TY - CONF A1 - Unger, Wolfgang T1 - Advanced surface chemical analysis of plasma modified polymers and plasma-polymers N2 - A comprehensive characterization of plasma modified polymer surfaces or plasma-polymerized thin films needs access to parameters as - concentration of saturated/unsaturated carbon species (e.g. aromaticity) or other double bonds as C=N or C=O, - branching, and - losses of crystallinty or other degrees of structural order. Furthermore the complex ageing phenomena of plasma modified polymers/plasma-polymers and the measurement of an in-depth distribution of chemical species are challenges for the analyst. The talk will display selected examples where such challenges have been met by using advanced methods of surface chemical analyses as Photoelectron Spectroscopy with variable excitation energy (“SyncXPS”), X-ray Absorption Spectroscopy (NEXAFS) at C, N and O K-edges and Time-of-Flight Secondary Mass Spectroscopy (ToF-SIMS) combined with Principal Component analysis (PCA). T2 - IAP workshop – IAP 2016 "Organic surface modifications by plasmas and plasma-polymers" CY - Nancy, France DA - 08.06.2016 KW - XPS KW - NEXAFS KW - SIMS KW - Plasmapolymer PY - 2016 AN - OPUS4-36725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzweber, M. A1 - Lippitz, Andreas A1 - Hesse, R. A1 - Hodoroaba, Vasile-Dan A1 - Werner, W. A1 - Denecke, R. A1 - Unger, Wolfgang T1 - Ionische Flüssigkeiten als Referenzmaterial in der Oberflächenanalytik N2 - Energiedispersive Röntgenspektroskopie (EDX) ist eine der meist verbreiteten Methoden zur Bestimmung der chemischen Zusammensetzung von Festkörpern und dünnen Schichten. Durch die technologische Weiterentwicklung energiedispersiver Röntgenspektrometer wurde die Leistungsfähigkeit auch im niederenergetischen Bereich unter 1 keV verbessert. Geeignete Testmaterialien zur Überprüfung der Leistungsfähigkeit im niederenergetischen Bereich in Übereinstimmung mit ISO 15632 sind kaum vorhanden und basieren hauptsächlich auf C K und F K Linien. Um gültige Resultate aus akkreditierten und zertifizierten Prüf- und Kalibrierlaboratorien in Übereinstimmung mit ISO/IEC 17025 zu gewährleisten sind regelmäßige Funktionsprüfungen der Spektrometer notwendig. In einer Machbarkeitsstudie wurde die Eignung einer bestimmten Substanz-klasse, nämlich ionische Flüssigkeiten, als Referenzmaterial zur routinemäßi-gen Überprüfung der Energieskala, der Energieauflösung und der Spektrometer Effizienz untersucht. Es kann gezeigt werden, dass mit einer einzigen Messung an einem einzigen Referenzmaterial mehrere Geräteparameter überprüft werden können. Damit ist es im niederenergetischen Bereich möglich regelmäßige Funktionsprüfungen von Spektrometern durchzuführen, aber auch die Leistungsfähigkeit verschiedener Spektrometer zu vergleichen. Beides kann sehr effizient durch einen einfachen qualitativen Vergleich mehrerer Spektren erreicht werden. Durch die Verwendung von ionischen Flüssigkeiten als Referenzmaterial, deren Stöchiometrie genau bekannt ist bzw. zertifiziert werden kann, können eventuell sogar die gängigen Modelle zur Matrixkorrektur validiert werden. Auch wäre eine Neubewertung von Fundamentalparametern (Fluoreszenzausbeute, Massenschwächungskoeffizienten usw.) von Elementen niedriger Ordnungszahl möglich. T2 - 19. Arbeitstagung Angewandte Oberflächenanalytik (AOFA) CY - Soest, Germany DA - 05.09.2016 KW - Ionische Flüssigkeiten KW - Referenzmaterial KW - Oberflächenanalytik PY - 2016 UR - http://www.awz-soest.fraunhofer.de/de/aofa2016.html AN - OPUS4-37322 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fréjafon, E. A1 - Salvi, O. A1 - Hazebrouck, B. A1 - Le Feber, M. A1 - López de Ipiña Peña, J. A1 - Unger, Wolfgang T1 - Creation of the European centre for risk management and safe innovation in nanomaterials & nanotechnologies (EC4SafeNano) N2 - Safe innovation & sustainable production with MNMs need that we: Understand risks and benefits (diagnostic, assessment) Identify and implement risk reduction strategies (manage) Communicate on residual risks (acceptance) Huge knowledge on characterization, hazards, diagnostic (science) Little effective use of it for operational risk management (expertise) Objectives of the centre: Bridge the gap between research and application (public, private), Bridge the gap between knowledge on risks and risk management, Balance between Science and Appliance, in a sustainable way: Efficient & Sustainable structure Collective, harmonized, shared expertise EU scale, internationally connected. T2 - Workshop "NanoSafety: from research to implementation" CY - Amsterdam, The Netherlands DA - 22.06.2016 KW - Nano materials KW - Risk management KW - Safe innovation PY - 2016 UR - http://nanomile.eu-vri.eu/news.aspx?lan=230&tab=2361&nid=991#n991 AN - OPUS4-36966 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Lippitz, A. A1 - Illgen, R. A1 - Ehlert, C. A1 - Girard-Lauriault, P.-L. A1 - Donskyi, Ievgen A1 - Haag, R. A1 - Adeli, M. T1 - Low pressure plasma, UV photo and wet chemical modification of graphite, graphene and carbon nano tubes N2 - Graphene is a two-dimensional carbon network with unique properties, including high mechanical stiffness, strength, and elasticity, outstanding electrical and thermal conductivity, and many others. Despite these advantages, its low solubility, poor reactivity and the limited accessibility of a well-defined basal plane are major challenges for applications. An ideal method to overcome these problems is the covalent attachment of functional molecules to its surface which enables further reactive modifications for specific applications. There is a number of different technologies for surface functionalization of graphene and related CNT materials. However, to get control on the functionalization process and to optimize the performance of the modified surfaces analytical tools for surface chemical characterization are required. X-ray absorption (NEXAFS) and photoelectron spectroscopy (XPS) have been identified to be rather powerful here. Specifically NEXAFS spectroscopy underpinned by quantum chemical spectrum simulations is unique in a way to address changes of aromaticity and defect formation at the graphene surface during functionalization. For relevant surface modification technologies, we present examples on how NEXAFS and XPS can perform well. All presented modifications aim on the production of platforms for defined functional 2D nanomaterials, as for example multifunctional hybrid architectures. In detail, we investigated: • Graphene and carbon nanotube functionalized by a Vacuum-Ultraviolet (VUV) induced photochemical process in NH3 or O2 atmospheres in order to introduce amino or hydroxy functionalities, respectively. • Br bonding on r.f. cw low pressure plasma brominated graphite surfaces by using Br2 and bromoform as plasma gases. • A wet chemical method for covalent functionalization of graphene sheets by a one-pot nitrene [2+1] cycloaddition reaction under mild conditions. Here a reaction between 2,4,6-trichloro-1,3,5-triazine and sodium azide with thermally reduced graphene oxide (TRGO) results in defined dichlorotriazine-functionalized graphene sheets. T2 - The 17th European Conference on Applications of Surface and Interface Analysis CY - Montpellier, France DA - 24.09.2017 KW - Graphene KW - XPS KW - NEXAFS PY - 2017 AN - OPUS4-42787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Fréjafon, Emeric A1 - Hazebrouck, Benoît T1 - Designing a sustainable European centre for risk management and safe innovation in nanomaterials & nanotechnologies (EC4SafeNano) N2 - A central challenge to ensure the sustainable production and use of nanotechnologies is to understand the risks for environment, health and safety associated with this technology and resulting materials and products, and to identify and implement practical strategies to minimize these risks. Knowledge about nanotechnology-enabled processes and products and related environment, health and safety issues is growing rapidly, achieved through numerous European or national R&D programs over the last decade, but effective use of this knowledge for risk management by market actors is lagging behind. The EC4SafeNano initiative (www.EC4SafeNano.eu) is an ongoing effort to build a European Centre for Risk Management and Safe Innovation in Nanomaterials and Nanotechnologies. EC4SafeNano aims to bridge the gap between scientific knowledge on hazard and risk, and ‘fit-for-purpose’ risk management tools and strategies supported by measurement and control methods. The consortium comprises 15 partners (INERIS (coordinator), EU-VRi, TNO, BAM, FIOH, VITO, SP, DEMOKRITOS, TECNALIA, Health and Safety Executive, NRCWE, Paris Lodron University Salzburg, Université Libre de Bruxelles, University of Birmingham and ENEA) from 11 European Member States with significant expertise on risk assessment and management, who already provide knowledge and technical services to public and private organizations, to industry and to public authorities and regulatory bodies. The overall objective of the EC4SafeNano project is to develop a distributed Centre of European Organisations offering services for Risk Management and Safe Innovation for Nanomaterials & Nanotechnologies. The Centre will be structured as a hub-based network of organizations managed by a core group of public-oriented bodies providing risk management and safe innovation support to all stakeholders. It will be operated with the support of Associated Partners so as to expand its capabilities, resources and services. It will interact with existing platforms and centres of excellence in nanosafety and foster the organization or development of national hubs mirroring the European hub. The Centre will seek financial support from stakeholders and service users to sustain the services in the longer term. The operational objectives of the project involve understanding and mapping the needs of the various stakeholders (private and public). It will identify the resources and capabilities and develop a range of harmonized services required to meet these needs. The construction of the centre will include putting in place and implementing processes to deliver and update services, to test and benchmark services, to evaluate the governance of the Centre, and developing a business plan to ensure self-sufficiency of the Centre beyond the project lifetime. A cornerstone of the project is to build a community for risk management and safe innovation for nanotechnology. Interested persons or organisations are invited to join this initiative as registered stakeholders or Associated Partners, to engage in focus networks and to help shape the future Centre. The poster will present the EC4SafeNano initiative and will detail the role of registered stakeholders and Associated Partners. T2 - UBA Scientific Stakeholder Meeting on Nanomaterials in the Environment CY - Dessau, Germany DA - 10.10.2017 KW - Risk management KW - Nanomaterials KW - Nanotechnologies PY - 2017 AN - OPUS4-42788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Huschke, Philip A1 - Unger, Jörg F. T1 - Nonlocal continuum damage modeling N2 - Nonlocal continuum damage modelung using the gradient enhanced damage model and the phase-field model for brittle fracture. T2 - WIBE 2016 CY - Garching, Germany DA - 13.10.2016 KW - Gradient enhanced KW - FEM KW - Damage KW - Phase-field PY - 2017 AN - OPUS4-42612 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Huschke, Philip A1 - Unger, Jörg F. T1 - Domain decomposition methods for fracture mechanics problems N2 - A finite element tearing and interconnecting (FETI) approach for phase-field models and gradient enhanced damage models is presented. These diffusive crack models can solve fracture mechanics problems by integrating a set of partial differential equations and thus avoid the explicit treatment of discontinuities. However, they require a fine discretization in the vicinity of the crack. FETI methods distribute the computational cost among multiple processors and thus speed up the computation. T2 - GACM 2017 CY - Stuttgart, Germany DA - 11.10.2017 KW - FEM KW - DDM KW - FETI PY - 2017 AN - OPUS4-42604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Huschke, Philip A1 - Unger, Jörg F. T1 - Domain decomposition methods for fracture mechanics problems N2 - Strain hardening ultra high performance fiber reinforced cementitious composites (UHPFRCC) exhibit increased strength, ductility, and energy absorption capacity when compared to their quasibrittle, unreinforced counterparts. A mesoscale finite element model can depict the underlying causes for the structural response of UHPFRCC and thus help to optimize the fiber content, the fiber dimensions, and the fiber orientation. The mesoscale model can either be used directly or as a representative volume element for a macroscopic model. We present a two-dimensional and a threedimensional mesoscale finite element model to simulate the structural response of strain hardening UHPFRCC. The mesoscale model employs an implicit gradient enhanced damage model for the cement matrix and a local bond stress-slip model for the bond between the cement matrix and the steel fibers. The steel fibers are modeled discretely as one-dimensional truss elements that are coupled to the cement matrix via bond elements. The tensile stress-strain response of UHPFRCC is a consequence of local matrix cracking and bond failure. Both phenomena can be depicted when modeling the cement matrix, the steel fibers, and the fiber-to-matrix bond explicitly. The second part of the talk deals with the efficient modeling of fracture and the prediction of crack initiation, propagation, merging, and branching through the computational domain. Phase-field models and gradient enhanced damage models can solve fracture mechanics problems by integrating a set of partial differential equations for the system and thus avoid the explicit treatment of discontinuities. The main attributes of these approaches are their simplicity and generality. However, they require a fine discretization in the region where the crack evolves. A finite element tearing and interconnecting (FETI) approach for the diffusive crack models is presented to distribute the computational cost among multiple processors and thus speed up the overall computation. T2 - ICAM 2017 CY - Garching, Germany DA - 20.05.2017 KW - FEM KW - FETI KW - DDM PY - 2017 AN - OPUS4-42605 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hupatz, H. A1 - Schröder, H. A1 - Heinrich, Thomas A1 - Lippitz, Andreas A1 - Unger, Wolfgang A1 - Schalley, C. T1 - Deposition of redox-switchable rotaxanes on surfaces N2 - Deposition of Redox-switchable rotaxanes on surfaces Nature has created molecular machines which can perform a variety of different tasks. They exhibit defined operational pathways and order, resulting in directed macroscopic effects. Within the last decades researchers have been developing numerous artificial molecular machines which are so far mostly operating in solution. However, this represents a major obstacle for the generation of a macroscopic output, due to the random orientation of molecules in solution. As a general approach to this problem, interfaces have been used to generate ordered arrays of functional molecules. Recently, we developed a new class of redox-switchable crown ether/ammonium-based [2]- and [3]rotaxanes which incorporate redox-active tetrathiafulvalene and naphthalene diimide units in their wheels resulting in emergent optoelectronic properties. Electrochemical stimuli influence the interactions between the two macrocycles of [3]rotaxanes and induce conformational changes. In a proof-of-principle study [2]pseudorotaxanes were deposited on gold surfaces by “click”-reaction to azide-terminated self-assembled monolayers to generate ordered arrays of redox-active rotaxanes on-surface. X-ray photoelectron spectroscopy (XPS) confirms the successful deposition of a rotaxane monolayer, though angle-resolved near-edge X-ray absorption fine structure spectroscopy (NEXAFS) exhibits poor order of the rotaxanes. Following, new terpyridine-stoppered rotaxanes will be synthesised opening a pathway for the deposition of [2]- and [3]rotaxanes in a layer-by-layer metal-mediated self-assembly procedure. This approach would allow for a programmed sequence of different rotaxanes in multilayers. Electrochemical on-surface switching will be investigated by angle-resolved NEXAFS spectroscopy, XPS, cyclic voltammetry and UV/Vis spectroscopy. A more detailed understanding of the electron-transfer between the surface and the different rotaxane layers as well as of the on-surface switching could give rise to potential applications like optoelectric data-storage devices or potential-driven molecular motors. T2 - Gordon Research Conference - Artificial Molecular Switches & Motors CY - Holderness, NH, USA DA - 11.06.2017 KW - Rotaxane KW - Immobilization KW - XPS KW - NEXAFS PY - 2017 AN - OPUS4-42843 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hupatz, H. A1 - Schröder, H. V. A1 - Heinrich, Thomas A1 - Schalley, C.A. A1 - Unger, Wolfgang T1 - Redox-Switchable Rotaxanes on Surfaces N2 - Nature has created molecular machines which can perform a variety of different tasks. They exhibit defined operational pathways and order, resulting in directed macroscopic effects. Within the last decades researchers have been developing numerous artificial molecular machines which are so far mostly operating in solution. However, this represents a major obstacle for the generation of a macroscopic output, due to the random orientation of molecules in solution. As a general approach to this problem, interfaces have been used to generate ordered arrays of functional molecules. Recently, we developed a new class of redox-switchable crown ether/ammonium-based [2]- and [3]rotaxanes which incorporate redox-active tetrathiafulvalene and naphthalene diimide units in their wheels resulting in emergent optoelectronic properties. Electrochemical stimuli influence the interactions between the two macrocycles of [3]rotaxanes and induce conformational changes. In a proof-of-principle study [2]pseudorotaxanes were deposited on gold surfaces by “click”-reaction to azide-terminated self-assembled monolayers to generate ordered arrays of redox-active rotaxanes on-surface. X-ray photoelectron spectroscopy (XPS) confirms the successful deposition of a rotaxane monolayer, though angle-resolved near-edge X-ray absorption fine structure spectroscopy (NEXAFS) exhibits poor order of the rotaxanes. Following, new terpyridine-stoppered rotaxanes will be synthesised opening a pathway for the deposition of [2]- and [3]rotaxanes in a layer-by-layer metal-mediated self-assembly procedure. This approach would allow for a programmed sequence of different rotaxanes in multilayers. Electrochemical on-surface switching will be investigated by angle-resolved NEXAFS spectroscopy, XPS, cyclic voltammetry and UV/Vis spectroscopy. A more detailed understanding of the electron-transfer between the surface and the different rotaxane layers as well as of the on-surface switching could give rise to potential applications like optoelectric data-storage devices or potential-driven molecular motors. T2 - GDCh-Wissenschaftsforum Chemie CY - Berlin, Germany DA - 10.09.2017 KW - NEXAFS KW - Rotaxane KW - XPS KW - Surface characterization PY - 2017 AN - OPUS4-42848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sobol, Oded A1 - Steiner, S. A1 - Albe, K. A1 - Froemling, T. A1 - Unger, Wolfgang T1 - The characterization of oxygen diffusion in (Na1/2Bi1/2)TiO3 piezo-ceramics by Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) N2 - The ferroelectric ceramic NBT and its solid solutions with barium titanate (BT) are examples for the most promising lead free materials to substitute the dominant Pb(Zr,Ti)O3 (PZT). Lead based material should generally be disregarded due to environmental and health reasons. However, there is no class of lead-free piezoelectric materials that can replace PZT entirely. Not only the often inferior ferroelectric properties but also the lack of understanding of the defect chemistry of NBT is still a challenge for the replacement of lead containing piezo-ceramics. Just recently it could be shown by Li et al. that NBT obtains extraordinarily high oxygen ionic conductivity when doped with Mg as acceptor. It was actually expected that doping just leads to a hardening of the ferroelectric properties. However, it became clear that the known defect chemical behavior of PZT cannot be extrapolated to NBT materials. Hence, to gain information on general doping effects a better defect chemical investigation is needed. This is particularly important for the applications with high reliability demands to investigate possible degradation and fatigue mechanisms. In the present work Time-of-flight-secondary ion mass spectrometry (ToF-SIMS) was used in order to observe the influence of different acceptor dopants (Fe, Ni, Al) on the oxygen diffusion in NBT. ToF-SIMS holds the ability to gain a full elemental distribution in a sub-micron resolution and was therefore chosen to provide the essential information on the favorable diffusion paths of oxygen in NBT in dependence of the chosen doping element. 18O was used as a tracer for oxygen as its natural abundance is only 0.2%. The doped NBT samples have been annealed for 5 h at 500°C in a 0.2 bar 18O-tracer atmosphere to be able to detect oxygen ion diffusion. ToF-SIMS investigations were conducted on a ToF-SIMS IV (ION TOF GmbH, Münster, Germany) using a Bi+ primary ion beam (25KeV in collimated burst alignment mode with a beam diameter of ~150 nm) and a Cs+ sputter beam (3KeV). The results illustrate the different impact of dopants on the diffusion properties which is evidence for a highly non-linear dependence on dopant type and concentration. T2 - 21st International Conference on Secondary Ion Mass Spectrometry - SIMS21 CY - Krakow, Poland DA - 10.09.2017 KW - ToF-SIMS KW - NBT KW - Piezoceramics PY - 2017 UR - http://sims.confer.uj.edu.pl/boa_poster.php?id=93 AN - OPUS4-42911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Donsky, I. S. A1 - Lippitz, Andreas A1 - Adeli, M. A1 - Haag, R. A1 - Unger, Wolfgang T1 - 2D nanomaterials with switchable pathogen binding N2 - Graphene derivatives have shown great promise in the field of pathogen binding and sensing. Due to their diverse applications, they show a variety of activities that range from bacterial adhesion to bacterial resistance. Therefore, domination of the graphene-pathogen interactions is highly relevant for producing 2D platforms with the desired applications. In order to gain control over the interactions between graphene and biosystems, mechanisms should be fully understood. The surface functionality of graphene is one of the most important factors that dominates its interactions with biosystems and pathogens. Covalent functionalization is a robust method through which functionality, chemical structure, and subsequently physicochemical properties of graphene are abundantly manipulated. A critical issue for preparing graphene-based 2D materials with a defined surface structure, however, is controlling the functionalization in terms of number, position, and type of functional groups. T2 - 9th Joint BER II and BESSY II User Meeting CY - Berlin, Germany DA - 13.12.2017 KW - Graphene KW - Functionalization KW - XPS KW - C Kedge NEXAFS PY - 2017 AN - OPUS4-43456 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wurzler, Nina A1 - Özcan Sandikcioglu, Özlem A1 - Radnik, Jörg A1 - Unger, Wolfgang T1 - The effect of flavins on the corrosion properties of stainless steels during initial stages of microbiologically influenced corrosion N2 - Microbiologically influenced corrosion (MIC) on steel occurs where the presence and activity of microbes change the localized conditions on the surface of a metal substrate. For instance, metal reducing bacteria (MRB) are capable of utilizing metal compounds in the passive layer on stainless steel as electron acceptors during their metabolism. This weakening of the passive film not only leads to an acceleration of the general corrosion processes, but also increases the susceptibility of stainless steels to pitting corrosion. Even though the electron transfer mechanisms are not yet fully understood, recent research shows that the secretion of electron shuttles like flavins contribute significantly to the extracellular electron transfer (EET). Electron shuttle molecules like riboflavin (RB) or flavin mononucleotide (FMN) are secreted by MRB after the transition from planktonic to sessile mode and exist in the biofilm at low concentrations. Therefore, they are precise early phase indicators of bacterial settlement. This project aims at clarifying the electrochemical interaction mechanisms of MRB with stainless steel surfaces, with a special focus on the role of the extracellular redox molecules. The analysis of corrosion processes as a function of chloride and flavin concentration have been performed by means of electrochemical methods. Due to the differences in their chemical structure, FMN and RB have shown significant differences in terms of their adsorption behavior and the stability of the formed films, which directly influences the electron transfer processes. Therefore, Electrochemical Quartz Crystal Microbalance (eQCM) studies have been performed on sputtered FeCr electrodes to investigate the adsorption/desorption kinetics of flavins. The results of electrochemical studies are complemented by the analysis of the changes in the passive film chemistry and the chemical composition of the adsorbed films by means of Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS). Changes in surface morphology have been investigated by means of Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).The presentation will summarize our results on the degradation mechanisms of passive films on stainless steel surfaces in the presence of flavins and provide useful insights from a fundamental aspect for the understanding of the initial stages of microbiologically influenced corrosion. T2 - 17TH EUROPEAN CONFERENCE ON APPLICATIONS OF SURFACE AND INTERFACE ANALYSIS CY - Montpellier, France DA - 24.09.2017 KW - Flavins KW - Microbiologically influenced corrosion KW - Stainless steel KW - MIC PY - 2017 AN - OPUS4-43402 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kjaervik, Marit A1 - Unger, Wolfgang A1 - Schwibbert, Karin A1 - Thissen, A. A1 - Dietrich, P. T1 - Surface characterisation of biological samples with near-ambient pressure XPS N2 - The principle of NAP-XPS is explained, together with its relevance for biological samples. Further, ongoing work on NAP-XPS measurements on E. coli biofilms is presented. T2 - Seminar AG Weinhart, FU Berlin CY - Freie Universität, Berlin, Germany DA - 05.12.2016 KW - NAP-XPS KW - Biofilms KW - Alginate KW - E. coli PY - 2017 AN - OPUS4-43331 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Beck, Uwe A1 - Griepentrog, Michael A1 - Hertwig, Andreas A1 - Sahre, Mario A1 - Unger, Wolfgang A1 - Hodoroaba, Vasile-Dan A1 - Krüger, Jörg T1 - Plasma Germany, Fachausschuss Normung, Berichtszeitraum Frühjahr 2018 - Herbst 2018 N2 - Der Vortrag gibt den aktuellen Stand der Normung im Bereich der Oberflächen-technik insbesondere der Oberflächenanalytik und der Oberflächenmess- und -prüftechnik wider. Vorgestellt wird der Status technischer Berichte, Normenentwürfe und Normen u.a. zur Charakterisierung von funktionellen Glasoberflächen für bioanalytische Anwendungen, zur Messung der Schichtdicke von Nanomaterialien mittels Ellipsometrie, zur Kalibrierung von Interferometern und Interferenzmikroskopen für die Formmessung, zur Rockwelleindringprüfung zur Bewertung der Schicht-haftung, zu den Grundlagen der Ellipsometrie, zur Messung der Schichtdicke mittels Wirbelstromverfahren, zur Schichtpotentialmessung von Mehrfach-Nickelschichten, zu Filtern und Augenschutzgeräten gegen Laserstrahlung sowie zur Bestimmung der Schichthaftung mittels Zugversuch. T2 - Fachausschuss Normung, Herbstsitzung CY - Jena, Germany DA - 06.11.2018 KW - Stand der Normung KW - Oberflächentechnik KW - Oberflächenanalytik KW - Oberflächenmesstechnik KW - Oberflächenprüftechnik PY - 2018 AN - OPUS4-48894 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Robens-Radermacher, Annika T1 - Combination of model reduction and adaptive subset simulation for structural reliability problems N2 - A safe and robust design is a key criterion when building a structure or a component. Ensuring this criterion can either be performed by fullfilling prescribed safety margins, or by using a full probabilistic approach with a computation of the failure probability. The latter approach is particularly well suited for complex Problems with an interaction of different physical penomena that can be described in a numerical model. The bottleneck in this approach is the computational effort. Sampling methods such as Markov chain Monte Carlo methods are often used to evaluate the system reliability. Due to small failure probabilities (e.g. 10^6) and complex physical models with already and extensive computational effort for a single set of parameters, these methods a prohibitively expensive. The focus of this contribution is to demonstrate the advantages of combining model reduction techniques within the concept a variance reducing adaptive sampling procedures. In the developed method, a modification of the adaptive subset simulation based on Papaioannou et al. 2015 is used and coupled with a limit state function based on Proper Generalized Decomposition (PGD) (Chinesta et al. 2011). In the subset simulation the failure probability is expressed as a product of larger conditional failure probabilities. The intermediate failure events are chosen as a decreasing sequence. Instead of solving each conditional probability with a Markov chain approach, an importance sampling approach is used. It is be shown that the accuracy of the estimation depends mainly on the number of samples in the last sub-problem. For model reduction, the PGD approach is used to solve the structural problem a priori for a given Parameter space (physical space plus all random parameters). The PGD approach results in an approximation of the problem output within a prescribed range of all input Parameters (load factor, material properties, ..). The approximation of the solution by a separated form allows an evaluation of the limit state function within the sampling algorithm with almost no cost. This coupled PGD – adaptive subset Simulation approach is used to estimate the failure probability of examples with different complexity. The convergence, the error propagation as well as the reduction in computational time is discussed. T2 - UNCECOMP 3rd International Conference on Uncertainty Quantification in Computational Sciences and Engineering CY - Crete, Greece DA - 26.06.2019 KW - Model reduction KW - Reliability analysis KW - Simulation KW - Finite Elemente Method (FEM) KW - Proper Generalized Decomposition (PGD) PY - 2019 AN - OPUS4-48479 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Robens-Radermacher, Annika A1 - Unger, Jörg F. T1 - Efficient reliability analysis coupling important sampling using adaptive subset simulation and PGD model reduction N2 - The key point of structural reliability analysis is the estimation of the failure probability (Pf), typically a rare event. This probability is defined as the integral over the failure domain which is given by a limit state function. Usually, this function is only implicit given by an underlying finite element simulation of the structure. It is generally not possible to solve the integral for Pf analytically. For that reason, simulation-based methods as well as methods based on surrogate modeling (or Response surface methods) has been developed. Nevertheless, these variance reducing methods still require a few thousand calculations of the underlying finite element model, making reliability Analysis computationally expensive for real applications. T2 - GAMM - Gesellschaft für Angewandte Mathematik und Mechanik e.V. CY - Vienna, Austria DA - 18.02.2019 KW - PGD model reduction PY - 2019 AN - OPUS4-48628 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Persson, K. A1 - Johansson Salazar-Sandoval, E. A1 - Ernstsson, M. A1 - Sundin, M. A1 - Wachtendorf, Volker A1 - Kunz, Valentin A1 - Unger, Wolfgang T1 - The EC4SafeNano Project - and the case study of Surface Chemical Transformations of Nano-TiO2 Samples upon Weathering N2 - A central challenge to ensure the sustainable production and use of nanotechnologies is to understand and effectively control the risks along the industrial innovation value chain. Knowledge about nanotechnology processes and nanosafety issues (hazards, fate, risk...) is growing rapidly but the effective use of this knowledge for risk management by market actors is lagging behind. EC4SafeNano (European Centre for Risk Management and Safe Innovation in Nanomaterials and Nanotechnologies) promotes a harmonized vision of expertise in risk assessment and management for the public and private sectors to enable the safe development and commercialization of nanotechnology. EC4SafeNano is operated together by major European risk institutes with the support of numerous associated partners, gathering all stakeholders involved in Nanomaterials and Nanotechnologies (regulators, industry, society, research, service providers...). In a case study the surface chemical transformations upon 2 different ageing procedures (long-term UV irradiation or swimming pool water) of a representative set of titanium dioxide nanoparticles has been investigated. The materials have been analyzed by various analytical techniques. Each method addresses different aspects of the complex endpoint surface chemistry. The multi technique approach allows evaluation of the capabilities and limitations of the applied methods regarding their suitability to address the endpoint surface chemistry and their sensitivity to identify even small surface chemical transformations. Results: - To obtain a comprehensive picture, it is insufficient to concentrate on a single analysis technique. - By using time-of-flight secondary ion mass spectrometry (ToF-SIMS) in combination with principal component analysis (PCA) it was possible to identify even subtle changes in the surface chemistry of the investigated materials. - A general trend that was observed for the UV-aged samples is the decrease of organic material on the nanomaterial surface. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 723623. T2 - FormulaX/NanoFormulation 2019 CY - Manchester, England, United Kingdom DA - 24.06.2019 KW - TiO2 nanoparticle KW - Surface Chemical Transformation KW - UV Weathering KW - SIMS KW - XPS KW - IR spectroscopy KW - EC4SafeNano PY - 2019 UR - https://www.formulation.org.uk/images/stories/FormulaX/Posters/P-14.pdf AN - OPUS4-48912 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Coelho Lima, Isabela A1 - Unger, Jörg F. T1 - Identification of model deficiencies in model parameter calibration N2 - Accurate and reliable assessment of transportation infrastructures (e.g. bridges) are crucial for ensuring public safety. Simulation-based engineering analyses can be used to assess and predict the health state of structures. Although some of the structural parameters necessary for such simulations cannot be directly measured, they can be inferred from Non-Destructive Testing data, in a typical inverse problem formulation. However, any prediction based on engineering models will never be an exact representation of reality, since many sources of uncertainties can be present: poor physical representation of the problem (model bias); measurement errors; uncertainty on inferred parameters; etc. Uncertainty quantification is, therefore, of utmost importance to ensure reliability of any decision based on the simulations. This paper investigates the application of the Modular Bayesian framework to perform structural parameter calibration while estimating a function for the model bias. The data for tests comes from an experimental setup and is represented as a combination of a physics-based model, a model bias term and an additive measurement error (considered to be known). In this approach, the inference problem is divided into 3 modules: the first and the second estimate the optimal hyper-parameters of Gaussian Processes (GP) to replace the physics-based and the model bias term, respectively; the third computes the posterior distribution of the structural parameters of interest, taking into account the GPs from the previous modules. By computing a bias-correction function and calibrating the parameters, the modular framework aims at improving the accuracy of the predictions. T2 - UNCECOMP 2019 CY - Crete, Greece DA - 24.06.2019 KW - Model Bias KW - Uncertainty quantification KW - Modular Bayesian KW - Structural Model Calibration PY - 2019 AN - OPUS4-48575 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pohl, Christoph A1 - Unger, Jörg F. T1 - Pore water state in heated concrete N2 - Spalling of concrete structures is a serious issue for their safety. A better understanding of the pore water distribution and state during a fire is a prerequisite for numerical approaches to such problems. Temperature-driven water transport in concrete consists of multiple phenomena, such as convection, diffusion, adsorption and dehydration. Distinguishing the different influences experimentally is difficult because typically they cannot be disentangled. A common experimental setup approximates a one-dimensional flow, and places temperature and pressure gauges along the propagation direction. For direct information about the water content inside a sample, methods such as NMR or neuron radiography are necessary. A multiphase model for the flow in porous media is presented, with dehydration and changes in the pore size distribution taken into consideration. NMR measurements for temperature-driven flow have been performed. The numerical and experimental results are compared for water transport at temperatures below the critical point. Since both the finite-element model and the experiment allow the distinction between adsorbed, capillary and bulk water, a more fine-grained view of the pore water state is obtained. T2 - CM4P - Computational methods in multi-scale, multi-uncertainty and multi-physics problems CY - Porto, Portugal DA - 15.07.2019 KW - Spalling KW - Porous media KW - Multiphase flow KW - Finite element method PY - 2019 AN - OPUS4-48707 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Diercks, Philipp A1 - Veroy, K. A1 - Robens-Radermacher, Annika A1 - Unger, Jörg F. T1 - Physically meaningful samples in randomized local model order reduction N2 - In this contribution, a methodology for fine scale modeling of large scale structures is proposed, which combines the variational multiscale method[1], domain decomposition and model order reduction. The influence of the fine scale on the coarse scale is modelled by the use of an additive split of the displacement field, addressing applications without a clear scale separation. Based on the work of Buhr and Smetana[2], local reduced spaces are constructed by solving an oversampling problem with random boundary conditions. Herein, we inform the boundary conditions by a global reduced problem and compare our approach using physically meaningful correlated samples with existing approaches using uncorrelated samples. The local spaces are designed such that the local contribution of each subdomain can be coupled in a conforming way, which also preserves the sparsity pattern of standard finite element assembly procedures. Several numerical experiments show the accuracy and efficiency of the method, as well as its potential to reduce the size of the local spaces and the number of training samples compared to the uncorrelated sampling. T2 - XVII International Conference on Computational Plasticity, COMPLAS 2023 CY - Barcelona, Spain DA - 05.07.2023 KW - Domain Decomposition KW - Localized model order reduction KW - Multiscale method KW - Variational Multiscale Method PY - 2023 AN - OPUS4-58658 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Diercks, Philipp A1 - Veroy, K. A1 - Robens-Radermacher, Annika A1 - Unger, Jörg F. T1 - Multiscale modeling of heterogeneous structures based on a localized model order reduction approach N2 - Many of today’s problems in engineering demand reliable and accurate prediction of failure mechanisms of mechanical structures. Thus, it is necessary to take into account the heterogeneous structure on the smaller scale, to capture the underlying physical phenomena. However, this poses a great challenge to the numerical solution since the computational cost is significantly increased by resolving the smaller scale in the model. Moreover, in applications where scale separation as the basis of classical homogenization schemes does not hold, the influence of the smaller scale on the larger scale has to be modelled directly. This work aims to develop an efficient concurrent methodology to model heterogeneous structures combining the variational multiscale method (VMM) [1] and model order reduction techniques (e. g. [2]). First, the influence of the smaller scale on the larger scale can be taken into account following the additive split of the displacement field as in the VMM. Here, also a decomposition of the global domain into subdomains, each containing a fine grid discretization of the smaller scale, is introduced. Second, local reduced approximation spaces for the smaller scale solution are constructed by exploring possible solutions for each subdomain based on the concept of oversampling [3]. The associated transfer operator is approximated by random sampling [4]. Herein, we propose to incorporate the actual physical behaviour of the structure of interest in the training data by drawing random samples from a multivariate normal distribution with the solution of a reduced global problem as mean. The local reduced spaces are designed such that local contributions of each subdomain can be coupled in a conforming way. Thus, the resulting global system is sparse and reduced in size compared to the direct numerical simulation, leading to a faster solution of the problem. T2 - ECCOMAS YIC CY - Porto, Portugal DA - 19.06.2023 KW - Multiscale Method KW - Variational Multiscale Method KW - Domain Decomposition KW - Model Order Reduction PY - 2023 AN - OPUS4-58251 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rosenbusch, Sjard Mathis A1 - Balzani, D. A1 - Unger, Jörg F. T1 - Mesh-convergence and gradient-enhanced models in blast simulations of concrete structures N2 - Blast experiments on reinforced concrete structures are often limited to small structures and therefore simple shock waves. Such experiments are carried out at the Bundesanstalt für Materialforschung und -prüfung (BAM) and the structural response is investigated using several measuring methods. Complex load scenarios that occur as a result of reflection of the shock wave in larger structures are harder to realise in practice. Numerical simulations for the propagation of the shock wave and the structural response can therefore be an alternative method for the investigation of blast loads on complex structures. For the simulation of concrete under impact and blast loads, several local constitutive models exist that are formulated as plasticity models with softening taken into account by introducing a scalar damage field. Local damage models however often lead to mesh-dependent results which do not converge with mesh refinement. In order to achieve meaningful predictions from numerical experiments, independence from the mesh is needed. In this contribution, the JH2 model (Johnson and Holmquist 1994) with a parameter set for concrete is investigated in a simple blast load scenario. The shockwave is implemented as a simplified Friedlander-curve and the overpressures are applied as a boundary condition for the structural simulation. In order to account for large displacements that can occur during blast loads, an updated Lagrangian formulation is utilised. A Runge-Kutta method with adaptive time stepping is used to advance the solution in time. The open source FEM software FEniCS (Logg et al. 2012) is used together with an implementation of the JH2 model which has been developed at BAM. An extensive convergence analysis with both timestep- and mesh-refinement is carried out to show the mesh dependency. In order to make the results independent of the mesh, possible nonlocal versions of the JH2 model with gradient-enhancement are presented. Since many damage models for concrete share the damage mechanism of the JH2 model, the application of the regularisation methods to more complex material models, like the RHT model (Grunwald et al. 2017), is also discussed. Advantages of a gradient-enhanced formulation to simulate dynamic strength increase of concrete, as suggested in (Häußler-Combe and Kitzig 2009), is discussed as well. T2 - ECCOMAS YIC 2023 CY - Porto, Portugal DA - 19.06.2023 KW - Gradient-Damage KW - Explicit Dynamics KW - Concrete Modeling KW - Mesh Convergence PY - 2023 AN - OPUS4-58717 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jafari, Abbas A1 - Vlachas, K. A1 - Chatzi, E. A1 - Unger, Jörg F. T1 - Bayesian finite element model updating using full-field measurements of displacements N2 - Finite element (FE) models are widely used to capture the mechanical behavior of structures. Uncertainties in the underlying physics and unknown parameters of such models can heavily impact their performance. Thus, to satisfy high precision and reliability requirements, the performance of such models is often validated using experimental data. In such model updating processes, uncertainties in the incoming measurements should be accounted for, as well. In this context, Bayesian methods have been recognized as a powerful tool for addressing different types of uncertainties. Quasi-brittle materials subjected to damage pose a further challenge due to the increased uncertainty and complexity involved in modeling crack propagation effects. In this respect, techniques such as Digital Image Correlation (DIC) can provide full-field displacement measurements that are able to reflect the crack path up to a certain accuracy. In this study, DIC-based full field measurements are incorporated into a finite element model updating approach, to calibrate unknown/uncertain parameters of an ansatz constitutive model. In contrast to the standard FEMU, where measured displacements are compared to the displacements from the FE model response, in the force-version of the standard FEMU, termed FEMU-F [1], displacements are applied as Dirichlet constraints. This enables the evaluation of the internal forces, which are then compared to measured external forces, thus quantifying the fulfillment of the momentum balance equation as a metric for the model discrepancy. In the present work, the FEMU-F approach is further equipped with a Bayesian technique that accounts for uncertainties in the measured displacements, as well. Via this modification, displacements are treated as unknown variables to be subsequently identified, while they are allowed to deviate from the measured values up to a certain measurement accuracy. To be able to identify many unknown variables; including constitutive parameters and the aforementioned displacements, the Variational Bayesian technique proposed in [2] is utilized as an approximative technique. A numerical example of a three-point bending case study is presented first to demonstrate the effectiveness of the proposed approach. The parameters of a gradient-enhanced damage material model [4] are identified using noisy synthetic data, and the effect of measurement noise is studied. The ability of the suggested approach on identifying constitutive parameters is then validated using real experimental data from a three-point bending test from [3]. The full field displacements required as input to the inference setup are extracted through a digital image correlation (DIC) analysis of the provided raw images. T2 - GACM-2023 - 10th GACM Colloquium on Computational Mechanics 2023 CY - Vienna, Austria DA - 10.09.2023 KW - Bayesian model updating KW - Full-field measurements KW - Gradient damage model PY - 2023 AN - OPUS4-58288 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strobl, Dominic A1 - Robens-Radermacher, Annika A1 - Ghnatios, Ch. A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Unger, Jörg F. T1 - Reduced Order Model with Domain Mapping for Temperature Field Simulation of Wire Arc Additive Manufacturing N2 - Additive manufacturing (AM) has revolutionized the manufacturing industry, offering a new paradigm to produce complex geometries and parts with customized properties. Among the different AM techniques, the wire arc additive manufacturing (WAAM) process has gained significant attention due to its high deposition rate and low equipment cost. However, the process is characterized by a complex thermal history, dynamic metallurgy, and mechanical behaviour that make it challenging to simulate it in real-time for online process control and optimization. In this context, a reduced order model (ROM) using the proper generalized decomposition (PGD) method is proposed as a powerful tool to overcome the limitations of conventional numerical methods and enable the real-time simulation of the temperature field of WAAM processes. Though, the simulation of a moving heat source leads to a hardly separable parametric problem, which is handled by applying a novel mapping approach. Using this procedure, it is possible to create a simple separated representation of the model, also allowing to simulate multiple layers. In this contribution, a PGD model is derived for the WAAM procedure simulating the temperature field. A good agreement with a standard finite element method is shown. The reduced model is further used in a stochastic model parameter estimation using Bayesian inference, speeding up calibrations and ultimately leading to a calibrated real-time simulation. T2 - SIM-AM 2023 CY - Munich, Germany DA - 26.07.2023 KW - Additive manufacturing KW - Reduced Order Model PY - 2023 AN - OPUS4-58253 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Robens-Radermacher, Annika A1 - Mezhov, Alexander A1 - Unger, Jörg F. A1 - Schmidt, Wolfram T1 - Temperature dependent modelling approach for early age behavior of printable mortars N2 - For extrusion-based 3D concrete printing, the early age mechanical behavior is influenced by various time dependent phenomena: structural build-up, plasticity as well as viscosity. The structural build-up is governing the stability and early-age strength development of the fresh printable cementitious materials and with that influencing the printability, buildability, and open time of the printing process. Generally, it is influenced by a number of factors, i.e. composition of the printable material, printing regime, and ambient conditions (temperature, humidity, etc.). There are several approaches to model the structural build-up of cementitious materials. All models are based on a time-dependent internal structural parameter describing the flocculation state, which is assumed to be zero after mixing and increases with time. The approaches differ in the definition of the time dependency (linear, exponential, bi-linear). Usually, the parameters are defined for a specific material composition without considering the influence of ambient conditions. In this contribution, the bi-linear structural build-up model [Kruger et al., Construction and Building Materials 224, 2019] is extended by the temperature influence. Temperature changes will occur in real life printing processes due to changing ambient conditions (summer, winter, day, night) as well as the printing process (pressure changes etc.) and have a significant impact on the structural build-up process: an increase of the temperature leads to a faster dissolution of cement phases, accelerates hydration and boosts the Brownian motion. For that reason, the model parameters are simulated as temperature dependent using an Arrhenius function. Furthermore, the proposed extended model is calibrated based on measurement data using Bayesian inference. A very good agreement of the predicted model data with the measured control data was reached. Additionally, the structural build-up model is integrated into a viscoelastic and elastoplastic mechanical model, simulating the whole mechanical behavior during layer deposition. T2 - Eighth International Symposium on Life-Cycle Civil Engineering (IALCCE 2023) CY - Milan, Italy DA - 03.07.2023 KW - 3D concrete printing KW - Material characterization KW - Structural build-up KW - Thixotropy KW - Model calibration PY - 2023 AN - OPUS4-58218 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strobl, Dominic A1 - Robens-Radermacher, Annika A1 - Ghnatios, C. A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Unger, Jörg F. T1 - Reduced Order Model for Temperature Field Simulation of Wire Arc Additive Manufacturing with Domain Mapping N2 - Additive manufacturing (AM) has revolutionized the manufacturing industry, offering a new paradigm to produce complex geometries and parts with customized properties. Among the different AM techniques, the wire arc additive manufacturing (WAAM) process has gained significant attention due to its high deposition rate and low equipment cost. However, the process is characterized by a complex thermal history making it challenging to simulate it in real-time for online process control and optimization. In this context, a reduced order model (ROM) using the proper generalized decomposition (PGD) method [1] is proposed as a powerful tool to overcome the limitations of conventional numerical methods and enable the real-time simulation of the temperature field of WAAM processes. These simulations use a moving heat source leading to a hardly separable parametric problem, which is handled by applying a novel mapping approach [2]. This procedure makes it possible to create a simple separated representation of the model, which allows to simulate multiple layers. In this contribution, a PGD model is derived for the temperature field simulation of the WAAM process. A good agreement with a standard finite element method is shown. The reduced model is further used in a stochastic model parameter estimation using Bayesian inference, speeding up calibrations and ultimately leading to a calibrated real-time simulation. T2 - MORTech 2023 - 6th International Workshop on Model Reduction Techniques CY - Paris, France DA - 22.11.2023 KW - Wire arc additive manufacturing KW - Reduced order modelling PY - 2023 AN - OPUS4-59105 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Andres Arcones, Daniel A1 - Weiser, M. A1 - Koutsoureladkis, D.-S. A1 - Unger, Jörg F. T1 - Evaluation of Model Bias Identification Approaches Based on Bayesian Inference and Applications to Digital Twins N2 - In recent years, the use of simulation-based digital twins for monitoring and assessment of complex mechanical systems has greatly expanded. Their potential to increase the information obtained from limited data makes them an invaluable tool for a broad range of real-world applications. Nonetheless, there usually exists a discrepancy between the predicted response and the measurements of the system once built. One of the main contributors to this difference in addition to miscalibrated model parameters is the model error. Quantifying this socalled model bias (as well as proper values for the model parameters) is critical for the reliable performance of digital twins. Model bias identification is ultimately an inverse problem where information from measurements is used to update the original model. Bayesian formulations can tackle this task. Including the model bias as a parameter to be inferred enables the use of a Bayesian framework to obtain a probability distribution that represents the uncertainty between the measurements and the model. Simultaneously, this procedure can be combined with a classic parameter updating scheme to account for the trainable parameters in the original model. This study evaluates the effectiveness of different model bias identification approaches based on Bayesian inference methods. This includes more classical approaches such as direct parameter estimation using MCMC in a Bayesian setup, as well as more recent proposals such as stat- FEM or orthogonal Gaussian Processes. Their potential use in digital twins, generalization capabilities, and computational cost is extensively analyzed. T2 - 5th ECCOMAS Thematic Conference on Uncertainty Quantificationin Computational Sciences and Engineering CY - Athens, Greece DA - 12.06.2023 KW - Digital Twin KW - Simulation Models KW - Uncertainty Quantification KW - Model Bias PY - 2023 UR - https://2023.uncecomp.org/ AN - OPUS4-58226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Diercks, Philipp A1 - Veroy, Karen A1 - Robens-Radermachre, Annika A1 - Unger, Jörg F. T1 - An efficient localized model order reduction framework for the shape optimization of additively manufactured lattice structures N2 - A common engineering practice is to optimize the geometry of a structure by an iterative process, in which an objective function is minimized by systematically choosing the value of design variables and computing the value of the objective function many times. However, regarding multiscale problems, this direct numerical approach is not feasible for a number of reasons. The model has to take into account both the structural and unit cell (UC) scale, because the objective function to be minimized is a global quantity, while the parameters are related to the shape or material parameters of the UC. In the absence of a clear separation of scales, the direct resolution of both scales in the numerical model leads to a significant increase in computational cost, which makes it impossible to repeatedly evaluate the model during the optimization process. The main goal of this contribution is to overcome the aforementioned limitations and develop a new efficient computational framework for the optimal design of lattice structures. To this end, parametric MOR is combined with DD methods. The change in geometry of each UC within the lattice is modelled by introducing a transformation that maps the reference to the physical domain. In offline simulations, suitable localized approximation spaces, that account for the change in geometry of the UC and its neighbours, are constructed using the concept of oversampling and random sampling. These are then integrated into a dual DD framework to derive a robust and scalable solver, i.e. a fast-to-evaluate reduced order model (ROM). The ROM is validated on the example of optimizing a concrete arc or pre-stressed multi beam structure minimizing its mass. T2 - 9th European Congress on Computational Methods in Applied Sciences and Engineering CY - Lisbon, Portugal DA - 03.06.2024 KW - Multiscale methods KW - Domain Decomposition KW - Model order reduction KW - Parameterized PDEs PY - 2024 AN - OPUS4-60412 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Robens-Radermacher, Annika A1 - Kujath, Cezary A1 - Bos, F. A1 - Mechtcherine, V. A1 - Unger, Jörg F. T1 - Advantages and challenges of data stores for interlaboratory studies – an example from mechanical test data of printed concrete structures N2 - Interlaboratory studies are common tools for collecting comparable data to implement standards for new materials or testing technologies. In the case of construction materials, these studies form the basis for recommendations and design codes. Depending on the study, the amount of data collected can be enormous, making manual handling and evaluation difficult. On the other hand, the importance of the FAIR (findable, accessible, interoperable, and reusable) principles for scientific data management, published by Wilkinson et al. in 2016, is constantly growing and changing the view on data usage. The benefits of using data management tools such as data stores/repositories or electronic laboratory notebooks are many. Data is stored in a structured and accessible way (at least within a group) and data loss due to staff turnover is reduced. Tools usually support data publishing and analysis interfaces. In this way, data can be reused years later to generate new knowledge with future insights. On the other hand, there are many challenges in setting up a data repository, such as selecting suitable software tools, defining the data structure, enabling data access, and understanding by others and ensuring maintenance, among others. This talk discusses the advantages and challenges of setting up and applying a data repository using the interlaboratory study on the mechanical properties of printed concrete structures carried out in RILEM TC 304-ADC as example. First, the definition of a suitable data structure including all information is discussed. The tool-dependent upload process is then described. Here, the data management system openBIS (open source software developed by ETH Zurich) is used. Since in most cases an open compute platform allowing access from different organisations is not possible or available due to data protection and maintenance issues, tool-independent export options are discussed and compared. Finally, the different query and analysis possibilities are demonstrated. T2 - RILEM spring convention & conference on advanced construction materials and processes for a carbon neutral society 2024 CY - Milan, Italy DA - 07.04.2024 KW - Data stores KW - Data structuring KW - Data evaluation KW - Automatization KW - Interlaboratory PY - 2024 UR - https://www.rilem.net/agenda/rilem-spring-convention-conference-on-advanced-construction-materials-and-processes-for-a-carbon-neutral-society-1530 AN - OPUS4-59906 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meng, Birgit A1 - Pirskawetz, Stephan A1 - Tamsen, Eric A1 - Unger, Jörg F. T1 - Betondesign digital - Potenziale für das Bauwesen N2 - Beton ist weltweit einer der wichtigsten Konstruktionswerkstoffe und zeichnet sich durch eine enorme Anpassungsfähigkeit an sich verändernde Anforderungen aus. Damit verbunden ist eine hohe und kontinuierlich zunehmende Komplexität hinsichtlich der Ausgangsstoffe, Rezepturen und des Herstellungsprozesses. Folglich setzt eine Ausschöpfung des technischen und umweltbezogenen Potenzials der Betonbauweise höchste Expertise bei den Einzelakteuren der Bauindustrie voraus. T2 - MatFo2022 „Vom Material zur Innovation: Digital, Neutral, Vital“ CY - Cologne, Germany DA - 14.11.2022 KW - Beton KW - Zement KW - Digitalisierung KW - Ontologien PY - 2022 UR - https://www.werkstofftechnologien.de/veranstaltungen/matfo2022-vom-material-zur-innovation-digital-neutral-vital AN - OPUS4-59140 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. T1 - Coupling of structural and material design N2 - The presentations discusses a use case for the optimization of concrete structures where structural and material design are integrated in a computational workflow. The workflow is based on both physics-based and data-based models and experimental data is used to calibrate/train these models with a specific focus on the integration of ucertainties. T2 - 2nd Technical Meeting of TG.SAG.2 CY - Hannover, Germany DA - 16.04.2024 KW - Coupling of structural and material design KW - Cement Hydration Model PY - 2024 AN - OPUS4-59999 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Diercks, Philipp A1 - Veroy, K. A1 - Robens-Radermacher, Annika A1 - Unger, Jörg F. T1 - Reduced order Approximations of fine scale edge basis functions within a variational multiscale approach N2 - In analyzing large scale structures, it is necessary to take into account the material heterogeneity for accurate failure prediction. However, this greatly increases the degrees of freedom in the numerical method thus making it infeasible. Moreover, in applications where scale separation as the basis of classical homogenization schemes does not hold, the influence of the fine scale on the coarse scale has to be modelled directly. This work aims to develop an efficient methodology to model heterogeneous structures combining the variational multiscale method and model order reduction techniques. Superposition-based methods assume a split of the solution field into coarse and fine scale contributions. In deriving practical methods, some form of localization is necessary to eliminate the fine-scale part from the coarse-scale equation. Hund and Ramm [2] discussed different locality constraints and in particular zero jump conditions enforced by a Lagrange-type method leading to a coupled solution scheme. In this contribution, a combination of the variational multiscale method and model order reduction techniques is applied to model the influence of the fine scale on the coarse scale directly. First, possible coarse and fine scale solutions are exploited for a representative volume element (RVE), specific to the material of interest, to construct local approximation spaces. For the local fine scale spaces different choices are presented, which ensure continuity between adjacent coarse grid elements. Therefore,the resulting global system takes into account, the effect of the fine scale on the coarse scale, is sparse and has much lower dimensions compared to the full system in the direct numerical simulation. The authors gratefully acknowledge financial support by the German Research Foundation (DFG), project number 394350870. This result is part of a project that has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement No. 818473). T2 - COMPLAS 2021 CY - Berlin, Germany DA - 07.09.2021 KW - Multiscale methods KW - Variational multiscale method KW - Model order reduction PY - 2021 AN - OPUS4-53289 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Streeck, C. A1 - Nutsch, A. A1 - Weser, J. A1 - Dietrich, Paul A1 - Rurack, Knut A1 - Beckhoff, B. T1 - Reference-free total reflection X-ray fluorescence analysis for quantification of functional groups on surfaces for bioanalytical applications T2 - ALTECH Symposium 2014 - Analytical techniques for precise characterization of nanomaterials, EMRS Spring Meeting 2014 CY - Lille, France DA - 2014-05-26 PY - 2014 AN - OPUS4-30971 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rurack, Knut A1 - Fischer, Tobias A1 - Dietrich, Paul A1 - Unger, Wolfgang A1 - Streeck, C. A1 - Nutsch, A. A1 - Weser, J. A1 - Beckhoff, B. T1 - Reference-free total reflection X-ray fluorescence analysis for surface functional group quantification of funtional groups on surfaces for bio-analytical applications T2 - E-MRS 2014 Spring Meeting CY - Lille, France DA - 2014-05-26 PY - 2014 AN - OPUS4-30787 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Choi, Changrok A1 - Park, J. S. A1 - Lippitz, Andreas A1 - Jung, D. A1 - Lee, T. G. A1 - Unger, Wolfgang T1 - Surface characterization of amine modified plasma PEG polymer by plasma blending technique T2 - 9th European Workshop on Secondary Ion Mass Spectrometry - SIMS Europe 2014 CY - Münster, Germany DA - 2014-09-07 PY - 2014 AN - OPUS4-31456 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Metrology for Surface Chemical Analysis at the Nanoscale: Status and Challenges T2 - ALTECH Symposium 2014 - Analytical techniques for precise characterization of nanomaterials, EMRS Spring Meeting 2014 CY - Lille, France DA - 2014-05-26 PY - 2014 AN - OPUS4-30970 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sobol, Oded A1 - Straub, Franka A1 - Holzlechner, Gerald A1 - Böllinghaus, Thomas A1 - Unger, Wolfgang T1 - In-situ elucidation of Deuterium flux in 2205 duplex stainless steel by secondary ion mass spectrometry T2 - SIMS Europe 2014 CY - Münster, Germany DA - 2014-09-07 PY - 2014 AN - OPUS4-31398 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Metrology for spatially resolved chemical analysis at the micro and nanometre scales T2 - CCQM Plenary Meeting 2014 CY - Paris, France DA - 2014-04-10 PY - 2014 AN - OPUS4-30969 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Wirth, Thomas A1 - Terborg, R. A1 - Kim, K. Y. A1 - Unger, Wolfgang T1 - Measurement of atomic fractions in Cu(In, Ga)Se2 films by Auger Electron Spectroscopy (AES) und Energy Dispersive Electron Probe Microanalysis (ED-EPMA) T2 - Microscopy and Microanalysis M&M 2014 CY - Hartford, CT, USA DA - 2014-08-02 PY - 2014 AN - OPUS4-31467 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzweber, Markus A1 - Traulsen, Christoph Hans-Henning A1 - Heinrich, T. A1 - Schalley, C. A. A1 - Unger, Wolfgang T1 - PCA assisted TOF-SIMS investigation of thin organic-inorganic (multi)layer systems T2 - 9th European Workshop on Secondary Ion Mass Spectrometry - SIMS Europe 2014 CY - Münster, Germany DA - 2014-09-07 PY - 2014 AN - OPUS4-31466 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Marineko, R. A1 - Rackwitz, Vanessa A1 - Bremser, Wolfram A1 - Unger, Wolfgang T1 - Determination of the k-Values of Cu-Au Alloys with ED- and WD-EPMA - Results of an inter-laboratory comparison T2 - Microscopy and Microanalysis M&M 2014 CY - Hartford, CT, USA DA - 2014-08-02 PY - 2014 AN - OPUS4-31470 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Titscher, Thomas A1 - Unger, Jörg F. T1 - Concrete mesostructure geometry modelling with growing and colliding hard spheres T2 - 11th World Congress on Computational Mechanics (WCCM XI); 5th European Conference on Computational Mechanics (ECCM V); 6th European Conference on Computational Fluid Dynamics (ECFD VI) CY - Barcelona, Spanien DA - 2014-07-20 PY - 2014 AN - OPUS4-32897 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Metrology for Surface Chemical Analysis at the Nanoscale: Status and Challenges T2 - AVS 61th International Symposium, Applied Surface Science Session CY - Baltimore, United States of Amercia DA - 2014-11-09 PY - 2014 AN - OPUS4-32394 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Establishing of reference methods and materials for toxilogical testing and physical-chemical characterisation of ENPs T2 - NanoValid 2nd technical review meeting CY - Brussels, Belgium DA - 2014-11-26 PY - 2014 AN - OPUS4-32393 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Options for standards for physical-chemical characterization of ENPs derived from NanoValid achievements T2 - CEN-CENELEC NanoValid Standardization Workshop CY - Brüssel, Belgium DA - 2014-11-28 PY - 2014 AN - OPUS4-32391 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lange, Nele A1 - Dietrich, Paul A1 - Holzweber, Markus A1 - Unger, Wolfgang A1 - Kulak, N. T1 - Selective Modifiction of Silicon Nitride using Click-Chemistry T2 - Potsdam Days on Bioanalysis 2014 CY - Potsdam, Germany DA - 2014-11-06 PY - 2014 AN - OPUS4-32120 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nietzold, Carolin A1 - Dietrich, Paul A1 - Lippitz, Andreas A1 - Panne, Ulrich A1 - Unger, Wolfgang A1 - Kamalakumar, A. A1 - Blanchard, V. T1 - XPS and NEXAFS study of biointerfaces for microarray applications T2 - BESSY user meeting 2014 CY - Berlin, Germany DA - 2014-12-04 PY - 2014 AN - OPUS4-32395 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Surface Chemical Analysis at BAM: R&D, Metrology, Standardization T2 - Analytikseminar, Insitute of Chemical Technologies and Analytics, Vienna University of Technology CY - Vienna, Austria DA - 2015-01-09 PY - 2015 AN - OPUS4-32927 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzweber, Markus A1 - Jungnickel, H. A1 - Unger, Wolfgang T1 - Organic Depth Profiling using large Argon Cluster Ion Beams T2 - 15th European Conference on Applications of Surface and Interface Analysis 2013 (ECASIA) CY - Forte Village Resort, Italia DA - 2013-10-13 PY - 2013 AN - OPUS4-32945 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -