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  • 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.
141

Electromagnetic Pulse Welding Process and Material Parameter Identification for High Speed Processes

Scheffler, Christian 14 July 2021 (has links)
Electromagnetic welding is an innovative, high-speed technology to manufacture mixed material joints. In this dissertation, an experimental-numerical method is presented to identify robust process windows of aluminum-copper and aluminum-steel compounds. The microstructural characteristics of these joints were investigated in detail. Moreover, an evaluation of the joint quality is presented and different numerical models were introduced for the simulation of macroscopic and microscopic effects. To improve the accuracy of the simulations, the strain rate sensitivity of the materials must be considered. For this purpose a high-speed setup for the identification of relevant viscoplastic material parameters, comprising an inverse evaluation strategy, was developed.
142

Schiebenockentechnologie an der Verbrennungskraftmaschine – Industriebeispiel für Modellierung und Auslegung unter Verwendung des alaska/ModellerStudios

Kuba, Teresa, Franke, Sören, Bär, Sebastian, Freudenberg, Heiko 24 May 2023 (has links)
Die Weiterentwicklung von Verbrennungsmotoren ist geprägt von einer Steigerung der Effizienz, optimaler Betriebslaststeuerung, einer Absenkung des spezifischen Verbrauchs und der Erfüllung geltender Abgasemissionsgesetzgebung. Die Optimierung des Ladungswechsels spielt dabei eine entscheidende Rolle. Eine Möglichkeit den Ladungswechsel optimal zu beeinflussen, ist der Einsatz von variablen Ventiltrieben zur Veränderung der Ventilhubbewegung sowie zur Verstellung der Steuerzeiten. thyssenkrupp Dynamic Components entwickelt und stellt Schiebenockensysteme als diskret schaltbare Ventiltriebsysteme her, welche die verschiedenen Ventilhubanforderungen über unterschiedliche Nockenprofile auf dem Schiebeelement nebeneinander abbilden können. Im Entwicklungs- und Auslegungsprozesses kommt eine Simulation des Bewegungs-, Beschleunigungs- und Abbremsverhaltens sowie der Kraftverläufe beim Verstellvorgang mittels einer Mehrkörpersimulation (MKS) in der Software alaska/ModellerStudio zum Einsatz. In diesem Beitrag wird das MKS-Modell des Schiebelements sowie der Abgleich des Modells mit Versuchen vorgestellt. Es folgt eine Darstellung von Optimierungsmöglichkeiten bereits in der Simulationsumgebung, bei denen die Kontaktnormalkräfte und Beschleunigungen in mehreren Iterationsschleifen auf den gewünschten Anwendungsfall angepasst werden können. Unter Berücksichtigung der Fertigungs- und Lagertoleranzen sowie des Verschleißverhaltens kann das System mit diesem Simulationstool bereits virtuell abgeprüft werden. / The advancement of internal combustion engines is characterized by an increase in efficiency, optimum operating load control, a reduction in specific consumption and compliance with applicable exhaust emission legislation. Optimization of the charge change plays a decisive role in this. One way of optimally influencing the charge change is to use variable valve trains to change the valve lift and adjust the timing. thyssenkrupp Dynamic Components develops and manufactures sliding cam systems as discretely switchable valve train systems that can feature the various valve lift requirements side by side via different cam profiles on the sliding element. A simulation of the motion, acceleration and deceleration behavior as well as the force curves during the sliding process by means of a multi-body simulation (MBS) in the alaska/ModellerStudio is applied in the development and design process. This presentation shows the MBS model of the sliding cam and the comparison of the model with test results. Various optimization options in the simulation environment present, how the contact normal forces and accelerations can be adapted in several iteration loops to the desired application. Taking into account the manufacturing and bearing tolerances as well as the wear behavior, this simulation tool allows to virtually check the sliding cam system.
143

Topology Optimized Unit Cells for Laser Powder Bed Fusion

Boos, Eugen, Ihlenfeldt, Steffen, Milaev, Nikolaus, Thielsch, Juliane, Drossel, Welf-Guntram, Bruns, Marco, Elsner, Beatrix A. M. 22 February 2024 (has links)
The rise of additive manufacturing has enabled new degrees of freedom in terms of design and functionality. In this context, this contribution addresses the design and characterization of structural unit cells that are intended as building blocks of highly porous lattice structures with tailored properties. While typical lattice structures are often composed of gyroid or diamond lattices, this study presents stackable unit cells of different sizes created by a generative design approach tomeet boundary conditions such as printability and homogeneous stress distributions under a given mechanical load. Suitable laser powder bed fusion (LPBF) parameterswere determined forAlSi10Mg to ensure high resolution and process reproducibility for all considered unit cells. Stacks of unit cells were integrated into tensile and pressure test specimens for which the mechanical performance of the cells was evaluated. Experimentally measured material properties, applied process parameters, and mechanical test results were employed for calibration and validation of finite element (FE) simulations of both the LPBF process as well as the subsequent mechanical characterization. The obtained data therefore provides the basis to combine the different unit cells into tailored lattice structures and to numerically investigate the local variation of properties in the resulting structures. / Durch die Einführung der Additiven Fertigung können neue Freiheitsgrade in Bezug auf Gestaltungsfreiheit und Funktionalität erreicht werden. In diesem Zusammenhang adressiert dieser Beitrag das Design und die Charakterisierung struktureller Einheitszellen als Bausteine für hochgradig poröse Gitterstrukturen mit maßgeschneiderten Eigenschaften. Während typische Gitterstrukturen oft auf Gyroid- oder Diamantstrukturen basieren, präsentiert dieser Beitrag stapelbare Einheitszellen unterschiedlicher Größe, die durch einen generativen Designansatz erstellt wurden. Hierdurch sollen verschiedene Randbedingungen wie eine gute Druckbarkeit und homogene Spannungsverteilung unter gegebenen mechanischen Lasten erreicht werden. Um eine hohe Auflösung und Reproduzierbarkeit der Einheitszellen zu erreichen, wurden für den verwendeten Werkstoff AlSi10Mg geeignete Druckparameter für das Laserstrahlschmelzen (LPBF) ermittelt. Stapel von Einheitszellen wurden in Zug- und Druckproben integriert, anhand derer die mechanische Stabilität der Zellen ermittelt wurde. Experimentell bestimmte Materialeigenschaften, die verwendeten Prozessparameter und die Ergebnisse der mechanischen Untersuchungen wurden anschließend für die Kalibrierung und Validierung Finiter Elemente (FE) Simulationen herangezogen, wobei simulationsseitig sowohl der Prozess des Laserstrahlschmelzens als auch die nachgelagerte mechanische Charakterisierung berücksichtigt wurden. Die hier präsentierten Ergebnisse sollen als Basis sowohl für eine gezielte Anordnung der Einheitszellen zu maßgeschneiderten Gitterstrukturen dienen als auch für die numerische Auswertung der lokal variierenden Eigenschaften der somit resultierenden Strukturen.
144

MiniPharm: A Miniaturized Pharmaceutical Process Development and Manufacturing Platform

Jaron ShaRard Mackey (14230133) 07 December 2022 (has links)
<p>  </p> <p>In the pharmaceutical industry, special care must be taken by companies to guarantee high quality medications that are free from byproducts and impurities. The development process involves various considerations including solvent selection, solubility screening, unit operation selection, environmental, and health impact evaluations. Traditionally, pharmaceutical manufacturing consisted of large, centralized facilities to meet pharmaceutical demands; however, there has been a recent shift toward distributed manufacturing. With distributed manufacturing platforms, rapidly changing supply chain needs can be met regionally in addition to supplying small-volume medications and personalized medicines to hospitals and pharmacies. To produce quality pharmaceuticals, distributed manufacturing platforms should integrate digital design, novel unit operations, and process analytical technology (PAT) tools for quality monitoring and control. In this dissertation, a process design and development framework is proposed and implemented for a small-scale pharmaceutical manufacturing platform: MiniPharm.</p> <p>Various approaches to process design are detailed in this dissertation, which include heuristic-based and digital or simulation-based design. For heuristic-based design, the knowledge of the researchers was utilized to provide unit operation evaluation and screening of process alternatives. In cases when unit operations were highly complex, digital or simulation-based design was utilized to conduct sensitivity analyses and simulation-based design of experiments. With the implementation of simulation-based design, material and time needs were reduced while gaining knowledge about the system. The integration of various unit operations comes with increased understanding of start-up dynamics and operational constraints. What was found to be the most successful approach was the combination of heuristics and digital design to combine researcher knowledge and experience with the information gained from process modeling and simulation to create process alternatives that utilized system dynamics to reach desired process outcomes. </p> <p>Additionally, MiniPharm was used for process model development at the small-scale. Various software packages have been made commercially available that focus on production scale; however, models for small-scale operations are not typically implemented in these packages. Models for unit operations were fit with collected experimental data to estimate model parameters for small-scale synthesis, liquid-liquid extraction, and crystallization unit operations. The models were implemented to better capture the heat and mass transfer of the milli-fluidic scale platform, which consist of unit operations housed within microchannels. MATLAB was utilized for estimation of parameters such as kinetic rate constants and overall mass transfer coefficients. These parameters were used for design space determination and process disturbance simulation. The exploration of the impact of various process parameters on quality attributes helps researchers gain a deeper understanding about the manufacturing process and helps to demonstrate how to control the process. </p> <p>An important aspect of MiniPharm is the process development progress that has been demonstrated. With the construction of a modular and reconfigurable platform, various process alternatives can now be experimentally validated. The integration of unit operations operated at a decreased scale makes MiniPharm an example of process intensification. The implementation of integrated unit operations decreases handling time of intermediates and reduces the overall footprint for manufacturing. Designed to allow for increased flexibility of operation, perfluoroalkoxy alkane (PFA) tubing was used for synthesis and purification. With PFA tubing clean in place procedures can be implemented using continuous solvent flow or the low cost, PFA tubing can be replaced. The modular nature of the platform also allows for the investigation of individual unit operations for performance evaluation. </p> <p>Finally, a novel continuous solvent switch distillation unit operation was designed and constructed along with customized reactor and crystallizers for process alternative screening for the synthesis and purification of two compounds: Diphenhydramine hydrochloride and Lomustine. Diphenhydramine hydrochloride is a low-value, high volume allergy medication commonly found in Benadryl and Lomustine is a high-value, low volume cancer medication used to treat glioblastoma and Hodgkin Lymphoma. The production of the compounds demonstrated the flexibility of the manufacturing platform to produce both a generic and a specialty medication. A versatile platform is needed for distributed manufacturing because of quickly changing supply chain needs. Overall, this dissertation successfully demonstrates the process design, development, and simulation for small-scale manufacturing.</p>
145

Investigation of VR as Visualization and Assembly-Simulation Tool

Götherström, Richard January 2024 (has links)
Across industries, Computer-aided design (CAD) programs are used to create vehicle parts. Simultaneously, virtual reality (VR) has become more common. Can these two co-existing technologies benefit one another? This thesis investigates how CAD modeling can be enhanced with the help of VR. Specifically, it focuses on importing CAD models during the runtime of a VR application, visualizing those models in real size. An additional feature includes the ability to interact with the imported CAD models, enabling assembly simulations. This thesis specifically explores how parts of electric autonomous trucks can be assembled in VR.  The results are moderately satisfying, with users expressing both satisfaction and dissatisfaction with certain aspects of VR as a tool in this context. However, only two users evaluated the application, indicating the need for a more extensive evaluation. / I flera industrier är CAD-program vanliga för att modellera delar till fordon. Samtidigt växer virtual reality (VR) fram och blir allt vanligare. Kan dessa två teknologier samexistera och dra nytta av varandra? Det här arbetet undersöker om CAD-modellering kan dra fördel av VR som ett verktyg för visualisering. En av de mer unika aspekterna av detta arbete är hur import av CAD-modeller under körtid  hanteras. En annan funktionalitet som undersöks är möjligheten att interagera med de importerade CAD-modellerna, vilket också öppnar för möjligheter att simulera monteringsprocesser. Resultatet var någorlunda tillfredsställande enligt intressenterna som utvärderade den slutgiltiga VR-applikationen. Det fanns aspekter som inte var helt tillfredsställande samtidigt som det fanns delar som var bra. Det ska beaktas att det endast var två intressenter som utvärderade den slutgiltiga applikationen, vilket indikerar att det behövs mer utvärdering för att fastställa ett gediget resultat.
146

Unapređenje kvaliteta alata za livenje pod pritiskom primenom tehnologija inženjerstva površina / Application of surface engineering technologies for improvement of diecasting tools quality

Terek Pal 21 September 2016 (has links)
<p>Proučavane su koroziona postojanost i tendencija lepljenja različitih<br />materijala u kontaktu sa tečnom Al&ndash;Si&ndash;Cu legurom. Ispitivanjem su<br />obuhvaćeni čelik za rad na toplo, plazma nitrirani čelik i dupleks<br />slojevi sa CrN, TiAlN, TiAlSiN i CrAlN prevlakama, različitog nivoa<br />površinske hrapavosti. Za ispitivanja pomenutih fenomena<br />primenjena je metoda izvlačenja, koja je unapređena kako bi se povećale<br />njena tačnost i verodostojnost simulacije procesa livenja. Korozioni<br />efekti su pojačani tako što su uzorci osim kratkog kontakta sa odlivkom<br />zadržavani i u dužim periodima u kontaktu sa tečnom legurom (5 i 20<br />min). Uprkos opštim stavovima, za ispitivane materijale je<br />ustanovljeno da su sile izvlačenja uzoraka iz Al&ndash;Si&ndash;Cu odlivaka<br />nezavisne od njihovog hemijskog sastava. Uticaj hrapavosti je izražen<br />kod uzoraka sa prevlakama kod kojih pri smanjenju hrapavosti dolazi do<br />povećanja sile izvlačenja. Sve ispitane prevlake su sklone mehaničkom<br />lepljenju Al&ndash;Si&ndash;Cu legure za svoje površine, ali sa aspekta korozije u<br />tečnom metalu značajno prevazilaze performanse čelika i plazma<br />nitriranog sloja. Duži kontakt livene legure sa površinama prevlaka<br />uzrokovao je niže vrednosti sila izvlačenja, što je posledica<br />oksidacije površina prevlaka. Ustanovljeno je da su ispitivane<br />prevlake inertne ka tečnoj leguri aluminijuma. Međutim, dolazi do<br />oksidacije i korozije materijala podloge kroz greške rasta koje su<br />prisutne u prevlakama. Stečena znanja o identifikovanim<br />mehanizmima habanja i propadanja zaštitnih slojeva prevlaka<br />poslužiće daljem razvoju dupleks slojeva namenjenih za zaštitu alata<br />za livenje pod pritiskom.</p> / <p>Corrosion resistance and soldering tendency of different materials in molten<br />Al&ndash;Si&ndash;Cu alloy were studied. Hot-working tool steel, plasma nitrided steel and<br />duplex layers with CrN, TiAlN, TiAlSiN and CrAlN top coatings, which were<br />produced to various degree of surface roughness, were covered by the study.<br />An ejection test was employed for investigation of the concerned phenomena.<br />The ejection test was improved in order to increase its accuracy and the<br />reliability of process simulation. Samples were examined in both short and<br />extended periods of contact (5 and 20 min) with liquid casting. Casting<br />solidification was extended in order to intensify the corrosion effects. Contrary<br />to common findings, it was found that the ejection force of the investigated<br />materials does not depend on their chemical composition. For the coated<br />samples, a pronounced dependence of the ejection force on the surface<br />roughness was found. The ejection force increases with decrease in surface<br />roughness. All investigated coatings are prone to mechanical soldering by Al&ndash;<br />Si&ndash;Cu alloy. Still, their corrosion resistance substantially exceeds the corrosion<br />resistance of steel and plasma nitrided layer. Longer exposure of coated<br />samples to cast alloy induced lower ejection forces, which is a consequence<br />of coatings oxidation. It was found that the investigated coatings are inert to<br />liquid aluminium. However, the underlying material undergoes oxidation and<br />corrosion through coating growth defects. The findings concerning the wear<br />mechanisms of protective layers support further development of duplex layers<br />intended for die casting tools protection.</p>

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