• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 196
  • 87
  • 82
  • 38
  • 29
  • 24
  • 11
  • 7
  • 7
  • 6
  • 6
  • 5
  • 4
  • 4
  • 4
  • Tagged with
  • 570
  • 103
  • 58
  • 57
  • 56
  • 45
  • 44
  • 37
  • 35
  • 35
  • 34
  • 33
  • 32
  • 31
  • 30
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
521

Tariffs Eliminations and Exchange Rate Fluctuations Relationships to Trade Elasticity

Kuevey, Folly Kuevey 01 January 2017 (has links)
The enactment of the North America Free Trade Agreement (NAFTA) was intended to reduce tariffs on most goods by 2008 among Canada, the United States, and Mexico, and to create the largest regional market outside the European Union. Early research conducted to investigate the relationships between tariffs elimination and trade volume focused mainly on macrolevel effects with mixed results, without acknowledging the possible influence from exchange rate fluctuations. After 20 years, NAFTA has provided the opportunity to observe a significant reduction in tariffs between 1994 and 2013. Skepticism regarding the relationship between trade liberalization and the regional economy, and the controversy still surrounding NAFTA, suggests that other factors might influence trade, making the current study relevant. The purpose of this study was to investigate possible relationships between exchange rate fluctuations and trade volume during a period when tariffs were eliminated. This study focused on 2 basic theories of preferential trade and the exchange rate, and data were collected on imports-exports between Mexico and the United States. Regression analyses showed a relationship between exchange rate fluctuation and trade volume when tariffs are eliminated. The findings may help exporters and unions understand the implications of other factors affecting trade. The findings may also help union leaders understand how other economic factors may have implication on global economy rather than focusing solely on trade agreements, and to better strategize in addressing social issues of concern related to globalization.
522

Mid-level representations for modeling objects / Représentations de niveau intermédiaire pour la modélisation d'objets

Tsogkas, Stavros 15 January 2016 (has links)
Dans cette thèse, nous proposons l'utilisation de représentations de niveau intermédiaire, et en particulier i) d'axes médians, ii) de parties d'objets, et iii) des caractéristiques convolutionnels, pour modéliser des objets.La première partie de la thèse traite de détecter les axes médians dans des images naturelles en couleur. Nous adoptons une approche d'apprentissage, en utilisant la couleur, la texture et les caractéristiques de regroupement spectral pour construire un classificateur qui produit une carte de probabilité dense pour la symétrie. Le Multiple Instance Learning (MIL) nous permet de traiter l'échelle et l'orientation comme des variables latentes pendant l'entraînement, tandis qu'une variante fondée sur les forêts aléatoires offre des gains significatifs en termes de temps de calcul.Dans la deuxième partie de la thèse, nous traitons de la modélisation des objets, utilisant des modèles de parties déformables (DPM). Nous développons une approche « coarse-to-fine » hiérarchique, qui utilise des bornes probabilistes pour diminuer le coût de calcul dans les modèles à grand nombre de composants basés sur HOGs. Ces bornes probabilistes, calculés de manière efficace, nous permettent d'écarter rapidement de grandes parties de l'image, et d'évaluer précisément les filtres convolutionnels seulement à des endroits prometteurs. Notre approche permet d'obtenir une accélération de 4-5 fois sur l'approche naïve, avec une perte minimale en performance.Nous employons aussi des réseaux de neurones convolutionnels (CNN) pour améliorer la détection d'objets. Nous utilisons une architecture CNN communément utilisée pour extraire les réponses de la dernière couche de convolution. Nous intégrons ces réponses dans l'architecture DPM classique, remplaçant les descripteurs HOG fabriqués à la main, et nous observons une augmentation significative de la performance de détection (~14.5% de mAP).Dans la dernière partie de la thèse nous expérimentons avec des réseaux de neurones entièrement convolutionnels pous la segmentation de parties d'objets.Nous réadaptons un CNN utilisé à l'état de l'art pour effectuer une segmentation sémantique fine de parties d'objets et nous utilisons un CRF entièrement connecté comme étape de post-traitement pour obtenir des bords fins.Nous introduirons aussi un à priori sur les formes à l'aide d'une Restricted Boltzmann Machine (RBM), à partir des segmentations de vérité terrain.Enfin, nous concevons une nouvelle architecture entièrement convolutionnel, et l'entraînons sur des données d'image à résonance magnétique du cerveau, afin de segmenter les différentes parties du cerveau humain.Notre approche permet d'atteindre des résultats à l'état de l'art sur les deux types de données. / In this thesis we propose the use of mid-level representations, and in particular i) medial axes, ii) object parts, and iii)convolutional features, for modelling objects.The first part of the thesis deals with detecting medial axes in natural RGB images. We adopt a learning approach, utilizing colour, texture and spectral clustering features, to build a classifier that produces a dense probability map for symmetry. Multiple Instance Learning (MIL) allows us to treat scale and orientation as latent variables during training, while a variation based on random forests offers significant gains in terms of running time.In the second part of the thesis we focus on object part modeling using both hand-crafted and learned feature representations. We develop a coarse-to-fine, hierarchical approach that uses probabilistic bounds for part scores to decrease the computational cost of mixture models with a large number of HOG-based templates. These efficiently computed probabilistic bounds allow us to quickly discard large parts of the image, and evaluate the exact convolution scores only at promising locations. Our approach achieves a $4times-5times$ speedup over the naive approach with minimal loss in performance.We also employ convolutional features to improve object detection. We use a popular CNN architecture to extract responses from an intermediate convolutional layer. We integrate these responses in the classic DPM pipeline, replacing hand-crafted HOG features, and observe a significant boost in detection performance (~14.5% increase in mAP).In the last part of the thesis we experiment with fully convolutional neural networks for the segmentation of object parts.We re-purpose a state-of-the-art CNN to perform fine-grained semantic segmentation of object parts and use a fully-connected CRF as a post-processing step to obtain sharp boundaries.We also inject prior shape information in our model through a Restricted Boltzmann Machine, trained on ground-truth segmentations.Finally, we train a new fully-convolutional architecture from a random initialization, to segment different parts of the human brain in magnetic resonance image data.Our methods achieve state-of-the-art results on both types of data.
523

Computation of Acoustic Wave Propagation Under Water / Beräkning av akustisk vågutbredning under vatten

Thörn, Frida January 2022 (has links)
In this thesis we look at acoustic wave propagation under water. We look in particular at waves generated by a point source and what happens with the propagation when we model the bottom as flat or as curvilinear. We assume the source to be working at a certain frequency and therefore we model this problem by solving the Helmholtz equation. Since Helmholtz equation has some unwanted numerical properties we are interested in finding new numerical methods that could accelerate the solver. In this thesis we use the Waveholtz iteration, which solves Helmholtz equation by connecting it to the time-dependent wave equation. We use finite differences and the SBP-SAT method to approximate the spatial problem numerically and for modelling the sea bottom we use curvilinear coordinates.  To compare the Waveholtz iteration we also solve Helmholtz equation with a naive solver. The naive solver consists of approximating the equation with finite differences and then solving the linear system of equation by some iterative solver, which for our tests will be GMRES. The results show that the Waveholtz iteration converges in less iterations than our naive solver. It also shows that the number of iterations stays unchanged when changing our discretization, which otherwise is a big problem for our naive solver. This allows us to increase the accuracy of our numerical solution without changing the computation time too much.  We show that the number of iterations increases according to theory for an increasing frequency, and that for open problems we even see a smaller increase. For certain resonant frequencies in Helmholtz equation we do not expect the Waveholtz iteration to converge. In the neighbourhood of these frequencies the convergence becomes slow and we need many iterations for a solution of a certain accuracy. By reformulating the Waveholtz iteration as a Krylov solution we can see that resonances in Helmholtz equation have a smaller impact of the convergence. / I detta examensarbete undersöker vi akustisk vågutbredning i vatten. Vi kollar specifikt på vågor som genereras av en punktkälla och vad som sker när vi modellerar botten som plan eller som kurvlinjär. Då vi antar att punktkällan arbetar vid en bestämd frekvens, kommer vi modellera det fysikaliska problemet genom att lösa Helmholtz ekvation. Helmholtz ekvation har dock några numeriska egenskaper som är oönskade, och därför finns ett intresse av att hitta nya numeriska metoder som löser ekvationen. I detta examensarbete undersöker vi Waveholtz iteration, som löser Helmholtz ekvation genom att koppla den till den tidsberoende vågekvationen. Vi använder finita differenser och SBP-SAT metoden för att approximera det rumsliga problemet numeriskt. För att ge en detaljerad beskrivning av botten använder vi kurvlinjära koordinater. För att jämföra Waveholtz iterationen med något löser vi även Helmholtz med hjälp av en naiv lösare. Den naiva lösaren består av att approximera problemet med finita differenser och sedan lösa det linjära systemet rakt av med en iterativ lösare (vilket för våra fall kommer vara GMRES). Resultatet visar att Waveholtz iteration konvergerar på ett lägre antal iterationer än vår naiva lösare. Det visar även att antalet iterationer inte förändras när vi ändrar diskretisering, vilket annars är ett problem för vår naiva lösare. Detta innebär att vi kan få en högre noggrannhet utan att förlänga beräkningstiden alltför mycket.  Vi visar även att antalet iterationer ökar som förväntat med en ökad frekvens, samt att för öppna problem så ökar antalet iteration mindre än enligt teorin. Vid vissa resonanta frekvenser i Helmholtz ekvation förväntar vi oss att Waveholtz iteration inte kommer konvergerar. I närheten av dessa frekvenser blir konvergensen långsam och vi behöver många iterationer för att lösa problemet. Genom att formulera Waveholtz iteration som en Krylov lösning kommer resonanser i Helmholtz ekvation ge en mindre negativ effekt på konvergensen än om den är formulerad som en fixpunkts iteration.
524

A Conductor's Guide to Lionel Daunais's Figures de danse

Murray, Brian C. (Brian Clark) 05 1900 (has links)
Lionel Daunais was an eminent and beloved 20th-century Québécois musician who contributed greatly to the performing arts in Canada. Through his work with the Trio Lyrique, Les Variétés Lyriques, and his numerous compositions, he wielded a potent sphere of influence on the Canadian musical landscape. Lionel Daunais's compositions constitute a significant oeuvre, comprising solo vocal works, song cycles, folksong arrangements, individual choral works, and multi-movement choral works. Marked by irresistible wit, the melodicism of French mélodie, and the absolute eminence of the text, Figures de danse is his most well-known multi-movement choral work. Daunais penned the earliest extant version of Figures de danse in 1947, however, the work emerged into Québec's choral scene in the mid-1970s via the establishment of the Alliance des Chorales du Québec. This set of tragicomic caricatures, which sets beautiful choral and piano writing to clever—and sometimes hilariously nonsensical—texts by Daunais himself, is accessible for performance by youth choirs, community choirs, university choirs, and professional choirs alike. Unfortunately, various factors (e.g. the separation of the choral and piano scores, local references, and score errors) often stymie its performance. The purpose of this dissertation is to ameliorate these challenges via a conductor's guide and to advocate for the performance of Daunais's chef-d'oeuvre.
525

[en] ADDITIVE MANUFACTURING FOR EMERGENCIES: REPLACEMENT PARTS FOR NON-INVASIVE VENTILATORS / [pt] MANUFATURA ADITIVA PARA EMERGÊNCIAS: REPOSIÇÃO DE PEÇAS PARA RESPIRADORES NÃO-INVASIVOS

RAPHAEL DE PINHO VINAGRE 31 August 2023 (has links)
[pt] Esta pesquisa examina as potencialidades e limitações da manufatura aditiva na produção de dispositivos médicos em resposta à crescente demanda global durante a pandemia da COVID-19. A pesquisa busca entender as implicações da adaptação de projetos, da conformidade com regulamentações e da criação de uma cadeia de produção resiliente e sustentável, utilizando impressoras 3D de baixo custo. Além disso, a pesquisa incita reflexões sobre a intersecção entre medicina e design, instigando novas pesquisas neste campo interdisciplinar. O estudo se aprofunda na análise de adaptações de design e na exploração de uma cadeia produtiva alternativa mais resiliente e com menor impacto ambiental. A pesquisa considera a possibilidade de utilizar resíduos hospitalares como matériaprima para a produção de componentes médicos, uma prática que pode reduzir custos de descarte e a pegada de carbono. Além disso, discute a implementação do DRAM (Design, Reciclagem e Manufatura Aditiva Distribuídos) em ambientes hospitalares para responder às demandas de saúde em cenários de interrupção da cadeia de suprimentos. A pesquisa levanta questões importantes sobre a fronteira entre medicina e tecnologia, destacando a importância da responsabilidade ética e social na evolução científica e tecnológica. Argumenta a importância da manutenção adequada dos equipamentos médicos e o papel vital que a manufatura aditiva pode desempenhar na produção rápida de peças de reposição, especialmente em situações de emergência, como a pandemia da COVID-19. Com uma análise detalhada do joelho, um projeto prático desenvolvido durante o mestrado, a pesquisa identifica a necessidade de reestruturação dos processos de fabricação, considerando fatores econômicos e geográficos. A experiência do projeto instigou discussões enriquecedoras sobre o papel do designer, a potência da tecnologia de fabricação digital e a relevância dessa atividade em situações de emergência. Finalmente, a pesquisa conclui que a Reciclagem Distribuída e a Manufatura Aditiva (DRAM) podem se apresentar como uma solução sustentável e descentralizada para a produção de itens críticos em hospitais. Sugere a possibilidade de implementação de um ciclo fechado de produção e consumo de materiais através da fabricação de filamentos a partir de resíduos no próprio local de cuidados de saúde. Isso não só reduziria a dependência de fornecedores externos e a pegada ambiental da produção, mas também poderia melhorar a eficiência e agilidade dos sistemas de saúde em situações de emergência. / [en] This Master s dissertation examines the potentialities and limitations of additive manufacturing in the production of medical devices in response to the growing global demand during the COVID-19 pandemic. The research seeks to understand the implications of project adaptations, compliance with regulations, and the creation of a resilient and sustainable production chain, using low-cost 3D printers. Furthermore, the research instigates reflections on the intersection between medicine and design, stimulating new research in this interdisciplinary field. The study delves into the analysis of design adaptations and explores an alternative production chain that is more resilient and has less environmental impact. The research considers the possibility of using hospital waste as raw material for the production of medical components, a practice that can reduce disposal costs and the carbon footprint. In addition, it discusses the implementation of DRAM (Distributed Recycling and Additive Manufacturing) in hospital environments to respond to health demands in scenarios of supply chain disruption. The research raises important questions about the frontier between medicine and technology, highlighting the importance of ethical and social responsibility in scientific and technological evolution. It argues the importance of proper maintenance of medical equipment and the vital role that additive manufacturing can play in the quick production of replacement parts, especially in emergency situations, such as the COVID-19 pandemic. With a detailed analysis of the elbow, a practical project developed during the master s program, the research identifies the need for restructuring manufacturing processes, taking into account economic and geographic factors. The project s experience instigated enriching discussions about the role of the designer, the power of digital manufacturing technology, and the relevance of this activity in emergency situations.
526

Влияние способа чистки оптических деталей на состояние полированных поверхностей : магистерская диссертация / Influence of the method of cleaning optical parts on the condition of polished surfaces

Кибалина, А. А., Kibalina, A. A. January 2021 (has links)
Рассмотрены существующие методы проведения операции чистки оптических поверхностей с целью удаления с нее всех загрязнений и создание необходимого состояния поверхности. Приведены результаты измерения краевого угла смачивания, который позволяет проанализировать, какие свойства обретает поверхность после чистки. Описан комплекс измерительного оборудования для определения угла смачивания поверхности жидкостью. / The existing methods of carrying out the operation of cleaning optical surfaces in order to remove all contaminants from it and create the required surface condition are considered. The results of measuring the contact angle of wetting are given, which makes it possible to analyze what properties the surface acquires after cleaning. A set of measuring equipment for determining the angle of surface wetting with a liquid is described.
527

Effektivisering av reservdelsflödet mellan OEM och centrallager : En fallstudie om materialflödet av reservdelar mellan tillverkande företags originaltillverkare (OEM) och centrallager / Streamlining the flow of spare parts between OEM andcentral warehouse

Ericsson, Mathilda, Eriksson, Viktor January 2023 (has links)
Syfte - Sjunkande marginaler hos primärprodukter har riktat ökad uppmärksamhet mot den lönsamma reservdelsverksamheten. Det finns dock utmaningar kring flödet av reservdelar, bland annat i) teoretiskt gap kring flödet av reservdelar, ii) behovet att effektivisera flöden av reservdelar, och iii) avsaknad av praktisk arbetsprocess. Med bas i dessa utmaningar har studiens syfte formulerats till ”Att utforma en arbetsprocess för effektivare materialflöde av reservdelar mellan OEM och centrallager för tillverkande företag”. Genom att identifiera och analysera effektivitetsvariabler som påverkar flödet av reservdelar, har en praktiskt tillämpbar arbetsprocess skapats för att effektivisera försörjningskedjan och fylla kunskapsgapet inom området. Metod - Denna studie är av typen enfallsstudie, som undersöker materialflödet av reservdelar och arbetsprocesser inom logistik. Data samlades in genom intervjuer och dokumentstudier för att identifiera effektivitetsvariabler. Studien kombinerar teori och empiri för att erhålla djupare förståelse av fallet och strävar efter att dra slutsatser och ge insikter som kan tillämpas inom logistikområdet i allmänhet. Resultat - Resultatet av studien redovisas en arbetsprocess som har utformats för att effektivisera materialflödet av reservdelar mellan OEM och centrallager. Genom att ha identifierat effektivitetsvariabler har studien prioriterat de variablerna med störst förbättringspotential. En arbetsprocess har utvecklats med konkreta förslag på förbättringar för att minska avstånd, kostnader och ledtider till centrallagret. Resultaten ger insikter om hur materialflödet kan effektiviseras mellan OEM och centrallager hos tillverkande företag. Implikationer - Resultatet av studien fyller kunskapsgapet genom att undersöka reservdelsflödet och dess koppling till effektivisering av försörjningskedjor. Genom att ha identifierat effektivitetsvariabler bidrar studien till ökad förståelse för hur företag kan effektivisera hanteringen av reservdelar. Studien adresserar viktiga utmaningar inom reservdelsförsörjningen genom att erbjuda praktiska lösningar och insikter till beslutsfattare för att skapa effektiva materialflöden. I studien har en arbetsprocess skapats, vilket kan hjälpa företag att effektivisera dess reservdelsflöden och undvika onödig resursförbrukning. Resultatet av studien kan fungera som en vägledning för företag som strävar efter att förbättra sitt materialflöde av reservdelar och öka sin övergripande effektivitet. Begräsningar - Studiens begränsningar är att enbart en enfallsstudie har utförts. Dessutom behandlas endast det materialflöde uppströms mellan OEM och centrallager som utgörs av det utvidgade försörjningskedjan. Därav undersöks inte materialflödet nedströms mot slutkund. / Purpose - Falling margins in primary products have directed increased attention to the profitable spare parts business. However, there are challenges around the flow of spare parts, including i) theoretical gap around the flow of spare parts, ii) the need to streamline the flow of spare parts, and iii) lack of practical work process. Based on these challenges, the purpose of the study has been formulated as "To design a work process for more efficient material flow of spare parts between OEM and central warehouse for manufacturing companies". By identifying and analyzing efficiency variables that affect the flow of spare parts, a practically applicable work process has been created to streamline the supply chain and fill the knowledge gap in the field. Method - This study is of the single-case study type, which examines the material flow of spare parts and work processes in logistics. Data were collected through interviews and document studies to identify efficiency variables. The study combines theory and empiricism to obtain a deeper understanding of the case and aims to draw conclusions and provide insights that can be applied within the field of logistics in general. Findings - The result of the study is a work process that has been designed to streamline the material flow of spare parts between the OEM and the central warehouse. By having identified efficiency variables, the study has prioritized those variables with the greatest potential for improvement. A work process has been developed with concrete proposals for improvements to reduce distance, costs, and lead-times to the central warehouse. The results provide insights into how the material flow can be made more efficient between the OEM and the central warehouse of manufacturing companies. Implications - The result of the study fills the knowledge gap by examining the flow of spare parts and its connection to the efficiency of supply chains. By having identified efficiency variables, the study contributes to increased understanding of how companies can streamline the handling of spare parts. The study addresses important challenges in spare parts supply by offering practical solutions and insights to decision makers to create efficient material flows. In this study, a work process has been created, which can help companies to streamline their spare parts flows and avoid unnecessary resource consumption. The result of the study can serve as a guide for companies that strive to improve their material flow of spare parts and increase their overall efficiency. Limitations - The study's limitations are that a single case study has been carried out. In addition, only the upstream material flow between the OEM and the central warehouse that constitutes the extended supply chain is treated. As a result, the material flow downstream towards the end customer is not investigated.
528

Role of Additive Manufacturing in Restructuring Supply Chains

Patil, Himali Kiran 12 1900 (has links)
Additive manufacturing (AM), commonly known as 3D printing, has been attracting attention from practitioners as well as academicians with its continuous evolution from being used primarily for prototyping to now end-product production. Despite this technology's current and future potential, few studies indicate that AM has not been extensively used across all industries. This dissertation addresses knowledge gaps by providing theoretical and empirical support for adopting AM through three essays that study the role of AM in restructuring supply chains. Essay 1 provides systematic support for AM implementation by developing a typology derived from technology-specific potentials and challenges to adopting AM. This study uses an exploratory research approach to collect and analyze data from semi-structured interviews of practitioners with deep knowledge of AM and supply chains from diverse industries. In Essay 2, our results show that AM adoption positively influences supply chain responsiveness and, in turn, reshoring decisions. Essay 3 compares different supply chain configurations based on traditional and AM. We developed a hybrid simulation model combining discrete event simulation and agent-based simulation and compared the performance in terms of wait time and costs. Our results indicate that under certain conditions, the centralized configuration delivers spare parts faster than the distributed configuration, contrary to previous literature findings. However, a hybrid configuration (a combination of centralized and decentralized) provides a better response (reduced wait time) than the traditional, centralized, and decentralized configurations. Collectively, the three essays provide academicians and practitioners with a more comprehensive understanding of how AM creates value for supply chains.
529

Polyfunkční dům - příprava a organizace výstavby / Multifunctional House - project planning and management of construction

Krč, Jan January 2014 (has links)
This master´s thesis deals with project planning and management of construction of multifunctional building. The main part of thesis are budget of object and schedules of work, which contain realization of reinforced concrete structure and other related works. Another part of thesis deals with the technical regulations about the implementation of horizontal and vertical parts of reinforced concrete structure and from finishing works about realization of inside plasters. Following this part there is design and schedule of using of appropriate building machines and small machinery for their implementation, design of site equipment, quality assurance of works performed, safety of work and minimization of environmental impact. The thesis contains also proposal of contract of work. This work does not deal with substructure of multifunctional building, because this is solved in bachelor thesis.
530

Multidisziplinäre Formoptimierung modularer Grundgeometrien für Druckgussbauteile mit strömungs- und strukturmechanischen Zielfunktionen / Multidisciplinary shape optimization of modular basic geometries for high pressure die castings with fluid dynamic and structural mechanic objective functions

Maurer, Simon Alexander 18 February 2016 (has links) (PDF)
Am Anfang des Entwicklungsprozesses eines Gussbauteils für die Automobilbranche steht klassischerweise die konstruktive Ausarbeitung und die Auslegung auf Zielgrößen, wie Festigkeit, Steifigkeit bzw. die Erfüllung der Crashlasten. Im nächsten Entwicklungsschritt wird, oftmals in Zusammenarbeit mit externen Lieferanten, das Werkzeugkonzept entwickelt und die Herstellbarkeit mit Hilfe von Gießsimulationen abgesichert. Bei der Fertigung verursachen streuende Prozessgrößen, wie etwa Geschwindigkeits- oder Temperaturniveaus, Schwankungen in der Leistungsfähigkeit des Endprodukts (z. B. lokale Bruchdehnung oder Zugfestigkeit). Maßnahmen zur Erhöhung der Prozessstabilität und zur Reduktion des Verschleißes konzentrieren sich oftmals auf die erfahrungsbasierte Verbesserung des Fertigungsprozesses und Anpassungen des Anguss- und Überlaufsystems. Größere Änderungen der Bauteilgeometrie sind häufig aus zeitlichen Gründen nicht mehr möglich. Das Ziel dieser Arbeit ist es daher, optimierte modularisierte Grundgeometrien, wie Rippen oder Umlenkungen, mit Hilfe von numerischen Formoptimierungen zu entwickeln, um diese schon von Anfang an in der Bauteilentwicklung zu berücksichtigen. Als Zielfunktionen dienen strömungs- und strukturmechanische Kenngrößen, um einerseits verschleißfördernde Mechanismen und füllungsbedingte Defekte zu reduzieren und andererseits die Beanspruchbarkeit zu erhöhen. Bei den Untersuchungen wird zusätzlich die Robustheit des Ergebnisses analysiert, um Verbesserungspotenziale auch bei streuenden Randbedingungen realisieren zu können. / The virtual development process of an automotive casting part usually begins with classical design tasks and analyses of material strength, stiffness and crash load cases. In the next step, often in cooperation with external suppliers, the tooling concept is developed and casting simulations are used to ensure manufacturability. During manufacturing there is a scatter in process parameters, such as flow velocity or temperature levels, which in turn cause a scatter in the performance of the final product (e.g. local elongation at fracture or ultimate tensile strength). Means to increase process stability and yield are often limited to knowledge-based improvements of the manufacturing process parameters and adaptations of the gating and overflow system. Major changes to the part geometry are usually no longer possible due to project time constraints. Therefore it is the goal of this thesis to optimize modularized basic geometries, like ribs or bends, by using numerical shape optimizations and employ them right from the beginning of the part development process. For the objective functions of the optimizations the disciplines of fluid dynamic filling and the resulting structural behaviour are considered. In addition, the resulting shape is analyzed with regards to robustness towards scatter in manufacturing operating conditions. By using these new modularized geometries the overall robustness of the final product is expected to be increased.

Page generated in 0.0485 seconds