@article{33657, author = {{Mirhosseini, Hossein and Tahmasbi, Hossein and Kuchana, Sai Ram and Ghasemi, Alireza and Kühne, Thomas}}, issn = {{0927-0256}}, journal = {{Computational Materials Science}}, keywords = {{Computational Mathematics, General Physics and Astronomy, Mechanics of Materials, General Materials Science, General Chemistry, General Computer Science}}, publisher = {{Elsevier BV}}, title = {{{An automated approach for developing neural network interatomic potentials with FLAME}}}, doi = {{10.1016/j.commatsci.2021.110567}}, volume = {{197}}, year = {{2021}}, } @inproceedings{33654, author = {{Balos, Vasileios and Elgabarty, Hossam and Wolf, Martin and Kühne, Thomas and Netz, Roland and Bonthuis, Douwe Jan and Kaliannan, Naveen and Loche, Philip and Kampfrath, Tobias and Sajadi, Mohsen}}, booktitle = {{Terahertz Emitters, Receivers, and Applications XII}}, editor = {{Razeghi, Manijeh and Baranov, Alexei N.}}, publisher = {{SPIE}}, title = {{{Ultrafast solvent-to-solvent and solvent-to-solute energy transfer driven by single-cycle THz electric fields}}}, doi = {{10.1117/12.2594143}}, year = {{2021}}, } @article{33656, author = {{Wang, Mengying and Ranjbar, Ahmad and Kühne, Thomas and Belosludov, Rodion V. and Kawazoe, Yoshiyuki and Liang, Yunye}}, issn = {{0008-6223}}, journal = {{Carbon}}, keywords = {{General Chemistry, General Materials Science}}, pages = {{370--378}}, publisher = {{Elsevier BV}}, title = {{{A theoretical investigation of topological phase modulation in carbide MXenes: Role of image potential states}}}, doi = {{10.1016/j.carbon.2021.05.026}}, volume = {{181}}, year = {{2021}}, } @article{33659, abstract = {{Abstract We performed a virtual materials screening to identify promising topological materials for photocatalytic water splitting under visible light irradiation. Topological compounds were screened based on band gap, band edge energy, and thermodynamics stability criteria. In addition, topological types for our final candidates were computed based on electronic structures calculated usingthe hybrid density functional theory including exact Hartree–Fock exchange. Our final list contains materials which have band gaps between 1.0 and 2.7 eV in addition to band edge energies suitable for water oxidation and reduction. However, the topological types of these compounds calculated with the hybrid functional differ from those reported previously. To that end, we discuss the importance of computational methods for the calculation of atomic and electronic structures in materials screening processes.}}, author = {{Ranjbar, Ahmad and Mirhosseini, Hossein and Kühne, Thomas}}, issn = {{2515-7639}}, journal = {{Journal of Physics: Materials}}, keywords = {{Condensed Matter Physics, General Materials Science, Atomic and Molecular Physics, and Optics}}, number = {{1}}, publisher = {{IOP Publishing}}, title = {{{On topological materials as photocatalysts for water splitting by visible light}}}, doi = {{10.1088/2515-7639/ac363d}}, volume = {{5}}, year = {{2021}}, } @article{33668, abstract = {{AbstractVaccinations, lockdowns and testing strategies are three potential elements of an effective anti-coronavirus, and in particular Covid-19, health policy. The following analysis considers - within a simple model - the potentially crucial role of a Corona testing approach in combination with a quarantine approach which is shown herein to be a substitute for broad lockdown measures. The cost of lockdowns/shutdowns are rather high so that – beyond progress in terms of a broad vaccination program – a rational testing strategy should also be carefully considered. Testing has to be organized on the basis of an adequate testing infrastructure which could largely be implemented in firms, schools, universities and public administration settings. As regards the cost of a systematic broad Covid-19 testing strategy, these could come close to 0.5% of national income if there are no vaccinations. The Testing & Quarantine approach suggested here – with tests for symptomatic as well as asymptomatic people - is based on a random sampling and would require rather broad and frequent testing; possibly one test per person every 7–10 days. At the same time, one should consider that the cost of further lockdowns/shutdowns of a duration of 1 month could be very high, such that a standard cost benefit analysis supports the testing approach suggested herein. Also, an optimal policy mix could be designed where both vaccinations and testing play a crucial role. As of late January 2021, no further lockdowns in Germany and other OECD countries would be necessary if a broad testing infrastructure can be established rather quickly. This in turn will reinforce economic optimism and help to jumpstart economic growth in Europe, the US and Asia in a solid way. The basic logic of the testing approach pointed out here for industrialized countries could also be applied in developing countries. The approach presented is complementary to the IMF analysis of Cherif/Hasanov.}}, author = {{Gries, Thomas and Welfens, Paul J. J.}}, issn = {{1612-4804}}, journal = {{International Economics and Economic Policy}}, keywords = {{Economics and Econometrics}}, number = {{1}}, pages = {{1--24}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Testing as an approach to control the Corona epidemic dynamics and avoid lockdowns}}}, doi = {{10.1007/s10368-021-00495-5}}, volume = {{18}}, year = {{2021}}, } @article{33667, abstract = {{AbstractIn light of the COVID-19 pandemic, we scrutinize what has been established in the literature on whether entrepreneurship can cause and resolve extreme events, the immediate and long-run impacts of extreme events on entrepreneurship, and whether extreme events can positively impact (some) entrepreneurship and innovation. Based on this, we utilize a partial equilibrium model to provide several conjectures on the impact of COVID-19 on entrepreneurship, and to derive policy recommendations for recovery. We illustrate that while entrepreneurship recovery will benefit from measures such as direct subsidies for start-ups, firms’ revenue losses, and loan liabilities, it will also benefit from aggregate demand-side support and income redistribution measures, as well as from measures that facilitate the innovation-response to the Keynesian supply-shock caused by the pandemic, such as access to online retail and well-functioning global transportation and logistics.}}, author = {{Gries, Thomas and Naudé, Wim}}, issn = {{2511-1280}}, journal = {{Economics of Disasters and Climate Change}}, keywords = {{General Medicine}}, number = {{3}}, pages = {{329--353}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Extreme Events, Entrepreneurial Start-Ups, and Innovation: Theoretical Conjectures}}}, doi = {{10.1007/s41885-021-00089-0}}, volume = {{5}}, year = {{2021}}, } @article{33681, author = {{da Silva, Marcos A.R. and Silva, Ingrid F. and Xue, Qi and Lo, Benedict T.W. and Tarakina, Nadezda V. and Nunes, Barbara N. and Adler, Peter and Sahoo, Sudhir K. and Bahnemann, Detlef W. and López-Salas, Nieves and Savateev, Aleksandr and Ribeiro, Caue and Kühne, Thomas and Antonietti, Markus and Teixeira, Ivo F.}}, issn = {{0926-3373}}, journal = {{Applied Catalysis B: Environmental}}, keywords = {{Process Chemistry and Technology, General Environmental Science, Catalysis}}, publisher = {{Elsevier BV}}, title = {{{Sustainable oxidation catalysis supported by light: Fe-poly (heptazine imide) as a heterogeneous single-atom photocatalyst}}}, doi = {{10.1016/j.apcatb.2021.120965}}, volume = {{304}}, year = {{2021}}, } @article{33675, abstract = {{The influence of different polymer side chains on the vapor phase infiltration with TMA is investigated and supported by DFT-calculations.}}, author = {{Mai, Lukas and Maniar, Dina and Zysk, Frederik and Schöbel, Judith and Kühne, Thomas and Loos, Katja and Devi, Anjana}}, issn = {{1477-9226}}, journal = {{Dalton Transactions}}, keywords = {{Inorganic Chemistry}}, number = {{4}}, pages = {{1384--1394}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Influence of different ester side groups in polymers on the vapor phase infiltration with trimethyl aluminum}}}, doi = {{10.1039/d1dt03753f}}, volume = {{51}}, year = {{2021}}, } @misc{27058, author = {{Wiecher, Carsten and Fischbach, Jannik and Greenyer, Joel and Vogelsang, Andreas and Wolff, Carsten and Dumitrescu, Roman}}, booktitle = {{arXiv preprint}}, title = {{{Integrated and Iterative Requirements Analysis and Test Specification: A Case Study at Kostal}}}, year = {{2021}}, } @inproceedings{29291, author = {{Zahera, Hamada Mohamed Abdelsamee and Heindorf, Stefan and Ngonga Ngomo, Axel-Cyrille}}, booktitle = {{Proceedings of the 11th on Knowledge Capture Conference}}, publisher = {{ACM}}, title = {{{ASSET: A Semi-supervised Approach for Entity Typing in Knowledge Graphs}}}, doi = {{10.1145/3460210.3493563}}, year = {{2021}}, } @inbook{29292, author = {{Feldhans, Robert and Wilke, Adrian and Heindorf, Stefan and Shaker, Mohammad Hossein and Hammer, Barbara and Ngonga Ngomo, Axel-Cyrille and Hüllermeier, Eyke}}, booktitle = {{Intelligent Data Engineering and Automated Learning – IDEAL 2021}}, isbn = {{9783030916077}}, issn = {{0302-9743}}, publisher = {{Springer International Publishing}}, title = {{{Drift Detection in Text Data with Document Embeddings}}}, doi = {{10.1007/978-3-030-91608-4_11}}, year = {{2021}}, } @inproceedings{29287, abstract = {{Knowledge graph embedding research has mainly focused on the two smallest normed division algebras, $\mathbb{R}$ and $\mathbb{C}$. Recent results suggest that trilinear products of quaternion-valued embeddings can be a more effective means to tackle link prediction. In addition, models based on convolutions on real-valued embeddings often yield state-of-the-art results for link prediction. In this paper, we investigate a composition of convolution operations with hypercomplex multiplications. We propose the four approaches QMult, OMult, ConvQ and ConvO to tackle the link prediction problem. QMult and OMult can be considered as quaternion and octonion extensions of previous state-of-the-art approaches, including DistMult and ComplEx. ConvQ and ConvO build upon QMult and OMult by including convolution operations in a way inspired by the residual learning framework. We evaluated our approaches on seven link prediction datasets including WN18RR, FB15K-237 and YAGO3-10. Experimental results suggest that the benefits of learning hypercomplex-valued vector representations become more apparent as the size and complexity of the knowledge graph grows. ConvO outperforms state-of-the-art approaches on FB15K-237 in MRR, Hit@1 and Hit@3, while QMult, OMult, ConvQ and ConvO outperform state-of-the-approaches on YAGO3-10 in all metrics. Results also suggest that link prediction performances can be further improved via prediction averaging. To foster reproducible research, we provide an open-source implementation of approaches, including training and evaluation scripts as well as pretrained models.}}, author = {{Demir, Caglar and Moussallem, Diego and Heindorf, Stefan and Ngonga Ngomo, Axel-Cyrille}}, booktitle = {{The 13th Asian Conference on Machine Learning, ACML 2021}}, title = {{{Convolutional Hypercomplex Embeddings for Link Prediction}}}, year = {{2021}}, } @inproceedings{29294, author = {{Nickchen, Tobias and Heindorf, Stefan and Engels, Gregor}}, booktitle = {{2021 IEEE Winter Conference on Applications of Computer Vision (WACV)}}, publisher = {{IEEE}}, title = {{{Generating Physically Sound Training Data for Image Recognition of Additively Manufactured Parts}}}, doi = {{10.1109/wacv48630.2021.00204}}, year = {{2021}}, } @misc{33733, author = {{Heindorf, Stefan}}, title = {{{Automatically generating instructions from tutorials for search and user navigation}}}, year = {{2021}}, } @inproceedings{26407, author = {{Piskachev, Goran and Krishnamurthy, Ranjith and Bodden, Eric}}, booktitle = {{2021 IEEE 21st International Working Conference on Source Code Analysis and Manipulation (SCAM)}}, title = {{{SecuCheck: Engineering configurable taint analysis for software developers}}}, year = {{2021}}, } @inproceedings{22463, author = {{Luo, Linghui and Schäf, Martin and Sanchez, Daniel and Bodden, Eric}}, booktitle = {{Proceedings of the 29th ACM Joint Meeting on European Software Engineering Conference and Symposium on the Foundations of Software Engineering}}, title = {{{IDE Support for Cloud-Based Static Analyses}}}, year = {{2021}}, } @inproceedings{33840, author = {{Karakaya, Kadiray and Bodden, Eric}}, booktitle = {{2021 IEEE 21st International Working Conference on Source Code Analysis and Manipulation (SCAM)}}, pages = {{181–186}}, title = {{{SootFX: A Static Code Feature Extraction Tool for Java and Android}}}, year = {{2021}}, } @article{23728, abstract = {{We demonstrate the integration of amorphous tungsten silicide superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides. We show proof-of-principle detection of evanescently coupled photons of 1550 nm wavelength using bidirectional waveguide coupling for two orthogonal polarization directions. We investigate the internal detection efficiency as well as detector absorption using coupling-independent characterization measurements. Furthermore, we describe strategies to improve the yield and efficiency of these devices.}}, author = {{Höpker, Jan Philipp and Verma, Varun B and Protte, Maximilian and Ricken, Raimund and Quiring, Viktor and Eigner, Christof and Ebers, Lena and Hammer, Manfred and Förstner, Jens and Silberhorn, Christine and Mirin, Richard P and Woo Nam, Sae and Bartley, Tim}}, issn = {{2515-7647}}, journal = {{Journal of Physics: Photonics}}, pages = {{034022}}, title = {{{Integrated superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides}}}, doi = {{10.1088/2515-7647/ac105b}}, volume = {{3}}, year = {{2021}}, } @inproceedings{21509, author = {{Müller, Stefanie Jutta Marianne and Kundisch, Dennis}}, location = {{Virtual Conference/Workshop}}, title = {{{Gesellschaftliche Transformationen durch die Steigerung (popmusik)kultureller Teil-habe mittels innovativer Preiskonzepte – ein interdisziplinärer Literaturüberblick}}}, year = {{2021}}, } @article{33895, abstract = {{Heat-assisted forming processes are becoming increasingly important in the manufacturing of sheet metal parts for body-in-white applications. However, the non-isothermal nature of these processes leads to challenges in evaluating the forming limits, since established methods such as Forming Limit Curves (FLCs) only allow the assessment of critical forming strains for steady temperatures. For this reason, a temperature-dependent extension of the well-established GISSMO (Generalized Incremental Stress State Dependent Damage Model) fracture indicator framework is developed by the authors to predict forming failures under non-isothermal conditions. In this paper, a general approach to combine several isothermal FLCs within the temperature-extended GISSMO model into a temperature-dependent forming limit surface is investigated. The general capabilities of the model are tested in a coupled thermo-mechanical FEA using the example of warm forming of an AA5182-O sheet metal cross-die cup. The obtained results are then compared with state of the art of evaluation methods. By taking the strain and temperature path into account, GISSMO predicts greater drawing depths by up to 20% than established methods. In this way the forming and so the lightweight potential of sheet metal parts can by fully exploited. Moreover, the risk and locus of failure can be evaluated directly on the part geometry by a contour plot. An additional advantage of the GISSMO model is the applicability for low triaxialities as well as the possibility to predict the materials behavior beyond necking up to ductile fracture.}}, author = {{Camberg, Alan Adam and Erhart, Tobias and Tröster, Thomas}}, issn = {{1996-1944}}, journal = {{Materials}}, keywords = {{General Materials Science}}, number = {{17}}, publisher = {{MDPI AG}}, title = {{{A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in Heat-Assisted Forming Operations}}}, doi = {{10.3390/ma14175106}}, volume = {{14}}, year = {{2021}}, } @book{33894, editor = {{Famula, Marta and Otto Eke, Norbert}}, publisher = {{Aisthesis}}, title = {{{Ästhetik im Vormärz. Jahrbuch Forum Vormärz Forschung 2020}}}, year = {{2021}}, } @inbook{33905, author = {{Famula, Marta}}, booktitle = {{Literatur und Kultur zwischen West und Ost. Imagination, Kommunikation und Wahrnehmung in regionalen Kulturräumen. Festschrift für Paul Martin Langner zum 65. Geburtstag}}, editor = {{Röskau-Ryde, Isabel and Kubacki, Artur}}, pages = {{125–135}}, publisher = {{Vandenhoeck & Ruprecht unipress}}, title = {{{Die Landstraße jenseits der Bedeutung. Peter Handkes spätes Drama Die Unschuldigen, ich und die Unbekannte am Rand der Landstraße}}}, year = {{2021}}, } @inbook{33904, author = {{Famula, Marta}}, booktitle = {{Ästhetik im Vormärz. Jahrbuch Forum Vormärz Forschung}}, editor = {{Otto Eke, Norbert and Famula, Marta}}, pages = {{95–112}}, publisher = {{Aisthesis}}, title = {{{Von der auf den Kopf gestellten Schönheit oder die Verneinung der Negation im Hässlichen. Zur dialektischen Funktion des Erhabenen und des Hässlichen bei Christian Hermann Weiße}}}, year = {{2021}}, } @article{33902, author = {{Famula, Marta}}, journal = {{Kosmos Dürrenmatt. Eine Annäherung an den Denker, Dichter und Maler. Berner Zeitschrift für Geschichte, H. 3. Sonderdruck Spiezer Tagung, in: Annelise Hüssy, Stefanie Leuenberger (Hgg.)}}, pages = {{45–60}}, title = {{{Vom Entschluss, die Welt zu bestehen. Dürrenmatts Ethik des ‚à la bande‘}}}, year = {{2021}}, } @inbook{33903, author = {{Famula, Marta and Otto Eke, Norbert}}, booktitle = {{Ästhetik im Vormärz. Jahrbuch Forum Vormärz Forschung 2020}}, editor = {{Otto Eke, Norbert and Famula, Marta}}, pages = {{11–15}}, publisher = {{Aisthesis}}, title = {{{Ästhetik im Vormärz – Zur Einführung}}}, year = {{2021}}, } @misc{33939, author = {{Famula, Marta}}, booktitle = {{Jahrbuch für internationale Germanistik, Jahrgang LIII – Heft 1 (2021)}}, pages = {{193–202}}, title = {{{Lukas Bärfuss: Malinois. Erzählungen. Wallstein: Göttingen 2019}}}, year = {{2021}}, } @article{21914, author = {{Meer, Philipp and Hartmann, Johanna and Rumlich, Dominik}}, issn = {{2192-9521}}, journal = {{European Journal of Applied Linguistics}}, number = {{2}}, pages = {{391--416}}, title = {{{Folklinguistic perceptions of Global Englishes among German learners of English}}}, doi = {{10.1515/eujal-2020-0014}}, volume = {{9}}, year = {{2021}}, } @inbook{33906, author = {{Famula, Marta}}, booktitle = {{Wiederholung im Theater. Zur deutschsprachigen Gegenwartsdramatik und ihrer Inszenierung, (= Gesellschaftskritische Literatur – Texte Autoren – Debatten 9)}}, editor = {{Langner, Paul Martin and Majkiewicz, Anna and Mirecka, Agata}}, pages = {{79–91}}, publisher = {{Vandenhoeck & Ruprecht unipress}}, title = {{{Das Unveränderliche und die Wiederholung. Die Rolle der Kontingenz in Max Frischs letztem Drama Triptychon}}}, year = {{2021}}, } @book{33899, editor = {{Famula, Marta and Mirecka, Agata and Langner, Paul Martin}}, publisher = {{Brill | Fink}}, title = {{{Drama zwischen Text und Bühne (Schriftenreihe seit 2021)}}}, year = {{2021}}, } @article{25046, abstract = {{While increasing digitalization enables multiple advantages for a reliable operation of technical systems, a remaining challenge in the context of condition monitoring is seen in suitable consideration of uncertainties affecting the monitored system. Therefore, a suitable prognostic approach to predict the remaining useful lifetime of complex technical systems is required. To handle different kinds of uncertainties, a novel Multi-Model-Particle Filtering-based prognostic approach is developed and evaluated by the use case of rubber-metal-elements. These elements are maintained preventively due to the strong influence of uncertainties on their behavior. In this paper, two measurement quantities are compared concerning their ability to establish a prediction of the remaining useful lifetime of the monitored elements and the influence of present uncertainties. Based on three performance indices, the results are evaluated. A comparison with predictions of a classical Particle Filter underlines the superiority of the developed Multi-Model-Particle Filter. Finally, the value of the developed method for enabling condition monitoring of technical systems related to uncertainties is given exemplary by a comparison between the preventive and the predictive maintenance strategy for the use case.}}, author = {{Bender, Amelie}}, issn = {{2075-1702}}, journal = {{Machines}}, keywords = {{prognostics, RUL predictions, particle filter, uncertainty consideration, Multi-Model-Particle Filter, model-based approach, rubber-metal-elements, predictive maintenance}}, number = {{10}}, title = {{{A Multi-Model-Particle Filtering-Based Prognostic Approach to Consider Uncertainties in RUL Predictions}}}, doi = {{10.3390/machines9100210}}, volume = {{9}}, year = {{2021}}, } @article{30698, author = {{Gröger, B. and Köhler, D. and Vorderbrüggen, J. and Troschitz, J. and Kupfer, R. and Meschut, G. and Gude, M.}}, journal = {{Production Engineering}}, title = {{{Computed tomography investigation of the material structure in clinch joints in aluminium fibre-reinforced thermoplastic sheets}}}, doi = {{10.1007/s11740-021-01091-x}}, year = {{2021}}, } @article{30699, author = {{Weiß, D. and Schramm, B. and Kullmer, G.}}, journal = {{Production Engineering}}, title = {{{Holistic investigation chain for the experimental determination of fracture mechanical material parameters with special specimens}}}, doi = {{10.1007/s11740-021-01096-6}}, year = {{2021}}, } @article{30696, author = {{Zirngibl, C. and Schleich, B. and Wartzack, S.}}, journal = {{Proceedings of the Design Society}}, pages = {{521}}, title = {{{Approach for the automated and data-based design of mechanical joints}}}, doi = {{10.1017/pds.2021.52}}, volume = {{1}}, year = {{2021}}, } @article{30700, author = {{Zirngibl, C. and Dworschak, F. and Schleich, B. and Wartzack, S.}}, journal = {{Production Engineering}}, title = {{{Application of reinforcement learning for the optimization of clinch joint characteristics}}}, doi = {{10.1007/s11740-021-01098-4}}, year = {{2021}}, } @article{30701, author = {{Römisch, D. and Popp, J. and Drummer, D. and Merklein, M.}}, journal = {{Production Engineering}}, title = {{{Joining of CFRT-steel hybrid parts via hole-forming and subsequent pin caulking}}}, doi = {{10.1007/s11740-021-01093-9}}, year = {{2021}}, } @article{30697, author = {{Lafarge, R. and Wolf, A. and Guilleaume, C. and Brosius, A.}}, journal = {{Minerals, Metals and Materials Series}}, pages = {{1461}}, title = {{{A New Non-destructive Testing Method Applied to Clinching}}}, doi = {{10.1007/978-3-030-75381-8_121}}, year = {{2021}}, } @article{30684, abstract = {{Due to stricter emission targets in the mobility sector and the resulting trend towards lightweight construction in order to reduce weight and consequently emissions, multi-material systems that allow a material to be placed in the right quantity and in the right place are becoming increasingly important. One major challenge that is holding back the rapid and widespread use of multi-material systems is the lack of adequate joining processes that are suitable for joining dissimilar materials. Joining processes without auxiliary elements have the advantage of a reduced assembly effort and no additional added weight. Conventional joining processes without auxiliary elements, such as welding, clinching, or the use of adhesives, reach their limits due to different mechanical properties and chemical incompatibilities. A process with potential in the field of joining dissimilar materials is joining without an auxiliary element using pin structures. However, current pin manufacturing processes are mostly time-consuming or can only be integrated barely into existing industrial manufacturing processes due to their specific properties. For this reason, the present work investigates the production of single- and multi-pin structures from high-strength dual-phase steel HCT590X + Z (DP600, t0 = 1.5 mm) by cold extrusion directly out of the sheet metal. These structures are subsequently joined with an aluminium sheet (EN AW-6014-T4, t0 = 1.5 mm) by direct pin pressing. For a quantitative evaluation of the joint quality, tensile shear tests are carried out and the influence of different pin heights, pin number, and pin arrangements, as well as different joining strategies on the joint strength is experimentally evaluated. It is proven that a single pin structure with a diameter of 1.5 mm and an average height of 1.86 mm achieves a maximum tensile shear force of 1025 N. The results reveal that the formation of a form-fit during direct pin pressing is essential for the joint strength. By increasing the number of pins, a linear increase in force could be demonstrated, which is independent of the arrangement of the pin structures.}}, author = {{Römisch, D. and Kraus, M. and Merklein, M.}}, journal = {{Journal of Manufacturing and Materials Processing}}, pages = {{25}}, title = {{{Experimental study on joining by forming of hct590x + z and en-aw 6014 sheets using cold extruded pin structures}}}, doi = {{10.3390/jmmp5010025}}, volume = {{5}}, year = {{2021}}, } @article{30682, abstract = {{Lightweight constructions become more and more important, especially in the mobility sector. In this industry, the increasingly strict regulations regarding the emissions of carbon dioxide can be achieved to a certain extent by reducing the vehicle weight. Thus, multi-material systems are used. Conventional joining techniques reach their limits when joining different materials due to different thermal expansion, unequal stiffness or chemical incompatibilities. This is why additional joining elements or adhesives are used. These must be viewed critically regarding a lightweight and resource-efficient production, since they add weight or complicate the recycling process of these components. Consequently, there is a great and growing need for new versatile joining technologies in order to overcome these challenges and to be able to react to changing process parameters and boundary conditions. Joining without an auxiliary element using pin structures formed directly from the sheet metal plane is one approach to meet these challenges. These pin structures are then joined by direct pressing into the joining partner. This is possible with a variety of material combinations, but is advantageous with regard to continuous fibre-reinforced thermoplastic composites (CFRTP), as the fibres do not have to be cut when joining CFRTP using pin structures. In this paper, the formability of pin structures made of a dual-phase steel DP600 (HCT590X + Z) is investigated. The extruded pin structures are joined by direct pin pressing with an EN AW-6014 to form tensile shear specimens. Different joining strategies are investigated to compare their influence on the joint strength. The results have shown that it is feasible to form suitable pins from a DP600 dual-phase steel to produce reliable connections with an aluminium sheet joined by direct pin pressing. }}, author = {{Römisch, D. and Kraus, M. and Merklein, M.}}, journal = {{Key Engineering Materials}}, pages = {{19--26}}, title = {{{Investigation of Different Joining by Forming Strategies when Connecting Different Metals without Auxiliary Elements}}}, doi = {{10.4028/www.scientific.net/kem.883.19}}, volume = {{883}}, year = {{2021}}, } @article{30718, abstract = {{The growing demands of resource-saving processes and products are leading to increasing importance of lightweight construction for the automotive industry. One approach is multi-material design, which uses high-strength steels and aluminium alloys in the production of vehicle bodies. Therefore, reliable processes for joining components with different mechanical properties and geometries are necessary. As conventional joining processes reach their limits, new versatile processes and methods are required which can adapt to different process conditions and disturbance variables. A widely used joining process to join different materials is self-piercing riveting as a joining by forming method, however it is characterised as inflexible to changing process conditions due to a linear process kinematic and rigid dies. An approach to extend the process limits is the application of a tumbling kinematic for the punch. Thus, an adapted tumbling strategy can be used to influence the joining process and to achieve a controlled material flow in order to manufacture tailored joints. For the fundamental investigation of the process, numerical investigations are necessary. In order to achieve high model quality a precise material modelling is crucial. Therefore, a characterisation of the materials HCT590X+Z and EN AW-6014 as typical materials of multi-material mixes and the rivet material 38B2 is performed. Due to the different stress conditions during tumbling self-piercing riveting suitable characterisation methods are selected and carried out.}}, author = {{Wituschek, S. and Lechner, M.}}, journal = {{ESAFORM 2021}}, title = {{{Material characterisation methods for a tumbling self-piercing riveting process}}}, doi = {{10.25518/esaform21.398}}, year = {{2021}}, } @article{30683, abstract = {{When joining lightweight parts of various materials, clinching is a cost efficient solution. In a production line, the quality of a clinch point is primarily controlled by measurement of dimensions, which are accessible from outside. However, methods such as visual testing and measuring the bottom thickness as well as the outer diameter are not able to deliver any information about the most significant geometrical characteristic of the clinch point, neck thickness and undercut. Furthermore, ex-situ destructive methods such as microsectioning cannot detect elastic deformations and cracks that close after unloading. In order to exceed the current limits, a new non-destructive in-situ testing method for the clinching process is necessary. This work proposes a concept to characterize clinch points in-situ by combining two complementary non-destructive methods, namely, computed tomography (CT) and ultrasonic testing. Firstly, clinch points with different geometrical characteristics are analysed experimentally using ex-situ CT to get a highly spatially resolved 3D-image of the object. In this context, highly X-ray attenuating materials enhancing the visibility of the sheet-sheet interface are investigated. Secondly, the test specimens are modelled using finite element method (FEM) and a transient dynamic analysis (TDA) is conducted to study the effect of the geometrical differences on the deformation energy and to qualify the TDA as a fast in-situ non-destructive method for characterizing clinch points at high temporal resolution. }}, author = {{Köhler, D. and Sadeghian, B. and Kupfer, R. and Troschitz, J. and Gude, M. and Brosius, A.}}, journal = {{Key Engineering Materials}}, pages = {{89--96}}, title = {{{A Method for Characterization of Geometric Deviations in Clinch Points with Computed Tomography and Transient Dynamic Analysis}}}, doi = {{10.4028/www.scientific.net/kem.883.89}}, volume = {{883}}, year = {{2021}}, } @article{30663, abstract = {{The use of clinch joints, e.g. vehicle structures, is determined by the reliability of the joint and its strength properties - in particular the fatigue strength. Clinch connections offer the advantage over form-closure and force-closure processes that they can also be used for hybrid material combinations. In order to be able to evaluate the influence of the geometry parameters such as e.g. undercut, neck thickness or also base thickness on the fatigue behavior, three clinch connections (in optimum and compromise design) with different tool parameters were designed and examined using the example of a joining task with aluminum sheet material. For this purpose, fatigue curves (F-N curves) in the range of high to very high numbers of load cycles (N = 105 to 107) were determined. In this load cycle range, a so-called "neck fracture" is mainly to be expected as the type of failure, whereas for quasi-static tests, a “buckling” is more likely to occur. The tests were carried out on single-cut overlapping shear tensile specimens. Metallographic and scanning electron microscopic examinations of the joints and the fracture surfaces served to identify the crack initiation site and to clarify the respective type of failure. Significant differences in the damage behaviour of the three clinching variants could be shown. This observation enables one step into the direction of fully understanding the relationship along the causal chain "joint requirements - joining process - fatigue strength". Thus the adaptability of the clinching process can be improved. }}, author = {{Ewenz, L. and Kalich, J. and Zimmermann, M. and Füssel, U.}}, journal = {{Key Engineering Materials}}, pages = {{65--72}}, title = {{{Effect of Different Tool Geometries on the Mechanical Properties of Al-Al Clinch Joints}}}, doi = {{10.4028/www.scientific.net/kem.883.65}}, volume = {{883}}, year = {{2021}}, } @article{30688, abstract = {{Thermally supported clinching (Hotclinch) is a novel promising process to join dissimilar materials. Here, metal and fibre-reinforced thermoplastics (FRTP) are used within this single step joining process and without the usage of auxiliary parts like screws or rivets. For this purpose, heat is applied to improve the formability of the reinforced thermoplastic. This enables joining of the materials using conventional clinching-tools. Focus of this work is the modelling on mesoscopic scale for the numerical simulation of this process. The FTRP-model takes the material behaviour both of matrix and the fabric reinforced organo-sheet under process temperatures into account. For describing the experimentally observed phenomena such as large deformations, fibre failure and the interactions between matrix and fibres as well as between fibres themselves, the usage of conventional, purely Lagrangian based FEM methods is limited. Therefore, the combination of contact-models with advanced modelling approaches like Arbitrary-Lagrangian-Eulerian (ALE), Coupled-Eulerian-Lagrangian (CEL) and Smooth-ParticleHydrodynamics (SPH) for the numerical simulation of the clinching process are employed. The different approaches are compared with regard to simulation feasibility, robustness and results accuracy. It is shown, that the CEL approach represents the most promising approach to describe the clinching process. }}, author = {{Gröger, B. and Hornig, A. and Hoog, A. and Gude, M.}}, journal = {{ESAFORM 2021 - 24th International Conference on Material Forming}}, title = {{{Modelling of thermally supported clinching of fibre-reinforced thermoplastics: Approaches on mesoscale considering large deformations and fibre failure}}}, doi = {{10.25518/esaform21.4293}}, year = {{2021}}, } @article{30685, abstract = {{Joints are an essential part of modern (lightweight) structures in a broad variety of applications. The reason for this is the rapidly increasing number of different material combinations needing to be joined in application areas like the automotive industry. It is currently common to use numerous auxiliary or standardized elements instead of individually adapted joining elements. This leads to a large number of different joining elements per product and thus to high costs. An innovative approach to overcoming this issue is the design, manufacture and setting of joint-specific joining elements. A good candidate for the manufacture of adapted joining elements of this type is the so-called friction spinning process. The joining elements formed in this way can be specifically adapted to the application in question in terms of both shape and mechanical properties. The part geometry required for the properties of a given joint is formed using a universal forming tool. This makes it possible to form a wide variety of sub geometries for the auxiliary joining part as a function of the prevailing joint condition, using a single forming tool and starting from the same semi-finished bar material. By applying different process strategies for the rotational speed and feed rate during the forming operation, the same part geometry can even be given different local mechanical properties. The following contribution presents the results of ongoing research work and includes the process concept, process properties, tooling and the results of experimental investigations into the joining of two sheet metal parts with help of this new joining process.}}, author = {{Wiens, E. and Wischer, C. and Homberg, W.}}, journal = {{ESAFORM}}, pages = {{4682}}, title = {{{Development of a novel adaptive joining technology employing friction-spun joint connectors (FSJC)}}}, doi = {{10.25518/esaform21.4682}}, year = {{2021}}, } @article{30664, abstract = {{Corrosion is a major cause for the failure of metallic components in various branches of the industry. Depending on the corrosion severity, the time until failure of the component varies. On the contrary, a study has shown that certain riveted metal joints, exposed to a short period of mechanical loading and corrosion, have greater fatigue limits. This study gives rise to the question how different corrosion exposure times affect joint metallic components. In the present research, a theoretical approach is developed in order to evaluate the influence of galvanic corrosion on joint integrity of clinched metal joints. At first, the framework for modeling galvanic corrosion is introduced. Furthermore, a simulative investigation of a clinching point is carried out based on the assumption that corrosion leads to a reduction of the contact area which leads to a local increase in contact pressure. For this purpose, the stiffness values of individual elements in a finite element model are reduced locally in the contact area of the undercut and the contact stress along a path is evaluated. Summarizing, a modeling approach is introduced to investigate corrosion effects on load-bearing behavior of clinched joints. }}, author = {{Harzheim, S. and Steinfelder, C. and Wallmersperger, T. and Brosius, A.}}, journal = {{Key Engineering Materials}}, pages = {{97--104}}, title = {{{A First Approach for the Treatment of Galvanic Corrosion and of Load-Bearing Capacity of Clinched Joints}}}, doi = {{10.4028/www.scientific.net/kem.883.97}}, volume = {{883}}, year = {{2021}}, } @article{30694, abstract = {{In recent years, clinching has gathered popularity to join sheets of different materials in industrial applications. The manufacturing process has some advantages, as reduced joining time, reduced costs, and the joints show good fatigue properties. To ensure the joint strength, reliable simulations of the material behaviour accounting for process-induced damage are expected to be beneficial to obtain credible values for the ultimate joint strength and its fatigue limit. A finite plasticity gradient-damage material model is outlined to describe the plastic and damage evolutions during the forming of sheet metals, later applied to clinching. The utilised gradient-enhancement cures the damage-induced localisation by introducing a global damage variable as an additional finite element field. Both, plasticity and damage are strongly coupled, but can, due to a dual-surface approach, evolve independently. The ability of the material model to predict damage in strongly deformed sheets, its flexibility and its regularization properties are illustrated by numerical examples.}}, author = {{Friedlein, J. and Mergheim, J. and Steinmann, P.}}, journal = {{Key Engineering Materials}}, pages = {{57}}, title = {{{A finite plasticity gradient-damage model for sheet metals during forming and clinching}}}, doi = {{10.4028/www.scientific.net/KEM.883.57}}, volume = {{883 KEM}}, year = {{2021}}, } @article{30689, abstract = {{Joining and local forming processes for fibre-reinforced thermoplastics (FRTP) like hole-forming or variations of the clinching process require an in-depth understanding of the process induced effects on meso-scale. For numerical modelling with a geometrical description of a woven fabric, adequate material models for a representative unit cell are identified. Model calibration is achieved employing a mesoscopic finite-element-approach using the embedded element method based on tensile tests of the consolidated organo-sheets and a phenomenological evaluation of photomicrographs. The model takes temperature dependent stiffness and fibre tension failure into account. }}, author = {{Gröger, B. and Hornig, A. and Hoog, A. and Gude, M.}}, journal = {{Key Engineering Materials}}, pages = {{49}}, title = {{{Temperature dependent modelling of fibre-reinforced thermoplastic organo-sheet material for forming and joining process simulations}}}, doi = {{10.4028/www.scientific.net/KEM.883.49}}, volume = {{883 KEM}}, year = {{2021}}, } @article{30720, abstract = {{Predicting the durability of components under mechanical loading combined with environmental conditions leading to corrosion is one of the most challenging tasks in mechanical engineering. Precise predictions are neccesary for lightweight design in transportation due to environmental protection. During corrosion often hydrogen is produced by electrochemical reactions. Hydrogen embrittlement is one of the most feared damage mechanisms for metal constructions leading to early and unexpected failure. Until now predictions are mostly done through costly experiments. In the present research, a first simple simulation model based on the fundamentals of electrochemistry and continuum damage mechanics is developed to couple the damage induced by the mechanical stress with the hydrogen embrittlement. Results of the durability are presented for the case of uniaxial cyclic loading for varying testing frequency.}}, author = {{Hofmann, M. and Shi, Y. and Wallmersperger, T.}}, journal = {{PAMM}}, title = {{{A first Model of Fatigue Corrosion of a Metal through Hydrogen Embrittlement}}}, doi = {{10.1002/pamm.202000122}}, volume = {{20}}, year = {{2021}}, } @article{30695, abstract = {{Due to their cost-efficiency and environmental friendliness, the demand of mechanical joining processes is constantly rising. However, the dimensioning and design of joints and suitable processes are mainly based on expert knowledge and few experimental data. Therefore, the performance of numerical and experimental studies enables the generation of optimized joining geometries. However, the manual evaluation of the results of such studies is often highly time-consuming. As a novel solution, image segmentation and machine learning algorithm provide methods to automate the analysis process. Motivated by this, the paper presents an approach for the automated analysis of geometrical characteristics using clinching as an example. }}, author = {{Zirngibl, C. and Schleich, B.}}, journal = {{Key Engineering Materials}}, pages = {{105}}, title = {{{Approach for the automated analysis of geometrical clinch joint characteristics}}}, doi = {{10.4028/www.scientific.net/KEM.883.105}}, volume = {{883 KEM}}, year = {{2021}}, } @inproceedings{34208, abstract = {{Computational homogenization is a powerful tool which allows to obtain homogenized properties of materials on the macroscale from the simulation of the underlying microstructure. The response of the microstructure is, however, strongly affected by variations in the microstructure geometry. The effect of geometry variations is even stronger in cases when the material exhibits plastic deformations. In this work we study a model of a steel alloy with arbitrary distributed elliptic voids. We model one single unit cell of the material containing one single void. The geometry of the void is not precisely known and is modeled as a variable orientation of an ellipse. Large deformations applied to the unit cell necessitate a finite elasto-plastic material model. Since the geometry variation is parameterized, we can utilize the method recently developed for stochastic problems but also applicable to all types of parametric problems — the isoparametric stochastic local FEM (SL-FEM). It is an ideal tool for problems with only a few parameters but strongly nonlinear dependency of the displacement fields on parameters. Simulations demonstrate a strong effect of parameter variation on the plastic strains and, thus, substantiate the use of the parametric computational homogenization approach.}}, author = {{Pivovarov, Dmytro and Mergheim, Julia and Willner, Kai and Steinmann, Paul}}, booktitle = {{PAMM}}, issn = {{1617-7061}}, number = {{1}}, publisher = {{Wiley}}, title = {{{Parametric FEM for computational homogenization of heterogeneous materials with random voids}}}, doi = {{10.1002/pamm.202000071}}, volume = {{20}}, year = {{2021}}, } @article{34087, author = {{Knust, Steffen and Ruhm, Lukas and Kuhlmann, Andreas and Meinderink, Dennis and Bürger, Julius and Lindner, Jörg and de los Arcos de Pedro, Maria Teresa and Grundmeier, Guido}}, issn = {{0377-0486}}, journal = {{Journal of Raman Spectroscopy}}, keywords = {{Spectroscopy, General Materials Science}}, number = {{7}}, pages = {{1237--1245}}, publisher = {{Wiley}}, title = {{{In situ backside Raman spectroscopy of zinc oxide nanorods in an atmospheric‐pressure dielectric barrier discharge plasma}}}, doi = {{10.1002/jrs.6123}}, volume = {{52}}, year = {{2021}}, }