benchmark problem of an edge crack in a circular hole and the results are shown to be in agreement with the analytic solution, despite the complicity of the geometry. The stress intensity factor (SIF) $K_{I}$ is computed and in both benchmark problems it is in agreement with their theoretical value.<br>Este trabajo ha sido parcialmente financiado por el proyecto FONDECYT 11130259

L’objectif de ce travail de thèse est de pouvoir intégrer totalement l’optimisation de forme des raidisseurs de capot dans un processus de conception industrielle et cela afin d’optimiser la forme et la distribution des raidisseurs dans un contexte multi-objectif (voire multi-disciplinaire) d’une structure 3D surfacique. Pour ce faire, nous avons tout d’abord établi un aperçu de l’état de l’art dans l’optimisation de forme des structures en classifiant les différentes méthodes de paramétrage de forme, en trois catégories ; les méthodes basées sur la géométrie (telle la paramétrisation d’un modèle de type CAO), les méthodes basées sur une grille fixe (telles que les méthodes d’optimisation topologique) et les méthodes basées sur le maillage (telles que les méthodes de régularisation du maillage). Toutefois, aucune de ces méthodes ne satisfait pleinement aux objectifs posés. Nous introduisons ainsi dans cette thèse la méthode FEM-CsG : Finite Element Mesh - Constructive surface Geometry. Imprégnée d’un fort contexte industriel, cette méthode propose une réponse à des contraintes telles que la possibilité de représenter la solution optimale par un ensemble de paramètres CAO, la possibilité d’adapter le modèle EF à l’analyse souhaitée et la garantie d’une représentation géométrique et d’un maillage robuste. En proposant d’intégrer des formes élémentaires paramétrées et prémaillées issues d’une bibliothèque de formes dans une structure coque 3D maillée par l’utilisation des variables issues de la CAO, la méthode FEM-CsG permet une évolution constante de la topologie guidée par l’optimisation. Ainsi, même si la topologie est modifiée la forme résultante reste conforme avec une représentation CAO par construction, correspondant davantage à la réalité des optimisations réalisées en avant-projet. La méthode FEM-CsG a été validée sur deux études de cas, de complexité variable, permettant de mettre en avant la robustesse de cette dernière. Ainsi, avec un choix intelligent et cohérent des variables de formes, les problèmes d’optimisation peuvent avec un nombre restreint de variables explorer un nombre important de topologies ou de formes. Les changements de topologies s’effectuent de manière continue, validant ainsi la méthode à tout type d’analyse souhaitée<br>The objective of this thesis work is to be able to completely integrate shape optimization of car inner hood stiffeners in a complex industrial process, in order to fully optimize the shape and distribution of the stiffeners in a multi-objective approach (or even multi-disciplinary) of a 3D surfacic structure. To this end, we established, at the outset, an insight of the state-of-the-art in shape optimization of structures by classifying the different shape parametrizations in three distinct categories : geometry-based methods (a shape parametrization such as a CAD model), grid-based methods (such as topology optimization methods) and mesh-based methods (such as morphing methods or mesh regulation). However, none of these methods fully satisfies the set objectives. Thus, we will introduce in this work the FEM-CsG method : Finite Element Mesh - Constructive surface Geometry. Bolstered by its strong industrial context, this method offers a response to such constraints, i.e. the possibility to represent the optimal solution by a system of CAD parameters, the possibility to adapt the FE model to the wanted analysis and the guarantee of a robust geometrical representation and mesh stability. We offer to incorporate premeshed parameterized elementary forms into a 3D sheet meshed structures. Hence, these forms are arising from a CAD parameterized elementary form library. Furthermore, the FEM-CsG method uses a set of operators acting on the mesh allowing a constant evolution of the topology guided by optimization. Therefore, even if the topology may vary, the resulting shapes comply with CAD representations by construction, a solution better reflecting the reality of optimizations performed during the preliminary development stage. The FEM-CsG method has been validated on two simple case studies in order to bring forward its reliability. Thus, with an intelligent and coherent choice of the design variables, shape optimization issues may, with a restrictive number of variables, explore an important number of shapes and topologies. Topology changes are accomplished in a continuous manner, therefore validating the FEM-CsG method to any desired analysis

У наш час завдання кінематичного аналізу механізмів найчастіше вирішуються графічними або аналітичними методами. З розвитком мов програмування та можливостей відповідних середовищ розробки стає можливою реалізація кінематичного аналізу плоских важільних механізмів програмними методами. Запропонована реалізація являється комбінованим графоаналітичним методом, оскільки аналітичне рішення засноване на графічних побудовах та рішенні відповідних геометричних задач. За допомогою мови програмування Processing реалізовано програмне забезпечення для кінематичного аналізу простих важільних механізмів. Кінематичний аналіз, важільний механізм, мова програмування Processing.<br>Nowadays, the problem of kinematic analysis of mechanisms is most often solved by graphical or analytical methods. According to the development of programming languages and the possibility of corresponding development environments, it becomes possible to implement the kinematic analysis of flat lever mechanisms using software methods. The proposed implementation is a combined graphoanalytical method, since the analytical solution is based on graphical constructions and the solution of the corresponding geometric problems. Using the programming language Processing implemented software for the kinematic analysis of simple lever mechanisms. Kinematic analysis, lever mechanism, programming language Processing.<br>В наше время задача кинематического анализа механизмов чаще всего решаются графическими или аналитическими методами. По развитию языков программирования и возможности соответствующих сред разработки становится возможна реализация кинематического анализа плоских рычажных механизмов программными методами. Предложен а реализация является комбинированном графоаналитическим методом, поскольку аналитическое решение основано на графических построениях и решении соответствующих геометрических задач. С помощью языка программирования Processing реализовано программное обеспечение для кинематического анализа простых рычажных механизмов. Кинематический анализ, рычажный механизм, язык программирования Processing.

This research aims at the specifics of Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) market. Through discussion of the digital model’s path since geometric construction till completion of a product the major trends are derived. Evolution of hardware for CAM challenges software developers to come up with new solutions. Growing numbers of CAD/CAM software proved to be considerable factor for incompatibility of data formats among systems. Therefore universal data exchange standards were claimed to enable communication. Also a few gaps of functionality among CAD/CAM software products encourages the development of new application, based on research. The set of functions to be integrated into application is supported theoretically according to researched information and tested practically during the realization of software. The most successful standards and tools are selected as the basis of new software. IGES (The Initial Graphics Exchange Specification) standard along with NURBS (Non-Uniform Rational BSpline) curves and surfaces is used for description of geometric data and OpenGL is used as drawing tool. Model analysis and modification for CAM includes following function description and realization: calculation of volume, non-uniform region scaling, 2D packing, curve control point reduction, curve conversion to lines and arcs. Testing results proves that most of the theoretic assumptions are correct and a development of such or similar software is truly... [to full text]

This investigation identifies how CAD models of typical automotive body assemblies could be defined to allow a continuous optimisation of the number of iterations required for the final design and the number of variants on the basis of Parametric Associative Design (PAD) and how methodologies for the development of surfaces, parts and assemblies of the automotive body can be represented and structured for a multiple re-use in a collaborative environment of concept phase of a Product Evolution (Formation) Process (PEP). The standardisation of optimised processes and methodologies and the enhanced interaction between all parties involved in product development could lead to improve product quality and reduce development time and hence expenses. The fundamental principles of PAD, the particular methodologies used in automotive body design and the principles of methodical development and design in general are investigated. The role which automotive body engineers play throughout the activities of the PEP is also investigated. The distribution of design work in concept teams of automotive body development and important methodologies for the design of prismatic profile areas is critically analysed. To address the role and distribution of work, 25 group work projects were carried out in cooperation with the automotive industry. Large assemblies of the automotive bodies were developed. The requirements for distributed design work have been identified and improved. The results of the investigation point towards a file based, well structured administration of a concept design, with a zone based approach. The investigation was extended to the process chain of sections, which are used for development of surfaces, parts and assemblies. Important methods were developed, optimised and validated with regard to an update safe re-use of 3D zone based CAD models instead of 2D sections. The thesis presents a thorough description of the research undertaken, details the experimental results and provides a comprehensive analysis of them. Finally it proposes a unique methodology to a zone based approach with a clearly defined process chain of sections for an update-safe re-use of design models.