TY - JOUR A1 - Berthold, J. A1 - Vrana, J. A1 - Heckel, Thomas A1 - Kanzler, D. A1 - Jatzlau, P. A1 - Große, C. T1 - Modellgestützte Bestimmung der Auffindwahrscheinlichkeit (POD) von Reflektoren bei der Ultraschallprüfung großer Schmiedeteile N2 - Bruchmechanische Untersuchungen werden zur Vorhersage der Lebensdauer und der Wartungszyklen benutzt. Dabei wird davon ausgegangen, dass auch Objekte ohne detektierte Anzeigen Materialfehler mit einer Reflektivität kleiner der Nachweisgrenze aufweisen können. Keine detektierte Anzeige bedeutet daher für Bauteilauslegung, dass sie eine konservative Annahme machen müssen: es wird angenommen, dass das Bauteil Materialfehler in Größe der Nachweisgrenze enthält. Dies macht die Nachweisgrenze zu dem die Lebensdauer limitierenden Faktor. Bei probabilistischen Methoden wird zusätzliches Wissen, wie Zuverlässigkeit und Fehlerauffindwahrscheinlichkeiten bei der zerstörungsfreien Prüfung mit in die Berechnung einbezogen, um zu konservative Annahmen zu vermeiden. Ziel ist es eine Model-Assisted-POD aufzubauen mit der die reale volumetrische Ultraschallprüfung großer Schmiedeteile nachgebildet werden kann. Die resultierende POD soll im Weiteren in bruchmechanischen Betrachtungen Verwendung finden. In vorangegangenen Arbeiten [Preißel2015] wurde dazu der Einfluss des Prüfrasters nach der DGZfP-Richtlinie US 07:2014 auf die Fehlerauffindwahrscheinlichkeit (parametrisch) simulativ betrachtet und die Simulationstechnik experimentell validiert. In diesem Paper werden die Ergebnisse von Preißel überprüft und um eine Prüfraster-Summen-POD, die das Szenario der realen Bauteilprüfung beschreibt, erweitert. Zudem wird eine experimentell validierte, simulative, nicht-parametrische POD für schrägliegende Defekte aufgebaut. Schließlich werden erste Untersuchungen zur Defektmorphologie vorgestellt. Diese Arbeit ist im Rahmen eines Studenten-Stipendiums der DGZfP entstanden. T2 - DGZfP DACH Tagung 2019 CY - Friedrichshafen, Germany DA - 27.05.2019 KW - Schmiedeteile KW - POD KW - Ultraschall KW - Zerstörungsfreie Prüfung PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-496796 UR - http://www.ndt.net/?id=24529 VL - 24 IS - 8 SP - 1 EP - 12 PB - NDT.net CY - Kirchwald AN - OPUS4-49679 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Titscher, Thomas A1 - Unger, Jörg F. A1 - Oliver, J. T1 - Implicit explicit integration of gradient enhanced damage models N2 - Quasi-brittle materials exhibit strain softening. Their modeling requires regularized constitutive formulations to avoid instabilities on the material level. A commonly used model is the implicit gradient-enhanced damage model. For complex geometries, it still Shows structural instabilities when integrated with classical backward Euler schemes. An alternative is the implicit–explicit (IMPL-EX) Integration scheme. It consists of the extrapolation of internal variables followed by an implicit calculation of the solution fields. The solution procedure for the nonlinear gradient-enhanced damage model is thus transformed into a sequence of problems that are algorithmically linear in every time step. Therefore, they require one single Newton–Raphson iteration per time step to converge. This provides both additional robustness and computational acceleration. The introduced extrapolation error is controlled by adaptive time-stepping schemes. This paper introduced and assessed two novel classes of error control schemes that provide further Performance improvements. In a three-dimensional compression test for a mesoscale model of concrete, the presented scheme was about 40 times faster than an adaptive backward Euler time integration. KW - Implicit explicit schemes KW - Gradient-enhanced damage model KW - Adaptive time stepping KW - Continuum damage KW - Robustness PY - 2019 DO - https://doi.org/10.1061/(ASCE)EM.1943-7889.0001608 SN - 0733-9399 SN - 1943-7889 VL - 145 IS - 7 SP - 04019040-1 EP - 04019040-13 PB - ASCE - American Society of Civil Engineers AN - OPUS4-48361 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bhuyan, Md Delwar Hossain A1 - Döhler, M. A1 - Lecieux, Y. A1 - Lupi, C. A1 - Thomas, J. A1 - Schoefs, F. A1 - Hille, Falk A1 - Mevel, L. T1 - Statistical Subspace-based Damage Localization on Saint-Nazaire Bridge Mock-Up N2 - The subject of damage localization is an important issue for Structural Health Monitoring (SHM) particularly in mechanical or civil structures under ambient excitation. In this paper, the statistical subspacebased damage localization method has been applied on a benchmark application, namely a 1/200 scale model of the Saint-Nazaire Bridge, which is a cable-stayed bridge located on the Loire River near the river’s mouth. The employed damage localization method combines data-driven features with physical parameter information from a finite element model in statistical tests, avoiding typical ill-conditioning problems of FE model updating. Damage is introduced in the mockup for cable failures on some of the 72 cables. The purpose of the experiment is to assess the capability of damage assessment methods to find a cable failure. T2 - International Operational Modal Analysis Conference CY - Copenhagen, Danmark DA - 13.05.2019 KW - Structural health monitoring KW - Damage localization KW - Cable-stayed bridge KW - Cable failure PY - 2019 SP - 1 EP - 9 AN - OPUS4-48243 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lippold, J. C. A1 - Böllinghaus, Thomas A1 - Richardson, I. T1 - Welding in the world - Update 2018 N2 - In 2018, the Journal "Welding in the World" published 6 issues that contained 120 papers and over 1300 pages of fundamental and applied research associated with materials joining and allied technologies. KW - Journal KW - Editorial Board KW - Year in Review PY - 2019 DO - https://doi.org/10.1007/s40194-018-00695-9 SN - 0043-2288 SN - 1878-6669 VL - 63 IS - 1 SP - 1 PB - Springer CY - Berlin AN - OPUS4-50064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sebald, M.A. A1 - Gebauer, J. A1 - Sommerfeld, Thomas A1 - Koch, Matthias T1 - First Synthesis of (−)-Altenuene-D3 Suitable as Internal Standard for Isotope Dilution Mass Spectrometry N2 - Metabolites from Alternaria fungi exhibit a variety of biological properties such as phytotoxic, cytotoxic, or antimicrobial activity. Optimization of a literature procedure culminated in an efficient total synthesis of (−)-altenuene as well as a stable isotope-labeled derivative suitable for implementation in a LC-MS/MS method for mycotoxin analysis. KW - Altenuene KW - Alternaria mycotoxins KW - Food safety KW - Isotope-labeled KW - SIDA-LC-MS/MS KW - Suzuki coupling PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-500696 DO - https://doi.org/10.3390/molecules24244563 SN - 1420-3049 VL - 24 SP - 4563 PB - MDPI CY - Basel AN - OPUS4-50069 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sarhan, R. M. A1 - Koopman, W. A1 - Schuetz, R. A1 - Schmid, Thomas A1 - Liebig, F. A1 - Koetz, J. A1 - Bargheer, M. T1 - The importance of plasmonic heating for the plasmondriven photodimerization of 4-nitrothiophenol N2 - Metal nanoparticles form potent nanoreactors, driven by the optical generation of energetic electrons and nanoscale heat. The relative influence of these two factors on nanoscale chemistry is strongly debated. This article discusses the temperature dependence of the dimerization of 4-nitrothiophenol (4-NTP) into 4,4′-dimercaptoazobenzene (DMAB) adsorbed on gold nanoflowers by Surface-Enhanced Raman Scattering (SERS). Raman thermometry shows a significant optical heating of the particles. The ratio of the Stokes and the anti-Stokes Raman signal moreover demonstrates that the molecular temperature during the reaction rises beyond the average crystal lattice temperature of the plasmonic particles. The product bands have an even higher temperature than reactant bands, which suggests that the reaction proceeds preferentially at thermal hot spots. In addition, kinetic measurements of the reaction during external heating of the reaction environment yield a considerable rise of the reaction rate with temperature. Despite this significant heating effects, a comparison of SERS spectra recorded after heating the sample by an external heater to spectra recorded after prolonged illumination shows that the reaction is strictly photo-driven. While in both cases the temperature increase is comparable, the dimerization occurs only in the presence of light. Intensity dependent measurements at fixed temperatures confirm this finding. KW - Nanoparticles KW - Plasmonic heating KW - Raman spectroscopy PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475140 DO - https://doi.org/10.1038/s41598-019-38627-2 SN - 2045-2322 VL - 9 IS - 1 SP - 3060, 1 EP - 8 PB - Nature Publishing Group AN - OPUS4-47514 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kotschate, Daniel A1 - Gohlke, Dirk A1 - Dobrovolskij, P. A1 - Vrana, J. A1 - Heckel, Thomas T1 - Herausforderungen bei der Prüfung von Schmiedeteilen durch Vorsatzkeile für Longitudinalwellenprüfköpfe N2 - Trotz moderner Sensortechnologien und Rekonstruktionsmethoden, findet die manuelle und automatisierte Ultraschallprüfung durch konventionelle Senkrecht- und Winkelprüfköpfe vielfach industriellen Einsatz. Um einen flexiblen Prüfeinsatz und die Prüfbarkeit von einfachen sowie komplexen Geometrien zu gewährleisten, werden dort oftmals Vorlaufkeile für die Winkelprüfung mit Longitudinalwellen angewendet um eine Anzeigenschräglage und deren Reflektivität auszugleichen bzw. zu verbessern. Durch den unterschiedlichen Aufbau, im Vergleich zu integrierten Scherwellen-Winkelprüfköpfen, können jedoch während der Prüfung Fehlanzeigen generiert werden. Diese fehlerhaften Anzeigen beruhen auf Mehrfachreflexionen und Wellenumwandlungen innerhalb des Vorlaufkeils, aufgrund der Geometrie und können im Feld nur bedingt von realen Anzeigen unterschieden werden. Dieser Beitrag zeigt die geometrische Betrachtung bei der Verwendung von Vorlaufkeilen und wurde experimentell durch die Bestimmung der Richtcharakteristik und dem Einsatz von elektrodynamischen Sonden validiert. Des Weiteren ermöglichen die so gewonnenen Abhängigkeiten einen vom Keilwinkel abhängigen Verstärkungsausgleich und somit eine korrekte Größenbestimmung durch einen geeigneten Vergleichsfehler. T2 - DACH-Jahrestagung 2019 CY - Friedrichshafen, Germany DA - 27.05.2019 KW - Richtcharakteristik KW - Vorlaufkeile KW - Mehrfachreflexion PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-480999 VL - 2019 SP - 1 EP - 7 PB - DGZfP Deutsche Gesellschaft für Zerstörungsfreie Prüfung AN - OPUS4-48099 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Perez, Jeffey Paulo H. A1 - Tobler, Dominique J. A1 - Thomas, Andrew N. A1 - Freeman, Helen M. A1 - Dideriksen, Knud A1 - Radnik, Jörg A1 - Benning, Liane G. T1 - Adsorption and reduction of arsenate during the Fe2+-induced transformation of ferrihydrite N2 - Iron (oxyhydr)oxides play an important role in controlling the mobility and toxicity of arsenic (As) in contaminated soils and groundwaters. However, dynamic subsurface geochemical conditions can potentially impact As sequestration since this is highly dependent on the dominant iron mineral phases present and the pathways through which they form. In this study, we investigated the Fe2+-induced transformation of As(V)-bearing ferrihydrite (As-FH) to more crystalline phases under relevant anoxic subsurface conditions. Specifically, we examined the influence of varying Fe2+(aq)/Fe(III)solid¬ ratios on the behavior and speciation of the mineral-bound As species during the mineralogical transformation of As-FH at pH 6.5 for 24 h. At lower Fe2+(aq)/Fe(III)solid¬ ratios (0.5 to 1), goethite, green rust sulfate (GR¬SO4) and lepidocrocite formed within the first 2 hours of the reaction, but only goethite and some unreacted FH remained after 24 h. At Fe2+(aq)/Fe(III)solid¬ ratio = 2, GRSO4 remained stable throughout the 24 h reaction, alongside goethite and unreacted FH. Despite >82% of the As-FH being transformed to goethite  GRSO4 in these reactions, no significant As release (>99.9% removal) was observed. However, while As remained mineral-bound, partial oxidation of the initially added As(V) was reduced to As(III), most likely, by the goethite-Fe2+(aq) redox couple. The extent of As(V) reduction increased from ~40% to ~50%, as the Fe2+(aq)/Fe(III)solid¬ ratio increased from 0.5 to 2. Overall, these results provide important insights into transformation pathways of iron (oxyhydr)oxide minerals in As contaminated, anoxic soils and sediments, and also demonstrate the great impact these can have on As oxidation state and, hence, toxicity and mobility in these environments. KW - Ferrihydrite KW - Mineral tranformation KW - XPS KW - Green rust KW - Goethite KW - XAS PY - 2019 DO - https://doi.org/10.1021/acsearthspacechem.9b00031 SN - 2472-3452 VL - 3 IS - 6 SP - 884 EP - 894 PB - ACS AN - OPUS4-48436 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yadav, Anur A1 - Iost, R. M. A1 - Neubert, T. J. A1 - Baylan, S. A1 - Schmid, Thomas A1 - Balasubramanian, Kannan T1 - Selective electrochemical functionalization of the graphene edge N2 - We present a versatile and simple method using electrochemistry for the exclusive functionalization of the edge of a graphene monolayer with metal nanoparticles or polymeric amino groups. The attachment of metal nanoparticles allows us to exploit surface-enhanced Raman scattering to characterize the chemistry of both the pristine and the functionalized graphene edge. For the pristine patterned graphene edge, we observe the typical edge-related modes, while for the functionalized graphene edge we identify the chemical structure of the functional layer by vibrational fingerprinting. The ability to obtain single selectively functionalized graphene edges routinely on an insulating substrate opens an avenue for exploring the effect of edge chemistry on graphene properties systematically. KW - Graphene KW - Nanoparticles KW - Nanosciences KW - Surface-enhanced Raman scattering KW - Atomic force microscopy PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474357 DO - https://doi.org/10.1039/C8SC04083D SN - 2041-6520 VL - 10 IS - 3 SP - 936 EP - 942 PB - Royal Society of Chemistry AN - OPUS4-47435 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bhuyan, Md Delwar Hossain A1 - Döhler, M. A1 - Lecieux, Y. A1 - Lupi, C. A1 - Thomas, J.-C. A1 - Schoefs, F. A1 - Hille, Falk A1 - Mevel, L. T1 - Statistical subspace based damage localization on Saint-Nazaire bridge mock-up N2 - The subject of damage localization is an important issue for Structural Health Monitoring (SHM) particularly in mechanical or civil structures under ambient excitation. In this paper, the statistical subspacebased damage localization method has been applied on a benchmark application, namely a 1/200 scale model of the Saint-Nazaire Bridge, which is a cable-stayed bridge located on the Loire River near the river’s mouth. The employed damage localization method combines data-driven features with physical parameter information from a finite element model in statistical tests, avoiding typical ill-conditioning problems of FE model updating. Damage is introduced in the mockup for cable failures on some of the 72 cables. The purpose of the experiment is to assess the capability of damage assessment methods to find a cable failure. T2 - 8. International Operational Modal Analysis Conference CY - Kopenhagen, Denmark DA - 12. Mai 2019 KW - Damage localization KW - Cable-stayed bridge KW - Cable failure KW - Structural health monitoring PY - 2019 SP - 1 EP - 9 AN - OPUS4-48183 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -