TY - CONF A1 - Omar, Hassan T1 - Invesitgation of Thin Film Interactions with Inorganic Surfaces N2 - Thin polymer films are of vital importance due to their low production costs and wide range of applications in sensors, electronics, and coatings. Their geometry is ideal for the study of confinement effects, specifically one-dimensional confinement, on the thermodynamic properties and segmental dynamics of polymers. For this investigation, films of PC are prepared on both glass and silica substrates to measure the dielectric and calorimetric behavior as a function of film thickness. The methodology consists of broadband dielectric spectroscopy (BDS), ellipsometry, and atomic force microscopy (AFM). Using ellipsometry, the glass transition shows an increase with decreasing film thickness. Compared to a previous investigation of PC where dilatometry was used, an increase in PC was seen, but now only at thicknesses below 20 nm. Therefore, the critical thickness of PC, where the bulk-like layer no longer percolates through the film, is dependent on the method probing the glass transition. The dielectric behavior shows a deviation from bulk behavior with decreasing film thickness, although still showing a Vogel-Fulcher-Tammann (VFT) temperature dependence for all films. The influence of the adsorbed layer on the molecular mobility was also addressed. T2 - Deutschen Physikalische Gesellschaft (DPG) Tagung CY - Regensburg, Germany DA - 04.09.2022 KW - Thin films KW - Adsorbed Layer KW - Broadband dielectric spectroscopy PY - 2022 AN - OPUS4-55706 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von Oertzen, Alexander T1 - Reporting of BAM, Explosives Division to the EU – HME Research Project and Activities of Forum of Notified Bodies for Explosives N2 - Work done by the forum of Notified Bodies for explosives, as reported by the chairman of the group, results, developments, and current research in the area of home made explosives. T2 - Meeting of the Working Group on Explosives for Civil Uses CY - Brussels, Belgium DA - 17.10.2016 KW - Notified body KW - Explosives KW - Home made explosives PY - 2016 AN - OPUS4-38017 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lexow, Jürgen T1 - IEA-IA-AMT Advanced materials for transport N2 - Materials properties strongly influence the energy combustion of vehicles. The IEA Technology Cooperation Program Advanced Materials for Transport presents its activity. T2 - IEA Transport Contact Group Meeting CY - Paris, France DA - 19.01.2016 KW - Internationale Energieagentur KW - Leightweighting KW - Globaler Kraftfahrzeugbestand KW - Treibhausgas KW - Internationale Zusammenarbeit KW - Total amout of cars in the world KW - International Energy Agency KW - Green house gas KW - International cooperation PY - 2016 AN - OPUS4-38023 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - On the modelling of the fatigue strength of am components N2 - The topic of the presentation consists in some basic considerations on the application of fracture mechanics to fatigue live and strengh prediction of metallic componends manufatured by additive manufacturing. These are based on an approach developed at BAM which comprises elements such as the elastic-plastic modelling of the cyclic crack driving force, a physically meaningfull determination of the initial crack size and multipile crack initiation and propagation due to variations of the local geometry and material charactaristics. Spezial emphasis is put to spezific aspects of materials composed by selectiv laser melting such as surface roughness, porosity and gradiants in the microstructure. N2 - Beschreibung der IBESS-Prozedur zur zukünftigen Anwendung zur Berechnung der Schwingfestigkeit von Schweißverbindungen T2 - Additive Manufracturing Benchmarks 2018 CY - Gaithersburg, Maryland, USA DA - 18.06.2018 KW - Structural Integrity KW - Fartigue Strength KW - Additive Manufacturing PY - 2018 AN - OPUS4-46062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - INPR A1 - Villani, P. A1 - Unger, Jörg F. A1 - Weiser, M. T1 - Adaptive Gaussian process regression for Bayesian inverse problems N2 - We introduce a novel adaptive Gaussian Process Regression (GPR) methodology for efficient construction of surrogate models for Bayesian inverse problems with expensive forward model evaluations. An adaptive design strategy focuses on optimizing both the positioning and simulation accuracy of training data in order to reduce the computational cost of simulating training data without compromising the fidelity of the posterior distributions of parameters. The method interleaves a goal-oriented active learning algorithm selecting evaluation points and tolerances based on the expected impact on the Kullback-Leibler divergence of surrogated and true posterior with a Markov Chain Monte Carlo sampling of the posterior. The performance benefit of the adaptive approach is demonstrated for two simple test problems. T2 - Algoritmy 2024 - Central-European Conference on Scientific Computing CY - Vysoké Tatry, Slovakia DA - 15.03.2024 KW - Active learning KW - Bayesian inverse problems KW - Gaussian Process Regression (GPR) KW - Parameter identification KW - Surrogate models PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600408 DO - https://doi.org/10.48550/arXiv.2404.19459 SN - 2331-8422 SP - 1 EP - 12 PB - Cornell University CY - Ithaca, NY AN - OPUS4-60040 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Short fatigue crack propagation in L-PBF 316L stainless steel N2 - Fracture mechanics is a key to fatigue assessment in AM metal components. Short fatigue cracks are initiated at defects and pronounced surface roughness intrinsic to AM. The subsequent crack-propagation is strongly influenced by microstructural interactions and the build-up of crack-closure. The aim of the present study is to give an insight into short-crack propagation in AM-metals. Fatigue crack propagation resistance curves were determined experimentally for AISI 316L manufactured by Laser Powder Bed Fusion (L-PBF) which was heat treated at three different temperatures. Differences in the build-up of the fatigue-crack propagation threshold in between the L-PBF specimens and compared to wrought material are due to the residual stress states, a pronounced roughness of the crack-faces in the L-PBF specimens and phase transformation in the vicinity of the crack-tip, resulting in increased crack-closure. This, together with crack-branching found along the crack path, enhances the resistance to the propagation of fatigue cracks. T2 - ASTM International Conference on Additive Manufacturing 2020 CY - Online meeting DA - 16.11.2020 KW - Additive Manufacturing KW - Cyclic R-Curve KW - Component assessment KW - L-PBF KW - 316L KW - Residual Stress KW - Fatigue Crack Growth PY - 2020 AN - OPUS4-51585 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hille, Falk A1 - Sowietzki, D. A1 - Makris, R. T1 - Luminescence-based early detection of fatigue cracks N2 - Classic non-destructive fatigue crack detection methods reveal the state of the fatigue damage evolution at the moment of application, generally not under operational conditions. The here introduced crack luminescence method realizes a clear visibility of the occurred and growing crack in loaded components during operation. Different established experiments show that due to the sensitive coating a crack Formation can be detected even in early stage under the premise the crack reached the surface. The coating consists of two layers with different properties and functions. The bottom layer emits light as fluorescence under UV radiation. The top layer covers the fluorescing one and prevents the emitting of light in case of no damage at the surface. In case of surface crack occurrence, the luminescent light is clearly noticeable by visual observations and also by standard camera equipment which makes automated crack detection possible as well. It is expected that crack luminescence can increase structural safety as well as reduce costs and time for inspections and preventive maintenance. KW - Coating KW - Fatigue KW - Crack damage detection KW - Luminescence PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-510517 DO - https://doi.org/10.1016/j.matpr.2020.02.338 SN - 2214-7853 SP - 1 EP - 5 PB - Elsevier CY - Amsterdam AN - OPUS4-51051 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Glaeser, J. A1 - Oberpaul, M. T1 - Exploiting termite nest microbiomes for antibiotic drug discovery by using an ultra-high throughput Microfluidics/FACS driven pipeline N2 - Bacterial infections are a global threat to human health1. Especially nosocomial infections with multidrug-resistant Gram-negative bacteria challenge public health systems and endanger successful treatment of patients in many modern medicine applications as e.g. organ transplant. In the last three decades classical approaches failed to find novel chemical scaffolds suitable for the development of antibiotics that reach the market and caused the modern antibiotics crisis1. Insect microbiomes produce potent antibiotics with low toxicity to eukaryotic cells to defend their hosts against entomopathogenic microorganisms2. In order to exploit insect microbiomes efficiently and to identify novel antibiotics producing bacteria, we implemented an ultra-high throughput Microfluidics/FACS (fluorescence-associated cell sorting) cultivation and screening pipeline. Here we present the technical aspects of our pipeline including downstream processing of identified producer strains and its suitability for antibiotics discovery. T2 - Tagung DGHM und VAAM Microbiology and Infection 2017 CY - Würzburg, Germany DA - 05.03.17 KW - Antibiotics KW - Micobiomes KW - Termites PY - 2017 AN - OPUS4-39903 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Blaeß, Carsten T1 - Crack healing in glasses and glass matrix composites N2 - Fundamental understanding of crack healing in glassy crystalline materials is very important for many applications, especially for sealing solid oxide fuel cells (SOFC) since cracks caused by sealing or thermal cycling still remain a substantial bottleneck in developing durable SOFC. Previous studies on soda lime silicate glass [Sin14] showed that crack healing is driven by viscous flow and that healing progress is proportional to time t and inverse viscosity η. This finding would allow to present healing data of a given glass for different temperatures in a master curve healing progress versus t/η. Such master curves would be a helpful tool in understanding crack healing kinetics. Against this background, crack healing in non-crystallizing sodium calcium silicate (NCS) and sodium borosilicate glasses (NBS) have been studied. Moreover, to evaluate the influence of micros structure in crystallized glass on crack healing process, glass matrix composites (GMC) where prepared out of NCS and zirconia as inert ceramic filler material mimicking a partially crystalline micro structure. Cracks were generated by Vickers indention and healed isothermally at different temperatures. Crack healing progress was monitored by optical and electron microscopy. Results show that the above mentioned proportionality actually applies for the studied glasses for which such a master curve could be obtained. In comparison to a non-crystallized glass, the effective viscosity of GMC is increased by rigid filler content. This effect substantially retards crack broadening during later healing stages, which often ends up in large pores. On the other hand, local viscous crack healing is still possible in larger glassy regions. This behavior seems to be very interesting for crack healing optimized sealants. T2 - 91. Jahrestagung HVG-DGG CY - Weimar, Germany DA - 29.05.2017 KW - Glass KW - Crack healing KW - Glass ceramic KW - Composite PY - 2017 AN - OPUS4-41351 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gawek, Marcel A1 - Szymoniak, Paulina A1 - Hülagü, Deniz A1 - Hertwig, Andreas A1 - Schönhals, Andreas T1 - Molecular Mobility of Thin Films and the Adsorbed Layer of Poly(2-vinylpyridine) N2 - The molecular dynamics of thin films and the adsorbed layer of poly(2-vinylpyridine) (P2VP) were investigated using broadband dielectric spectroscopy (BDS) and spectroscopic ellipsometry. Thin films of P2VP were prepared on silicon substrates and characterized to understand the influence of film thickness on the thermal glass transition temperature (Tg) and molecular mobility. The ellipsometric study revealed a decrease in Tg with decreasing film thickness, attributed to the enhanced mobility at the polymer/air interface. The adsorbed layer, prepared via the solvent leaching approach, exhibited a higher Tg compared to the bulk, indicating reduced molecular mobility due to strong polymer substrate interactions. The dielectric measurements were carried out in two different electrode configurations, crossed electrode capacitors (CEC) and nanostructured electrodes (NSE), where the latter allows for a free surface layer at the polymer/air interface. The relaxation rates of the α-relaxation measured in the CEC geometry collapse into one chart independent from the film thickness. For the thin films measured in the NSE arrangement the relaxation rates slow down with decreasing film thickness which was discussed as related to a stronger interaction of the P2VP segments with the native SiO2 at the surface of the silicon substrate compared to aluminum. It is worth to note that the effect of the enhanced mobility at the polymer/air interface is not observed in the dielectric measurements. BDS measurements in NSE geometry identified an additional relaxation process (α*-relaxation) in thin films, which was more pronounced in the adsorbed layer. This process is hypothesized to be related to molecular fluctuations within the adsorbed layer including the adsorption/desorption dynamics of segments or to a Slow Arrhenius Process (SAP) related to the equilibration dynamics deep in the glassy state. KW - Thin polymer films PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-637181 DO - https://doi.org/10.1039/d5sm00539f SN - 1744-6848 SP - 1 EP - 12 PB - Royal Society of Chemistry (RSC) AN - OPUS4-63718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thuy, Maximilian A1 - Pedragosa-Rincon, M. A1 - Niebergall, Ute A1 - Oehler, H. A1 - Alig, I. A1 - Böhning, Martin T1 - Environmental Stress Cracking of High-Density Polyethylene Applying Linear Elastic Fracture Mechanics N2 - The crack propagation rate of environmental stress cracking was studied on high-density polyethylene compact tension specimens under static loading. Selected environmental liquids are distilled water, 2 wt% aqueous Arkopal N100 solution, and two model liquid mixtures, one based on solvents and one on detergents, representing stress cracking test liquids for commercial crop protection products. The different surface tensions and solubilities, which affect the energetic facilitation of void nucleation and craze development, are studied. Crack growth in surface-active media is strongly accelerated as the solvents induce plasticization, followed by strong blunting significantly retarding both crack initiation and crack propagation. The crack propagation rate for static load as a function of the stress intensity factor within all environments is found to follow the Paris–Erdogan law. Scanning electron micrographs of the fracture surface highlight more pronounced structures with both extensive degrees of plasticization and reduced crack propagation rate, addressing the distinct creep behavior of fibrils. Additionally, the limitations of linear elastic fracture mechanisms for visco-elastic polymers exposed to environmental liquids are discussed. KW - Crack propagation KW - Environmental stress cracking KW - Fracture toughness KW - Crop protection products KW - High-density polyethylene KW - Craze–crack mechanism KW - Linear elastic fracture mechanics KW - Stress intensity factor PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-550476 DO - https://doi.org/10.3390/polym14122415 SN - 2073-4360 VL - 14 IS - 12 SP - 1 EP - 21 PB - MDPI CY - Basel AN - OPUS4-55047 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -