TY - CONF A1 - Unger, Wolfgang A1 - Darlatt, Erik A1 - Traulsen, C. H.-H. A1 - Richter, S. A1 - Poppenberg, J. A1 - Heinrich, T. A1 - Schalley, C. A. T1 - Controlled Layer-by-Layer Assembly of Tetraactram Macrocycles based on Coordination Chemistry T2 - 15th European Conference on Applications of Surface and Interface Analysis CY - Cagliari, Italy DA - 2013-10-13 PY - 2013 AN - OPUS4-29557 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rades, Steffi A1 - Wirth, Thomas A1 - Unger, Wolfgang T1 - Investigation of Nanoparticles by Auger electron spectroscopy (AES) T2 - 15th European Conference on Applications of Surface and Interface Analysis (ECASIA 13) CY - Cagliari, Italy DA - 2013-10-13 PY - 2013 AN - OPUS4-30131 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzweber, Markus A1 - Lippitz, Andreas A1 - Unger, Wolfgang T1 - Investigation of the Liquid Surface Structure of Ionic Liquids by ERXPS and NEXAFS T2 - 5th Joint BER II and BESSY II User Meeting CY - Berlin, Germany DA - 2013-12-04 PY - 2013 AN - OPUS4-29959 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang T1 - Metrology for Nano-Analysis: Establishing Reference Methods for Characterizing Nano-Materials T2 - Workshop on Advanced Characterization of Nanomaterials CY - Zaragoza, Spain DA - 2013-09-19 PY - 2013 AN - OPUS4-29865 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Titscher, Thomas A1 - Robens-Radermacher, Annika A1 - Coelho Lima, Isabela T1 - Stochastische Modellkalibrierung eines digitalen Zwillings N2 - Motivation: Ein Digitaler Zwilling repräsentiert ein reales Objekt in der digitalen Welt. Die Digitalen Zwillinge sind aus Daten und Modellen/Algorithmen aufgebaut und kontinuierlich über Sensoren mit der realen Welt gekoppelt. Anwendung z.B. Modellbewertung, Monitoring, Schadensdetektion. T2 - VIPO Symposium 2021 CY - Bauhaus-Universität Weimar DA - 09.07.2021 KW - Digitaler Zwilling KW - Modellkalibrierung KW - Modelanpassung KW - Bayesian Inferenz PY - 2021 AN - OPUS4-53063 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Titscher, Thomas A1 - Coehlo Lima, Isabela A1 - Unger, Jörg F. T1 - Model selection and model calibration for a digital twin N2 - The quality of a model - and thus its predictive capabilities - is influenced by numerous uncertainties. They include possibly unknown boundary and initial conditions, noise in the data used for its calibration and uncertainties in the model itself. Here, the latter part is not only restricted to uncertain model parameters, but also refers to the choice of the model itself. Inferring these uncertainties in an automatic way allows for an adaption of the model to new data sets and for a reliable, reproducible model assessment. Note that similar concepts apply at the structural level, where a continuously updated digital twin allows virtual measurements at inaccessible positions of the structure and a simulation based lifetime prediction. This work presents an inference workflow that describes the difference of measured data and simulated model responses with a generic interface that is independent from the specific model or even the geometry and can easily incorporate multiple data sources. A variational Bayesian inference algorithm is then used to a) calibrate a set of models to given data and to b) identify the best fitting one. The developed concepts are applied to a bridge Demonstrator equipped with displacement sensors, force sensors and a stereophotogrammetry system to perform a system identification of the material parameters as well as a real-time identification of a moving load. T2 - 6th GAMM AG Data Workshop CY - Berlin, Germany DA - 20.10.2020 KW - Digital twin KW - Demonstrator PY - 2020 AN - OPUS4-51532 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Titscher, Thomas A1 - Robens-Radermacher, Annika A1 - Muth, Thilo A1 - Coelho Lima, Isabela T1 - Stochastische Modellkalibrierung eines digitalen Zwillings N2 - Ein Digitaler Zwilling repräsentiert ein reales Objekt in der digitalen Welt. Die Digitalen Zwillinge sind aus Daten und Modellen/Algorithmen aufgebaut und kontinuierlich über Sensoren mit der realen Welt gekoppelt. Anwendung z.B. Modellbewertung, Monitoring, Schadensdetektion. T2 - DVM-Online-Workshop "Grundlagen und Beispiele zur Digitalisierung für die Materialforschung und -prüfung" CY - Online meeting DA - 20.10.2020 KW - Modellkalibrierung KW - Stochastischen Verfahren KW - Realtime model updating KW - Demonstrator PY - 2020 AN - OPUS4-52175 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stockmann, Jörg M. A1 - Radnik, Jörg A1 - Bütefisch, S. A1 - Busch, I. A1 - Weimann, T. A1 - Passiu, C. A1 - Rossi, A. A1 - Unger, Wolfgang T1 - New Test Specimen for the Determination of the Field of View of Small-Area XPS N2 - Small-area/spot photoelectron spectroscopy (SAXPS) is a powerful tool for the investigation of small surface features like microstructures of electronic devices, sensors or other functional surfaces. For evaluating the quality of such microstructures, it is crucial to know whether a small signal in a spectrum is an unwanted contamination of the field of view (FoV), defined by the instrument settings, or it originated from outside. The aperture has a major influence on the signal-contribution from the outside. For the evaluation of the FoV, we determined the Au4f intensities measured with the center of the FoV aligned with the center of the spot and normalized to the Au4f intensity determined on the Au-film. With this test specimen, it was possible to characterize the FoV: The signal-contribution from the outside is reduceable down to lower than 50 %, when the aperture is 30 % of the structure dimension for our Kratos AXIS Ultra DLD system. T2 - Kratos User's Meeting 2020 CY - Online meeting DA - 21.09.2020 KW - Small Area XPS KW - Reference Material KW - Imaging XPS KW - Field of View PY - 2020 AN - OPUS4-51413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Robens-Radermacher, Annika A1 - Held, Felix A1 - Coelho Lima, Isabela T1 - Efficient reliability analysis with model reduction techniques N2 - One of the most important goals in civil engineering is to guaranty the safety of constructions. National standards prescribe a required failure probability in the order of 10-6 (e.g. DIN EN 199:2010-12). The estimation of these failure probabilities is the key point of structural reliability analysis. Generally, it is not possible to compute the failure probability analytically. Therefore, simulation-based methods as well as methods based on surrogate modelling or response surface methods have been developed. Nevertheless, these methods still require a few thousand evaluations of the structure, usually with finite element (FE) simulations, making reliability analysis computationally expensive for relevant applications. The aim of this contribution is to increase the efficiency of structural reliability analysis by using the advantages of model reduction techniques. Model reduction is a popular concept to decrease the computational effort of complex numerical simulations while maintaining a reasonable accuracy. Coupling a reduced model with an efficient variance reducing sampling algorithm significantly reduces the computational cost of the reliability analysis without a relevant loss of accuracy. T2 - MathMet2019 CY - Lisbon, Portugal DA - 20.11.2019 KW - Reliability method KW - Numerical example PY - 2019 AN - OPUS4-49989 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Müller, Anja A1 - Heinrich, Thomas A1 - Tougaard, S. A1 - Werner, W. S. M. A1 - Hronek, M. A1 - Kunz, Valentin A1 - Benemann, Sigrid A1 - Hodoroaba, Vasile-Dan A1 - Radnik, Jörg A1 - Stockmann, Jörg M. A1 - Nirmalananthan-Budau, Nithiya A1 - Geißler, Daniel A1 - Sparnacci, K. A1 - Unger, Wolfgang T1 - Determining thickness and completeness of the shell for polymer core shell nanoparticles by XPS, ToF SIMS and T SEM N2 - Core-shell nanoparticles (CSNPs) have become indispensable in various industrial applications. However, their real internal structure usually deviates from an ideal core-shell structure. To control how the particles perform with regard to their specific applications, characterization techniques are required that can distinguish an ideal from a non-ideal morphology. In this work, we investigated PTFE-PMMA (four samples) and PTFE-PS (six samples) polymer CSNPs with constant core diameter (45 nm) but varying shell thickness (4-50 nm). As confirmed by transmission scanning electron microscopy (T-SEM), the shell completely covers the core for the PTFE-PMMA nanoparticles, while the encapsulation of the core by the shell material is incomplete for the PTFE-PS nanoparticles. X-ray photoelectron spectroscopy (XPS) was applied to determine the shell thickness of the nanoparticles. The software SESSA V2.0 was used to analyze the intensities of the elastic peaks and the QUASES software package to evaluate the shape of the inelastic background in the XPS Survey spectra. For the first time, nanoparticle shell thicknesses are presented which are exclusively based on the analysis of the XPS inelastic background. Furthermore, principal component analysis (PCA) assisted time-of-flight secondary ion mass spectrometry (ToF-SIMS) of the PTFE-PS nanoparticle sample set revealed a systematic variation among the samples and, thus, confirmed the incomplete encapsulation of the core by the shell material. Opposed to that, no variation is observed in the PCA scores plots of the PTFE-PMMA nanoparticle sample set. Consequently, the complete coverage of the core by the shell material is proved by ToF-SIMS with a certainty that cannot be achieved by XPS and T-SEM. T2 - 18th European Conference on Applications of Surface and Interface Analysis (ECASIA) CY - Dresden, Germany DA - 15.09.2019 KW - Core-shell nanoparticles KW - Polymers KW - ToF-SIMS KW - XPS KW - XPS background analysis PY - 2019 AN - OPUS4-49187 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Diercks, Philipp A1 - Robens-Radermacher, Annika A1 - Unger, Jörg F. T1 - A hyper reduced domain decomposition approach for modeling nonlinear heterogeneous structures N2 - Many of today's problems in engineering demand reliable and accurate prediction of failure mechanisms of mechanical structures. Herein it is necessary to take into account the often heterogeneous structure on the fine scale, to capture the underlying physical phenomena. However, an increase of accuracy by dissolving the fine scale inevitably leads to an increase in computational cost. In the context of multiscale simulations, the FE2 method is widely used. In a two-level computation, the fine scale is depicted by a boundary value problem for a representative volume element (RVE), which is then solved in each integration point of the macro scale to determine the macroscopic response. However, the FE2 approach in general is computationally expensive and problematic in the special case of concrete structures. Here rather large RVEs are necessary to sufficiently represent the meso-structure, such that separation of scales cannot be assumed. Therefore, the aim is to develop an efficient approach to modeling nonlinear heterogeneous structures using domain decomposition and reduced order modeling. T2 - ECCOMAS Young Investigators Conference 2019 CY - Krakow, Poland DA - 01.09.2019 KW - Model order reduction KW - Proper orthogonal decomposition KW - Discrete empirical interpolation method KW - Multiscale KW - Domain Decomposition PY - 2019 AN - OPUS4-48942 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nymark, P. A1 - Hongisto, V. A1 - Radnik, Jörg A1 - Unger, Wolfgang A1 - Kohonen, P. A1 - Haase, A. A1 - Jensen, K. A. A1 - Grafström, R. T1 - Grouping of representative nanomaterials is efficiently executed by combining high-throughput-generated biological data with physicochemical data N2 - Grouping of nanomaterials (NM) promises to serve effectively to reduce the extensive safety testing needs associated with regulatory risk assessment. Key challenges in this task are how to rapidly and cost-efficiently generate the needed data, and how to best combine structural material characteristics with biological effects data. Herein, we performed NM grouping from combining existing physiochemical data with high-throughput screening (HTS)-derived hazard assessment data generated in the human lung epithelial cell line BEAS-2B. Twenty-one NMs from the European Joint Research Centre´s Representative Nanomaterials Repository (diverse nanoforms of substances ZnO, SiO2 and TiO2) and five reference chemicals were analyzed by HTS assays for cytotoxicity/cell viability (CellTiterGlo, Dapi-staining), oxidative stress (8-OHdG), apoptosis (Caspase-3), and DNA damage repair (γH2AX). Additionally, physicochemical data relevant for grouping of NMs under REACH (ECHA, 2017 Appendix R.6-1) were collated for 15 of the NMs, including from EU-funded projects (NanoReg2, caLIBRAte) and the OECD Testing Programme of Nanomaterials. The diverse data types were scaled, normalized and integrated using a newly developed scoring pipeline inspired by the US-EPA Toxicological Prioritization Index (ToxPi). Results demonstrated that the in vitro-derived hazard data permitted substance-based grouping of the selected NMs, whereas integration of physicochemical data deepened the grouping of specific nanoforms within each substance group. Furthermore, a case study on 10 TiO2 NMs showed that hazard-based grouping allowed for read across of physicochemical data between 6 NMs acting as source nanoforms and 4 NMs acting as target nanoforms. The ToxPi tool and scoring pipeline permitted transparent visualization of the final grouping, while giving equal weight to different types of data/results related to structure and biology. Overall, this study aligns fully with the ECHA recommendations for grouping of NM (Appendix R.6-1), i.e. i) to aim at identification of criteria for grouping nanoforms (and non-nanoforms) within one substance, and ii) to provide additional information beyond physicochemical data to support read across between nanoforms. T2 - Eurotox 2019 CY - Helsinki, Finland DA - 08.09.2019 KW - Grouping KW - Nanomaterials KW - Regulatory risk assesment KW - High-throughput screening PY - 2019 AN - OPUS4-49439 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Robens-Radermacher, Annika A1 - Held, Felix A1 - Unger, Jörg F. T1 - Efficient reliability analysis by combining uncertain measurement data, Bayesian model updating and reduced order modeling N2 - The efficiency of structural model updating and the subsequent reliability analysis is increased by using the advantages of reduced order models. Coupling a reduced model of the structure of interest with a Bayesian model updating approach or an reliability analysis to estimate the failure probability reduce the computational cost of such complex analyses drastically. T2 - 8th Workshop on High-Dimensional Approximation (HDA) 2019 CY - Zurich, Switzerland DA - 09.09.2019 KW - Reduced order modeling KW - Bayesian model updating PY - 2019 AN - OPUS4-49035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Radnik, Jörg A1 - Kunz, Valentin A1 - Schneider, Markus A1 - Nymark, Penny A1 - Grafström, Roland A1 - Unger, Wolfgang T1 - Combining surface analytic and toxicity data for safer nanomaterials N2 - Nanomaterials are present in our everyday life. Paint coats, sunscreens, catalysts and additives for tyres are good examples for the use of such materials in mass-market products. The problem of the safety of nanomaterials is recognized as a problem for health and environment, which lead to the special registration of nanomaterials according to an annex of REACH as of 2020. But a great problem for the risk assessment of nanomaterials that several factors could influence the hazardous nature of them. Additional to composition, crystal structure, size and shape the surface properties of such particles belong to these parameters for risk assesment. The reason for the relevance of the surface is obvious: the smaller the particle, the higher is the share of the surface. Additionally, the surface is the region of the particle which interacts with the surrounding which is another crucial factor for the understanding the effect of a nanomaterial on health and environment. In the OECD Testing Programme on Manufactured Nanomaterials exists consequently an Endpoint 4.30 Surface Chemistry in Chapter 4. PHYSICAL AND CHEMICAL PROPERTIES. In summary, there is obviously a need for a correlation between surface chemical analytic data and toxicity. To fill in this gap, we present surface analytic results obtained with X-ray photoelectron spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry and correlate them with cytotoxic data gain by high-throughput screening experiments. It must be noted, that these experiments were done at the same set of titania materials taken from the JRC (Joint Research Centre of the European Union) Nanomaterials Repository. As material TiO2 was chosen due to its widespread use in consumer products, e.g. paint coats and sunscreens. With this new approach a better understanding of the influence of surface properties on the toxicity can be expected leading to a better risk assessment of these materials. T2 - ECASIA 2019 CY - Dresden, Germany DA - 15.09.2019 KW - Risk assessment KW - Nanomaterials KW - Surface analytic KW - Toxicology PY - 2019 AN - OPUS4-49090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kjaervik, Marit A1 - Dietrich, P. A1 - Thissen, A. A1 - Schwibbert, Karin A1 - Brown, J. A1 - Hardie, K. A1 - Unger, Wolfgang T1 - Model systems and sample preparation for surface characterisation of bacteria and biofilms by near-ambient pressure XPS N2 - Bacterial samples are typically freeze dried or cryo-prepared prior to XPS analysis to allow for measurements in ultra-high vacuum (UHV). The sample environment in the near-ambient pressure (NAP) XPS instrument EnviroESCA allows for measurements in up to 15 mbar water vapor, thus, sample preparation is no longer restricted to UHV-compatible techniques. For instance, biofilms grown in medium can be transferred directly from the medium to the measurements chamber, maintaining a humid environment throughout the measurements. Considering the complexity of bacterial samples, sample preparation must be carefully considered in order to obtain meaningful and reproducible results. In this talk, various strategies for sample preparation of bacteria and biofilms for NAP-XPS measurements will be discussed. Model systems of planktonic bacteria, artificial biofilms resembling the exopolysaccharide matrix and biofilms have been characterised in various conditions. The stability and homogeneity of the samples was assessed by monitoring the C1s core level peak at different sample locations. The quality of the XPS-spectra is also influenced by the gas environment, which will be exemplified by core level spectra of P. Fluorescens acquired in air, water vapor and ultra-high vacuum. T2 - 18th European conference on applications of surface and interface analysis (ECASIA) CY - Dresden, Germany DA - 15.09.2019 KW - NAP-XPS KW - Biofilms KW - Bacteria KW - E. coli KW - XPS PY - 2019 AN - OPUS4-49189 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stockmann, Jörg M. A1 - Radnik, Jörg A1 - Bütefisch, S. A1 - Busch, I. A1 - Passiu, C. A1 - Rossi, A. A1 - Unger, Wolfgang T1 - A new reference material for the determination of the Field of View of Small Area XPS N2 - Small Area Photoelectron Spectroscopy (XPS) is a powerful tool for investigating small surface features. It is often unclear, if the signal in the spectrum is an unwanted contamination of the Field of View (FoV) or is it originated from outside. The reason is, that XPS-spectra are affected by beam shapes. Scheithauer proposed to measure Pt apertures of different diameters and normalize the Pt4f count rate by a second measurement on the Pt metal. New reference materials were developed and tested in the VAMAS TWA2 A22 Project. T2 - ECASIA 2019 CY - Dresden, Germany DA - 15.09.2019 KW - Reference material KW - Small Area XPS KW - Selected Area XPS KW - Small Spot XPS KW - Field of Analysis PY - 2019 AN - OPUS4-49236 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Titscher, Thomas A1 - Robens-Radermacher, Annika A1 - Strobl, Dominik A1 - Klawonn, Alexander A1 - Tamsen, Erik A1 - Jafari, Abbas A1 - Rosenbusch, Sjard Mathis T1 - Digital Twins for monitoring purposes N2 - In materials and component research, artificial intelligence methodologies will lead to massive upheavals in the coming years. The processes of material development, material processing, lifetime prediction and material characterization will change significantly. By combining AI methods and new forms of knowledge representation, the data-based management of product life cycles will take on new qualities. To address this emerging field of research Fraunhofer IWM set up the online workshop »AI Methods for Fatigue Behavior Assessment and Component Lifetime Prediction« T2 - Workshop “AI for materials fatigue assessment and machine component lifetime prediction” CY - Online meeting DA - 24.11.2021 KW - Digital twin KW - Model calibration KW - Parameter estimation KW - Ontology for model calibration PY - 2021 AN - OPUS4-53846 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Coehlo Lima, Isabela A1 - Jafari, Abbas A1 - Titscher, Thomas A1 - Robens-Radermacher, Annika T1 - Digital twins for monitoring purposes - uncertainty, model bias and model order reduction N2 - A safe and robust performance is a key criterion when building and maintaining structures and component. Ensuring this criterion at different stages of the lifetime can be supported by applying continuous monitoring concepts. The latter usually can serve multiple purposes, including the determination of material parameters for the design phase, the evaluation of the actual loading/environmental conditions (instead of using conservative estimates that are usually larger) and evaluating or predicting the true performance of the structure (thus decreasing the model bias). In this context, a digital twin of the structure has many benefits. It allows to introduce virtual sensors to “measure” sensor information that is e.g. inaccessible or unmeasureable. In order to efficiently use monitoring techniques in the context of a digital twin, it is important to consider the complete chain of information including the choice of sensors, the data processing and structuring, the modelling assumptions, the numerical simulation and finally the stochastic nature of the model prediction. In this presentation, challenges in this context are discussed with a specific focus on Bayesian model updating of the digital twin, accounting for both parameter updates as well as model bias that results from the limitations of modelling assumption. A bottleneck in this approach is the computational effort related to sampling methods such as Markov chain Monte Carlo methods that require many evaluations of the forward model. An alternative to the expensive computation of the forward model for updating the digital twin is the combination with model reduction techniques such as the Proper General Decomposition [1, 2]. The results are illustrated for several examples and scale, ranging from digitals twin for material tests in the lab over lab scale structural digital twins up to damage identification in field experiments. T2 - MMLDT-CSET 2021 Mechanistic Machine Learning and Digital Twins for Computational Science, Engineering & Technology CY - San Diego, CA, USA DA - 26.09.2021 KW - Digital twin for monitoring purposes KW - Model bias KW - Model order reduction PY - 2021 AN - OPUS4-53881 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jafari, Abbas A1 - Titscher, Thomas A1 - Chatzi, E. A1 - Unger, Jörg F. T1 - Variational Bayesian inference of a gradient-enhanced damage material model N2 - A finite element model is calibrated in terms of parameters of the constitutive law; namely the gradient damage model. The method of Variational Bayesian is used for this purpose. The study has been done based on synthetic data. T2 - YIC Young Investigators Conference CY - Online meeting DA - 07.07.2021 KW - Stochastic inference KW - Material model updating KW - Variational Bayesian KW - Gradient-enhanced damage PY - 2021 UR - https://yic2021.upv.es/ AN - OPUS4-54033 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jafari, Abbas A1 - Titscher, Thomas A1 - Chatzi, E. A1 - Unger, Jörg F. T1 - Stochastic parameter estimation of a gradient-enhanced damage material model of concrete using variational Bayesian inference N2 - A gradient-enhanced damage material model for concrete simulated by means of the finite element (FE) method is calibrated with respect to important parameters of the involved constitutive law by using the Variational Bayesian method. T2 - UNCECOMP - 4th International Conference on Uncertainty Quantification in Computational Sciences and Engineering CY - Online meeting DA - 28.06.2021 KW - Stochastic model updating KW - Variational Bayesian KW - Gradient-enhanced damage KW - Concrete PY - 2021 AN - OPUS4-54034 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. T1 - Combining Data and Simulation Models in real time - A Digital Twin for Bridge monitoring N2 - Im Rahmen des Vortrages wurde das Konzept eines digitalen Zwillings vorgestellt und an verschiedenen Beispielen angefangen von einem Laborversuch über Kleinversuche bis zum Realmaßstab dargestellt. N2 - During the lecture, the concept of a digital twin was presented and illustrated with various examples starting from a laboratory experiment to small-scale and real-scale experiments. T2 - EURAD Second Annual Event (2022) CY - Online meeting DA - 28.03.2022 KW - Digital Twin KW - Bridge Monitoring KW - Simulation Models PY - 2022 UR - https://igdtp.eu/event/eurad-annual-event-2/ AN - OPUS4-54639 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Titscher, Thomas A1 - Robens-Radermacher, Annika A1 - Unger, Jörg F. T1 - Model calibration and damage detection for a digital twin N2 - Numerical models are an essential tool in predicting and monitoring the behavior of civil structures. Inferring the model parameters is a challenging tasks as they are often measured indirectly and are affected by uncertainties. Digital twins couple those models with real-world data and can introduce additional, systematic sensor uncertainties related to the sensor calibration, i.e. uncertain offsets and calibration factors. In this work, the challenges of data processing, parameter identification, model selection and damage detection are explored using a lab-scale cable stayed bridge demonstrator. By combining force measurements in the cables with displacement measurements from both laser and stereo-photogrammetry systems, the elastic parameters of a three-dimensional finite element beam model are inferred. Depending on the number of sensors and the number of datasets used, parametrizing the sensor offsets and factors, leads to model with over 100 parameters. With a real-time solution of the problem in mind, a highly efficient analytical variational Bayesian approach is used to solve it within seconds. An analysis of the required assumptions and limitations of the approach, especially w.r.t. to the computed evidence, is provided by a comparison with dynamic nested sampling in a simplified problem. Finally, by inferring the value of additional damage parameters along the bridge, the method is successfully used to detect the location of an artificially introduced weak spot in the demonstrator bridge. T2 - ECCOMAS 2022 CY - Oslo, Norway DA - 05.06.2022 KW - Bayesian identification KW - Digital twin KW - Variational Bayesian KW - Damage detection PY - 2022 AN - OPUS4-55083 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. Herein, it is necessary to take into account the heterogeneous structure on the lower scale, to capture the underlying physical phenomena. However, this poses a great challenge to the numerical solution as the computational cost is significantly increased by resolving the lower scale in the model. Moreover, in applications where scale separation as the basis of classical homogenization schemes does not hold, the influence of the lower scale on the upper 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 lower scale on the upper 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 lower scale, is introduced. Second, reduced approximation spaces for the upper and lower scale solution are constructed by exploring possible solutions for each subdomain based on a representative unit cell. 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. The authors gratefully acknowledge financial support by the German Research Foundation (DFG), project number 394350870, and by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Grant agreement No. 818473). T2 - The 8th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS) 2022 CY - Oslo, Norway DA - 05.06.2022 KW - Multiscale methods KW - Variational multiscale method KW - Domain decomposition KW - Model order reduction PY - 2022 AN - OPUS4-55117 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Robens-Radermacher, Annika A1 - Coelho Lima, Isabela A1 - Unger, Jörg F. T1 - Efficient model identification using a PGD forward model - Influence of surrogate accuracy and converergence approach N2 - There is a rising attention of using numerical models for effcient structural monitoring and ensuring the structure's safety. Setting up virtual models as twin for real structures requires a model identification process calculating the unknown model parameters, which mostly are only indirectly measurable. This is a computationally very costly inverse optimization process, which often makes it unfeasible for real applications. Effcient surrogate models such as reduced order models can be used, to overcome this limitation. But the influence of the model accuracy on the identification process has then to be considered. The aim is to automatically control the influence of the model's accuracy on the identification. Here, a variational Bayesian inference approach[3] is coupled with a reduced forward model using the Proper Generalized Decomposition (PGD) method. The influence of the model accuracy on the inference result is studied and measured. Therefore, besides the commonly used Bayes factor the Kullback-Leibler divergences between the predicted posterior pdfs are proposed. In an adaptive inference procedure, the surrogate's accuracy is iteratively increased, and the convergence of the posterior pdf is analysed. The proposed adaptive identification process is applied to the identification of spatially distributed damage modeled by a random eld for a simple example with synthetic data as well as a small, reinforced bridge with real measurement data. It is shown that the proposed criteria can mirror the influence of the model accuracy and can be used to automatically select a suffciently accurate surrogate model. T2 - The 8th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS) 2022 CY - Oslo, Norway DA - 05.06.2022 KW - Model order reduction KW - Model identification KW - Bayes factor KW - PGD KW - Kullback-Leibner divergence PY - 2022 AN - OPUS4-55112 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 - PGD model with domain mapping of Bead-on-Plate weld simulation for wire arc additive manufacturing N2 - Numerical simulations are essential in predicting the behavior of systems in many engineering fields and industrial sectors. The development of accurate virtual representations of actual physical products or processes allows huge savings in cost and resources. In fact, digital twins would allow reducing the number of real, physical prototypes, tests, and experiments, thus also increasing the sustainability of the production processes and products’ lifetime. Standard numerical methods fail in providing real time simulations, especially for complex processes such as additive manufacturing applications. This work aims to build up a reduced order model for efficient wire arc additive manufacturing simulations by using the proper generalized decomposition (PGD) [1,2] method. Model order reduction is a popular concept to decrease the computational effort, where each evaluation of the reduced forward model is faster than evaluations using classical methods, even for complex models. The simulation of a moving heat source leads to a hardly separable parametric problem, which is solved by a new mapping approach [3]. Using this procedure, it is possible to create a simple separated representation of the forward model. In this contribution, a PGD model is derived for the first part of wire arc additive manufacturing: bead-on-plate weld. An excellent agreement with a standard finite element method is shown. The reduced model is further used in a model calibration set up, speeding up calibrations and ultimately leading to an optimized real-time simulation. T2 - The 8th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS) 2022 CY - Oslo, Norway DA - 05.06.2022 KW - PGD KW - Model calibration KW - Hardly separable problem KW - Additive manufacturing PY - 2022 AN - OPUS4-55111 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jafari, Abbas A1 - Titscher, Thomas A1 - Chatzi, E. A1 - Unger, Jörg F. T1 - Variational Bayesian inference of damage in concrete material using spatially-dense data N2 - Numerical simulators, such as finite element models, have become increasingly capable of predicting the behaviour of structures and components owing to more sophisticated underlying mathematical models and advanced computing power. A common challenge lies, however, in calibrating these models in terms of their unknown/uncertain parameters. When measurements exist, this can be achieved by comparing the model response against measured data. Besides uncertain model parameters, phenomena like damage can give rise to further uncertainties; in particular, quasi-brittle materials, like concrete, experience damage in a heterogeneous manner due to various imperfections, e.g. in geometry and boundary conditions. This hardens an accurate prediction of the damaged behaviour of real structures that comprise such materials. In this study, which draws from a data-driven approach, we use the force-version of the finite element model updating method (FEMU-F) to incorporate measured displacements into the identification of the damage parameters, in order to cope with heterogeneity. In this method, instead of conducting a forward evaluation of the model and comparing the model response (displacements) against the data, we impose displacements to the model and compare the resulting force residuals with measured reaction forces. To account for uncertainties in the measurement of displacements, we endow this approach with a penalty term, which reflects the discrepancy between measured and imposed displacements, where the latter is assumed as unknown random variables to be identified as well. A Variational Bayesian approach is used as an approximating tool for computing posterior parameters. The underlying damage model considered in this work is a gradient-enhanced damage model. We first establish the identification procedure through two virtual examples, where synthetic data (displacements) are generated over a certain spatially-dense set of points over the domain. The procedure is then validated on an experimental case-study; namely a 3-point bending experiment with displacement measurements resulting from a digital image correlation (DIC) analysis. T2 - MSE 2022 CY - Online meeting DA - 27.09.2022 KW - Heterogeneity KW - Gradient damage KW - Model updating KW - Variational Bayesian KW - Concrete PY - 2022 AN - OPUS4-56625 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 - Real-time Bead-on-Plate weld Simulation for Wire Arc Additive Manufacturing using Reduced Order modelling coupled with stochastic model Calibration N2 - Numerical simulations are essential in predicting the behavior of systems in many engineering fields and industrial sectors. The development of accurate virtual representations of actual physical products or processes (also known as digital twins) allows huge savings in cost and resources. In fact, digital twins would allow reducing the number of real, physical prototypes, tests, and experiments, thus also increasing the sustainability of production processes and products’ lifetime. Standard numerical methods fail in providing real time simulations, especially for complex processes such as additive manufacturing applications. This work aims to use a reduced order model for efficient wire arc additive manufacturing simulations, calibrations and real-time process control. Model reduction, e.g. the proper generalized decomposition [1,2] method, is a popular concept to decrease the computational effort. A new mapping approach [3] was applied to simulate a moving heat source with the proper generalized decomposition. Using this procedure even complex models can be simulated in real-time. The physical model is later on calibrated with the use of a stochastic model updating process and the reduced order model, leading to an optimized real-time simulation. In this contribution, a proper generalized decomposition model for a bead-on-plate wire arc additive manufacturing is presented. It is also coupled with a stochastic model updating process identifying the heat source characteristics as well as the boundary conditions of the transient thermal problem, whereas the heat source shape is simulated using a Goldak heat source T2 - 15th World Congress on Computational Mechanics (WCCM-XV) CY - Yokohama, Japan DA - 31.07.2022 KW - Wire arc additive manufacturing KW - Reduced order modelling KW - Model calibration PY - 2022 AN - OPUS4-55576 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Robens-Radermacher, Annika T1 - A Database for Analyzing Round Robin Data N2 - FAIR (findable, accessible, interoperable and reusable) data usage is one of the main principals that many of the research and funding organizations include in their strategic plans, which means that following the main principals of FAIR data is required in many research projects. The definition of data being FAIR is very general, and when implementing that for a specific application or project or even setting a standardized procedure within a working group, a company or a research community, many challenges arise. In this contribution, an overview about our experience with different methods, tools and procedures is outlined. We begin with a motivation on potential use cases for the applications of FAIR data with increasing complexity starting from a reproducible research paper over collaborative projects with multiple participants such as Round-Robin tests up to data-based models within standardization codes, applications in machine learning or parameter estimation of physics-based simulation models. In a second part, different options for structuring the data are discussed. On the one hand, this includes a discussion on how to define actual data structures and in particular metadata schema, and on the other hand, two different systems for storing the data are discussed. The first one is the openBIS system, which is an open-source Lab notebook and PostgreSQL based data management system. A second option are a semantic representations using RDF based ontologies for the domain of interest. In a third section, requirements for workflow tools to automate data processing are discussed and their integration into reproducible data analysis is presented with an outlook on required information to be stored as metadata in the database. Finally, the presented procedures are exemplarily demonstrated for the calibration of a temperature dependent constitutive model for additively manufactured mortar. Metadata schemata for a rheological measurement setup are derived and implemented in an openBIS database. After a short review of a potential numerical model predicting the structural build-up behaviour, the automatic workflow to use the stored data for model parameter estimation is demonstrated. T2 - RILEM Spring Convention CY - Rabat, Morocco DA - 06.03.2023 KW - Database for Analyzing KW - Round Robin Data KW - Safety in technology and chemistry PY - 2023 AN - OPUS4-57348 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mezhov, Alexander A1 - Robens-Radermacher, Annika A1 - Zhang, Kun A1 - Kühne, Hans-Carsten A1 - Unger, Jörg F. A1 - Schmidt, Wolfram T1 - Temperature Impact on the Structural Build-Up of Cementitious Materials - Experimental and Modelling Study N2 - With increasing focus on industrialized processing, investigating, understanding, and modelling the structural build-up of cementitious materials becomes more important. The structural build-up governs the key property of fresh printable materials -- buildability -- and it influences the mechanical properties after the deposition. The structural build-up rate can be adjusted by optimization of the mixture composition and the use of concrete admixtures. Additionally, it is known, that the environmental conditions, i.e. humidity and temperature have a significant impact on the kinetic of cement hydration and the resulting hardened properties, such as shrinkage, cracking resistance etc. In this study, small amplitude oscillatory shear (SAOS) tests are applied to examine the structural build-up rate of cement paste subject to different temperatures under controlled humidity. The results indicate significant influences of the ambient temperature on the intensity of the re-flocculation (Rthix) rate, while the structuration rate (Athix) is almost not affected. A bi-linear thixotropy model extended by temperature dependent parameters coupled with a linear viscoelastic material model is proposed to simulate the mechanical behaviour considering the structural build-up during the SAOS test. T2 - Third RILEM International Conference on Concrete and Digital Fabrication (Digital Concrete 2022) CY - Loughborough, UK DA - 27.06.2022 KW - Structural build-up KW - Rheological properties KW - Modelling PY - 2022 AN - OPUS4-55581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tamsen, Erik A1 - Unger, Jörg F. T1 - Towards an automatic optimization framework for performance oriented precast concrete design N2 - The aim of the project LeBeDigital is to present opportunities of digitalization for concrete applications and show a way towards a performance oriented material design. Due to the high complexity of the manufacturing process of concrete and the range of parameters affecting the effective composite properties, a global optimization is challenging. Currently, most optimization is only carried out on a narrow scope related to the respective players, e.g. a mix optimization for a target strength, or a design optimization for minimum weight, using a given mix. To enable a path toward a full global optimization requires a reproducible chain of data, accessible for all contributors. We propose a framework based on an ontology, which automatically combines experimental data with numerical simulations. This not only simplifies experimental knowledge transfer, but allows the model calibration and the resulting simulation predictions to be reproducible and interpretable. In addition to an optimized set of parameters, this setup allows to study the quality and uncertainty of the data and models, as well as giving information about optimal experiments to improve the data set. We will present the proposed optimization workflow, using the example of a precast concrete element. The contribution will focus on the workflow and challenges of an interoperable FEM formulation. T2 - Material Science and Engineering, MSE Congress 2022 CY - Darmstadt, Germany DA - 27.09.2022 KW - Performance oriented concrete design KW - Ontology KW - Optimization workflow PY - 2022 AN - OPUS4-56208 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Robens-Radermacher, Annika A1 - Tamsen, Erik T1 - Data provenance - from experimental data to trustworthy simulation models and standards N2 - Data provenance - from experimental data to trust worthy simulation models and standards Jörg F. Unger, Annika Robens-Radermacher, Erik Tamsen Bundesanstalt für Materialforschung und -prüfung (BAM). Unter den Eichen 87, 12205 Berlin, Germany FAIR (findable, accessible, interoperable and reusable) data usage is one of the main principals that many of the research and funding organizations include in their strategic plans, which means that following the main principals of FAIR data is required in many research projects. The definition of data being FAIR is very general, and when implementing that for a specific application or project or even setting a standardized procedure within a working group, a company or a research community, many challenges arise. In this contribution, an overview about our experience with different methods, tools and procedures is outlined. We begin with a motivation on potential use cases for the applications of FAIR data with increasing complexity starting from a reproducible research paper over collaborative projects with multiple participants such as Round-Robin tests up to data-based models within standardization codes, applications in machine learning or parameter estimation of physics-based simulation models. In a second part, different options for structuring the data are discussed. On the one hand, this includes a discussion on how to define actual data structures and in particular metadata schema, and on the other hand, two different systems for storing the data are discussed. The first one is the open BIS system, which is an opensource Lab notebook and Postgre SQL based data management system. A second option are a semantic representations using RDF based ontologies for the domain of interest. In a third section, requirements for workflow tools to automate data processing are discussed and their integration into reproducible data analysis is presented with an outlook on required information to be stored as metadata in the database. T2 - 4th International Congress on Materials & Structural Stability CY - Rabat, Morocco DA - 08.03.2023 KW - Data provenance KW - Experimental data to trustworthy KW - Simulation models and Standards PY - 2023 AN - OPUS4-57333 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Unger, Wolfgang T1 - From k-values to elemental composition by EMPA (EDX & WDX) N2 - k-values (k-ratio, K-value) is defined as ratio of the X-ray photon intensity I measured for a particular characteristic peak from the unknown sample to the value measured for the same X-ray peak from a reference material of known composition under identical conditions of beam energy, spectrometer efficiency and electron dose. T2 - CCQM - Surface and Micro/Nano Analysis Working Group (SAWG) Meeting for 2016 CY - Paris, France DA - 19.04.2016 KW - k-values KW - EPMA KW - EDX KW - WDX PY - 2016 AN - OPUS4-35794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. A1 - Coehlo Lima, Isabela A1 - Jafari, Abbas A1 - Titscher, Thomas A1 - Robens-Radermacher, Annika T1 - Digital Twins for materials and structures N2 - A safe and robust performance is a key criterion when building and maintaining structures and components. Ensuring this criterion at different stages of the lifetime can be supported by applying continuous monitoring concepts. The latter usually can serve multiple purposes, including the determination of material parameters for the design phase, the evaluation of the actual loading/environmental conditions (instead of using conservative estimates that are usually larger) and evaluating or predicting the true performance of the structure (thus decreasing the model bias). In this context, a digital twin of the structure has many benefits. In addition, it allows to introduce virtual sensors to “measure” sensor information that is e.g. inaccessible or unmeasureable. In the limit, the remaining useful life of a structure can be interpreted as a property that can be “measured” indirectly via the numerical model in combination with real sensor data. In order to efficiently use monitoring techniques in the context of a digital twin, it is important to consider the complete chain of information including the choice of sensors, the data processing and structuring, the modelling assumptions, the numerical simulation and finally the stochastic nature of the model prediction. In this presentation, challenges in this context are discussed with a specific focus on Bayesian model updating of the digital twin, accounting for both parameter updates as well as model bias that results from the limitations of modelling assumption. A bottleneck in this approach is the computational effort related to sampling methods such as Markov chain Monte Carlo methods that require many evaluations of the forward model. An alternative to the expensive computation of the forward model for updating the digital twin is the combination with model reduction techniques such as the Proper General Decomposition. The results are illustrated for several examples and scales, ranging from digitals twin for material tests in the lab over lab scale structural digital twins up to damage identification in field experiments. T2 - 1st International Workshop on Metrology for virtual measuring instruments CY - Berlin, Germany DA - 21.09.2021 KW - Digital twin for monitoring KW - Digital Twins for materials and structures PY - 2021 AN - OPUS4-53879 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Donskyi, Ievgen A1 - Lippitz, Andreas A1 - Haag, Rainer T1 - NEXAFS and XPS analysis of functionalized graphene surfaces for bio applications N2 - Graphene prepared from Graphene oxide (GO) is used as a platform for functional 2D nanomaterials with diverse applications ranging from bios ensors to antimicrobial surfaces. C and N K-edge NEXAFS and XPS spectroscopies at BESSY’s HE-SGM beamline have been used to prove and control covalent functionalization of graphenic materials at ambient conditions for the synthesis of functional 2D-surfaces. T2 - 8th Jouint BER II and BESSY II User Meeting CY - Berlin, Germany DA - 7.12.2016 KW - XPS KW - NEXAFS KW - Graphene PY - 2016 AN - OPUS4-38683 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tamsen, Erik A1 - Unger, Jörg F. T1 - Towards an automatic optimization framework for performance oriented precast concrete design N2 - Concrete has a long history in the construction industry and is currently one of the most widely used building materials. Especially precast concrete elements are frequently utilized in construction projects for standardized applications, increasing the quality of the composite material, as well as reducing the required building time. Despite the accumulated knowledge, continuous research and development in this field is essential due to the complexity of the composite combined with the ever-growing number of applications and requirements. Especially in view of global climate change, design aspects as CO2 emissions and resource efficiency require new mix designs and optimization strategies. A result of the material’s high complexity and heterogeneity on multiple scales is that utilizing the full potential with changing demands is highly challenging, even for the established industry. We propose a framework based on an ontology, which automatically combines experimental data with numerical simulations. This not only simplifies experimental knowledge transfer, but allows the model calibration and the resulting simulation predictions to be reproducible and interpretable. This research shows a way towards a more performance oriented material design. Within this talk we present our workflow for an automated simulation of a precast element, demonstrating the interaction of the ontology and the finite element simulation. We show the automatic calibration of our early-age concrete model [1, 2], to improve the prediction of the optimal time for the removal of the form work. T2 - The 8th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS) 2022 CY - Oslo, Norway DA - 05.06.2022 KW - Performance oriented concrete design KW - Early-age concrete KW - Precast concrete KW - Ontology KW - Optimization workflow PY - 2022 AN - OPUS4-55302 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kjaervik, Marit A1 - Dietrich, P. A1 - Thissen, A. A1 - Schwibbert, Karin A1 - Unger, Wolfgang T1 - Characterisation of biofilms with near-ambient pressure XPS N2 - A drawback for X-ray photoelectron spectroscopy is that the measurements must be performed under ultra-high vacuum, which limits the type of samples which can be studied. However, by applying a differentially pumped aperture positioned close to the surface, even wet samples can be measured at near ambient pressure while the energy analyser is still under ultra-high vacuum, as illustrated below. Successful XPS-measurements with pressure up to 30 mbar have been reported using this approach, which opens up a new world of possibilities for ambient pressure measurements with XPS. While there are examples where NAP-XPS has been used to study electrochemical processes and heterogeneous catalysis, little attention has been paid to its potential use in biological materials. Until now, bacteria have only been characterised with conventional XPS, which requires tedious sample preparation usually involving freeze drying, a treatment that may degrade biological sample constituents. By studying biological samples in their native wet states, new insight about composition, absorption and transport of drugs through cell membranes and extracellular polymeric substance (EPS) layers can be obtained. Both artificial model-films of exopolysaccharides and biofilms of Escherichia Coli have been characterised at pressures ranging from ultra-high vacuum to 15 mbar by using SPECS’ EnviroESCA NAP-XPS instrument and conventional XPS. By applying antimicrobials to model biofilms, some of which are known to be resistant towards the antimicrobial in question, the distribution of antimicrobials in biofilms has been studied. Measurement capabilities and limitations of the approach will be discussed. T2 - European conferene on applications of surface and interface analysis (ECASIA 17) CY - Montpellier, France DA - 25.09.2017 KW - NAP-XPS KW - E. coli KW - Biofilms KW - Alginate PY - 2017 AN - OPUS4-42561 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Wernicke, Pascal A1 - Hufschläger, Daniel T1 - Pulse compression for air-coupled ferroelectret and thermoacoustic transducers N2 - The main advantage of air-coupled ultrasonic testing is the absence of a liquid couplant, which can damage some materials. However, most air-coupled testing scenarios have the challenge of low signals and a signal-to-noise ratio (SNR) several orders of magnitude lower than with couplant-assisted techniques. Since this challenge of small SNR also exists in radar technology, the pulse compression used there was adapted and applied to the physical conditions of air-coupled ultrasonic testing. This paper presents ultrasonic transmission measurements on a carbon-fibre-reinforced polymer plate using two experimental setups: 1) a thermoacoustic transmitter and an optical microphone and 2) a pair of ferroelectret transducers as transmitter and receiver. Thermoacoustic transmitters convert electrical energy to heat, which causes the air to expand thus producing acoustic waves. The optical microphone is based on a Fabry-Perot interferometer. Ferroelectrets are charged cellular polymers, having piezoelectric properties and excellent acoustic matching to air. Both thermoacoustic transmitters and ferroelectrets are non-linear regarding the relationship between the excited sound pressure and the excitation voltage. Due to these physical boundary conditions, unipolar coding was used to modulate the excitation signals. Various codes were tested, and parameters of the excitation pulses were varied to find the optimal combination for each experimental setup. The application of pulse compression to the combination of thermoacoustic transmitter and optical microphone increased the signal-to-noise ratio by up to 16 dB and for the ferroelectret transducers by up to 23 dB. T2 - 30th International Congress on Sound and Vibration CY - Amsterdam, Netherlands DA - 08.07.2024 KW - Pulse compression KW - Air-coupled ultrasonic transducers KW - Ferroelectret KW - Thermoacoustics PY - 2024 AN - OPUS4-60733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Berger, Anka T1 - Exchange of experts - UN methods according to UN-MTC N2 - The presentation is an overview about the UN methods and the procedure regarding the classification of self-reactive substances and organic peroxides according to the UN-Manual of Tests and Criteria. T2 - Exchange of Experts - BAM, Fachbereich 2.3 and Korea Fire Institute (KFI) CY - Berlin, Germany DA - 25.06.2024 KW - UN-Manual of Tests and Criteria KW - UN-Methods KW - Classification of Dangerous Goods KW - Self-reactive substances KW - Organic peroxides PY - 2024 AN - OPUS4-60732 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Radnik, Jörg A1 - Kjaervik, Marit A1 - Unger, Wolfgang T1 - Surface chemical analysis surface chemical analysis of cells and biofilms N2 - The status of the planned technical report "Surface characterization of biomaterials" will be presented. T2 - ISO TC201 Meeting CY - Online meeting DA - 05.09.2020 KW - X-ray photoelectron spectroscopy KW - X-ray spectroscopy KW - Biomaterials KW - Standardization PY - 2020 AN - OPUS4-51197 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zorn, Sebastian A1 - Unger, Jörg F. T1 - A probabilistic method for identification of vehicle loads and system parameters for reinforced concrete bridges N2 - In this work, a method for vehicle load identification is proposed. It involves Bayesian Analysis and (quasi-)static importance functions in order to estimate vehicle positions, velocities and weights. The structure is modeled with finite elements in order to generate model predictions for different load configurations. The model predictions are compared to the actual measured data to identify the most probable loading configuration for that measurement. This involves the use of enhanced Monte Carlo simulations such as MCMC to reduce the computational effort. T2 - IRF2016 - Integrity Reliability Failure CY - Porto, Portugal DA - 24.07.2016 KW - Model update KW - Load identification KW - Bayesian inference PY - 2016 AN - OPUS4-37062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - TY - CONF A1 - Kindrachuk, Vitaliy A1 - Unger, Jörg F. A1 - Titscher, Thomas T1 - Multisurface damage-plasticity constitutive model for concrete 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 - OPUS4-32898 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. T1 - Comparison of higher order methods in time and space for the numerical simulation of ultrasonic wave propagation 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, Spain DA - 2014-07-20 PY - 2014 AN - OPUS4-32901 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Holzweber, Markus A1 - Benemann, Sigrid A1 - Unger, Wolfgang T1 - What about ionic liquids as a "hot" reference material candidate to check your EDS below 1 keV? T2 - EMAS 2015 - 14th European Workshop on MODERN DEVELOPMENTS AND APPLICATIONS IN MICROBEAM ANALYSIS CY - Portoroz, Spain DA - 2015-05-03 PY - 2015 AN - OPUS4-33100 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Jörg F. T1 - Hierarchical multiscale models for localization phenomena within the framework of FE2-X1 T2 - Computational Modelling of Concrete and Concrete Structures CY - St. Anton am Arlberg, Austria DA - 2014-03-24 PY - 2014 AN - OPUS4-32902 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Rades, Steffi A1 - Karlsson, R. A1 - Reuther, R. T1 - NanoValid - Developing Reference Methods for Nanomaterials T2 - Workshop Bundesbehörden/VCI/VdMi "Messstrategien und Messmethoden für Nanomaterialien" CY - Berlin, Germany DA - 2015-09-08 PY - 2015 AN - OPUS4-34060 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bütefisch, S. A1 - Weimann, T. A1 - Busch, I. A1 - Danzebrink, H. A1 - Gross, Thomas A1 - Unger, Wolfgang A1 - Wirth, Thomas T1 - New Reference Material for Imaging XPS (X-ray Photoelectron Spectroscopy) Instrument Characterization T2 - 17th International Conference on Sensors and Measurement Technology (SENSOR 2015) CY - Nürnberg, Germany DA - 2015-05-19 PY - 2015 AN - OPUS4-34184 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 - Weigel, W. T1 - Charakterisierung von organischen Nanofunktionsschichten für biosensorische Anwendungen T2 - Workshop 7: 23. Neues Dresdner Vakuumtechnisches Kolloquium, Beschichtung und Modifizierung von Kunststoffoberflächen CY - Dresden DA - 2015-10-14 PY - 2015 AN - OPUS4-34683 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzlechner, Gerald A1 - Sobol, Oded A1 - Straub, Franka A1 - Böllinghaus, Thomas A1 - Unger, Wolfgang T1 - ToF-SIMS as a Metrology Tool to Support Materail and Analytical Science T2 - 4th WMRIF Young Scientist Workshop CY - Denver, Colorado USA DA - 2014-09-08 PY - 2014 AN - OPUS4-34684 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Unger, Wolfgang A1 - Dietrich, Paul A1 - Streeck, C. A1 - Fischer, Tobias A1 - Glamsch, Stephan A1 - Ray, S. A1 - Ehlert, Christopher A1 - Lippitz, Andreas A1 - Nutsch, A. A1 - Kulak, N. A1 - Shard, A.G. A1 - Rurack, Knut A1 - Beckhoff, B. T1 - Traceable and Absolute Quantification of Silane Molecules on Silica Surfaces T2 - 16th European Conference on Applications of Surface and Interface Analysis (ECASIA 15) CY - Granada, Spain DA - 2015-09-28 PY - 2015 AN - OPUS4-34807 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rades, Steffi A1 - Salge, T. A1 - Unger, Wolfgang A1 - Hodoroaba, Vasile-Dan T1 - Automated analysis of nanoparticles by high-resolution transmission scanning electron microscopy and energy dispersive X-ray spectroscopy T2 - International Summer Workshop - Nanoscience meets Metrology CY - Eriche, Italy DA - 2015-07-27 PY - 2015 AN - OPUS4-33873 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -