Friction stir welded AISI 304 metal sheets for application in food implants. - In: THERMEC 2021, (2021), S. 63-68
Stainless steels are indispensable materials in many industrial fields. They can be easily shaped and joined by traditional welding methods. Some problematics such as possible decrease in corrosion resistance at the welding bead and in the heat-effected zone, residual stress, crack formation and distortions may take place after welding. Friction Stir Welding (FSW) may be used for joining stainless steels in a single pass and for optimising microstructure and mechanical properties of the processed region. The application of FSW to the widely used AISI304 stainless steel is investigated in food implants. The mechanical properties together with corrosion resistance and surface finishing are characterized. A high energy input is chosen for the welding (2000 rpm tool rotational speed and 50 mm/min advancing speed). The stirred zone (SZ) is characterized by optical microscopy. Vickers microhardness in the SZ results 37% higher than in the base material. Tensile tests highlight elongations up to 40% keeping maximum stress values at 600 MPa. All samples pass accelerated corrosion tests that simulate 20 years of cleaning cycles in a typical food implant.
Influence of tool geometry and process parameters on the properties of friction stir spot welded multiple (AA 5754 H111) aluminium sheets. - In: Materials, ISSN 1996-1944, Bd. 14 (2021), 5, 1157, insges. 23 S.
https://doi.org/10.3390/ma14051157
Numerical modeling of an inductively coupled plasma torch using OpenFOAM. - In: Computers & fluids, Bd. 216 (2021), 104807
A customized code using the free and fully open-source CFD software package OpenFOAM was developed to simulate a two-dimensional axisymmetric model of an inductively coupled plasma torch. To efficiently calculate the high-frequency magnetic fields generated by the inductive coil, a technique based on the vector potential formulation of Maxwell's equations was implemented using the block coupled matrix solver provided by the foam-extend toolbox. While the fluid equations for the inner torch region are solved under the assumption of a laminar flowing argon plasma under atmospheric pressure and local thermodynamic equilibrium conditions, the electromagnetic equations are solved on an overlapping mesh extended far outside the torch. Moreover, a novel technique for initializing the plasma solver by separately precomputing the velocity and temperature fields is presented. Using this approach our plasma solver can run in both steady-state and transient modes. The implementation has been validated by means of analytical methods, and the simulation results of the Tekna-PL50 plasma torch have been compared against literature data. The results obtained using the OpenFOAM code are in good agreement with those of the commercial CFD codes.
https://doi.org/10.1016/j.compfluid.2020.104807
Effect of thermoplastic morphology on mechanical properties in laser-assisted joining of polyamide 6 with aluminum. - In: Welding in the world, ISSN 1878-6669, Bd. 65 (2021), 4, S. 699-711
This paper examined the joining zone between semi-crystalline polyamide 6 and aluminum EN AW 6082 in laser-based joining and evaluated the mechanical properties of the joint. The joint tests were carried out in overlap configuration and a characterized in terms of energy per unit length. The mechanical properties were examined to the point of cohesive failure. An increasing energy per unit length resulted in a reduced crosshead displacement in short-term testing and a decreased fatigue strength. Further material testing was carried out locally at various positions within the joining zone. The mechanical properties were correlated with results of a hardness test, thermoplastic morphology, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). By combining the findings with heat-treated samples at elevated temperatures, secondary crystallization was identified and evidenced as a primary effect among the changes in mechanical properties due to the heat treatment of the thermoplastic material.
https://doi.org/10.1007/s40194-020-01048-1
Influence of different Ni coatings on the long-term behavior of ultrasonic welded EN AW 1370 cable/EN CW 004A arrestor dissimilar joints. - In: Welding in the world, ISSN 1878-6669, Bd. 65 (2021), 3, S. 429-440
The increasing demand for energy-efficient vehicles requires suitable methods for cost and weight reduction. This can be achieved by the replacement of copper by aluminum, in particular for the on-board power systems. However, the complete substitution is restricted by the mechanical and physical material properties of aluminum as well as challenges in the aluminum copper interface. The challenges concern the corrosion vulnerability and the occurrence of brittle intermetallic compounds (IMC) which can negatively influence the mechanical properties and the electrical conductivity. Therefore, current investigations focus on the one hand on the realization of dissimilar aluminum copper joints by suitable joining technologies, like ultrasonic welding, and on the other hand on the assurance of a sufficient prevention against harmful corrosion effects. In cases where the joint cannot be protected against corrosion by sealing, nickel coatings can be used to protect the joint. In the present study, the influence of electroless, electroplated, and sulfamate nickel coatings was investigated regarding the long-term stability. The joints were performed as industry-related arrester connections, consisting of EN AW 1370 cables and EN CW 004A terminals. The samples were exposed to corrosive as well as electrical, thermal, and mechanical stress tests according to current standards and regulations.
https://doi.org/10.1007/s40194-020-01030-x
Adapted Process Model for Manufacturing Within Production Networks. - In: Production at the leading edge of technology, (2021), S. 611-620
The paper concentrates on the external elimination of bottlenecks by using congruent shared capacities within a non-hierarchical organized network. The study assumes that the capacity of assembly can be adapted by increasing the resources of the company. Conversely, the capacity of production is restricted by technological requirements and regulated by machine resources.To relieve capacity by external measures within a non-hierarchical organized network, an adapted process model is required. For this purpose, critical issues for the process flow within a network are identified and necessary regulations suggested.The paper presents the possibility of integrating the adapted approach into the operations management process as well as into systems of production planning and control and deduces the necessary information that is required to ensure the economic viability of bottleneck removal.
Application of a mobile measuring device for the planar evaluation of the current in-situ stress condition in glass. - Delft : TU Delft Open. - 1 Online-Ressource (11 Seiten)Online-Ausgabe: Challenging Glass 7 : Conference on Architectural and Structural Applications of Glass, Ghent University, September 2020 / editors Jan Belis (Ghent University, Ghent, Belgium), Freek Bos (Eindhoven University of Technology, Eindhoven, the Netherlands), Christian Louter (Technische Universität Dresden, Dresden, Germany). - Delft : TU Delft Open, 2020. - ISBN 978-94-6366-296-3
The load-bearing capacity of glass as a structural material as well as sustainability and resistance of a built-in glass against appearing loads and forces is assuming an ever-greater importance. Next to analytical and numerical calculations of maximum load-bearing capacity and the ultimate limit state, there is no generally accepted standardized non-destructive inspection method available, with which it is possible to estimate the prevalent load situation and predominant stress conditions, particularly in relation to mechanical or adhered connections. Within the research project “BiGla”, a measuring instrument based on photoelasticity was developed, which enables to measure and monitor occurring load states during the installation process, as well as the utilization of glass components subjected to significant load changes during their life cycle. Based on the combined examination of photoelasticity and its synergism with the finite element analysis it becomes possible to transfer qualitative measurement results into quantitative evaluations of predominant stress conditions. Achieved results, gained during experimental investigations under laboratory conditions, as well as during extensive field tests, are presented in this publication.
https://doi.org/10.7480/cgc.7.4487
Formabtrag an mineralischen Gläsern mit ultrakurz gepulster Laserstrahlung. - Ilmenau : Universitätsverlag Ilmenau, 2020. - 1 Online-Ressource (175 Seiten). - (Fertigungstechnik - aus den Grundlagen für die Anwendung ; Band 9)
Technische Universität Ilmenau, Dissertation 2020
In: Ilmenau : Universitätsverlag Ilmenau
Im Rahmen der vorliegenden Arbeit wurden Abtragsverfahren zur Formgebung optischer Komponenten aus mineralischem Glas mittels ultrakurz gepulster Laserstrahlung untersucht. Für diese Untersuchungen wurden ein experimenteller ps- und ein fs-Aufbau konzipiert, umgesetzt, optimiert und charakterisiert sowie Analysemethoden zur Probenbewertung entwickelt. Aus den Untersuchungen zu den ausgewählten Gläsern ergibt sich, dass mit Verwendung ultrakurzer Laserpulse prinzipiell das gesamte Materialspektrum bearbeitbar ist, wenngleich sich die Bearbeitungsergebnisse unterscheiden. Für einen schichtweisen Abtrag wurden plausible Parameterräume definiert, in denen der Ablationsprozess stabil in Bezug auf ausgewählte Zielgrößen beschrieben werden kann. Experimentell zeigten sich der glasspezifischen Bandlücke sowie der applizierten Wellenlänge nach steigende Grenzwerte für die zur Ablation notwendigen Fluenz. Beim Vergleich der Pulsdauerregime zeigte sich, dass für einen einsetzenden ps-Abtrag höhere Fluenzwerte als für einen fs-Abtrag appliziert werden müssen. Die Untersuchungen haben veranschaulicht, dass sich, in Relation zu einem spezifischen Vorbearbeitungszustand von Quarzglas, mit zunehmendem Abtrag, also mehreren Überfahrten, und unter Zuhilfenahme einer gezielten Partikelabfuhr ein Gleichgewicht der Rauheit auf der Oberfläche einstellte und man von einer Sättigungsrauheit sprechen kann. Für dieses Abtragsverhalten an Glas wurde ein Modell für den 2,5D-Formabtrag mit ausgewählten Parametern aufgestellt und Aussagen zum notwendigen Konditionierabtrag getroffen. Gleichzeitig ergab sich nach Erreichen des Sättigungswertes ein konstantes Ablationsregime, welches einen linearen Abtrag pro Überfahrt ermöglichte. Für eine an den Zielgrößen (Rauheit, induzierte optische Gangunterschiede, Abtragstiefe sowie Abtragsraten) ausgerichtete Auswahl von Bearbeitungsparametern sind Schädigungstiefen bestimmt worden. Es zeigte sich, dass die ermittelten Werte z. T. geringer sind als typische Schädigungen durch das Fein- und Feinstschleifen (< 15 [my]m) und somit dazu beitragen den folgenden Polierprozess zu verkürzen. Ein schichtweiser Abtrag mit ultrakurzen Pulsen kann als Substitutionstechnologie für den formgebenden Schleifprozess angesehen werden. Die ermittelten Zeitspanvolumina lagen im applizierten Laserparameterfeld mit < 14 mm^3/min deutlich über den Werten des Fein- und Feinstschleifens mit ≈ 2 mm^3/min. In weiteren Untersuchungen zum Laserabtrag mit Scanprofilen konnten funktionelle Zusammenhänge beschrieben und nachgewiesen werden, die einen ortsvariablen Glasabtrag ermöglichen.
https://nbn-resolving.org/urn:nbn:de:gbv:ilm1-2020000104
Predicting the quality of high-power connector joints with different machine learning methods. - In: 2020 10th International Online Conference Electric Drives Production Conference (EDPC), (2020), insges. 9 S.
State-of-the-art manufacturing processes used in the electric drive production show a high degree of automation and provide a large amount of process data. Often these data remain unused even though they contain potentially valuable process information. The efficient processing and evaluation of these data bears enormous potential for improving the electric drives production, for example with regard to contacting processes. Innovative machine learning (ML) methods already proved to be a powerful tool for big data set evaluation and continuously enter the manufacturing domain. However, the comprehensive and feasible ML application in manufacturing is hindered by the large effort necessary for adequate data preparation. This work lays the foundation for ML application in ultrasonic metal welding and related contacting techniques, which play an important role in the electric drives production. Therefore, on the one hand side, a data pipeline is developed which covers necessary steps of data preparation. On the other hand side, two data sets generated with a validated US metal welding process model are processed with the data pipeline and quality prediction is performed with three different regression methods, which include classical linear regression as well as advanced ML methods as a neural network. For quality prediction, the mean absolute percentage error reaches values as low as 6.9 %.
https://doi.org/10.1109/EDPC51184.2020.9388211
Einfluss des Verhältnisses aus Drehrichtung und Geschwindigkeit am FSW-Werkzeug auf die Ermüdungsfestigkeit von Aluminiumlegierungen. - In: Schweissen und Schneiden, ISSN 0036-7184, Bd. 72 (2020), 9, S. 558-565