Universität Stuttgart

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Publication Type: search.filters.UBSTyp.KonferenzbeitragStart date: 1979

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Now showing 1 - 10 of 1025
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    A fully coupled thermomechanical 3D model for all phases of friction stir welding
    (2016) Hoßfeld, Max
    Although friction stir welding (FSW) has made its way to industrial application particularly in the last years, the FSW process, its influences and their strong interactions among themselves are still not thoroughly understood. The lack of understanding mainly arises from the adverse observability of the actual process with phenomena like material ow and deposition, large material deformations plus their complex thermo-mechanical interactions determining the weld formation and its mechanical properties. A validated numerical process model may be helpful for closing this gap as well as for an isolated assessment of individual influences and phenomena. Hereby such a model will be a valuable assistance for process and especially tool development. In this study a Coupled Eulerian-Lagrangian (CEL) approach with Abaqus V6.14 is used for modeling the whole FSW process within one continuous model. The resolution reached allows not only simulating the joining of two sheets into one and real tooling geometries but also burr and internal void formation. Results for temperature fields, surface and weld formation as well as process forces are shown and validated.
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    Post-processing tools for nonlinear fe analysis of concrete structures
    (1990) Cervenka, Vladimir; Pukl, Radomir; Eligehausen, Rolf
    Finite clement analysis of the cracking process in concrete structures brings new requirements for the post-processing environment. Crack direction and location are important for identification of the failure mode. The problem have been solved in the finite element program SBETA which was developed by the authors for simulation of the failure processes in reinforced concrete structures. The post-processing system creates the graphical images of crack patterns. Graphical sequences for simulation can be generated.
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    Verantwortung für die Technik - ein Institutionenproblem
    (1991) Hubig, Christoph
    Grundsätzlich gilt, daß der moralische Diskurs über die Redeweise von Haftung hinaus auf Institutionen und Organisationen ausgedehnt werden muß. Institutionen oder Organisationen, die die Gesellschaft mit unkalkulierbaren Risiken oder Makrorisiken belasten, indem sie sich z. B. der gesellschaftlichen Kontrolle durch Produktionsverlagerung entziehen, verdienen es, moralisch sanktioniert zu werden mit allen Konsequenzen für ihren gesellschaftlichen und ökonomischen Einfluß. Die gängige Denkweise, daß Politik und Ökonomie einem anderen Kalkül zuzuordnen sei als dem moralischen, muß verabschiedet werden. Darüber hinaus muß aber schrittweise gewährleistet werden, daß die Institutionen wissenschaftlicher und technischer Innovationen, sowohl was Entwicklung als auch Produktion betrifft, in politisch angreifbarer Weise repräsentiert werden.
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    Using PRIMA-DBMS as a testbed for parallel complex-object processing
    (1992) Hübel, Christoph; Mitschang, Bernhard; Gesmann, Michael; Grasnickel, Andreas; Käfer, Wolfgang; Schöning, Harald; Härder, Theo
    The PRIMA-DBMS approach is explained by introducing PRIMA's architecture and query processing framework. The PRIMA-DBMS constitutes a testbed that is flexible enough to support evaluation and validation of quite a variation of different strategies for complex-object processing taking into account different parallelization levels and different hardware environments. Thus, PRIMA marks an important step towards our main research goal concerning measures for efficient complex-object processing: the measures that are in competition with each other are query optimization, query evaluation strategies, and massive storage, that all benefit from parallelism. The programming environment that supports the parallel DBMS processing is introduced with special emphasis on its ability for parametrization and configuration. A case study of the PRIMA testbed illustrates our first investigations and demonstrates a methodology for evaluation and tuning of PRIMA configurations.
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    Usable and fast interactive mental face reconstruction
    (2023) Strohm, Florian; Bâce, Mihai; Bulling, Andreas
    We introduce an end-to-end interactive system for mental face reconstruction - the challenging task of visually reconstructing a face image a person only has in their mind. In contrast to existing methods that suffer from low usability and high mental load, our approach only requires the user to rank images over multiple iterations according to the perceived similarity with their mental image. Based on these rankings, our mental face reconstruction system extracts image features in each iteration, combines them into a joint feature vector, and then uses a generative model to visually reconstruct the mental image. To avoid the need for collecting large amounts of human training data, we further propose a computational user model that can simulate human ranking behaviour using data from an online crowd-sourcing study (N=215). Results from a 12-participant user study show that our method can reconstruct mental images that are visually similar to existing approaches but has significantly higher usability, lower perceived workload, and is faster. In addition, results from a third 22-participant lineup study in which we validated our reconstructions on a face ranking task show a identification rate of , which is in line with prior work. These results represent an important step towards new interactive intelligent systems that can robustly and effortlessly reconstruct a user’s mental image.
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    Influence of protection lips on the frictional torque of rotary shaft seals
    (2024) Olbrich, Christoph; Feldmeth, Simon; Bauer, Frank
    Rotary shaft seals are used to seal rotating machine parts. In most cases one single sealing lip (main lip) contacts the shaft and separates the fluid on one side from the environment on the other side. To prevent the entry of other fluids and or particles, seals with additional protection lips are used (two lips), especially in heavily contaminated environments. When the protection lip contacts the shaft, a vacuum can form between the main lip and the protection lip, leading to increased contact pressure and friction. The increased frictional torque generates more heat and leads to overheating in the contact area between the lip and the shaft. Test runs conducted on a friction torque test bench with various seal configurations confirm that the two lips influence each other. Higher frictional torques and contact temperatures occur, when the volume between the lips isn't vented. This shows the importance of venting.
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    Rasselgeräuschprüfstand zur Untersuchung von Fahrzeuggetrieben
    (2011) Fietkau, Peter; Baumann, Axel; Bertsche, Bernd
    In diesem Aufsatz wird der Klapper- und Rasselgeräuschprüfstand am Institut für Maschinenelemente der Universität Stuttgart vorgestellt. Der Prüfstand wurde speziell entwickelt, um die bei Fahrzeuggetrieben auftretenden Losteilgeräusche (Klapper- und Rasselgeräusche) untersuchen zu können. Neben der Beschreibung des allgemeinen Prüfstandsaufbaus wird genauer auf das Regelungskonzept sowie die verwendete Messtechnik eingegangen. Diese zeichnet sich unter anderem durch eine hochgenaue Erfassung der Drehschwingungen aus. Dadurch ist es möglich, Relativbewegungen im Betrieb von im Eingriff stehenden Zahnrädern hochauflösend aufzuzeichnen. Abschließend werden einige exemplarische Messungen dargestellt.
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    Tidal current turbine wake and park layout in transient environments
    (2014) Arnold, Matthias; Cheng, Po Wen; Daus, Philipp; Biskup, Frank
    Due to orbital velocities of the waves, the characteristics of tidal current turbines change over time. Therefore the induction factor and subsequent the wake is time dependent. Within the present research this time dependency is investigated by using Computational Fluid Dynamics (CFD) with Virtual Free Surface (VFS) and Actuator Disc (ACD) models. Based on this setup several different wave and current scenarios are simulated and analyzed with respect to the transient velocities in the turbine wake. Special respect is taken to the velocity undulations radiated by the changing apparent velocities in the rotor plane. These undulations move with the wake of the tidal current turbines and increase wave loads on 2nd row turbines in a park. This paper presents an efficient method for simulation of wave and park interactions and investigates dynamic turbine wakes under a large variety of parameters. Based on these simulations a suggestion for a tidal park design with respect to a balance of fatigue loads and power output is concluded.
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    Stream finishing of additively manufactured AlSi10Mg PBF-LB parts: influence on surface quality and fatigue behaviour
    (2024) Wexel, Helena; Kramer, Steffen; Schubert, Johannes; Schulze, Volker; Zanger, Frederik