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PublicationFeasibility study of joining of carbon fibre-reinforced polymer composites and aluminium alloys by electron beam welding for use in lightweight construction( 2023-05-12)In recent years, new solutions to reduce the weight of components used in the automotive, railway, and aircraft industries have been researched. Carbon Fibre Composites (CFC) have been used to replace metals in products requiring lightweight construction, such as aircraft or high-performance vehicles due to their exceptional mechanical strength. However, the use of CFCs is limited by the reason of their poor thermal conductivity, particularly on components requiring effective dissipation of power losses. To respond to the requirements, the idea of the material combination of metals and polymer-based composites is proposed. In this study, electron beam welding is used for the joining of aluminium alloys and polymer-based composites. Within the experiments, the relevant process parameters such as beam current, welding speed, and heat input have been optimized to achieve the welding of the aluminium alloys. Then, the joining of aluminium alloys and carbon fibre-reinforced polymer composites has been investigated through the optimized welding process parameters for aluminium alloys. Conclusions are drawn regarding the carbon-fibre reinforced polymer composites (PA6-CF) and aluminium alloys (AlMg3) being joinable through electron beams.
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PublicationPraktische Anwendung der SysML v2 API am Beispiel von MCAD und Simulation( 2023)Modellbasiertes Systems Engineering als transdiziplinärer Ansatz soll Domänen verbinden - dazu wurde schon mehrfach der Ansatz eines integrierten Systemmodells postuliert. Häufig herrscht jedoch eine Vielzahl an Datensilos der unterschiedlichen Domänen vor, die sich über Importe und Exporte sowie proprietäre Tool-Schnittstellen austauschen. Dadurch entstehen teilweise Datenverluste bei der Konvertierung und hohe Kosten für die Konfiguration und Wartung der Schnittstellen. Die SysML v2 eröffnet mit ihrer API die Möglichkeit, bidirektional mit Systemmodellen zu interagieren. Das bedeutet, dass sowohl Informationen aus dem Systemmodell gelesen, als auch in die Modelle geschrieben werden können. Die Veröffentlichung beleuchtet die API an sich sowie die damit verbundenen Möglichkeiten am Beispiel der MCAD-Konstruktion und der Simulation eines Produktes. Grundlage dafür bildet das Beispiel der Entwicklung eines Staubsaugerroboters.
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PublicationA life cycle assessment of joining processes in the automotive industry, illustrated by the example of an EV battery case( 2023)
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PublicationMechanical properties of laser welded joints of wrought and heat-treated PBF-LB/M Inconel 718 parts depending on build direction( 2023)Laser-based Powder Bed Fusion of Metal (PBF-LB/M) is a broadly used metal additive manufacturing (AM) method for fabricating complex metallic parts, whose sizes are however limited by the build envelope of PBF-LB/M machines. Laser welding arises as a valid joining method for effectively integrating these AM parts into larger assemblies. PBF-LB/M components must usually be stress-relieved before they can be separated from the build plate. An additional heat treatment can be beneficial for obtaining homogeneous mechanical properties across the seam or for the formation of desired precipitations in nickel-based-alloys. Therefore, the tensile performance of laser welded hybrid (AM/wrought) and AM-AM tensile samples of Inconel 718 is examined after undergoing three different heat treatments and considering three relevant build directions. It can be shown that the build orientation is an influencing factor on weld properties even after two applied heat treatments.
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PublicationAnalysis and recycling of bronze grinding waste to produce maritime components using directed energy deposition( 2021)Additive manufacturing promises a high potential for the maritime sector. Directed Energy Deposition (DED) in particular offers the opportunity to produce large-volume maritime components like propeller hubs or blades without the need of a costly casting process. The post processing of such components usually generates a large amount of aluminum bronze grinding waste. The aim of the presented project is to develop a sustainable circular AM process chain for maritime components by recycling aluminum bronze grinding waste to be used as raw material to manufacture ship propellers with a laser-powder DED process. In the present paper, grinding waste is investigated using a dynamic image analysis system and compared to commercial DED powder. To be able to compare the material quality and to verify DED process parameters, semi-academic sample geometries are manufactured.
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PublicationInertial Measurement Unit based Human Action Recognition for Soft-Robotic Exoskeleton( 2021)Absence from work caused by overloading the musculoskeletal system lowers the life quality of the worker and gains unnecessary costs for both the employer and the health system. Exoskeletons can present a solution. Typically, such systems struggle with stiffness and discomfort and primarily a lack of battery lifetime. Soft-robotic exoskeletons offer a possibility to overcome these problems by increasing the system flexibility, not limiting the supported DoF and being actuator and joint together. Since soft-robotic exoskeletons can be designed only using power when supporting the wearer, it is possible to increase the battery lifetime by only acting on those actions for which the wearer needs support. Dealing with controls for soft-robotic exoskeleton one major difficulty is to find a compromise between saving energy and supporting the wearer. Having an action-depending control can reduce the supported actions to cover only relevant ones and increase the lifetime of the battery. The system conditions are to detect the user actions in real-time and distinguish between actions which require support and those which do not. We contribute an analysis and modification of human action recognition(HAR) benchmark algorithms from activities of the daily living, transferred them onto industrial use cases containing short and mid-term action and reduce the models to be compatible using embedded computers for real-time recognition on soft exoskeletons. We identified the most common challenges for inertial measurement units based HAR and compare the best-performing algorithms using a newly recorded data set overhead car assembly for industrial relevance. As a benchmark data set we focused on the "Opportunity" data set. By introducing orientation estimation, we were able to increase the F1 scores by up to 0.04. With an overall F1 score without a Null-class of up to 0.883, we were able to lay the foundation to use HAR for action dependent force support.
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PublicationProduction environment of tomorrow (ProMo)( 2021)Small defects in the grain or major damage to a moulded part or tool can bring production to a standstill. SMEs in particular have neither the personnel nor the equipment to repair such damage on their own, so they send it to specialised contractors. The repair process is carried out manually, depending on the accuracy requirements, and is usually completed by a finishing process. This work requires qualified personnel and, at the same time, requires a lot of time in case of larger damages. In this paper we present a way to map the Maintenance, Repair and Operations (MRO) process chain in a partially automated manner. The symbiosis of individual technologies results in a significantly increased efficiency of the MRO process chain, which continues to focus on people and their process knowledge. While Directed Energy Deposition (DED) for the MRO of moulded parts is used widely, usually a high manual effort in measuring the component geometries and teaching of the machine tool paths is necessary. However, there are clear advantages compared to the manufacture of new parts or manual laser welding repair. At the same time, the resource and energy requirements can often be significantly reduced compared to new part production. ProMo focuses on automating the time-consuming machine programming by reducing the number of necessary work steps in CAD/CAM-based program creation. Based on a subsequent robot-guided scan, a digital actual 3D model is generated. Due to intelligent path planning algorithms, no manual programming of the robot is necessary and at the same time it is possible to detect components of different sizes, shapes and covers in this system with a minimum of effort. In addition, the operator passes on elementary information, such as the approach path of the milling head, to the subsequent processes by means of finger gestures and can thus significantly reduce tedious CAM programming steps. Now, the scanned component is transferred to a 3D-CAD model and a target/actual comparison is created for the damaged areas. Those are milled out in a defined manner and then restored using DED.
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PublicationModel-Based Systems Engineering (MBSE) as computer-supported approach for cooperative systems development( 2020)With rising globalization and a trend towards Cyberphysical systems (CPSs) as well as smart products the demand for cross-company and interdisciplinary collaboration increases. To handle the complexity of these systems and products Model-Based Systems Engineering (MBSE), as an enhanced form of Systems Engineering (SE), has emerged in engineering and is adopted by many companies. While this approach tries to cope with the current complexity trends, it does address the collaborative aspect of product creation only in a small scope. This paper shall address the combination of MBSE and collaboration in engineering to form a computer-supported approach for collaborative systems development.
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PublicationAutomated tool-path generation for rapid manufacturing and numerical simulation of additive manufacturing LMD geometries( 2019)In additive manufacturing (AM) Laser Metal Deposition (LMD), parts are built by welding layers of powder feedstock onto a substrate. Applications for steel powders include forging tools and structural components for various industries. For large parts, the choice of tool-paths influences the build-rate, the part performance and the distortions in a highly geometry-dependent manner. With weld-path lengths in the range of hundreds of meters, a reliable, automated tool path generation is essential for the usability of LMD processes. In this contribution, automated tool-path generation approaches are shown and their results are discussed for arbitrary geometries. The investigated path strategies are the classical approaches: ""Zig-zag-"" and ""contour-parallel-strategies"". After generation, the tool-paths are automatically formatted into g-code for experimental build-up and ASCII for a numerical simulation model. Finally, the tool paths are discussed in regards to volume-fill, microstructure and porosity for the experimental samples. This work presents a part of the IGF project 18737N ""Welding distortion simulation"" (FOSTA P1140)
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PublicationA Process Model for Enhancing Digital Assistance in Knowledge-Based Maintenance( 2019)Digital transformation and evolution of integrated computational and visualisation technologies lead to new opportunities for reinforcing knowledge-based maintenance through collection, processing and provision of actionable information and recommendations for maintenance operators. Providing actionable information regarding both corrective and preventive maintenance activities at the right time may lead to reduce human failure and improve overall efficiency within maintenance processes. Selecting appropriate digital assistance systems (DAS), however, highly depends on hardware and IT infrastructure, software and interfaces as well as information provision methods such as visualization. The selection procedures can be challenging due to the wide range of services and products available on the market. In particular, underlying machine learning algorithms deployed by each product could provide certain level of intelligence and ultimately could transform diagnostic maintenance capabilities into predictive and prescriptive maintenance. This paper proposes a process-based model to facilitate the selection of suitable DAS for supporting maintenance operations in manufacturing industries. This solution is employed for a structured requirement elicitation from various application domains and ultimately mapping the requirements to existing digital assistance solutions. Using the proposed approach, a (combination of) digital assistance system is selected and linked to maintenance activities. For this purpose, we gain benefit from an in-house process modeling tool utilized for identifying and relating sequence of maintenance activities. Finally, we collect feedback through employing the selected digital assistance system to improve the quality of recommendations and to identify the strengths and weaknesses of each system in association to practical use-cases from TU Wien Pilot-Factory Industry 4.0.
