Evalutionary algorithms for ship hull skinning approximation

Traditionally, the design process of a hull involves simulation using clay models. This must be done cautiously, accurately and efficiently in order to sustain the performance of ship. Presently, the current technology of Computer Aided Design, Manufacturing, Engineering and Computational Fluid Dynamic has enabled a 3D design and simulation of a hull be done at a lower cost and within a shorter period of time. Besides that, automated design tools allow the transformation of offset data in designing the hull be done automatically. One of the most common methods in constructing a hull from the offset data is the skinning method. Generally, the skinning method comprised of skinning interpolation and skinning approximation. Skinning interpolation constructs the surface perfectly but improper selection of parameterization methods may cause bumps, wiggles, or uneven surfaces on the generated surface. On the other hand, using the skinning surface approximation would mean that the surface can only be constructed closer to data points. Thus, the error between the generated surface and the data points must be minimized to increase the accuracy. Therefore, this study aims to solve the error minimization problem in order to produce a smoother and fairer surface by proposing Non Uniform Rational B-Spline surface using various evolutionary optimization algorithms, namely, Gravitational Search Algorithm, Particle Swarm Optimization and Genetic Algorithm. The proposed methods involve four procedures: extraction of offset data from line drawing plan; generation of control points; optimization of a surface; and validations of hull surfaces. Validation is done by analyzing the surface curvature and errors between the generated surface and the given data points. The experiments were implemented on both ship hull and free form models. The findings from the experiments are compared with interpolated skinning surface and conventional skinning surface approximation. The results show that the optimized skinning surfaces using the proposed methods yield a smaller error, less control points generation and feasible surfaces while maintaining the shape of the hull

Geometric Modeling of Cellular Materials for Additive Manufacturing in Biomedical Field: A Review

Advances in additive manufacturing technologies facilitate the fabrication of cellular materials that have tailored functional characteristics. The application of solid freeform fabrication techniques is especially exploited in designing scaffolds for tissue engineering. In this review, firstly, a classification of cellular materials from a geometric point of view is proposed; then, the main approaches on geometric modeling of cellular materials are discussed. Finally, an investigation on porous scaffolds fabricated by additive manufacturing technologies is pointed out. Perspectives in geometric modeling of scaffolds for tissue engineering are also proposed

Subdivision Directional Fields

We present a novel linear subdivision scheme for face-based tangent directional fields on triangle meshes. Our subdivision scheme is based on a novel coordinate-free representation of directional fields as halfedge-based scalar quantities, bridging the finite-element representation with discrete exterior calculus. By commuting with differential operators, our subdivision is structure-preserving: it reproduces curl-free fields precisely, and reproduces divergence-free fields in the weak sense. Moreover, our subdivision scheme directly extends to directional fields with several vectors per face by working on the branched covering space. Finally, we demonstrate how our scheme can be applied to directional-field design, advection, and robust earth mover's distance computation, for efficient and robust computation

Modèles d’intégration des designers créatifs dans les processus de conception industriels

Many studies show that industrial design is key to triggering, fostering andsustaining innovation. However, the unique capacities of creation and innovationof industrial designers make it challenging for them to thrive within industrialenvironments.The challenge for companies is to create the optimal work environment forthose professionals, while ensuring their work can be integrated smoothly intothe existing industrial design processes. We assume this dilemma is partiallystemming from the intensive use of sequential design models in the industry.Design tools were developed on the assumption that creative front end andproduct development should be separated.We introduce here a new model, aiming at depicting accurately the reasoningmodes and the nature of the object being designed with the digital ComputerAided Design (CAD) suites. This model is the result of the joint mobilization offour academic fields : computer, cognitive and management science and designtheories. Dassault Systèmes and their CATIA software have proven to be an excellentresearch environment for such questions. As we have been thinking, thenew model (laminated) makes three new hypothesis. Those unheard assertionshave been suggested and validated with this thesis :1/ Some specific design workshops are able to provide simultaneously robust andgenerative design capacities. We call this characteristic «acquired originality».2/ The object representations within by the software are not the result of successiverefinements but derive directly from a parameterized set of rules.3/ Industrial designers have specific requirements for CAD tools, different fromtheir engineers and artists counterparts because what they design is fundamentallydifferent. IDs generate conceptual models using a mass singularity technique.Those results sketch the emergence of a new generation of CAD tools forindustrial designers and able to foster innovation.De décisifs et puissants enjeux d'innovation ainsi que de renouvellement del'identité des objets bouleversent le monde industriel. De telles aptitudes créativessont usuellement associées aux designers industriels. Cependant, ces professionnelsne sont actuellement pas intégrés dans les processus numériques deconception.Afin de décrire ce paradoxe, nous formulons l'hypothèse que, l'omniprésencedans l'industrie de modèles de la conception de type séquentiel, qui juxtaposentcréativité et développement produit, entrave l'intégration des designers industrielsau sein des processus industriels. En effet, en compartimentant la conceptionen silos, ce type de modèles généralistes inhibe les méthodes spécifiquesdes concepteurs créatifs. Bien plus, les outils numériques adjoints au modèle séquentielétant calqués sur sa logique, ils reproduisent et les inconvénients d'unetelle structuration.En mobilisant quatre disciplines académiques qui traitent des outils numériques,à savoir les sciences informatiques, cognitives, de gestion et les théoriesde la conception, nous élaborons un nouveau modèle «dit stratifié». Ce dernierrévèle les modes de raisonnement empruntés par les concepteurs créatifs ainsique la nature des produits élaborés dans les environnements logiciels. A ce titre,l'entreprise Dassault Systèmes ainsi que la suite CATIA se sont révélés un substratde recherche idéal. Comme attendu, notre nouveau modèle propose desassertions inédites qui sont validées au cours de notre travail. Nous avons alorsdémontré que :1/ Certains ateliers de conception favorisent simultanément robustesse et générativité.Nous qualifions cette nouvelle propriété d'«originalité acquise».2/ Les avatars dans le logiciel ne résultent pas d'un raffinement progressif del'objet mais sont plutôt l'instanciation d'une base de règles paramétrée.3/ Les designers industriels requièrent des outils distincts de ceux employés parles artistes 3D ou les ingénieurs, de par la nature de leur conception. Plus exactement,ces professionnels génèrent des modèles conceptuels selon une logiquede singularité de masse.Ces résultats offrent ainsi la perspective engageante de l'émergence d'unenouvelle génération d'outils numériques de conception. Ces outils inédits serontaptes à intégrer les designers industriels et à proposer de l'innovation à la d

Transverse Isotropic and Orthotropic Composites: Experiments, Identification and Finite Element Analysis

Die konstitutive Modellierung und numerische Analyse des Verhaltens von Verbundwerkstoffen, insbesondere von transversal isotropen und orthotropen Werkstoffen, hat in der Industrie große Aufmerksamkeit bekommen. Dies ist vor allem durch die Verwendung von Verbundwerkstoffen für ein breites Spektrum von Anwendungen in verschiedenen Branchen erkennbar. Vorteile von Verbundwerkstoffen wie hohe Festigkeit und Flexibilität bei der Konstruktion machen diese attraktiv. Aufgrund vieler Designfaktoren bei Verbundwerkstoffen, wie zum Beispiel das Verbinden mit anderen Bauteilen, sind Löcher in Laminaten unvermeidlich. Die Fasern werden in der Regel durch Bohren eines Lochs im Laminat bzw. unterbrochen. Alternativ können die Fasern um die Löcher herum gelegt werden. Eines der Ziele dieser Arbeit ist es, herauszufinden, ob die Tendenz zum Bruch, d.h. die zugehörige Spannungsverteilung zu untersuchen. Um die beiden Fälle (Faserumlenkung versus gerader Faser) zu vergleichen und einen tieferen Einblick in den Prozess durch Simulationen zu erhalten, wird ein konstitutives Modell der transversalen Isotropie für den Fall kleiner Verzerrungen hergleitet. Das Modell ist in das in-house Finite-Elemente Programm TASAFEM implementiert worden. Eine große Herausforderung stellt die Beschreibung der räumlich verteilten Faserorientierungen für den Fall, dass die Fasern um das Loch herumgelegt werden. Zunächst wird die Verteilung der Fasern mit Hilfe der Stromlinienfunktion modelliert, um die inhomogenen Faserorientierungen für die FE-Simulationen zu erhalten. Um die Genauigkeit der Simulationen zu erhöhen, werden B-Splines verwendet, um die Faserrichtungen entsprechend den experimentellen Beobachtungen zu modellieren. Im sehr breiten Bereich der geometrischen Modellierung insbesondere bei CAD-Anwendungen (Computer-Aided Design) werden B-Splines häufig zur Beschreibung von Kurven und Flächen verwendet, vor allem aufgrund ihrer mathematischen Eigenschaften und ihrer hohen Flexibilität. Hierbei werden die Eigenschaften von Tangentenvektoren an Koordinatenflächen ausgenutzt, um die Richtungen zu bestimmen. Eine weitere Herausforderung bei den durchgeführten Simulationen ist die Identifikation der erforderlichen Materialparameter für das verwendete Materialmodell. Zu diesem Zweck werden verschiedene Experimente durchgeführt, um die Parameter eindeutig zu bestimmen. Zum Schluss wird der gesamte Prozess der Modellierung, Simulation und Identifizierung der Materialparameter durch spezielle Tests validiert. Orthotrope Laminate gehören zu den am häufigsten verwendeten Laminaten in industriellen Anwendungen. Die Untersuchungen werden daher auf orthotrope Laminate ausgeweitet. Das Ziel ist es, das Verhalten auch auf orthotrope Laminate auf der Grundlage identifizierter Parameter zu übertragen. Es wird ein konstitutives Modell der Orthotropie für den Fall kleiner Dehnungen angewandt und in den in-house-Code TASAFEM implementiert. Auch hier besteht die Herausforderung, der Materialparameter von orthotropen Laminaten bereitzustellen, die für die erforderlichen FE-Simulationen notwendig sind. Die Materialparameter werden im Rahmen eines Least-Square-Ansatzes mit Hilfe von Messdaten eines digitalen Bildkorrelationssystems identifiziert. Zu diesem Zweck sind verschiedene Versuche wie Zug-, Scher-, Druck- und Zugschertests durchgeführt worden. Diese sind zur Identifikation der neun Materialparameter der linearen, orthotropen Elastizität herangezogen worden. Im nächsten Schritt ist es notwendig, den numerischen Ansatz mit experimentellen Messungen zu validieren. Zur Validierung werden Proben verwendet, bei denen die Proben mit zwei senkrechten Faserrichtungen ausgestattet sind. Hierbei wird das Loch nach dem Herstellungsprozess der Proben gebohrt. Zum Schluss wird ein Vergleich zwischen den Ergebnissen der Finite-Elemente-Simulationen und den experimentellen Ergebnissen vorgestellt.In today’s engineering industry, constitutive modeling and numerical analysis of the behavior of composite materials, particularly transversely isotropic and orthotropic materials, have gained a lot of attention. This is mainly due to the usage of composites for a wide range of applications in different industries. Moreover, the advantages of composites such as high strength and flexibility in design make these materials attractive. Due to many factors in the design of composites, holes in laminates are unavoidable. Fibers are usually cut by drilling a hole into laminates. Alternatively, fiber can be bypassed around holes in order to reduce the fracture tendency around a hole, or to achieve different stress distributions. One of the goals of this work is to compare these cases: In one case, fibers were bypassed around the hole while fibers were cut in the other case by drilling a hole. In order to compare these cases and to get a deeper insight into the process using simulations, a constitutive model of transverse isotropic for the small strain case is applied based on large strain theory. The model is implemented in the in-house finite element program TASAFEM. One major challenge of this simulation is to determine the fiber orientations. To begin with, the circumplacement of fibers is modeled using the streamline function to obtain the inhomogeneous fiber direction for finite element simulations. In order to increase the precision of simulations, the B-spline method is used to model the fiber directions according to the experimental observations. In the broad field of geometric modeling and computer-aided design (CAD), it is common to use B-splines to describe curves and surfaces which is mainly due to their mathematical properties and their flexibility. Another challenge regarding the simulations is to identify the required parameters for the presented material model. Several different experiments are carried out in this regard. Finally, the whole process of modeling, simulation, and material parameter identification is validated by means of validation tests. Orthotropic laminates belong to the most commonly used laminates in industrial applications. The investigation is extended to orthotropy laminates, where we have fibers in two directions, and our aim is to predict the behavior of orthotropy laminates based on the calculated parameters. A constitutive model of orthotropy for the small strain case is applied and implemented in the inhouse code TASAFEM. Another challenge in this work is to calculate the material parameters of orthotropy laminates as a basis for finite element simulations. The material parameters are identified within a least-square approach with the help of optical results of a digital image correlation system. For this purpose, different experiments such as tensile, three rail shear, lap shear and compression tests are carried out. Nine material parameters of linear elastic for orthotropy case are identified. In the next step, it is necessary to validate the numerical approach with experimental observations. The validation examples are performed as theses samples have fibers in two perpendicular directions, where the hole is drilled after the production process. Finally, a comparison between the finite element simulations and the experimental results is provided

Realistic Visualization of Accessories within Interactive Simulation Systems for Garment Prototyping

In virtual garment prototyping, designers create a garment design by using Computer Aided Design (CAD). In difference to traditional CAD the word "aided" in this case refers to the computer replicating real world behavior of garments. This allows the designer to interact naturally with his design. The designer has a wide range of expressions within his work. This is done by defining details on a garment which are not limited to the type of cloth used. The way how cloth patterns are sewn together and the style and usage of details of the cloth's surface, like appliqués, have a strong impact on the visual appearance of a garment to a large degree. Therefore, virtual and real garments usually have a lot of such surface details. Interactive virtual garment prototyping itself is an interdisciplinary field. Several problems have to be solved to create an efficiently usable real-time virtual prototyping system for garment manufacturers. Such a system can be roughly separated into three sub-components. The first component deals with acquisition of material and other data needed to let a simulation mimic plausible real world behavior of the garment. The second component is the garment simulation process itself. Finally, the third component is centered on the visualization of the simulation results. Therefore, the overall process spans several scientific areas which have to take into account the needs of each other in order to get an overall interactive system. In my work I especially target the third section, which deals with the visualization. On the scientific side, the developments in the last years have shown great improvements on both speed and reliability of simulation and rendering approaches suitable for the virtual prototyping of garments. However, with the currently existing approaches there are still many problems to be solved, especially if interactive simulation and visualization need to work together and many object and surface details come into play. This is the case when using a virtual prototyping in a productive environment. The currently available approaches try to handle most of the surface details as part of the simulation. This generates a lot of data early in the pipeline which needs to be transferred and processed, requiring a lot of processing time and easily stalls the pipeline defined by the simulation and visualization system. Additionally, real world garment examples are already complicated in their cloth arrangement alone. This requires additional computational power. Therefore, the interactive garment simulation tends to lose its capability to allow interactive handling of the garment. In my work I present a solution, which solves this problem by moving the handling of design details from the simulation stage entirely to a completely GPU based rendering stage. This way, the behavior of the garment and its visual appearance are separated. Therefore, the simulation part can fully concentrate on simulating the fabric behavior, while the visualization handles the placing of surface details lighting, materials and self-shadowing. Thus, a much higher degree of surface complexity can be achieved within an interactive virtual prototyping system as can be done with the current existing approaches