La fabrication de grandes pièces structurelles aéronautiques en alliage d’aluminium nécessite la réalisation de multiples étapes de mise en forme (laminage, matriçage, forgeage…), de traitements thermiques et usinage. Pendant ces étapes de fabrication, les différents chargements thermomécaniques subis par la pièce avant son usinage induisent des déformations plastiques ainsi que des modifications de la microstructure qui sont sources de contraintes résiduelles. A ces contraintes résiduelles issues de l’histoire thermomécanique de la pièce, viennent s’ajouter celles issues directement de l'étape d'usinage. En effet lors de cette étape jusqu’à 90% de la matière initiale d'une pièce peut être retirée en utilisant des conditions de coupe parfois sévères. Les pièces aéronautiques présentent parfois des géométries complexes avec des parois minces. Ainsi, pendant et à l’issue de l’usinage, la géométrie de la pièce usinée se trouve fortement modifiée et une redistribution des contraintes résiduelle est alors à l’œuvre. Ces contraintes résiduelles qu’elles soient héritées ou induites par le procédé, influencent fortement la géométrie finale obtenue et sont une des causes principales de non-conformité des pièces avec les tolérances dimensionnelles du produit fini. Engendrant une perte conséquente pour les industries manufacturières. Au cours de ce travail de thèse, nous nous sommes concentrés sur la prise en compte de ces deux types de contraintes résiduelles dans un modèle numérique de prédiction des distorsions. Nous nous sommes uniquement focalisés sur les pièces en aluminium issues de l’aéronautique. Nous avons ainsi couplé des modèles numériques avancés d’immersion et de remaillage avec un logiciel industriel existant afin de proposer une nouvelle solution numérique, rapide et robuste. En se basant sur les hypothèses de la littérature nous avons décidé de simuler l’usinage comme un enlèvement de matière massif où la trajectoire de l’outil et les machine seront négligées. L’objectif numérique est donc de proposer une méthode qui puisse rendre compte de la redistribution des contraintes résiduelles au sein de la pièce. Chaque étape de la gamme d’usinage est ainsi représentée par une étape de remaillage où le « volume usiné » sera supprimé du maillage pour céder ensuite sa place à un calcul mécanique permettant de rendre compte de la réorganisation des contraintes et les déformations qu’elle induisent. Ce processus itératif, réalisé dans un environnement parallèle a nécessité de nombreux développements numériques. Ainsi une nouvelle stratégie de remaillage et de repartitionnement a été proposée pour pouvoir obtenir un maillage à même de capturer les contraintes résiduelles issues de l’usinage en proche surface ainsi que pour réduire de manière significative les temps de calcul liés aux modifications de la géométrie par la découpe. Un modèle d’élasticité linéaire simplifié a aussi été ajouté au programme pour réduire le coût numérique des calculs mécaniques et permettre de traiter des problèmes de taille plus conséquente sur des ordinateurs de puissance raisonnable. Afin de confirmer les résultats obtenus par ces calculs, les simulations ont été comparées à des résultats expérimentaux tirés de la littérature et réalisés spécifiquement pour ce travail de thèse. / The manufacture of large aeronautical structural parts made of aluminium alloys requires multiple forming steps (rolling, die forging, forging, etc.), heat treatment and machining. During these manufacturing steps, the various thermomechanical loads suffered by the part before its machining induce plastic deformations as well as modifications of the microstructure which are sources of residual stresses. In addition to these residual stresses resulting from the thermomechanical history of the part, others result directly from the machining step. Indeed, during this step, up to 90% of the raw material of a part can be removed using sometimes severe cutting conditions. Aeronautical parts sometimes have complex geometries with thin walls. Thus, during and after machining, the geometry of the machined part is significantly modified by the redistribution of residual stresses at work. These residual stresses, whether inherited or induced by the process, strongly influence the final geometry obtained and are one of the main causes of non-conformity of the parts with the dimensional tolerances of the finished product. This results in a significant loss for manufacturing industries. In this thesis work, we focused on considering these two types of residual stresses in a numerical model predicting distortions. We focused only on aluminium parts from the aeronautics industry. We have thus coupled advanced numerical fitting and remeshing models with existing industrial software to provide a new numerical solution, fast and efficient. Based on the assumptions in the literature, we decided to model machining as a massive material removal where tool path and interaction with the machine will be neglected. The numerical objective is therefore to propose a method that can account for the redistribution of residual stresses within the part. Each step of the machining plan is thus represented by a remeshing step where the "machined volume" will be removed from the mesh followed by a mechanical computation to account for the reorganization of stresses and the deformations they induce. This iterative process, carried out in a parallel environment, required many numerical developments. Thus, a new remeshing and repartitioning strategy has been proposed to obtain a mesh capable of capturing the residual stresses resulting from near-surface machining and to significantly reduce the calculation times associated with changes in geometry through cutting. A simplified linear elasticity model has also been added to the approach to reduce the numerical cost of mechanical computation and allow for larger problems to be addressed on computers of reasonable power. In order to confirm the results obtained by these computations, the simulations were compared with experimental results from the literature and carried out specifically for this thesis work.

<div>Aluminum alloy sheets are typically manufactured from cast slabs by multi-step rolling and annealing process. This process is very energy intensive, especially in the homogenization process after casting, which usually is conducted at 480 to 580 ℃ for up to 48 h. To reduce the </div><div>processing steps and energy, a shear-based single-step deformation process, large strain extrusion machining (LSEM), was used to create strips from AA6013-T6 with and without preheating of the workpiece. Continuous strips were obtained from this alloy with low workability. Flow patterns through the thickness of the strips exhibited primary shear with grains inclined steeply to the faces of the strips, modified to varying degrees by secondary shear from friction with the tools at the surfaces. Through control of the deformation parameters (strain, strain rate and temperature), a wide range of microstructure could be achieved. In high-temperature LSEM, dynamic recrystallization occurs at lower temperatures than in commercial hot rolling processes. </div><div><br></div><div>LSEM was performed directly on the as-cast AA6013 without homogenization. By appropriate combination of strain and strain rate, continuous strips were obtained in a single step without preheating directly from the as-cast workpiece. The highly deformed LSEM strip has enhanced workability. It can be cold rolled with at least 73% reduction in a single step without cracking. The strips were characterized by strong shear texture with partial {111} and <110> fibers. After annealing, a mixed texture containing simple shear texture and other texture develops. The annealed strips are expected to have better formability than commercial ones made by rolling.<br></div><div><br></div><div>In comparison, multi-step warm-rolling and cold rolling were performed on the as-cast AA6013. The as-cast material was preheated to 300 ℃ and rolled with 12% reduction per pass till the same effective strain as the LSEM. The warm-rolled strips were then cold-rolled with the same reductions as those on LSEM strips. The results showed that during warm rolling process, cracking occurs on the strips before reaching the same effective strain and the warm-rolled strips can only be further cold rolled with reduction less than 26% before cracking, compared with 73% reduction without cracking for LSEM strips.<br></div><div><br></div><div>Based on the simple shear LSEM process, a novel way to produce aluminum strip/sheet material is introduced. The alloys are cast into disk-shape workpiece and then transferred to the LSEM line. In this line, continuous strips/sheets are obtained in a single step at room temperature. The materials are then coiled if needed and cold rolled to the final gauge. Finally, the strips/sheets are solution treated for further deformation processing. In this method, the conventional homogenization and hot rolling, including reversing and multi-stand hot rolling, are replaced by a single-step LSEM process at room temperature.<br></div>

Orientador: Marcos Valerio Ribeiro / Resumo: The development of new materials is extremely important, due to the need to obtain materials with good properties and low cost. There is a continuing need to improve tools for machining materials that have high strength at elevated temperatures that meet the vermicular cast iron. Small advances in the development of new tools could mean important aspects in the field of machining, in addition to making the market more competitive. The set of production and application of ceramic cutting tools in the machining processes of vermicular cast iron (GJV450) needs further advances, being an object of great industrial interest. In this context, the present work determined the best application condition of the ceramic tools based on Alumina (Al2O3), doped with magnesium oxide (MgO) on a laboratory scale, in the machining without cutting fluid of the vermicular iron class GJV450 in comparison with a commercial carbide tool coated with alumina, based on the need for machining vermicular cast iron in industries and foundries. For turning vermicular cast iron with a ceramic tool, the parameters used were cutting speeds of 300-350-400-450-500-550-600-650 m / min; feed of 0.1-0.3 mm / rev and machining depth of 0.5 -1.0 mm and for the carbide tool, cutting speeds of 150-250-350-450 m / min; feed rate of 0.1-0.3 mm / rev and machining depth of 0.5 -1.0 mm. The previously defined input variables (Vc, f, ap), were correlated with the output variables such as roughness (Ra and Rt), power, acous... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Manufacturing of components with complex internal features, e.g. for medical applications, aeronautics or automobile industry, is challenging. Those components are often machined in temporarily and locally separated production stages. As results of these separated stages form deviations and positioning errors increase, which lead to additional efforts for the quality assurance. The technology aimed within the project SwitchECM is expected to allow the machining of different complex features of one workpiece in one single production stage and shall simultaneously allow a high precision. For this purpose, a multi-cathode system will be developed, in which separated cathodes can be switched with specific parameters, depending on the requirements of the pre-defined features. This study will show the capability to machine the workpiece with different parameter sets but the same cathode and device as fundamental work for the machining with a multi-cathode system. Therefore the surface and dissolution characteristics for the material 1.4301 were used to design the process. The machining tasks were determined to deburring and edge shaping. In the experiments, the parameters voltage and working time were selected depending on the final geometry. It will be shown that the deburring task can be handled with nearly no edge shaping and the edge shaping task is suitable to adjust different edge geometries.

Under år 2008 uppskattades den totala produktionen av kugghjul inom bilindustrin till 2000 – 2500 miljoner detaljer, varav 1000 - 1400 miljoner av dessa är av hög kvalité [1]. För precisionskugghjul med modul under 1 mm kan tidsbegränsning och kostnader kopplade till design av skärverktyget elimineras genom att tillämpa en flexibel tillverkningsmetod som tillexempel abrasiv vattenskärning (AWJM). Denna studie undersöker designen av ett hybridtillverkningssystem konfigurerat kring AWJM samt föreslår finbearbetningsprocess via konventionella bearbetningsmetoder. Den tekniska möjligheten att producera kuggring av hög precision testas med en 5-axlig vattenjetmaskin och utvärderas enligt kvalitets nivåer för DIN-standard. För detta ändamål studerades ett kugghjul med modul 0,55 mm, 199 tänder, 110 mm i ytterdiameter och 72 mm i innerdiameter samt en tjocklek på 6 mm gjord av Armox T500, höghållfast stål. Resultaten visar på hög potential att uppnå ISO standardkvalité för kugghjul. Vissa kvalitetsegenskaper, definierade i DIN- och ISO-standarder, till exempel ytfinhet med låga värden; Ra 0,8 μm, uppnås vid användning av AWJM. Andra kvalitetskännetecken som profilavvikelse är relaterade till parametrar som skäreffekt, matningshastighet, mängd abrasivmedel, etc. Framtagna värden sträcker sig från Q10 och Q11 enligt DIN3967 vilket möjliggör slutoperationer som till exempel slipning. Geometrisk avvikelse, på ovansidan, gav en maximalt värde på 7 μm med en standardavvikelse på 4 μm. Jetstrålens eftersläpning observerades och kan kompenseras för medan resultatet av rundade hörn existerar i alla skärning med AWJ. Radiell förskjutning, tandtjocklek och index avvikelser visar värden som kan förbättras tillsammans med processoptimering, maskinkalibrering och eliminering av inneboende positionsavvikelser i maskinen. Varje enskild geometri kräver specifika processparametrar och CAM-programmens algoritmer behöver vidare optimeras för arbeten med tämligen små geometrier. / Production of gears for the automotive industry during 2008 is estimated to have been between 2000 – 2500 million pieces, from which 1000 to 1400 million pieces were high quality gears [1]. For precision gears with module below 1 mm, the time limitations and costs associated with the design of the cutting tool can be eliminated by using a flexible manufacturing technology such as Abrasive WaterJet Machining (AWJM). This project investigates the design of a hybrid manufacturing system configured by use of AWJM and proposed finishing processes using conventional machining methods. The technical feasibility is analysed to produce high precision ring gears using a 5-axes AWJM system to achieve DIN standards quality levels. For this purpose, a gear with a module of 0.55 mm, 199 teeth and 110 mm in the outer diameter and 130 teeth and 72 mm in the inner diameter with a thickness of 6 mm is studied; the selected material is Armox T500, a high strength steel. The results indicate high potential of producing ISO quality standard gears. Certain quality characteristics defined in DIN and ISO standards, for instance surface roughness – values as low as Ra 0.8 μm, are possible to achieve accurately by using AWJM. Others quality features as profile deviation, are related to parameters as cutting power, feed rate, abrasive feed rate, etc. The displayed values ranged Q10 and Q11 according to DIN3967 which allows for use of further finishing operations such as grinding. The top geometry deviations of a 0.3 mm cut, display a maximum value of 7 μm with an average value of 4 μm. Observed jet lag effects can be improved. Rounded corner effect exists in all AWJ cuts. Runout, tooth thickness and index deviations show values that can be improved together with process optimization, machine calibration and elimination of machine inherent positioning deviations. Each particular geometry needs specific process parameters and CAM software algorithms need further optimization for working with rather small design geometries.

New environmental regulations as well as the increasing industrial competitiveness have set new more demanding rules on the manufacturing industry. In order to abide by those rules not only from the legal point of view but also to be able survive, manufacturing has to be more sustainable from many aspects, especially the economical one. One way to achieve the previous target is an unfortunately often oversighted aspect of the industry sector, the maintenance strategy. Condition based maintenance, CBM, can be used successfully in the industry and accurate estimation of spindle life time can lead to large savings in downtime and cost. CBM requires accurate sensors and equipment in order to get the right indicators whether equipment performance is deteriorating or not. One performance factor when planning a machining process is chatter vibration and one way to avoid this deteriorating phenomenon is to choose cutting parameters that allow stable machining. Various types of sensors are available for vibration and other CBM related measurements. Depending on the situation, the most applicable sensor is selected. The core of this thesis is to investigate the usefulness of measurements with the contactless excitations and response unit in terms of condition based maintenance. In the first part of the thesis, some of the theoretical aspects of maintenance are extensively elaborated upon and later on, the experimental part is presented along with the results’ discussion. The hardware required by the experiments has been provided by KTH and the experiments took place in two of an automotive industry’s production sites. There have been two visits at site A and one at site B, apart from the initial meetings. The measurements have been analyzed with the use of MATLAB. / Nya miljöregler samt ökande industriell konkurrens har satt nya mer krävande regler för tillverkningsindustrin. För att följa dessa regler, inte bara ur rättslig synpunkt utan också för att kunna överleva, behöver tillverkningen ske mer hållbar ur många aspekter, särskilt den ekonomiska. Ett sätt att uppnå målen är via, en tyvärr ofta underskattad metod, underhållsstrategin. Tillståndsbaserat underhåll, CBM, kan användas med framgång inom branschen och korrekt uppskattning av spindellivstid kan leda till stora besparingar genom minskade driftstopp och kostnader. CBM kräver noggranna sensorer och utrustning för att få rätt indikatorer för att avgöra om utrustningens prestanda försämras eller ej. En prestationsavgörande faktor vid planering av bearbetningsprocesser är vibrationer. Ett sätt att undvika dessa försämrade fenomen är att välja skärparametrar som tillåter stabil bearbetning. Olika typer av sensorer finns tillgängliga för vibrations- och andra CBM-relaterade mätningar. Beroende på situation, väljs den mest lämpliga sensorn. Kärnan i denna rapport är att undersöka nyttan av mätningar med en beröringsfri excitations- och mätenhet för tillståndsbaserat underhåll. I de första avsnitten av rapporten redogörs några av de teoretiska aspekterna av underhåll och i de senare är den experimentella delen presenterad, tillsammans med diskussion kring resultat. Hårdvaran som krävs för experimenten har tillhandahållits av KTH och experimenten ägde rum på två produktionsanläggningar hos en fordonstillverkare. Det har varit två besök på plats A och ett besök på plats B, bortsett från inledande möten. Mätningarna har analyserats med hjälp av MATLAB.

The objective of this thesis is to find and develop methods that enhance and support the creation of evolvable master process plans with possibilities to challenge productivity and meet changing design requirements. The condition for achieving this is primarily that both the fundamental thinking and the results behind a process plan can be described. How should this be done? The focus is laid on process planning of gear transmission parts for heavy vehicles like trucks and coaches. Process planning is the activity where design and manufacturing are brought together with the common target to achieve both a competitive product and production process. There are many factors that influence the process planner when a new product or process shall be introduced for production. Process planning is, in most cases, performed by an experienced, skilled person but without any defined methodology or way of working. Much of the process planning is based on the retrieval of solutions already used. Much research effort has been devoted to developing systems for computer-aided process planning (CAPP). Yet CAPP systems have not been accepted and spread over a wide front within the manufacturing industry, much because of the functional incompleteness combined with the difficulties of adopting knowledge and changing requests. A method for systematic process planning is proposed as a way to perform and describe the procedure of creating a process plan. The method facilitates the interpretation and understanding of the plan, not only immediately for the process planner responsible, but also for designers, engineers, researchers and other interest groups involved in a manufacturing process. In the last chapter is a case study regarding manufacturing of a bevel gear pinion presented to exemplify use of the proposed method for systematic process planning. / KUGG

Studies of mechanics and deformation in metal cutting operations have been largely limited to steady-state processes assuming constant forces and shear strain of cutting. However, ‘transient’ or varying deformation conditions are frequently encountered in manufacturing processes, when one or more processing parameters vary during the progress of the cut. Such conditions impose a lower overall strain on the resulting chip and affect the cutting forces and energies. In this study, the transient deformation characteristics are studied through the analysis of chip attributes (hardness and shape change) in a periodic cutting technique, Modulation Assisted Machining (MAM). In MAM, a sinusoidal modulation is superimposed on the tool feed, resulting in periodic engagement between the tool and workpiece. Deformation is confined to a specific volume of material and is also transient due to varying local conditions, manifesting an inhomogeneous and lower shear strain compared to steady-state cutting. A wide variety of deformation conditions from near steady-state to completely transient was achieved through the control of modulation frequency, which determines the contact length in each cutting cycle. Particles produced at lower frequencies exhibit increased hardness, consistent with the deformation more approaching steady state. Micro-indentation tests performed on each particle tracked the local variations in hardness along the length of cut, which agreed well with the non-uniform shape change observed on the cross-section of the particles. Microstructural examination of the chips made with and without modulation helped further describe the different deformation modes acting under periodic and continuous cutting conditions. MAM is also a valuable technique for metal powder processing. Individual chip particles are produced during each modulation cycle with controllable shape and size, and composition identical to that of the workpiece. Advantages of the process include a significant reduction in the specific energy of production, zero compositional variance and a tight distribution of particle sizes compared to atomization. Implications of scaling up the process for large-scale production and the possible applications of the metal particles made with MAM are highlighted.

Les techniques d’usinage avancées sont un élément indispensable du développement des industries manufacturières. L’une de ces techniques, l’usinage à grande vitesse, constitue le sujet principal de cette thèse de doctorat. Ainsi, l’objectif majeur des travaux vise à améliorer la précision de contour dans le contexte de l’usinage multiaxes à grande vitesse de surfaces de forme libre, en agissant directement au niveau des boucles de commande d’axe. Pour cela, une première étape consiste à élaborer une stratégie permettant d’estimer le plus précisément possible l’erreur de contour pour différentes configurations de l’outil. Cette erreur de contour est ensuite minimisée grâce à l’adaptation hors ligne, pour un profil de pièce donné, des gains proportionnel et d’anticipation des régulateurs des boucles d’asservissement de la position de chaque axe. L’adaptation de ces gains est réalisée via un algorithme d’optimisation à l’aide d’un modèle non-linéaire du comportement de la machine, en considérant en particulier les frottements sur chacun des axes. L’optimisation permettant d’obtenir les gains des correcteurs des boucles de régulation tient compte des contraintes en termes de limitations cinématiques des axes (vitesse, accélération et jerk), de stabilité des boucles d’asservissement et de limites au niveau des courants des moteurs. Afin d’en faciliter la mise en oeuvre dans un cadre industriel, les stratégies développées s’avèrent directement implantables au sein des commandes numériques actuellement sur le marché, exploitant toutes les possibilités de la structure de commande classique de l’entraînement d’axe. / The advanced machining techniques are always the backbone of the manufacturing industries. Among such techniques, high speed machining is the main subject of this PhD thesis. Indeed, the main objective of this work is to improve the contouring accuracy in multi-axis high speed machining of free-form surfaces, directly acting inside the axis control loops. To do that, a first step aims at elaborating a strategy to estimate as accurately as possible the contour error for different tool configurations. This contour error is then minimized by means of an off-line adaptation for a given profile of the proportional and feedforward gains of the axis position loop controllers. This gain adaptation is performed via an optimization algorithm that considers a nonlinear model of the machine behaviour, in particular including friction related to each axis. This optimization leading to the controllers gains takes into account several constraints, including the axis kinematic (velocity, acceleration and jerk) limitations, the stability of the controlled loops and the motor current limits. Finally, to help their integration within an industrial framework, the developed strategies can be directly implemented in commercial CNC, by exploiting all possibilities of the classical control structure of axis drive.

The thesis deals with electron beam micromachining of nonmetallic materials like glass, ceramics and plastics. A brief description of the device on which the experiments were carried out is included; the author has participated on its development. Main topic is experimental study of influence of main electron beam parameters on results of machining. Examined parameters include accelerating voltage, beam current, focusing and speed of machining. Influence of beam deflection is analyzed. Method of sequential machining by repeated passes of the electron beam is presented. Main examined materials are quartz glass, alumina and selected plastics. The usefulness of the technology is shown by several practical applications.