Now showing 1 - 10 of 283
  • Publication
    Precision Glass Molding of Fused Silica Optics
    ( 2024-05-28)
    Karimova, Albina
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    Fused silica glass products have exceptional properties that make them ideal for optical components in cutting-edge technologies. The traditional manufacturing process has limitations in scalability and cost. Glass molding offers a sustainable solution for series production of optical components. However, the transferability of glass molding to mass production is challenging due to high forming temperatures. This research focuses on enabling a high temperature molding process for fused silica optics through material screening, numerical simulation, and real experiments. The findings contribute to the development of a high temperature molding process for mass production.
  • Publication
    Assessing the Environmental and Economic Impact of Wire Arc Additive Manufacturing
    Additive Manufacturing (AM) has continuously been integrated in the modern production landscape and complements traditional manufacturing processes by allowing the creation of complex three-dimensional objects through layer-by-layer material deposition. Especially with new design opportunities and short lead times it has significant impact on different industrial sectors such as healthcare, automotive and aerospace. Compared to other AM technologies, Wire Arc Additive Manufacturing (WAAM) has a particularly high material deposition rate and a high degree of flexibility when building large components. Therefore, WAAM has great potential for efficient and resilient production. To quantify this potential the environmental and economic impact must be assessed. The presented study focuses Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) and presents a general methodology for impact analysis as well as a transfer to WAAM. The methodology consists of four steps in accordance with ISO 14044:2006: goal and scope definition, inventory analysis (environmental/economic), environmental impact assessment/cost aggregation, interpretation. For the transfer to WAAM a cradle-to-gate analysis is conducted. The relevant process chain leads from alloy production to the WAAM product manufacturing. The methodology generates relative data, so the final assessment of WAAM must be set into context with alternative processes.
  • Publication
    Surrogate modeling for multi-objective optimization in the high-precision production of LiDAR glass optics
    ( 2024-04-24) ;
    Paria, Hamidreza
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    This study addresses the ever-increasing demands on glass optics for LiDAR systems in autonomous vehicles, highlighting the pivotal role of the recently developed Nonisothermal Glass Molding (NGM) in enabling the mass production of complex and precise glass optics. While NGM promises a significant advancement in cost- and energy-efficient solutions, achieving the requisite shape and form accuracy for high-precision optics remains a persistent challenge. The research focuses on expediting the development phase, presenting a methodology that strategically utilizes a sparse dataset for determining optimized molding parameters with a minimized number of experimental trials. Importantly, our method highlights the exceptional ability of a robust surrogate model to precisely predict the accuracy outputs of glass optics, strongly influenced by numerous input molding parameters of the NGM process. This significance emphasizes the surrogate model, which emerges as a promising alternative to inefficient traditional methods, such as time-consuming experiments or computation-intensive simulations, particularly in the realm of high-precision production for LiDAR glass optics. In contributing to optics manufacturing advancements, this study also aligns with contemporary trends in digitalization and Industry 4.0 within modern optics production, thereby fostering innovation in the automotive industry.
  • Publication
    Life cycle analysis results for engine blisk LCA
    Purpose - The aviation industry has seen consistent growth over the past few decades. To maintain its sustainability and competitiveness, it is important to have a comprehensive understanding of the environmental impacts across the entire life cycle of the industry, including materials, processes and resources; manufacturing and production; lifetime services; reuse; end-of-life; and recycling. One important component of aircraft engines, integral rotors known as Blisks, are made of high-value metallic alloys that require complex and resource-intensive manufacturing processes. The purpose of this paper is to assess the ecological and economical impacts generated through Blisk production and thereby identify significant ‘hot-spots’. Design/methodology/approach - This paper focuses on the methodology and approach for conducting a full-scale Blisk life cycle assessment (LCA) based on ISO 14040/44. Unlike previous papers in the European Aerospace Science Network series, which focused on the first two stages of LCA, this publication delves into the "life cycle impact assessment" and "interpretation" stages, providing an overview of the life cycle inventory modeling, impact category selection and presenting preliminary LCA results for the Blisk manufacturing process chain. Findings - The result shows that the milled titanium Blisk has a lower CO2 footprint than the milled nickel Blisk, which is less than half of the global warming potential (GWP) of the milled nickel Blisk. A main contributor to GWP arises from raw material production. However, no recycling scenarios were included in the analysis, which will be the topic of further investigations. Originality/value - The originality of this work lies in the detailed ecological assessment of the manufacturing for complex engine components and the derivation of hot spots as well as potential improvements in terms of eco-footprint reduction throughout the products cradle-to-gate cycle. The LCA results serve as a basis for future approaches of process chain optimisation, use of "greener" materials and individual process improvements.
  • Publication
    An optimization approach for a milling dynamics simulation based on Quantum Computing
    ( 2024-02-01) ;
    Danz, Sven
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    Kienast, Pascal
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    König, Valentina
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    Since the machining of complex aerospace components, like integral compressor-rotors (blade integrated disks), is very cost-intensive, optimizing the process by means of process simulations is an active field of research. With the rise of Quantum Computing, a new instrument with high optimization potential is moving into focus. In this paper, a possible application of Quantum Computing for the machining simulation of multi-axis milling of thin-walled aerospace components is discussed. For this reason, a simulation framework used for the milling simulation is analyzed and each component is evaluated separately in relation to Quantum Computing. Parts of the Harrow, Hassidim, and Lloyd algorithm are proposed to enhance the Finite-Element simulation-based component, like the modal analysis for dynamics simulation. This algorithm can solve linear system problems with exponential speed-up over the classical method. The paper presents a roadmap on how the classical steps of a modal analysis for dynamics simulation could be replaced by quantum algorithms based on quantum phase estimation. The implementation of the first working steps is presented to validate this approach. The linear system problem, arising from the dynamics simulation, is analyzed in detail and a minimal value problem of linear coupled oscillators is derived.
  • Publication
    Machinability study in orthogonal cutting of additively manufactured Inconel 718 with specifically induced porosity
    ( 2024-02-01) ;
    Li, Yupeng
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    Boseila, Jonas
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    Schleifenbaum, Johannes Henrich
    In comparison to conventional manufacturing technologies, additive manufacturing (AM) offers great design freedom, the integration of functions into components, new lightweight design concepts and high material efficiency. In aerospace and turbomachinery, this technology is increasingly coming into focus, especially the laser-based powder bed fusion of metals (PBF-LB/M) process. PBF-LB/M is already used for some aerospace components, which are often exposed to high thermal and mechanical loads. Dependent on the component geometry, support structures are required for AM, which then usually have to be removed by machining. One suitable support structure is the use of material with specifically induced porosity. This ensures good heat dissipation and thus homogeneous component properties, high retention forces and short process times in PBF-LB/M. However, the machinability of porous, additively manufactured material has hardly been researched so far. One preliminary investigation of milling porous, additively manufactured Inconel 718, though, showed significantly poorer machinability of the porous material compared to the dense material. To further examine this phenomenon, this paper presents the results of fundamental machinability studies with porous, additively manufactured Inconel 718 in orthogonal cutting. The investigations with tungsten carbide cutting tools on a special fundamental test rig include the analysis of the cutting force, the chip geometry, the chip temperature and the surface quality. The research results provide explanations for the poorer machinability of the porous material and derived approaches for improving the machinability in future studies.
  • Publication
    Initial experiments to regenerate the surface of plasma-facing components by wire-based laser metal deposition
    ( 2024)
    Tweer, Jannik
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    Dorow-Gerspach, Daniel
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    Loewenhoff, Thorsten
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    Wirtz, Marius
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    Linsmeier, Christian
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    Natour, Ghaleb
    Plasma-facing components (PFC) in nuclear fusion reactors are exposed to demanding conditions during operation. The combination of thermal loads, plasma exposure as well as neutron induced damage and activation limits the number of materials suitable for this application. Due to its properties, tungsten (W) is foreseen as plasma-facing material (PFM) for the future DEMOnstration power plant. It is considered suitable due to its exceptionally high melting point, excellent thermal conductivity, low tritium retention and low erosion resistance during plasma exposure. But even tungsten armored PFCs have a limited lifetime due to, among other factors, surface erosion and the resulting thickness reduction of the armor material. In-situ local deposition of tungsten by means of additive manufacturing (AM) could counteract surface erosion and thus increase the service life span of PFCs. After evaluation of the potential AM processes qualified for this task, the wire-based laser metal deposition (LMD-w) process was selected as the most suitable process. First trials were conducted to examine if it is possible to reliably deposit tungsten onto tungsten substrate using the LMD-w process. In these first studies, single welding beads were generated, and in later experiments, entire layers were created from several welding beads which are arranged next to each other. To ensure reproducibility of the results, the substrate temperature was kept constant. Further experiments aimed at the elimination or minimization of problems such as oxidation, occurrence of balling defects, porosity, cracking, surface waviness and insufficient connection to the substrate. To increase the welding bead quality, the input parameters like laser power, deposition velocity, wire feed rate, inert gas flow, as well as the wire position were optimized. Furthermore, stacking of several layers, as well as the remelting of an already created layer, were carried out and investigated. This study represents the first steps in testing the feasibility of an in-situ surface regeneration concept for PFCs.
  • Publication
    Numerical Modeling of the Redistribution of Residual Stresses in Deep Rolled Cross Bores in Shafts from GJS700-2
    ( 2024)
    Uhlmann, Lars
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    Reissner, Felix-Christian
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    Rathnakar, Shashaank Nambla
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    Herrig, Tim
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    Lightweight design efforts are generally limited by highly stressed areas. In the case of shafts with cross bore the cross bore forms a notch. Due to geometry and position, those notches lead under cyclic torsional loading to stress peaks in the component, which appear as highly stressed areas. In order to counteract tensile stress peaks, compressive residual stresses may be induced into the surface layer by means of surface treatments such as deep rolling. The induction of compressive residual stresses may delay crack initiation and growth. When deep rolled components are subsequently subjected to cyclic loading, the induced residual stresses are redistributed until a stable residual stress state is established, which is decisive in the assessment of the fatigue strength. The influence of deep rolling on the surface properties of cross bores in shafts made of GJS700 and the redistribution behavior of the induced residual stresses under subsequent cyclic torsional loading is mostly unknown. The objective of this work was therefore to identify the cause-effect relationships between the deep rolling parameters (pressure, overlap) as well as the cyclic loading and the resulting surface properties. Therefore, experimental investigations of deep rolling and of the subsequent cyclic torsional loading were carried out. Subsequently, the process sequence was modeled numerically consisting of a deep rolling and a torsion model. The experimental tests were used to validate the models. Finally, the cause-effect relationships between the deep rolling parameters on the residual stresses and the redistribution due to cyclic torsional loading were investigated.
  • Publication
    Data-driven indirect punch wear monitoring in sheet-metal stamping processes
    ( 2024)
    Unterberg, Martin
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    Becker, Marco
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    Niemietz, Philipp
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    The wear state of the punch in sheet-metal stamping processes cannot be directly observed, necessitating the use of indirect methods to infer its condition. Past research approaches utilized a plethora of machine learning models to infer the punch wear state from suitable process signals, but have been limited by the lack of industrial-grade process setups and sample sizes as well as their insufficient interpretability. This work seeks to address these limitations by proposing the sheared surface of the scrap web as a proxy for the punch wear and modeling its quality from acoustic emission signals. The experimental work was carried out in an industrial-grade fine blanking process setting. Evaluation of the model performances suggests that the utilized regression models are capable of modeling the relationship between acoustic emission signal features and sheared surface quality of the scrap webs. Subsequent model inference suggests adhesive wear on the punch as a root cause for the sheared surface impairment of the scrap webs. This work represents the most extensive modeling effort on indirect punch wear monitoring in sheet-metal stamping both from a model prediction and model inference perspective known to the authors.
  • Publication
    Influence on the Bead Geometry in Laser Metal Deposition with Wire
    ( 2023-09-28)
    Weidemann, Tizia
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    Abuabiah, Mohammad
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    Shaqour, Bahaa
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    Plapper, Peter
    Laser metal deposition with wire (LMD-w) is a promising additive manufacturing technology, which attracts interest due to the low waste of material, the flexible application possibilities along the production chain and the improved metallurgical properties compared to powder-based processes. However, the complex handling of the technology and the resulting low process stability inhibit the broad industrial application. In particular, the varying bead geometry prevents automation and series production. To improve the geometric accuracy, it is necessary to understand influencing parameters. For this purpose, a parameter study is carried out in the present work. Different combinations of laser power, wire feed rate, traverse speed and welding angle are set, and the deposited beads are evaluated in terms of height and width. A factorial design experiment with the Box-Behnken was used to analyse and understand the interaction of these parameters on the deposited beads.