Tesi sul tema "Multi-Material optimization"

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 32-33).
Topology optimization is a field extending to the built environment. Traditionally, optimization focuses mainly on monolithic structures but recently, developments have been made toward determining algorithms for multi-material optimization. A preexisting algorithm is modified to broaden the type of design possible with the method. The algorithm uses a three-phase design problem, a void phase and two other materials, and implements Heaviside Projection Method (HPM) and Rational Approximation of Material Properties (RAMP) method and employs the Method of Moving Asymptotes (MMA) as the gradient based optimizer. Three distinct object projection shapes are proposed, a horizontal, a vertical and a diagonal. The horizontal shaped inclusion enables designs such as, longitudinal reinforced concrete beam design of variable length bars. The vertical shaped inclusion enables designs of columns. The diagonal shaped inclusion allows for design of rebar within more slanted sections of optimized topology. The proposed algorithm is tested on two examples, the cantilever beam and the MBB beam, showing that it works as expected.
by Oluwanifemi O. Ajayi.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-56).
In the built environment, there is a growing emphasis on sustainable, energy efficient design that reduces carbon emissions. However, until recently, most efforts have focused only on reducing operational carbon [1]. As a result, the carbon embodied in construction materials, especially in a building's structural system, is becoming a larger contributor to the total carbon impacts of a building. Material type and quantity are important in determining the extent of this contribution because both will affect the amount of carbon emitted from the material production. For example, two common materials for truss structures are timber and steel. While timber's embodied carbon coefficient (kg[subscript CO2e]/kg[subscript material]) and density are lower than that of steel, its much lower strength means that it may not always result in the least-emitting structural design. As a result, the choice of the more sustainable material for any given member is dependent on factors such as the truss span or shape. Multi-material structures offer a solution to create efficient structures with a lower environmental impact. In this thesis, an embodied carbon optimization investigates truss structures of various spans and studies how multi-material and single-material designs compare. This research introduces a new approach for multi-material designs for the optimization of embodied carbon and demonstrates the advantages of using structural optimization and multi-material designs for sustainability. Keywords.: Optimization, embodied carbon, sustainable structures, truss structures
by Brenda G. Stern.
M. Eng.

In this work, the effectiveness of multi-objective design optimization using metamodeling techniques and an internal state variable (ISV) plasticity damage material model as a design tool is demonstrated. Multi-objective design optimization, metamodeling, and ISV plasticity damage material models are brought together to provide a design tool capable of meeting the stringent structural design requirements of today and of the future. The process of implementing this tool are laid out, and two case studies using multi-objective design optimization were carried out. The first was the optimization of a Chevrolet Equinox rear subframe. The optimized subframe was 12% lighter and met design requirements not achieved by the heavier initial design. The second case was the optimization of a Formula SAE front upright. The optimized upright meets all the design constraints and is 22% lighter.

The work herein is, in part, motivated by the idea of creating optimized, actuating structures using additive manufacturing processes (AM). By developing a consistent, repeatable method for designing and manufacturing multi-material compliant mechanisms, significant performance improvements can be seen in application, such as increased mechanism deflection. There are three distinct categories of research that contribute to this overall motivating idea: 1) investigation of an appropriate multi-material topology optimization process for multi-material jetting, 2) understanding the role that manufacturing constraints play in the fabrication of complex, optimized structures, and 3) investigation of an appropriate process for embedding actuating elements within material jetted parts. PolyJet material jetting is the focus of this dissertation research as it is one of the only AM processes capable of utilizing multiple material phases (e.g., stiff and flexible) within a single build, making it uniquely qualified for manufacturing complex, multi-material compliant mechanisms. However, there are two limitations with the PolyJet process within this context: 1) there is currently a dearth of understanding regarding both single and multi-material manufacturing constraints in the PolyJet process and 2) there is no robust embedding methodology for the in-situ embedding of foreign actuating elements within the PolyJet process. These two gaps (and how they relate to the field of compliant mechanism design) will be discussed in detail in this dissertation. Specific manufacturing constraints investigated include 1) "design for embedding" considerations, 2) removal of support material from printed parts, 3) self-supporting angle of surfaces, 4) post-process survivability of fine features, 5) minimum manufacturable feature size, and 6) material properties of digital materials with relation to feature size. The key manufacturing process and geometric design factors that influence each of these constraints are experimentally determined, as well as the quantitative limitations that each constraint imposes on design.
Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, February 2012.
"December 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 129-131).
A beam delivery and transport system were designed for the use in MIT Materials Test Facility (M2TF). The purpose of this beam delivery system was to design a 36 MeV Proton Cyclotron for DPA accumulation and a 100 MeV Helium Cyclotron for irradiation failure and volumetric helium accumulation simulation. The purpose of the beam transport system was to incorporate the two cyclotrons into the beam transport system and transport their beams to the target chamber, the location of the target sample. The cyclotrons were designed using Opera-3D and Acfields. The beam transport system was designed using TRANSPORT. The shielding analysis for the entire facility was designed using SolidWorks and calculated with MCNP/X The design specification of M2TF with respect to beam energy, current density, and control were achieved based on these design tools and previously developed analytic methods. The design process for the cyclotrons resulted in a 4.3T lsochronous Proton Cyclotron and 3.9T Isochronous Helium Cyclotron. A beam transport system connected the cyclotrons to the target chamber with three doublet quadrupoles and one dipole bending magnet The shielding calculation proved the total effect dose rate in rem/year for the final design facility was safe for operational workers.
by Tyler Christopher Sordelet.
S.M.

The optimal design of energy systems is a challenge due to the large design space and the complexity of the tightly-coupled multi-physics phenomena involved. Standard design methods consider a reduced design space, which heavily constrains the final geometry, suppressing the emergence of design trends. On the other hand, advanced design methods are often applied to academic examples with reduced physics complexity that seldom provide guidelines for real-world applications. This dissertation offers a systematic framework for the optimal design of energy systems by coupling detailed physical analysis and topology optimization. Contributions entail both method-related and application-oriented innovations. The method-related advances stem from the modification of topology optimization approaches in order to make practical improvements to selected energy systems. We develop optimization models that respond to realistic design needs, analysis models that consider full physics complexity and design models that allow dramatic design changes, avoiding convergence to unsatisfactory local minima and retaining analysis stability. The application-oriented advances comprise the identification of novel optimized geometries that largely outperform industrial solutions. A thorough analysis of these configurations gives insights into the relationship between design and physics, revealing unexplored design trends and suggesting useful guidelines for practitioners. Three different problems along the energy chain are tackled. The first one concerns thermal storage with latent heat units. The topology of mono-scale and multi-scale conducting structures is optimized using both density-based and level-set descriptions. The system response is predicted through a transient conjugate heat transfer model that accounts for phase change and natural convection. The optimization results yield a large acceleration of charge and discharge dynamics through three-dimensional geometries, specific convective features and optimized assemblies of periodic cellular materials. The second problem regards energy distribution with district heating networks. A fully deterministic robust design model and an adjoint-based control model are proposed, both coupled to a thermal and fluid-dynamic analysis framework constructed using a graph representation of the network. The numerical results demonstrate an increased resilience of the infrastructure thanks to particular connectivity layouts and its rapidity in handling mechanical failures. Finally, energy conversion with proton exchange membrane fuel cells is considered. An analysis model is developed that considers fluid flow, chemical species transport and electrochemistry and accounts for geometry modifications through a density-based description. The optimization results consist of intricate flow field layouts that promote both the efficiency and durability of the cell.

Dans le contexte de la transition énergétique et de l'électrification des usages, l'amélioration des performances des actionneurs électromagnétiques passe obligatoirement par des processus d'optimisation du dimensionnement. De telles méthodologies ont d'ores et déjà été mises en place, mais se focalisent principalement sur des géométries préalablement paramétrées, ce qui limite l'espace des possibles. Les travaux menés dans le cadre de cette thèse visent alors à mettre en place une méthodologie d'optimisation topologique efficace, capable de répartir au mieux les distributions de matériaux (fer, air, conducteurs, aimants) nécessaires pour générer une machine synchrone dans sa globalité, sans paramétrage de sa géométrie. Pour ce faire, une méthodologie d'optimisation topologique multi-matériaux à densité a été développée. Son application à l'optimisation d'un stator triphasé met en évidence l'importance des procédés de pénalisation, de filtrage et de contrôle sur l'algorithme d'optimisation. La méthodologie est ensuite étendue à la conception d'une machine entière : bien que performantes, les meilleures structures obtenues comportent des barrières de flux sans tenue mécanique. Après incorporations de contraintes de rigidité des rotors, la méthode aboutit à des structures performantes et connexes en un temps de calcul raisonnable, ce qui démontre la pertinence de ce type d'approches dans la conception d'actionneurs électromagnétiques. À terme, l'intégration de l'ensemble des physiques qui interviennent dans les spécifications du cahier des charges dès les phases préliminaires permettrait d'économiser temps et argent dans la conception de machines électriques innovantes
In the context of energy transition and the electrification of applications, improving the performance of electromagnetic actuators inevitably involves dimensioning optimization processes. Such methodologies have already been implemented but focus mainly on previously parameterized geometries, which limits the space of possibilities. This thesis aims to develop an efficient topological optimization methodology capable of optimizing the distribution of materials (iron, air, conductors, magnets) required to generate a synchronous machine in its entirety without parameterizing its geometry. To this end, a multi-material density topological optimization methodology has been developed. Its application to optimizing a three-phase stator highlights the importance of penalization, filtering, and control processes in the optimization algorithm. The procedure is then extended to the design of an entire machine: although efficient, the best structures obtained include flux barriers with no mechanical strength. After incorporating rotor stiffness constraints, the method produces high-performance, related structures in a reasonable computation time, demonstrating the relevance of this type of approach to the design of electromagnetic actuators. Eventually, integrating all the physics involved in specifications right from the preliminary phases will save time and money in designing innovative electrical machines

The thesis has been performed in cooperation with a Swedish manufacturing company. The manufacturing site of the company is currently implementing a new machine layout in one of its workshops. The new layout will increase the product flow to another workshop on the site. The goal of the thesis was to evaluate the current transportation system and suggest viable alternatives for the future product flow. By means of discrete event simulation these alternative solutions would be modelled and subsequently optimized to determine if their performance is satisfactory. An approximated investment cost of the solutions would also be estimated. By performing a literature review and creating a frame of reference, a set of relevant methodologies were selected to provide a foundation to the project. Following these methodologies, the current state of transportation was identified and mapped using Value Stream Mapping. Necessary data from the current flow was identified and collected from the company computer systems. This data was deemed partly inaccurate and further verification was needed. To this end, a combination of Genchi Genbutsu, assistance from onsite engineers and a time study was used to verify the unreliable data points. The data sets from the time study and the company data which was deemed valid were represented by statistical distributions to provide input for the simulation models. Two possible solutions were picked for evaluation, an automated guided vehicle system and a tow train system. With the help of onsite personnel, a Kaizen Event was performed in which new possible routing for the future flow was evaluated. A set of simulation models portraying the automated guided vehicle system and the tow train system were developed with the aid of simulation software. The results from these models showed a low utilization of both systems. A new set of models were developed, which included all the product flows between the workshops. The new flows were modelled as generic pallets with the arrival distribution based on historical production data. This set of models were then subject for optimization with regard to the work in process and lead time of the system. The results from the optimization indicates the possibility to reduce the overall work in process by reducing certain buffer sizes while still maintaining the required throughput. These solutions were not deemed to be ready for implementation due to the low utilization of the transportation systems. The authors instead recommend expanding the scope of the system and including other product flows to reach a high utilization.

Microdispositivos piezelétricos tem uma vasta aplicação em mecânica de precisão, como, por exemplo, manipulação de células, microcirurgias, equipamentos de nanotecnologia e principalmente em microeletromecanismos (MEMS). Os microdispositivos piezelétricos considerados nesta tese essencialmente consistem de uma estrutura multi-flexível atuada por duas ou mais piezocerâmicas, que geram deslocamentos e forças em direções e regiões pré-determinadas do domínio, ou seja, a estrutura multi-flexível atua como um transformador mecânico amplificando e alterando os deslocamentos gerados pelas piezocerâmicas nos movimentos de atuação. O desenvolvimento destes microdispositivos piezelétricos em sua grande maioria não utiliza ferramentas sistemáticas e genéricas. A complexidade dos movimentos de atuação torna o desenvolvimento dos microdispositivos piezelétricos complexo, principalmente devido ao surgimento de movimentos indesejados ou acoplados durante a sua atuação. Portanto, é necessário um método sistemático e eficiente como o método de otimização topológica (MOT), que incorpore na sua formulação as principais exigências de projeto dos microdispositivos, como apresentado nesse trabalho. O MOT implementado é baseado na abordagem CAMD (Distribuição Contínua da Distribuição de Material), onde as pseudo-densidades são interpoladas nos nós de cada elemento finito, resultando numa distribuição contínua de material no domínio. Um método adjunto foi implementado para o cálculo das sensibilidades. São consideradas três formulações. A primeira denominada de MAPs (Multi-Atuadores Piezelétricos) considera as regiões piezocerâmicas fixas, otimizando apenas a estrutura multi-flexível no domínio de projeto. Nesta formulação materiais não-piezelétricos (como, por exemplo, Alumínio) e vazio são distribuídos no domínio de projeto, mantendo as regiões piezocerâmicas fixas e homogêneas. Para validar os resultados obtidos com essa formulação foram fabricados protótipos de nanoposicionadores $XY$, que foram caracterizados experimentalmente utilizando técnicas de interferometria laser, considerando excitação quasi-estática. No entanto, essa primeira formulação impõe restrições no problema, limitando a optimalidade da solução obtida pela otimização topológica. Assim, surgiu a necessidade de desenvolver uma segunda formulação, que permite distribuir simultaneamente material não-piezelétrico, piezelétrico e vazio no domínio de projeto, denominada de LOMPs (Localização Ótima do Material Piezelétrico). A formulação dos LOMPs obtém simultaneamente a localização do material piezelétrico na estrutura flexível otimizada pela OT, e inclui também uma variável de projeto para determinar o ângulo ótimo entre as direções de polarização e do campo elétrico. Nesta formulação como as posições dos eletrodos não são conhecidas, ``a priori\'\', é utilizado como abordagem aplicar um campo elétrico constante para determinar a localização do material piezelétrico e conseqüentemente dos eletrodos. Finalmente, foi explorado o conceito de materiais com gradação funcional (MGFs) no projeto dos MAPs. Os MGFs apresentam uma distribuição contínua de materiais na sua microestrutura, não possuindo interface entre os materiais distribuídos, o que possibilita aumentar a vida útil do dispositivo piezelétrico. Assim, foi implementado uma terceira formulação denominada de MAPs MGFs, que permite obter a gradação ótima de materiais piezelétricos e não-piezelétricos no domínio piezocerâmico dos MAPs, conjuntamente com a topologia da estrutura multi-flexível. Essa formulação foi estendida para projetar atuadores bilaminares MGFs. Todas as formulações desenvolvidas utilizam uma função multi-objetivo, que permite controlar a rigidez e a flexibilidade minimizando o movimento acoplado, de cada movimento de atuação. Os exemplos numéricos são limitados a modelos bi-dimensionais, utilizando o estado plano de tensões e deformações mecânicas e elétricas, uma vez que a grande maioria das aplicações dos microdispositivos piezelétricos são bi-dimensionais.
Microtools offer significant promise in a wide range of applications such as cell manipulation, microsurgery, nanotechnology processes, and many other fields. The microtools considered in this doctoral thesis essentially consist of a multi-flexible structure actuated by two or more piezoceramic devices that when each piezoceramic is actuated, it generates an output displacement and force at a specified point of the domain and direction. The multi-flexible structure acts as a mechanical transformer by amplifying and changing the direction of the piezoceramic output displacements. Thus, the development of microtools requires the design of actuated flexible structures that can perform complex movements. The development of these microtools is still in the beginning and it can be strongly enhanced by using design tools. In addition, when multiple piezoceramic devices are involved, coupling effects in their movements become critical, especially the appearance of undesired movements, which makes the design task very complex. One way to avoid such undesirable effects is the use of a systematic design method, such as topology optimization, with appropriate formulation of the optimization problem. The topology optimization method implemented is based on the CAMD (Continuous Approximation of Material Distribution) approach where fictitious densities are interpolated at each finite element, providing a continuum material distribution in the domain. The corresponding sensitivity analysis is presented using the adjoint method. Three formulations are considered. The first formulation, called Piezoelectric Multi-Actuators (PMAs), keeps fixed piezoceramic positions in the design domain and only the flexible structure is designed by distributing some non-piezoelectric material (Aluminum, for example). $XY$ Piezoelectric Nanopositioner are manufactured and experimentally analyzed to validate the results of the topology optimization obtained using this formulation. Experimental analyses are conducted using laser interferometry to measure displacement, while considering a quasi-static excitation. However, this first formulation imposes a constraint to the position of piezoelectric material in the optimization problem limiting the optimality of the solution. Thus, the second formulation presented, called LOMPs, allows the simultaneous distribution of non-piezoelectric and piezoelectric material in the design domain, to achieve certain specified actuation movements. The optimization problem is posed as the simultaneous search for an optimal topology of a flexible structure as well as the optimal position of piezoceramics in the design domain and optimal rotation angle of piezoceramic material axes that maximize output displacements or output forces at a specified point of the domain and direction. When the distribution of a non-piezoelectric conductor material and a piezoceramic material is considered in the design domain, the electrode positions are not known ``a priori\'\'. To circumvent this problem, an electric field is applied as electrical excitation. Finally, the concept of functionally graded materials (FGM) is applied to PMAs design. FGMs are special materials that possess continuously graded properties without interfaces which can increase lifetime of piezoelectric devices. Thus, a third formulation is implemented to find the optimum gradation and polarization sign variation of piezoceramic FGMs, while simultaneously optimizing the multi-flexible structural configuration. This formulation is extended to design bimorph type FGM actuators. For all developed formulations, a multi-objective function is defined that controls the stiffness and flexibility, minimizing the coupling movement of each actuated movement. The present examples are limited to two-dimensional models because most part of the applications for such micro-tools are planar devices.

Le transport de matières dangereuses est connu pour son haut risque potentiel pour le réseau routier. Un accident peut avoir de graves conséquences pour la santé publique et l’environnement sur une longue période. L’optimisation du transport de matières dangereuses est une problématique importante. Cette thèse propose, pour la première fois dans la littérature, une stratégie de réservation de voies pour le transport de matières dangereuses. L’objectif est de proposer des itinéraires pour le transport de matières dangereuses qui minimisent à la fois le risque potentiel et l’impact négatif sur le trafic dans un réseau de transport dû à la réservation de voies. Dans cette thèse, nous nous focalisons sur deux nouveaux problèmes : l’optimisation de transport de matières dangereuses grâce à la stratégie de réservation de voies dans un réseau de transport selon si le risque dépend de l’instant de passage (appelé LRPTDR) ou pas (appelé LRPTIR). Pour chaque problème étudié, nous proposons un nouveau modèle d’optimisation multi-critères. Pour le LRPTIR, nous développons d’abord une méthode combinant la méthode de ε-contrainte et la logique floue pour obtenir des solutions Pareto-optimales et une solution préférée en fonction des critères du gestionnaire. Ensuite,une méthode qui combine le « cut-and-solve » and le « cutting plane» est proposée pour réduire le temps de calcul. Pour le LRPTDR, une méthode de « cut-and-solve » est appliquée, dans laquelle une nouvelle technique de « piecing cut » et une stratégie de relaxation partielle sont développées pour améliorer la performance. Les performances des algorithmes proposés sont évaluées à l’aide d’instances générées aléatoirement. Les résultats numériques montrent que les algorithmes proposés sont plus performants que le logiciel commercial CPLEX pour les problèmes étudiés
Hazardous material transportation is well-known for its high potential risk. An accident may cause very serious economic damage and negative impacts on the public health and the environment over the long term. Optimization for hazardous material transportation is an important issue. For the first time in the literature, this thesis introduces the lane reservation strategy into the hazardous material transportation problem. The goal is to obtain a best compromise between the impact on normal traffic due to lane reservation and the transportation risk.In this thesis, we focus on two novel problems: hazardous material transportation problem via lane reservation in networks with time-invariant and time-dependent risk, called LRPTIR and LRPTDR, respectively. For these problems, multi-objective integer programming and multi-objective mixed integer programming models are formulated, respectively. For the LRPTIR, we first develop an ε-constraint and fuzzy-logic based method to obtain Pareto optimal solutions and a preferred solution. Then a cut-and-solve and cutting plane combined method is proposed to reduce the computational time. For the LRPTDR, an improved cut-and-solve based ε-constraint method is proposed, in which a new technique of generating piercing cuts is developed and a partial integral relaxation strategy is applied. The performance of the proposed algorithms is evaluated by randomly generated instances. Computational results demonstrate that for the considered problems, the cut-and-solve method outperforms software package CPLEX

Les procédés de fabrication de pièces mécaniques par enlèvement de matière (tournage, fraisage, perçage, ...) connaissent une utilisation massive dans l’industrie aéronautique et l’automobile. Les pièces obtenues par ces procédés doivent satisfaire à des propriétés géométriques, métallurgiques et à des caractéristiques de qualité. Pour répondre à ces exigences, plusieurs essais expérimentaux basés sur le choix des conditions de coupe sont souvent nécessaires avant d’aboutir à une pièce satisfaisante. Actuellement, ces méthodes empiriques basées sur l’expérience des fabricants et des utilisateurs des outils coupants sont souvent très longues et coûteuses, donnent une large plage de choix des paramètres en fonction de leurs besoins. Toutefois, le coût très élevé d’un essai limite fondamentalement le nombre d’expériences, avoir une pièce respectant les caractéristiques souhaitées avec un coût acceptable devient une tâche difficile
Manufacturing processes of mechanical parts by removal of material (turning, milling, drilling ...) have extensive use in aeronautic and automobile industry. The components obtained using these methods must satisfy geometric properties, metallurgical and quality characteristics. To meet these requirements, several experimental tests based on the selection of cutting conditions are often necessary before manufacturing. Currently, these empirical methods based on the experience of manufacturers and users of cutting tools (charts, diagrams with experimental findings, ...) are often very lengthy and costly. However, the high cost of a trial limits the number of experiments, so to have a deserted component with an acceptable cost is a difficult task. The importance of cutting conditions monitored by limitations is related to the type of material to be machined, since it determines the behavior of the machining

A ce jour, les solutions de stockage d'énergie apparaissent comme des solutions pertinentes permettant d'atteindre les cibles énergétiques futures et de répondre aux exigences environnementales actuelles. Le but de cette thèse est d’optimiser un système de stockage d'énergie thermique innovant basé sur un échangeur eau – matériaux à changement de phase. Ce système est couplé à l’architecture énergétique multi-sources d’un îlot composé de trois bâtiments à énergie positive situé à Lyon : l’îlot HIKARI. Afin de disposer d’un outil numérique robuste pour pouvoir optimiser cette technologie, un modèle numérique du système de stockage d’énergie thermique a été développé dans le but de reproduire le comportement du système de stockage de référence. Une fois fini, le modèle a été validé en trois étapes: une numérique et deux expérimentales. Dans un premier temps il a été validé numériquement, en comparant ses résultats avec un modèle conçu en adoptant une approche numérique différente (« Computational Fluid Dynamics »), dans un second temps il a été validé à l’échelle réelle en exploitant les données in-situ du système de HIKARI. Enfin, le modèle numérique a été validé expérimentalement grâce à un prototype expérimental conçu et réalisé à l’ENTPE dans le cadre des travaux de cette thèse reproduisant le comportement du système de stockage étudié. Après avoir été validé, le modèle a été utilisé pour procéder à l’optimisation de sa performance en utilisant la technique des algorithmes génétiques. L’analyse des résultats de ces simulations a notamment abouti sur des recommandations de dimensionnement et d’usage pour l’Ilot HIKARI et des bâtiments futurs intégrant la technologie de stockage étudiée. La thèse a été financée par l’Agence de l’environnement et de la maîtrise de l’énergie (ADEME) dans le cadre du projet « Optimisation des architectures Énergétiques multi-sources couplées aux techniques avancées du stockage d'énergie dans le bâtiment » en partenariat avec Bouygues immobilier et Manaslu – CMDL
One of the most promising technics used in building applications for energy efficiency purposes is the thermal energy storage (TES). Despite the thorough research on TES techniques of the last years, the release to market of cost effective technologies is quite recent. The aim of this study is to optimize the energetic behavior of an innovative TES technology consisting on a water/PCM exchanger that is part of the multi-energy production and storage systems of HIKARI, a positive energy district located in Lyon and consisting of three buildings. In order to optimize this innovative technic, a numerical model reproducing the functioning of the reference system was created. In order to make a numerical validation a second numerical model was developed using a different software based on a different numerical method and, once the in situ data obtained from the reference system monitoring, a first experimental validation was obtained. Subsequently, an innovative experimental prototype reproducing the behavior of the reference PCM-Water heat exchanger has been realized, in order to validate and calibrate the numerical model and carry out a large amount of operating scenarios. Once the model numerically and experimentally validated, the optimization of the HIKARI’s cold storage system technology has been obtained using Genetic Algorithms (GAs) finding the best values to allocate to four characteristics of the cold storage system, in order to minimize two predefined objective functions linked to its functioning. This work was supported by the French Agency for Environment and Energy Management (ADEME) and it was part of the project “Optimization of innovative energy storage technologies when coupled to multi-sources energy architectures”, in cooperation with Bouygues immobilier and Manaslu – CMDL

Replenishment is an important process in automotive industries. It is the process by which parts required at assembly lines are stored and organized in assembly lines supermarket. Over many years replenishment have been done with the aim of positively impacting the varying demand frequency of articles in multi flows mixed-model assembly lines (MMALs) operating in just-in-time (JIT) fashion. However, a series of successive replenishment actions have negative impacts on the number of reallocation movements of parts within volume flows of supermarkets especially within a context of multi-flows supermarkets (MFSs). The cost of movements of parts within the supermarket has not been taken into consideration in previous replenishment methods. This is a significant problem since both un-optimized reallocation movements, and articles misplacement resolutions lead to production halts which cost assembly plants valuable time and money. Therefore, this research study proposes a replenishment method that optimizes flow of material within multi-flow assembly lines supermarkets and hence reduces the cost due to reallocation movement of multi-flow assembly lines supermarkets. The proposed method has been evaluated in the context of Volvo automobile engine assembly plant in Skövde. The proposed replenishment method has been evaluated by conducting an experiment using real-world data for the assembly plant in context. Performance metrics such as accuracy, F1-score, precision, sensitivity, and specificity were used to demonstrate the utility and validity of the proposed method. The evaluation results showed that the proposed method for optimizing material flow in supermarkets performed better than the existing method. In addition to utility, the proposed method provides contribution to knowledge by providing means for the industry to adopt replenishment method that takes into consideration the cost of reallocation movements of the parts within the supermarket.

L’amplification optique large bande à base de SOA est devenue indispensable pour la montée en débit des systèmes de transmissions optiques et pour pouvoir exploiter au mieux la bande optique des fibres optiques. Ce travail présente une étude théorique et expérimentale d’un SOA large bande passante développé par Alcatel Thales III-V Lab dans le cadre des projets ANR AROME et UltraWIDE. Dans cette thèse, nous avons d’abord effectué une modélisation semi-phénoménologique du gain matériau et du coefficient de gain d’une structure à base de multi-puits quantiques avec un nombre réduit de paramètres. L’intégration de notre modèle dans un modèle de SOA déjà développé au laboratoire a montré son efficacité pour restituer quantitativement le comportement statiques (gain, facteur de bruit) des nouvelles structures SOA large bande sur une large plage de longueurs d’onde (> 110 nm), de courants d’alimentation et de puissances optiques. A l’aide de ce modèle, nous avons étudié l’influence de la structure du SOA sur la bande passante pour un gain cible en jouant sur la longueur, le nombre d’électrode et le courant d’alimentation du SOA. Nous avons mis en évidence qu’une structure bi-électrodes n’apportait pas d’amélioration de la bande passante optimisée par rapport au cas mono-électrode. En revanche, la structure bi-électrode permet d’optimiser la puissance de saturation et le facteur de bruit du SOA, sans sacrifier ni le gain maximal ni la bande passante optique. Nous avons aussi montré que, pour ce type de composants, une augmentation de la puissance optique injectée pouvait être compensée par une augmentation du courant d’alimentation pour maintenir une large bande passante optique. Nous avons également mis en place deux techniques d’élargissement de la bande passante optique de SOA à large bande. La première technique est fondée sur le filtrage en réflexion spectralement sélectif (ESOA). Le dispositif expérimental a permis d’amplifier simultanément 8 canaux CWDM dans une bande passante (définie à −1 dB) de 140 nm. La deuxième technique, basée sur un amplificateur hybride Raman-SOA, a fourni une bande passante optique (définie à −1 dB) de 89 nm avec un gain de 17 dB. Nous avons ainsi pu réaliser une transmission simultanée de 5 canaux CWDM allant jusqu’à 10 Gb/s sur 100 km
SOA-based optical amplification became crucial for increasing optical system capacity and to benefit from the broad bandwidth of optical fibers. In this work we present both theoretical and experimental studies for a new broadband SOA developed by Alcatel Thales III-V lab in the framework of AROME and UltraWIDE ANR projects.We developed firstly a semi-phenomenological model for both the material gain and the gain coefficient of a multi-quantum well -based SOA structure with a reduced set of parameters. This material gain model has been integrated in an existing SOA model and proved its performance in reproducing steady state behavior of this new broadband SOA (gain and noise figure) for a wide range of wavelengths, input powers and bias currents. Thanks to this model, we studied the influence of the SOA geometrical structure on the optical bandwidth for a given target gain, by varying length, number of electrodes and bias current. We showed that two-electrode SOA structures do not provide any improvement of the bandwidth compared to the one-electrode case. However, the two-electrode structure allows the optimization of both the SOA saturation power and the noise figure, without sacrificing neither the maximum gain nor the optical bandwidth. We have also shown that for this kind of component, an increase in the injected optical power could be compensated by an increase in the supply current to maintain a wide optical bandwidth.We have also investigated two techniques to widen the optical bandwidth of our broadband SOA. The first one is based on a modification of the SOA structure by introducing a selective reflection filter (ESOA). Its experimental implementation allowed the amplification of an 8-CWDM-channel comb in a bandwidth (defined at -1 dB) of 140 nm. The second one, based on a hybrid Raman-SOA amplifier, provided an optical bandwidth (defined at -1 dB) of 89 nm with a gain of 17 dB. With this last technique, we were able to achieve a 5-CWDM-channel comb transmission up to 10 Gb/s over 100 km

Im Bereich der industriellen Metallurgie und Kristallzüchtung treten bei zahlreichen Anwendungen, wo magnetische Wechselfelder zur induktiven Beeinflussung von leitfähigen Werkstoffen eingesetzt werden, auch Strömungen mit freier Oberfläche auf. Das Anwendungsspektrum reicht dabei vom einfachen Aufschmelzen eines Metalls in einem offenen Tiegel bis hin zur vollständigen Levitation. Auch der sogenannte RGS-Prozess, ein substratbasiertes Kristallisationsverfahren zur Herstellung siliziumbasierter Dünnschichtmaterialien, ist dafür ein Beispiel. Um bei solchen Prozessen die Interaktion von Magnetfeld und Strömung zu untersuchen, ist die numerische Simulationen ein wertvolles Hilfsmittel. Für beliebige dreidimensionale Probleme werden entsprechende Berechnungen bisher durch eine externe Kopplung kommerzieller Programme realisiert, die für Magnetfeld und Strömung jeweils unterschiedliche numerische Techniken nutzen. Diese Vorgehensweise ist jedoch im Allgemeinen mit unnötigem Rechenaufwand verbunden. In dieser Arbeit wird ein neu entwickelter Methodenapparat auf Basis der FVM vorgestellt, mit welchem sich diese Art von Berechnungen effizient durchführen lassen. Mit der Implementierung dieser Methoden in foam-extend, einer erweiterten Version der quelloffenen Software OpenFOAM, ist daraus ein leistungsfähiges Werkzeug in Form einer freien Simulationsplattform entstanden, welches sich durch einen modularen Aufbau leicht erweitern lässt. Mit dieser Plattform wurden in foam-extend auch erstmalig dreidimensionale Induktionsprozesse im Frequenzraum gelöst.

Indiana University-Purdue University Indianapolis (IUPUI)
Topology Optimization is a technique that allows for the obtaining structures which maximize the use of the material. This is done by intelligently deciding the binary distribution of solid material and void, in a discretized given space. Several researchers have provided methods to tackle binary topology optimization. New ef- forts are focused on extending the application for multi-phase optimizations. At the industrial level, several components designed are made up of more than one material to reduce weight and production costs. The objective of this work is to implement the algorithm of Hybrid Cellular Automaton for multi-material topology optimiza- tion. The commonly used interpolation rule SIMP, which allows to relate the design variables to the mechanical properties of the material, is replaced by ordered SIMP interpolation function. The multiple volume constraints are applied sequentially, starting with the most elastic material. When a constraint is satisfied, the elements assigned to this material remain passive by a defined number of iterations to promote the convergence of the solution. Examples are shown for static and dynamic loads. The work demonstrates the versatility of algorithms based on control systems to solve problems of multiple phases and transient response fields.

This study proposes an approach for solving density-based multi-material topology optimization of cracked structures using Peridynamics. The alternating active-phase algorithm is utilized to transform the multi-material problem into a series of binary phase topology optimization sub-problems. Instead of the conventional mesh-based methods, the Peridynamics theory (PD) is used as a tool to model the behaviour of the materials and solve for the displacement field. The most significant advantage of PD is its ability to model discontinuities in a relatively straightforward manner. Thus, in the present work, the effect of cracks as a discontinuity is investigated on the optimal multi-material topologies. The Solid Isotropic Material with Penalty (SIMP) method is utilized to define the material properties as a function of the design variables. Also, the optimization problem is solved through the Optimality Criteria (OC) approach. The proposed method is compared to the results reported in the literature by executing three numerical examples that investigate the effect of the direction of an interior crack on the optimal topologies. Moreover, the efficiency of the proposed approach is verified by solving several examples where we aim at minimizing the compliance of the structure with and without initial cracks.
Graduate

碩士
國立雲林科技大學
工業工程與管理研究所碩士班
95
The material handling system ( MHS ) is the most complex component of an advanced flexible manufacturing system ( FMS ). It utilizes various functions and resource to regulate the part movement from one work-center to another. The material handling action occupies most of the production action, therefore the practice and theory of MHS possess decisive influence in the production management and operating cost. We apply simulation software to build up an flexible manufacturing system and adopt the response surface methodology ( RSM ). It can help us to realize the full potential design, schedule and control in AGV system. In this research, we consider two different objectives: Average throughput and Average AGV utility rate. System parameters of AGV amount, AGV speed, AGV dispatching rule, batch and machine dispatching rule were considered. We combine average throughput with average AGV utility rate to from a single desirability function to find optimal parameters of system.

The present dissertation seeks to optimize the unit cell of a two-dimensional cellular material, pursuing the minimization of the peak equivalent stress in the microstructure. This class of materials is particularly relevant to the design of lightweight structures. By minimizing the peak stress in the microstructure, it is possible to use material in a more rational way. Given the periodic nature of the problem, asymptotic homogenization is employed to compute the stress distribution in the microstructure when a macroscopic load is applied, since periodicity boundary conditions are imposed. With this being a purely conceptual study, only three macroscopic loads are considered: the hydrostatic, biaxial, and pure shear ones. Initially, the single-material problem is solved through shape optimization. Then, the potential to reduce the peak equivalent stress through the introduction of additional material phases is explored. Also with shape optimization, the in uence of one additional material phase is studied. Additionally, topology optimization is used to discover the functionally graded material that minimizes the peak stress in the microstructure. The obtained results show that an increased design exibility always leads to milder stress states. The known theoretical results were successfully replicated, with minimal error measures associated. By increasing the number of material phases in the microstructure, peak stress reduction are attainable. A uniformly stressed microstructure is possible to obtain, by means of a functionally graded material.

All proposed methods are demonstrated by several 2D and 3D examples which have been extensively studied in the recent literature of topology optimization.
The fourth-order nonlinear parabolic C-H equations with elasticity are solved by a powerful nonlinear implicit mutigrid algorithm. To validate its correctness and efficiency, I first use it for the quadternary C-H equations without elasticity and get good results. To my best knowledge, it is the first simulation for such C-H models composed of more than three phases both in 2D and 3D.
The Optimization of Structural Topology (OST) is a breakthrough in product design because it can optimize size, shape and topology synchronously under different physical constraints. It has promising applications in industry ranging from automobile and aerospace engineering to micro electromechanical system.
Then this dissertation introduces a gradient flow in the norm of H-1 for the problem of multi-material structural topology optimization in 2/3D with a generalized Cahn-Hilliard (C-H) model with elasticity. Unlike the traditional C-H model applied to spinodal separation which only has bulk energy and interface energy, the generalized model couples the macroscopic elastic energy (mean compliance) into the total free energy. As a result, the grain morphology is not random islands or zigzag web-like objects but regular truss or bar structure. Although disturbed by elastic energy, the C-H system still keeps its two most important properties: mass conservation and energy dissipation. Therefore, it is unnecessary to compute the Lagrange multipliers for the volume constraints and make extra effort to minimize the mean compliance (elastic energy) for the optimization of structural topology. On the other hand, when pure phases separate from disordered original state, their boundaries will merge and split resulting in natural and flexible topology variation. Such aforementioned properties make the C-H model especially suitable for the problem of optimization of multi-material structural topology.
This dissertation also extends the famous Solid Isotropic Material with Penalization (SIMP) model from 2D to 3D for topology optimization of the structure with single material. A short 177-line Matlab code including 3D Finite Element Method (FEM), filter technique, Optimality Criteria (OC) algorithm and bisection method is listed in appendix A for clear understanding of this model in 3D.
This dissertation first substitutes the nonlinear diffusion method for filter process in the optimization of structural topology. Filtering has been a major technique used in a homogenization-based method for topology optimization of structures. It plays a key role in regularizing the basic problem into a well-behaved setting. But it has a drawback of smoothing effect around the boundary of material domain. A diffusion technique is presented here as a variational approach to the regularization of the topology optimization problem. A nonlinear or anisotropic diffusion process not only leads to a suitable problem regularization but also exhibits strong "edge"-preserving characteristics. Thus, it shows that the use of the nonlinear diffusions brings desirable effects of boundary preservation and even enhancement of lower-dimensional features such as flow-like structures. The proposed diffusion techniques have a close relationship with the diffusion methods and the phase-field methods of the fields of materials and digital image processing.
Zhou Shiwei.
"December 2005."
Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6713.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (p. 140-151).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.

碩士
國立高雄應用科技大學
機械工程系
105
In this study, mold flow analysis and Taguchi experimental methods were both applied to investigate the injection molding parameter’s effects on the shrinking property of a multi-material toothbrush. The material used for the skin layer, injected first, of the toothbrush is PP, while TPE is for the core layer. Both PP and TPE are nonpolar materials, so good bonding between the two can be expected. A rotation tool system was built and used to mold the toothbrush before this study take place. To shorten the cycle time, the cooling times for the first and second shots must be the same in this continuous manufacturing process. 　　 First, we found the influence of each parameter on shrinkage by Moldex3D simulation analysis, and used Taguchi experimental method to find the optimization parameter combinations. The amount of shrinkage was improved to 3.78 mm from original 8.5 mm. Because the core TPE layer was covered by the PP skin layer, and TPE was injected after PP, taking the heat out from the TPE core has to go through PP skin layer, the cooling efficiency is low. To further improve the shrinkage problem, we tried to inject the TPE core layer first in the simulation, so the TPE core can receive better cooling. The results indicated that the amount of shrinkage can be improved to 3.65 mm from 8.50 mm with 60 seconds cooling.

Dissertação de mestrado em Polymer Engineering
When industries need to make components with two or more materials using just one mould and one machine, they use multi-material injection moulding techniques. One of these techniques is the core back moulding that allows the subsequent injection of two different materials without opening the mould, commonly used for parts with simple geometry, normally a rigid part involved with an elastomer. These moulds are very complex in its structure, therefore the design of the mould, its construction and assembly need to be carefully done to avoid part defects. Moreover, multi-material injection moulding may be a challenge regarding the adhesion between materials, being dependent on materials compatibility, materials rheological characteristics and injection moulding conditions used. The present dissertation addresses the development of a core back mould for the production of a complex bi-material part for the automotive industry and the study of the processing conditions that best promote the adhesion between the materials used. For that different tools where used such as Solidworks for the mould design, and DOE for the design of experiments. The mould development went through several steps such as the design of the injection, cooling, ejection and gas trap systems. Then the mould components were machined and assembled. Finally, the mould was tested and the parts were analysed. A study about the adhesion of the materials in this type of moulds and how the processing conditions influence the interface quality was realised. To simplify that study, a Design of Experiments was performed. This method is used to reduce the number of tests, assuring the reliability of the results. Finally, to analyse the adhesion of the parts, tensile tests were performed. It was concluded that the mould had a good performance. Parts were successfully made and the strength of the joints evaluate. It was concluded that the adhesion between materials was more efficient in the part extremities comparing with the middle zones. These results are attributed to the location of the gate and also the complex geometry of the part. Furthermore, the processing conditions influence the strength of the joint region. The set of values that would optimise PP/EPDM joints are the injection temperature of the second material of 200ºC, the mould temperature of 40ºC and the injection pressure of 80bar.
Quando as indústrias necessitam de fazer componentes com dois ou mais materiais utilizando apenas um molde e uma máquina, utilizam técnicas de moldação por injeção multi-material. Uma destas técnicas é a moldação core back que permite a subsequente injeção de dois materiais diferentes sem abertura do molde, normalmente utilizada para peças com geometria simples, como uma peça rígida envolvida com um elastómero. Estes moldes são muito complexos, pelo que a conceção do molde, a sua construção e montagem precisam de ser realizadas cuidadosamente para evitar defeitos nas peças. Além disso, a moldação multi-material pode ser um desafio no que respeita à adesão entre os materiais, dependendo da compatibilidade dos materiais, características reológicas e condições de processamento. A presente dissertação aborda o desenvolvimento de um molde core back para a produção de uma peça bi-material para a indústria automóvel e o estudo das condições de processamento que melhor promovem a adesão entre os materiais utilizados. Para isso são utilizadas diferentes ferramentas, tais como Solidworks para o desenho do molde, e DOE. O desenvolvimento do molde passou por várias etapas, tais como a conceção dos sistemas de injeção, arrefecimento, ejeção e escape de gás. Em seguida, os componentes do molde foram maquinados e montados. Finalmente, o molde foi testado e as peças foram analisadas. Foi realizado um estudo sobre a adesão dos materiais neste tipo de moldes e como as condições de processamento influenciam a qualidade da interface. Para simplificar esse estudo, foi realizado um Design of Experiments. Este método é utilizado para reduzir o número de ensaios, assegurando a fiabilidade dos resultados. Finalmente, para analisar a adesão das peças, foram realizados ensaios de tração. Concluiu-se que o molde tinha um bom desempenho. As peças foram produzidas com sucesso e a resistência da zona de união foi avaliada. Concluiu-se que a adesão entre os materiais era mais eficiente nas extremidades das peças, em comparação com as zonas médias. Estes resultados devem-se à localização do ponto de injeção e também à complexa geometria da peça. Além disso, as condições de processamento influenciam a resistência da zona de união. O conjunto de valores que otimizariam a adesão da peça PP/EPDM são a temperatura de injeção do segundo material de 200ºC, a temperatura do molde de 40ºC e a pressão de injeção de 80bar.

Indiana University-Purdue University Indianapolis (IUPUI)
Traumatic Brain Injuries (TBI) are one of the most apprehensive issues today. In recent years a lot of research has been done for reducing the risk of TBI, but no concrete solution exists yet. Helmets are one of the protective devices that are used to prevent human beings from mild TBI. For many years some kind of foam has been used in helmets for energy absorption. But, in recent years non-traditional solutions other than foam are being explored by different groups. Focus of this thesis is to develop a completely new concept of energy absorption for helmet liner by diverting the impact forces in radial directions normal to the direction of impact. This work presents a new design of an advanced layered composite (ALC) for energy dissipation through action of a 3D array of compliant mechanisms. The ALC works by diverting incoming forces in multiple radial directions and also has design provisions for reducing rotational forces. Design of compliant mechanism is optimized using multi-material topology optimization algorithm considering rigid and flexible material phases together with void. The design proposed here needs to be manufactured using the advanced polyjet printing additive manufacturing process. A general and parametric design procedure is explained which can be used to produce variants of the designs for different impact conditions and different applications. Performance of the designed ALC is examined through a benchmark example in which a comparison is made between the ALC and the traditional liner foam. An impact test is carried out in this benchmark example using dynamic Finite Element Analysis in LS DYNA. The comparison parameters under consideration are gradualness of energy absorption and peak linear force transmitted from the ALC to the body in contact with it. The design in this article is done particularly for the use in sports helmets. However, the ALC may find applications in other energy absorbing structures such as vehicle crashworthy components and protective gears. The ultimate goal of this research is to provide a novel design of energy absorbing structure which reduces the risk of head injury when the helmet is worn.

Indiana University-Purdue University Indianapolis (IUPUI)
Topology optimization allows designers to obtain lightweight structures considering the binary distribution of a solid material. The introduction of cellular material models in topology optimization allows designers to achieve significant weight reductions in structural applications. However, the traditional topology optimization method is challenged by the use of cellular materials. Furthermore, increased material savings and performance can be achieved if the material and the structure topologies are concurrently designed. Hence, multi-scale topology optimization methodologies are introduced to fulfill this goal. The objective of this investigation is to discuss and compare the design methodologies to obtaining optimal macro-scale structures and the corresponding optimal meso-scale material designs in continuum design domains. These approaches make use of homogenization theory to establish communication bridges between both material and structural scales. The periodicity constraint makes such cellular materials manufacturable while relaxing the periodicity constraint to achieve major improvements of structural performance. Penalization methods are used to obtain binary solutions in both scales. The proposed methodologies are demonstrated in the design of stiff structure and compliant mechanism synthesis. The multiscale results are compared with the traditional structural-level designs in the context of Pareto solutions, demonstrating benefits of ultra-lightweight configurations. Errors involved in the mult-scale topology optimization procedure are also discussed. Errors are mainly classified as mesh refinement errors and homogenization errors. Comparisons between the multi-level designs and uni-level designs of solid structures, structures using periodic cellular materials and non-periodic cellular materials are provided. Error quantifications also indicate the superiority of using non-periodic cellular materials rather than periodic cellular materials.

Im Bereich der industriellen Metallurgie und Kristallzüchtung treten bei zahlreichen Anwendungen, wo magnetische Wechselfelder zur induktiven Beeinflussung von leitfähigen Werkstoffen eingesetzt werden, auch Strömungen mit freier Oberfläche auf. Das Anwendungsspektrum reicht dabei vom einfachen Aufschmelzen eines Metalls in einem offenen Tiegel bis hin zur vollständigen Levitation. Auch der sogenannte RGS-Prozess, ein substratbasiertes Kristallisationsverfahren zur Herstellung siliziumbasierter Dünnschichtmaterialien, ist dafür ein Beispiel. Um bei solchen Prozessen die Interaktion von Magnetfeld und Strömung zu untersuchen, ist die numerische Simulationen ein wertvolles Hilfsmittel. Für beliebige dreidimensionale Probleme werden entsprechende Berechnungen bisher durch eine externe Kopplung kommerzieller Programme realisiert, die für Magnetfeld und Strömung jeweils unterschiedliche numerische Techniken nutzen. Diese Vorgehensweise ist jedoch im Allgemeinen mit unnötigem Rechenaufwand verbunden. In dieser Arbeit wird ein neu entwickelter Methodenapparat auf Basis der FVM vorgestellt, mit welchem sich diese Art von Berechnungen effizient durchführen lassen. Mit der Implementierung dieser Methoden in foam-extend, einer erweiterten Version der quelloffenen Software OpenFOAM, ist daraus ein leistungsfähiges Werkzeug in Form einer freien Simulationsplattform entstanden, welches sich durch einen modularen Aufbau leicht erweitern lässt. Mit dieser Plattform wurden in foam-extend auch erstmalig dreidimensionale Induktionsprozesse im Frequenzraum gelöst.