TY - JOUR A1 - Gottlieb, Cassian A1 - Millar, Steven A1 - Grothe, S. A1 - Wilsch, Gerd T1 - 2D evaluation of spectral LIBS data derived from heterogeneous materials using cluster algorithm N2 - Laser-induced Breakdown Spectroscopy (LIBS) is capable of providing spatially resolved element maps in regard to the chemical composition of the sample. The evaluation of heterogeneous materials is often a challenging task, especially in the case of phase boundaries. In order to determine information about a certain phase of a material, the need for a method that offers an objective evaluation is necessary. This paper will introduce a cluster algorithm in the case of heterogeneous building materials (concrete) to separate the spectral information of non-relevant aggregates and cement matrix. In civil engineering, the information about the quantitative ingress of harmful species like Cl−, Na+ and SO2−4 is of great interest in the evaluation of the remaining lifetime of structures (Millar et al., 2015; Wilsch et al., 2005). These species trigger different damage processes such as the alkali-silica reaction (ASR) or the chloride-induced corrosion of the reinforcement. Therefore, a discrimination between the different phases, mainly cement matrix and aggregates, is highly important (Weritz et al., 2006). For the 2D evaluation, the expectation-maximizationalgorithm (EM algorithm; Ester and Sander, 2000) has been tested for the application presented in this work. The method has been introduced and different figures of merit have been presented according to recommendations given in Haddad et al. (2014). Advantages of this method will be highlighted. After phase separation, non-relevant information can be excluded and only the wanted phase displayed. Using a set of samples with known and unknown composition, the EM-clustering method has been validated regarding to Gustavo González and Ángeles Herrador (2007). KW - LIBS KW - Concrete KW - EM-clustering KW - Heterogeneity PY - 2017 DO - https://doi.org/10.1016/j.sab.2017.06.005 SN - 0584-8547 VL - 2017 IS - 134 SP - 58 EP - 68 PB - Elsevier B.V. AN - OPUS4-40644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maierhofer, Christiane A1 - Krankenhagen, Rainer A1 - Röllig, Mathias A1 - Rehmer, Birgit A1 - Gower, M. A1 - Baker, G. A1 - Lodeiro, M. A1 - Aktas, A. A1 - Monte, C. A1 - Adibekyan, A. A1 - Gutschwager, B. T1 - Defect characterisation of tensile loaded CFRP and GFRP laminates used in energy applications by means of infrared thermography N2 - The increased use of fibre reinforced plastic (FRP) composites for improved efficiency and reliability in energy related applications, e.g. wind and marine turbine blades, nacelles, oil and gas flexible risers, also increases the demand for innovative non-destructive testing technologies. In this contribution, results concerning the characterisation of CFRP and GFRP during and after quasi-static tensile loading are presented. It includes the measurement of optical properties in the infrared spectral range, tensile loading tests with the observation of the temperature distribution at one or both sides of the specimens using an infrared camera for the preparation and monitoring of intended natural defects, and active thermography inspections after tensile loading. It is shown that the defect preparation was successful. Thermographic monitoring during and active thermography testing after tensile loading enable the detection of the lateral extend of the generated defects. Differences between CFRP and GFRP materials are discussed. KW - Tensile loading KW - Fibre reinforced composites KW - Active and passive thermography KW - Emissivity PY - 2017 DO - https://doi.org/10.1080/17686733.2017.1334312 SN - 1768-6733 SN - 2116-7176 VL - 15 IS - 1 SP - 17 EP - 36 PB - Taylor and Francis CY - London AN - OPUS4-40968 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Volkmar A1 - Molnarne, Maria T1 - Flammability of gases in focus of European and US standards N2 - The presentation will discuss the difference between EU and US standards for the determination of explosion (flammability) limits and limiting oxygen concentration. Small differences observed in measured values can be traced back to the different test apparatuses and criteria. The discrepancies can be much greater in the case of limiting oxygen concentration because of the high amount of inert gases and the corresponding low laminar burning velocities. The paper describes some examples and the influence of the chosen criteria on the results. The European and US standards use the criteria of flame propagation in open test vessels and of pressure rise in closed ones. The examples discussed show that flame propagation is still possible at very small pressure rise values, as observed much below the pressure rise criterion of usual standards. However, flame propagation in a process plant can cause an accident or explosion and must be avoided. Therefore, the flame propagation criterion is recommended to be used in chemical safety engineering. The European safety database CHEMSAFE contains expertevaluated safety data for cases where the determination method and criteria are known. Flammability characteristics based on the pressure rise criterion may suffice in certain cases, e.g. for explosion protection in closed vessels without any connecting pipes. KW - Flammability KW - Limiting oxygen concentration KW - Test methods KW - Standards PY - 2017 DO - https://doi.org/10.1016/j.jlp.2017.05.012 SN - 0950-4230 SN - 1873-3352 VL - 48 SP - 297 EP - 304 PB - Elsevier CY - Amsterdam AN - OPUS4-40980 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krütt, Enno T1 - Ermüdungsbedingte Degradation von Fahrbahnbeton - Einfluss auf den Stofftransport T1 - Fatigue-induced degradation of deck concrete influence on the material transport N2 - In den letzten 15 Jahren hat im deutschen Autobahnnetz die Anzahl von Schäden an Betonfahrbahnen, die vor 2005 er-richtet wurden zugenommen. Dies führt oft zu einer Vermin-derung der Lebensdauer von 30 auf 10 bis 15 Jahre. Trotz umfassender Untersuchungen wurde die Ursache bis jetzt nicht eindeutig geklärt, jedoch scheint die Alkali-Kieselsäure-Reaktion (AKR) hierbei eine Rolle zu spielen. Vor diesem Hintergrund wurden AKR-Performance-Tests entwickelt, die jedoch die mechanischen Einwirkungen aus Klima und Ver-kehr nicht berücksichtigen. Aus diesem Grund wurde eine AKR-Forschergruppe von der Deutschen Forschungsgemein-schaft ins Leben gerufen, welche sich experimentell und auf Simulationsebene mit diesem Thema befasst. Inhalt dieses Beitrages sind ausgewählte Ergebnisse des an der BAM bear-beiteten experimentellen Projektteils, welche in eine auf die Auswirkung einer mechanischen Degradation fokussierte Promotionsarbeit einfließen. Ziel der ausgewählten Untersuchung ist es, den Einfluss einer mechanisch induzierten Betondegradation auf den Stofftrans-port herauszuarbeiten. Hierzu wird ein großformatiger Balken einem zyklischen Vier-Punkt Biegezugversuch mit einer Anzahl von 5 Mio. Lastwechseln unterzogen. Während des Versuches findet ein Schadensmonitoring mit verschiedenen zerstörungsfreien Prüftechniken statt. Hierzu zählen Deh-nungsmessungen, Schallemissionsanalyse und Ultraschall-messungen. Nach dem zyklischen Belastungs-versuch werden kleinformatige Probekörper aus dem belasteten Balken entnommen. Als Referenz dienen unbelas-tete Probekörper aus der gleichen Herstellungscharge. Die Oberflächen der entnommenen Probekörper werden in einem kapillaren Saugversuch zum einen mit deionisiertem Wasser und zum anderen mit einer 3,6 %igen NaCl-Lösung beauf-schlagt. Während der Saugversuche dienen verschiedene zerstörungsfreie bzw. -arme Messmethoden dazu, die Feuch-teaufnahme bzw. -verteilung in den Probekörpern zu messen. Hierzu gehören neben der Gravimetrie die Messung mit NMR (Nuclear-Magnetic-Resonance) sowie TDR (Time-Domain-Reflectometry). Nach den Saugversuchen wird die Na- und Cl-Verteilung an den mit NaCl-Lösung beaufschlagten Pro-bekörpern zerstörend mittels LIBS (Laser-Induced-Breakdown-Spectroscopy) ermittelt. Erste Ergebnisse zeigen, dass die zyklische Ermüdungsdegradation den Stofftransport tendenziell verstärkt. KW - Degradation KW - Stofftransport KW - Fahrbahnbeton PY - 2017 SN - 0005-9900 SN - 1437-1006 VL - 112 IS - 7 SP - 458 EP - 458 AN - OPUS4-41097 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bochnig, M. S. A1 - Oh, M.-J. A1 - Nagel, T. A1 - Jost-Brinkmann, P.-G. A1 - Ziegler, Fred T1 - Comparison of the shock absorption capacities of different mouthguards N2 - In this in vitro study, the protective qualities of different mouthguard types were examined during small hard object collisions. The aim was to investigate inconclusive aspects of hard inserts, nylon nets, and air spaces as reinforcements in the anterior region and the protection qualities of ethylene vinyl acetate (EVA). Five different mouthguards with a labial thickness between 2 mm and 11 mm made of materials of varying stiffness were investigated. As a negative control, the same experiments were performed without a mouthguard. Different combinations of EVA and labial inserts ((polyethylene terephthalate glycol-modified [PETG]), nylon mesh, air space) were tested. Using a stainless steel pendulum device, blows of different energy (0.07-2.85 joules) were applied to the center of the crown of a pivoted tooth in a custom-built jaw model. A laser Doppler vibrometer measured the tooth deflection, while an acceleration sensor attached to the pendulum measured the braking accelerations. Tooth deflection was reduced up to 99.7% compared to no mouthguard, and the braking acceleration was reduced up to 72.2% by increasing the mouthguards' labial thickness in combination with labial inserts of different stiffness and a built-in air space between the front teeth and the mouthguard. The mouthguards made of soft materials (EVA with nylon mesh) showed slightly better protection qualities than the more rigid mouthguards of similar thickness (PETG; P<.05). However, with increasing impact energy, their protective capacities decreased to a greater extent than the stiffer mouthguards. The combination of increased labial thickness and labial inserts of varying stiffness and eventually an air space offers the best protection capacities for hard, small object collisions. KW - Shock absorbtion KW - Hard object collisions KW - Mouthguard PY - 2017 DO - https://doi.org/10.1111/edt.12324 SN - 1600-4469 VL - 33 IS - 3 SP - 205 EP - 213 PB - John Wiley & Sons, Ltd CY - Hoboken, NJ, USA AN - OPUS4-41098 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dutto, Paola A1 - Stickle, M. M. A1 - Pastor, M. A1 - Manzanal, D. A1 - Yague, A. A1 - Tayyebi, S. A1 - Lin, C. A1 - Elizalde, M. D. ED - Cervera, Miguel T1 - Modelling of fluidised geomaterials: the case of the Aberfan and the Gypsum tailings impoundment flowslides N2 - The choice of a pure cohesive or a pure frictional viscoplastic model to represent the rheological behaviour of a flowslide is of paramount importance in order to obtain accurate results for real cases. The principal Goal of the present work is to clarify the influence of the type of viscous model—pure cohesive versus pure frictional—with the numerical reproduction of two different real flowslides that occurred in 1966: the Aberfan flowslide and the Gypsum tailings impoundment flowslide. In the present work, a depth-integrated model based on the v-pw Biot–Zienkiewicz formulation, enhanced with a diffusion-like equation to account for the pore pressure Evolution within the soil mass, is applied to both 1966 cases. For the Aberfan flowslide, a frictional viscous model based on Perzyna viscoplasticity is considered, while a pure cohesive viscous model (Bingham model) is considered for the case of the Gypsum flowslide. The numerical approach followed is the SPH method, which has been enriched by adding a 1D finite difference grid to each SPH node in order to improve the description of the pore water evolution in the propagating mixture. The results obtained by the performed simulations are in agreement with the documentation obtained through the UK National Archive (Aberfan flowslide) and the International Commission of large Dams (Gypsum flowslide). KW - Aberfan flowslide KW - SPH KW - Landslide propagation modelling KW - Perzyna viscoplasticity PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-410493 DO - https://doi.org/10.3390/ma10050562 SN - 1996-1944 VL - 10 IS - 5 SP - 562, 1 EP - 562, 21 AN - OPUS4-41049 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kohler, C. A1 - Nikfalazar, M. A1 - Heunisch, Andreas A1 - Schulz, Bärbel A1 - Mikolajek, M. A1 - Rabe, Torsten A1 - Jakoby, R. A1 - Binder, J. T1 - Implementation of Ba0.6Sr0.4TiO3-ZnO-B2O3 based tunable microwave phase shifters in LTCC technology N2 - Tunable dielectric Ba0.6Sr0.4TiO3-ZnO-B2O3 thick-films were analyzed regarding their integration potential into the LTCC technology. Therefore, tunable loaded line phase shifters based on metal-insulator-metal varactors with single- and double- printed BST thick-films were fabricated and co-sintered inside a four layer LTCC module. Microstructural and chemical investigations showed a sufficient compatibility and adhesion between the silver, BST composite and LTCC layers and a resulting morphology depending on the processing route. The microwave characterization of the LTCC-embedded phase shifters revealed comparable results to phase shifters with the same design on alumina substrates. KW - Thick films KW - Dielectric materials KW - Electroceramics PY - 2017 DO - https://doi.org/10.1111/ijac.12687 SN - 1546-542X SN - 1744-7402 VL - 14 IS - 4 SP - 574 EP - 582 PB - Wiley CY - Hoboken, NY, USA AN - OPUS4-41086 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daly, M. A1 - Burnett, T. L. A1 - Pickering, E. J. A1 - Tuck, O. C. G. A1 - Léonard, Fabien A1 - Kelley, R. A1 - Withers, P. J. A1 - Sherry, A. H. T1 - A multi-scale correlative investigation of ductile fracture N2 - The use of novel multi-scale correlative methods, which involve the coordinated characterisation of matter across a range of length scales, are becoming of increasing value to materials scientists. Here, we describe for the first time how a multi-scale correlative approach can be used to investigate the nature of ductile fracture in metals. Specimens of a nuclear pressure vessel steel, SA508 Grade 3, are examined following ductile fracture using medium and high-resolution 3D X-ray computed tomography (CT) analyses, and a site-specific analysis using a dual beam plasma focused ion beam scanning electron microscope (PFIB-SEM). The methods are employed sequentially to characterise damage by void nucleation and growth in one volume of interest, allowing for the imaging of voids that ranged in size from less than 100 nm to over 100 mm. This enables the examination of voids initiated at carbide particles to be detected, as well as the large voids initiated at inclusions. We demonstrate that this multi-scale correlative approach is a powerful tool, which not only enhances our understanding of ductile failure through detailed characterisation of microstructure, but also provides quantitative information about the size, volume fractions and spatial distributions of voids that can be used to inform models of failure. It isfound that the vast majority of large voids nucleated at MnS inclusions, and that the volume of a void varied according to the volume of its initiating inclusion raised to the power 3/2. The most severe voiding was concentrated within 500 mm of the fracture surface, but measurable damage was found to extend to a depth of at least 3 mm. Microvoids associated with carbides (carbide-initiated voids) were found to be concentrated around larger inclusion-initiated voids at depths of at least 400 mm. Methods for quantifying X-ray CT void data are discussed, and a procedure for using this data to calibrate parameters in the Gurson-Tvergaard Needleman (GTN) model for ductile failure is also introduced. KW - Gurson model KW - SA508 KW - Correlative tomography KW - Void nucleation & growth KW - X-ray computed tomography PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-414547 UR - http://www.sciencedirect.com/science/article/pii/S1359645417302203?via%3Dihub DO - https://doi.org/10.1016/j.actamat.2017.03.028 VL - 130 SP - 56 EP - 68 PB - Elsevier AN - OPUS4-41454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilke, Manuel A1 - Kabelitz, Anke A1 - Zimathies, Annett A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Crystal structure and in situ investigation of a mechanochemical synthesized 3D zinc N-(phosphonomethyl)glycinate N2 - The mechanochemical synthesis of the zinc N-(phosphonomethyl)glycinate Zn(O₃PCH₂NH₂CH₂CO₂) H₂O is presented. The structure was solved from powder X-ray diffraction (PXRD) data. In the three-dimensional pillared structure, the Zn atoms are coordinated tetrahedrally. In situ investigations of the reaction process with synchrotron PXRD and Raman spectroscopy reveal a two-step process including the formation of an intermediate. KW - Mechanochemistry KW - Metal phosphonate KW - In situ PY - 2017 DO - https://doi.org/10.1007/s10853-017-1121-7 SN - 0022-2461 SN - 1573-4803 VL - 52 IS - 20 SP - 12013 EP - 12020 PB - Springer CY - New York AN - OPUS4-41490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Matoga, D. A1 - Roztocki, K. A1 - Wilke, Manuel A1 - Emmerling, Franziska A1 - Oszajca, M. A1 - Fitta, M. A1 - Bałanda, M. T1 - Crystalline bilayers unzipped and rezipped: solid-state reaction cycle of a metal–organic framework with triple rearrangement of intralayer bonds N2 - We present a series of remarkable structural transformations for a family of layered metal–organic frameworks (MOFs) in a three-step solid-state reaction cycle. The cycle represents new dynamic behavior of 2D coordination polymers and involves the sequence of reactions: {[Mn2(ina)4(H2O)2]·2EtOH}n (JUK-1) → {(NH4)2[Mn(ina)2(NCS)2]}n·xH2O (JUK-2) → {[Mn2(ina)2(Hina)2(NCS)2]}n (JUK-3) → JUK-1 (Hina = isonicotinic acid), each accompanied by rearrangement of intralayer coordination bonds and each induced by a different external stimulus. In situ investigation of the first step of the cycle by combined synchrotron X-ray diffraction and Raman spectroscopy reveals direct mechanochemical unzipping of JUK-1 bilayers to respective JUK-2 layers with reaction rates dependent on the milling conditions. In contrast, the reverse zipping of JUK-2 layers involves two steps and proceeds through a new MOF (JUK-3) whose structure was elucidated by powder X-ray diffraction. Magnetic measurements confirm conversions of manganese nodes in the reaction cycle. The findings indicate the possibility of developing coordination-based assemblies with large structural responses for use in smart stimuli-responsive systems and sensor technologies. KW - Mechanochemistry KW - In situ KW - XRD KW - MOF PY - 2017 UR - http://pubs.rsc.org/is/content/articlehtml/2017/ce/c7ce00655a DO - https://doi.org/10.1039/C7CE00655A VL - 19 SP - 2987 EP - 2995 AN - OPUS4-41517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -