TY - JOUR A1 - Selleng, Christian A1 - Meng, Birgit A1 - Gröger, K. A1 - Fontana, Patrick T1 - Einflussgrößen auf die Wirksamkeit einer Wärmebehandlung von Ultrahochfestem Beton (UHFB) T1 - Influencing factors for the effectivity of heat treatment of ultrahigh performance concrete (UHPC) N2 - Mittels Wärmebehandlung lassen sich die hervorragenden Eigenschaften von UHFB nochmals verbessern. Die für eine optimale Umsetzung relevanten Randbedingungen werden aktuell in der Fachwelt diskutiert. In dieser Veröffentlichung werden die Ergebnisse eines Forschungsprojekts vorgestellt, das die Wirkung verschiedener Einflussgrößen bei der Wärmebehandlung auf die Eigenschaften von UHFB zum Thema hatte. Dabei wurden die Art des Schutzes gegen das Austrocknen, die Vorlagerungszeit und die Haltezeit variiert. Um die zugrunde liegenden Prozesse zu verstehen, wurde der Phasenbestand mittels Röntgendiffraktometrie untersucht. Die höchsten Druckfestigkeiten des UHFB ließen sich bei einer Wärmebehandlung mit Wasserlagerung erzielen, da hierbei eine weitere Hydratation begünstigt wird. Vergleichsweise niedriger waren die Steigerungen bei einer Behandlung mit Schutz vor Austrocknung, während eine ungeschützte Behandlung zu deutlich geringeren Festigkeiten führte. Die Vorlagerungszeit beträgt im Idealfall einige Tage, um die Ausbildung eines offenbar günstigen Ausgangsgefüges sicherzustellen. Die Haltezeit sollte möglichst ausgedehnt sein, weil die Hydratation entsprechend lange gefördert wird. Im oberflächennahen Bereich war unter bestimmten Bedingungen eine Zonierung zu beobachten, deren Ursachen und Folgen, insbesondere in Bezug auf die Dauerhaftigkeit, weitere Forschung erfordern. KW - Ultra-Hochleistungsbeton KW - Wärmebehandlung KW - Behandlungsparameter KW - Vorlagerungszeit KW - Haltezeit KW - Festigkeitssteigerung KW - Zonierung KW - Ettringit PY - 2017 DO - https://doi.org/10.1002/best.201600059 SN - 0005-9900 VL - 112 IS - 1 SP - 12 EP - 21 PB - Ernst & Sohn AN - OPUS4-39171 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wiedmann, A. A1 - Weise, Frank A1 - Kotan, E. A1 - Müller, H. S. A1 - Meng, Birgit T1 - Effects of fatigue loading and alkali-silica reaction on the mechanical behaviour of pavement concrete N2 - The primary aim of this paper is to analyze the impact of mechanical pre-damage and alkali–silica reaction (ASR) on the fracture mechanical properties of pavement concrete. For this purpose, a four point bending test was applied to large format beams to produce a defined level of cyclic pre-damage. The fatigue-induced concrete degradation process was simultaneously recorded using a testing procedure specifically developed for the purpose. In addition, fatigue-induced cracks on extracted drilling cores were spatially visualized and quantified using micro X-ray 3D-computed tomography (3D-CT). The storage of the small-format test specimens, with and without cyclic pre-damage, in an ASR-conducive environment showed that pre-damage leads to an increase in ASR damage processes. Subsequent structural mechanical investigations on small format specimens with and without pre-damage show that fatigue loading and ASR significantly influence fracture mechanical parameters of the concrete. KW - Acoustic emissions analysis KW - Alkali-silica reaction KW - Concrete pavement KW - Fatigue loading KW - Fracture energy KW - Monitoring of damage KW - Tensile strength KW - Ultrasonic velocity PY - 2017 DO - https://doi.org/10.1002/suco.201600179 SN - 1751-7648 SN - 1464-4177 VL - 18 IS - 4 SP - 539 EP - 549 PB - Ernst & Sohn AN - OPUS4-41007 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Przondziono, R. A1 - Timothy, J. J. A1 - Weise, Frank A1 - Krütt, Enno A1 - Breitenbücher, R. A1 - Meschke, G. A1 - Hofmann, M. T1 - Degradation in concrete structures due to cyclic loading and its effect on transport processes - Experiments and modeling N2 - According to the objectives of the research group 1498, this paper deals with degradation effects in concrete structures that are caused by cyclic flexural loading. The goal is to determine their influence on the fluid transport processes within the material on the basis of experimental results and numerical simulations. The overall question was, to which extent the ingress of externally supplied alkalis and subsequently an alkali-silica reaction are affected by such modifications in the microstructure. Degradation in the concrete microstructure is characterized by ultrasonic wave measurements as well as by microscopic crack analysis. Furthermore, experiments on the penetration behavior of water into the investigated materials were performed. The penetration behavior into predamaged concrete microstructures was examined by the classical Karsten tube experiment, nuclear magnetic resonance method, and time domain reflectometry techniques. In order to create an appropriate model of the material's degradation on the water transport, the Darcy law was applied to describe the flow in partially saturated concrete. Material degradation is taken into account by an effective permeability that is dependent on the state of degradation. This effective permeability is obtained by the micromechanical homogenisation of the flow in an Representative Elementary Volume (REV) with distributed ellipsoidal microcracks embedded in a porous medium. The data gained in the microscopic crack analysis is used as input for the micromechanical model. Finite element simulations for unsaturated flow using the micromechanical model were compared with the experimental results showing good qualitative and quantitative agreement. KW - Alkali ingress KW - Alkali-silica reaction KW - Computational model for unsaturated flow KW - Cyclic loading KW - Degradation KW - Micromechanics model KW - Transport processes PY - 2017 DO - https://doi.org/10.1002/suco.201600180 SN - 1751-7648 SN - 1464-4177 VL - 18 IS - 4 SP - 519 EP - 527 PB - Ernst & Sohn AN - OPUS4-41008 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Philipp A1 - Miccoli, Lorenzo A1 - Fontana, Patrick A1 - Ziegert, C. T1 - Development of partial safety factors for earth block masonry N2 - The main aim of the research was the development of a first valid database for material parameters of earth block masonry (EBM) with particular regard to statistical characteristics. A solid database is needed for the determination of the materials partial safety factor. Therefore, compressive strength tests were carried out with two types of earth blocks and two types of prefabricated earth mortar. The evaluation has shown that the mean variation of the compressive strength was remarkably less than expected, which indicates high quality standards of the components earth block and mortar with regard to industrial production. Using the reliability method, a partial safety factor for EBM subjected to compression was determined on the basis of these test results. The findings have shown that a common calculation method for EBM based on partial safety factors following the valid masonry construction standard is feasible. KW - Partial safety factor KW - Earth block masonry (EBM) KW - Reliability KW - Compressive strength PY - 2017 DO - https://doi.org/10.1617/s11527-016-0902-9 SN - 1871-6873 SN - 1359-5997 VL - 50 IS - 1 SP - 1 EP - 14 PB - Springer AN - OPUS4-38937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Häusler, Ines A1 - Moeck, P. A1 - Volz, K. A1 - Neumann, W. T1 - Orientation relationships of Mn0.75Ga0.25As crystallites on and within GaAs determined by scanning nano beam electron diffraction N2 - Mn0.75Ga0.25As crystallites, partially embedded on and fully embedded within a single crystalline matrix of GaAs formed during metal organic vapor phase epitaxy (MOVPE) of Mn-rich (Mn,Ga)As on (001) oriented GaAs wafers. Phase and orientation analysis of these crystallites were performed with scanning nano beam electron diffraction (SNBED). The investigation of plan-view specimens using a liquid nitrogen cooling stage enabled the phase and orientation analysis of partially embedded ferromagnetic a-phase particles. In all specimens the following two orientation relationships (O) between the a-phase particles and the GaAs matrix were determined: O1: [1-2.0] Mn0.75Ga0.25As || [110] GaAs and [10.2] Mn0.75Ga0.25As || [-110] GaAs O2: [10.2] Mn0.75Ga0.25As || [110] GaAs and [1-2.0] Mn0.75Ga0.25As || [-110] GaAs. The study of cross-sectional specimens enabled the analysis of fully embedded crystallites. It could be unambiguously detected that a fully embedded crystallite has the structure of the atomically ordered monoclinic β' phase. The β' phase crystallite consists of two domains which are related in twin positions to each other. The orientation relations of the different particles are illustrated by color coded stereographic projections. KW - (Mn,Ga)As crystallites KW - Scanning nano beam electron diffraction KW - Crystal phase determination KW - Orientation mapping KW - STEM/TEM imaging PY - 2017 DO - https://doi.org/10.1002/crat.201600261 SN - 1521-4079 SN - 0232-1300 VL - 52 IS - 1, Special Issue: Anniversary Issue: 50 Years of Crystal Research & Technology SP - 138 EP - 145 PB - Wiley AN - OPUS4-38939 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weltschev, Margit A1 - Schwarzer, Stefanie T1 - Vergleich der Spannungsrissbeständigkeit von Polyethylen und Polyethylenterephthalat als Werkstoffe für Verpackungen zum Transport von Gefahrgütern T1 - Comparison of the environmental stress cracking behavior of polyethylene and polyethylene terephthalate as materials for dangerous goods packagings N2 - Seitens der Industrie besteht großes Interesse, Polyethylenterephthalat (PET) als Werkstoff für Verpackungen zum Transport von Gefahrgütern einzusetzen, da aufgrund der hohen Fes-tigkeit und Steifigkeit von PET die Wanddicken und somit die Kosten der Verpackungen reduziert werden können. Die Prüfung der Spannungsrissbeständigkeit von Polyethylenformstoffen als Werkstoffe von Verpackungen erfolgt mit Labormethoden unter Verwendung einer Standardflüssigkeit als Prüfmedium für die Spannungsrisse auslösende Wirkung auf Polyethylen (PE), wodurch Zeit und Kosten der Prüfungen reduziert werden. Ziel dieser Arbeit war es, eine Laborprüfmethode zum Vergleich der Spannungsrissbeständigkeit von PE und PET auf ihre Anwendbarkeit zu prüfen, wie z.B. den Full Notch Creep Test (FNCT). Es wurde untersucht, ob die Prüfkörper aus PE und PET mit umlaufender Kerbe in dieser durch die chemische Industrie entwickelten und von der BAM konzipierten Apparatur auf der Basis des FNCT zu messbaren Ergebnissen unter Einfluss eines Ölsäureamidethoxylates als Netzmittel bei 50 °C führen. Die Testergebnisse bestätigten die Eignung des Prüfverfahrens für die acht eingesetzten Formstoffe aus PE. Dieses Prüfverfahren konnte nicht für PET angewandt werden, da die Prüfkörper aufgrund der hohen Festigkeit und Steifigkeit des PET beim Kerbvorgang zerbrachen. Die gleiche Aussage konnte für den Nachweis der der Spannungsrissbeständigkeit von Verpackungen, der in der BAM Gefahrgutregel BAM-GGR 015 beschrieben wird, getroffen werden. Die einzige Möglichkeit zum Nachweis der Spannungsrissbeständigkeit von PET besteht in der Durchführung von Stapeldruckprüfungen. N2 - The chemical industry has expressed great interest in using polyethylene terephthalate (PET) as material for packagings for the transport of dangerous goods. Due to the high strength and stiffness of PET, the wall thickness and the costs of packagings can be reduced. For packaging made of polyethylene (PE), tests to prove the stress cracking resistance used laboratory methods with a standard liquid, simulating the stress cracking effect on PE. These tests reduce time and costs. The aim of this work was to find a laboratory method to compare the stress cracking resistance of PE and PET, such as the full notch creep test (FNCT). It was investigated whether testing specimens made of PE and PET with a full coplanar notch around the middle of the specimens show weakening after the impact of a tensile force in solution of an oleic amide ethoxylate at 50 degrees C in a test device on the basis of the FNCT, which was developed by the chemical industry and designed by BAM. The test results confirmed the suitability of the method for eight PE grades. This method could not be used for PET because the specimens broke during notching due to the high stiffness and strength. The same statement applies for the proof of stress cracking resistance of PE packagings according to "Dangerous Goods Rule BAM-GGR 015" defined by BAM. In conclusion, the only way to provide information about the stress cracking resistance of PET is to perform stacking tests. KW - Gefahrgutverpackung KW - Spannungsrissbeständigkeit KW - Polyethylen KW - Polyethylenterephthalat KW - FNCT KW - Stapeldruckprüfung PY - 2017 DO - https://doi.org/10.3139/120.110966 SN - 0025-5300 VL - 59 IS - 1 SP - 29 EP - 34 PB - Carl Hanser Verlag GmbH & Co. KG CY - München AN - OPUS4-38926 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Linhares, F.N. A1 - Kersch, M. A1 - Niebergall, Ute A1 - Leite, M.Ch.A.M. A1 - Altstädt, V. A1 - Furtado, C.R.G. T1 - Effect of different sulphur-based crosslink networks on the nitrile rubber resistance to biodiesel N2 - Biodiesel possesses some comparable physical properties to petroleum diesel in addition to its improved environmental benefits. Nonetheless, both fuels differ greatly with respect to their chemical compositions. Therefore, the compatibility of the materials, which are commonly employed in contact with diesel, must also be assured for biodiesel. This paper assessed the influence of sulphur-based curing systems on the resistance of nitrile rubber to soybean biodiesel. Formulations were prepared using highacrylonitrile-content nitrile rubber by employing a two-level experimental design. The amounts of two different accelerators and sulphur were varied to achieve different types of vulcanisation systems. Thermal analyses, mechanical tests and microscopy analyses were conducted to evaluate the behaviour of the material after contact with biodiesel. The results showed that the choice of the accelerator played an important role on the resistance of the rubber to the biofuel, and crosslink density was not a key factor with respect to the resistance. KW - Soyean oil KW - Nitrile rubber KW - Compatibility KW - Vulcanisation system KW - Biodiesel KW - Resistance PY - 2017 DO - https://doi.org/10.1016/j.fuel.2016.11.060 SN - 0016-2361 SN - 1873-7153 VL - 191 SP - 130 EP - 139 AN - OPUS4-39006 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Miccoli, Lorenzo A1 - Gerrard, C. A1 - Perrone, C. A1 - Gardei, André A1 - Ziegert, C. T1 - A collaborative engineering and archaeology project to investigate decay in historic rammed earth structures: The case of the Medieval preceptory in Ambel N2 - This study assesses the structural vulnerability of part of a later medieval earthen building at Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military Orders. An inspection of its morphology and materials coupled with the results of an extensive campaign of static monitoring reveals marked structural inhomogeneities, the product of more than a thousand years of construction, failure, and repair from the 10th century to the present day. Building materials are inappropriately juxtaposed, there are discontinuities between construction phases and fundamental concerns remain over the long-term stability of the structure. The current condition of the structure is mainly influenced by structural discontinuities introduced at the time of construction, the unintended consequences of repair and modification and the material decay that has affected the base of the rammed earth walls. The overall findings of the static monitoring show that there is no related damage, variations in crack widths are related to the building seasonal cycle. While static analysis is an essential prerequisite before a suitable maintenance program can be fully defined, this study argues that no evaluation of the structural behavior of any historic building can afford to ignore its archaeological “biography” of modification and repair. KW - Archaeology KW - Historical earthen building KW - Materials characterization KW - Rammed earth KW - Static monitoring PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-396274 DO - https://doi.org/10.1080/15583058.2016.1277283 VL - 11 IS - 5 SP - 636 EP - 655 PB - Taylor & Francis Group AN - OPUS4-39627 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Asadujjaman, Asad A1 - Bertin, Annabelle A1 - Schönhals, Andreas T1 - Dielectric analysis of the upper critical solution temperature behaviour of a poly(acrylamide-coacrylonitrile) copolymer system in water N2 - A copolymer consisting of acrylamide (AAm) and acrylonitrile (AN) in aqueous solution was investigated using broadband dielectric spectroscopy at frequencies between 10⁻¹ Hz and 10⁶ Hz in the temperature range from 2 °C to 60 °C. This system shows an UCST phase behavior. The phase transition and aggregation behavior is monitored by both the temperature and frequency dependence of the complex conductivity σ*(f, T), where the AN fraction and the concentration of the solution were varied. Additionally, the dielectric data are compared with the results obtained from dynamic light scattering measurements. The temperature dependence of the DC conductivity (σDC) of the copolymer solution is monitored and the phase transition temperature (PTT) of the poly(AAm-co-AN) copolymer is deduced from a change in the T-dependence of the DC conductivity. The change in σDC can be explained by decreased effective charge carrier mobility and a reduction of the effective charge number density at temperatures below the phase Transition temperature of the poly(AAm-co-AN) solution. A pronounced interfacial polarization effect on the frequency dependence of the real part of the conductivity (σ') is observed at temperatures below the phase Transition temperature. The charge carriers are blocked at the formed aggregates giving rise to this interfacial polarization. The dependence of the interfacial polarization on the acrylonitrile fraction in the copolymer and the concentration of the solution is studied in detail and conclusions concerning the internal structures of the copolymer aggregates are drawn. KW - Thermoresponsive polymres PY - 2017 DO - https://doi.org/10.1039/c6sm02684b SN - 1744-6848 SN - 1744-683X VL - 13 IS - 12 SP - 2384 EP - 2393 PB - Royl Society of Chemistry Publishing AN - OPUS4-39556 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Schick, Ch. A1 - Schönhals, Andreas T1 - Unexpected behavior of ultra-thin films of blends of polystyrene/poly(vinyl methyl ether) studied by specific heat spectroscopy N2 - Specific heat spectroscopy (SHS) employing AC nanochip calorimetry was used to investigate the glassy dynamics of ultra-thin films (thicknesses: 10 nm–340 nm) of a polymer blend, which is miscible in the bulk. In detail, a Poly(vinyl methyl ether) (PVME)/Polystyrene (PS) blend with the composition of 25/75 wt. % was studied. The film thickness was controlled by ellipsometry while the film topography was checked by atomic force microscopy. The results are discussed in the framework of the balance between an adsorbed and a free surface layer on the glassy dynamics. By a self-assembling process, a layer with a reduced mobility is irreversibly adsorbed at the polymer/substrate interface. This layer is discussed employing two different scenarios. In the first approach, it is assumed that a PS-rich layer is adsorbed at the substrate. Whereas in the second approach, a PVME-rich layer is suggested to be formed at the SiO2 substrate. Further, due to the lower surface tension of PVME, with respect to air, a nanometer thick PVME-rich surface layer, with higher molecular mobility, is formed at the polymer/air interface. By measuring the glassy dynamics of the thin films of PVME/PS in dependence on the film thickness, it was shown that down to 30 nm thicknesses, the dynamic Tg of the whole film was strongly influenced by the adsorbed layer yielding a systematic increase in the dynamic Tg with decreasing the film thickness. However, at a thickness of ca. 30 nm, the influence of the mobile surface layer becomes more pronounced. This results in a systematic decrease in Tg with the further decrease of the film thickness, below 30 nm. These results were discussed with respect to thin films of PVME/PS blend with a composition of 50/50 wt.%as well as literature results. KW - Ultra thin polymer films PY - 2017 DO - https://doi.org/10.1063/1.4978505 SN - 0021-9606 SN - 1089-7690 VL - 146 IS - 20 SP - 203321-1 EP - 203321-9 PB - AIP Publishing AN - OPUS4-39558 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meschut, G. A1 - Janzen, V. A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Frei, J. T1 - Charakterisierung des Bruch- und Festigkeits verhaltens von widerstandspunktgeschweißten Aluminiumverbindungen N2 - Die Reduktion des Fahrzeuggewichts ist ein wesentlicher Ansatz zur Ver-ringerung des Energie- und Ressourcenverbrauchs und damit zur Senkung der CO2-Emissionen im Automobilbau. In der Karosserieentwicklung kann der vermehrte Einsatz von Aluminiumwerkstoffen einen bedeutenden Beitrag dazu leisten. Im preissensitiven Umfeld des Karosseriebaus etabliert sich das bei Stahlanwendungen genutzte Widerstandspunktschweißen zunehmend auch für Aluminiumverbindungen. Verfahrensbedingte Herausforderungen, wie verkürzte Elektrodenstandzeiten und mangelnde Kenntnis über den Einfluss von Imperfektionen auf die Festigkeit, begrenzen dennoch die Weiterverbreitung des Verfahrens und stellen die Prozessrobustheit insgesamt in Frage. Im Rahmen des hier vorgestellten Forschungsvorhabens wurden das Auftreten verschiedener Brucharten experimentell untersucht und Prognosefunktionen zur Abschätzung der Tragfähigkeit von Widerstandspunktschweißverbindungen unter verschiedenen Belastungsfällen erstellt. Anschließend wurde der Einfluss von Oberflächenrissen und Rissen in der Schweißlinse auf die Scherzugfestigkeit sowohl experimentell als auch simulativ analysiert. KW - Aluminium KW - Widerstandspressschweißen KW - Rissbildung KW - Festigkeit KW - Werkstofffragen PY - 2017 UR - http://www.schweissenundschneiden.de/article/charakterisierung-des-bruch-und-festigkeitsverhaltens-von-widerstandspunktgeschweissten-aluminiumverbindungen/ VL - 69 IS - 3 SP - 126 EP - 133 PB - DVS Media GmbH AN - OPUS4-39577 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dieck, S. A1 - Rosemann, Paul A1 - Kromm, Arne A1 - Halle, T. T1 - Reversed austenite for enhancing ductility of martensitic stainless steel N2 - The novel heat treatment concept, “quenching and partitioning” (Q&P) has been developed for high strength steels with enhanced formability. This heat treatment involves quenching of austenite to a temperature between martensite start and finish, to receive a several amount of retained austenite. During the subsequent annealing treatment, the so called partitioning, the retained austenite is stabilized due to carbon diffusion, which results in enhanced formability and strength regarding strain induced austenite to martensite transformation. In this study a Q&P heat treatment was applied to a Fe-0.45C-0.65Mn-0.34Si-13.95Cr stainless martensite. Thereby the initial quench end temperature and the partitioning time were varied to characterize their influence on microstructural evolution. The microstructural changes were analysed by dilatometer measurements, X-ray diffraction and scanning electron microscopy, including electron backscatter diffraction. Compression testing was made to examine the mechanical behaviour. It was found that an increasing partitioning time up to 30 min leads to an enhanced formability without loss in strength due to a higher amount of stabilized retained and reversed austenite as well as precipitation hardening. T2 - 19th Chemnitz Seminar on Materials Engineering – 19. Werkstofftechnisches Kolloquium CY - Chemnitz, Germany DA - 16.03.2017 KW - Quenching and partitioning KW - Martensitic stainless steels KW - Heat treatment KW - Transformation induced plasticity KW - High ductility PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-395328 DO - https://doi.org/10.1088/1757-899X/181/1/012034 SN - 1757-899X SN - 1757-8981 VL - 181 IS - Conference 1 SP - Article UNSP 012034, 1 EP - 8 PB - IOP Publishing CY - Bristol, UK AN - OPUS4-39532 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gottlieb, Cassian A1 - Millar, Steven A1 - Günther, Tobias A1 - Wilsch, Gerd T1 - Revealing hidden spectral information of chlorine and sulfur in data of a mobile Laser-induced Breakdown Spectroscopy system using chemometrics N2 - For the damage assessment of reinforced concrete structures the quantified ingress profiles of harmful species like chlorides, sulfates and alkali need to be determined. In order to provide on-site analysis of concrete a fast and reliable method is necessary. Low transition probabilities as well as the high ionization energies for chlorine and sulfur in the near-infrared range makes the detection of Cl I and S I in low concentrations a difficult task. For the on-site analysis a mobile LIBS-system (k = 1064 nm, Epulse ≤ 3 mJ, t = 1.5 ns) with an automated scanner has been developed at BAM. Weak chlorine and sulfur signal intensities do not allow classical univariate analysis for process data derived from the mobile system. In order to improve the analytical performance multivariate analysis like PLS-R will be presented in this work. A comparison to standard univariate analysis will be carried out and results covering important parameters like detection and quantification limits (LOD, LOQ) as well as processing variances will be discussed (Allegrini and Olivieri, 2014 [1]; Ostra et al., 2008 [2]). It will be shown that for the first time a low cost mobile system is capable of providing reproducible chlorine and sulfur analysis on concrete by using a low sensitive system in combination with multivariate evaluation. KW - LIBS KW - Chemometrics KW - Building materials PY - 2017 DO - https://doi.org/10.1016/j.sab.2017.04.001 SN - 0584-8547 VL - 132 SP - 43 EP - 49 PB - Elsevier B.V. AN - OPUS4-40066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Joester, Maike A1 - Seifert, Stephan A1 - Emmerling, Franziska A1 - Kneipp, Janina T1 - Physiological influence of silica on germinating pollen as shown by Raman spectroscopy N2 - The process of silicification in plants and the biochemical effects of silica in plant tissues are largely unknown. To study the molecular changes occurring in growing cells that are exposed to higher than normal concentration of silicic acid, Raman spectra of germinating pollen grains of three species (Pinus nigra, Picea omorika, and Camellia japonica) were analyzed in a multivariate classification approach that takes into account the variation of biochemical composition due to species, plant tissue structure, and germination condition. The results of principal component analyses of the Raman spectra indicate differences in the utilization of stored lipids, a changed mobilization of storage carbohydrates in the pollen grain bodies, and altered composition and/or structure of cellulose of the developing pollen tube cell walls. These biochemical changes vary in the different species. KW - Silica KW - Raman spectroscopy KW - Principal component analysis PY - 2017 DO - https://doi.org/10.1002/jbio.201600011 SN - 1864-063X SN - 1864-0648 VL - 10 IS - 4 SP - 542 EP - 552 AN - OPUS4-40090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weltschev, Margit T1 - Auswahl eines Kennwertes für den Vergleich des mechanischen Leistungsniveaus von Polyethylenformstoffen für Gefahrgutverpackungen T1 - Parameter selection for the comparison of the mechanical level of performance of polyethylene molding materials for packagings of dangerous goods N2 - Zum Vergleich der Polyethylenformstoffe für eine Bauart von Gefahrgutverpackungen und IBC wurden die Materialkennwerte: Schmelze-Massefließrate MFR, Dichte D, Kerbschlag-zähigkeit acN bei -30 °C, Spannungsrissbeständigkeit (bestimmt mit dem Full Notch Creep Test) und Beständigkeit gegen oxidativen Abbau Ox (bestimmt durch den prozentualen Anstieg des MFR in Salpetersäure) in der DIN EN 15507 – Verpackung – Verpackungen zur Beförderung gefährlicher Güter – Vergleichende Werkstoffprüfung von Polyethylensorten ausgewählt. Das Ziel der Untersuchungen war die Auswahl eines Kennwertes für die Bestimmung des mechanischen Leistungsniveaus von Polyethylenformstoffen, da unter Druck Verpackungen beulen oder knicken. Zur Auswahl standen drei Prüfverfahren: a) Bestimmung der Biegesteifigkeit S nach DIN 53 350 (Prinzip von Ohlsen). b) Bestimmung der Biegefestigkeit σfM und Biegedehnung ɛfM nach DIN EN ISO 178 c) Bestimmung der Druckkraft Fmax und Verformung dL bei Fmax nach DIN EN ISO 604. Die Prüfmethode zur Bestimmung der Biegesteifigkeit nach DIN 53 350 eignet sich zum Vergleich des mechanischen Leistungsniveaus der Formstoffe. Zur Verbesserung der Reproduzierbarkeit der Ergebnisse sollte der Skalierungsbereich der Prüfapparatur erweitert wer-den, um genauere Messergebnisse zu erzielen. Der Dreipunktbiegeversuch nach DIN EN ISO 178 eignet sich bei verformungsfähigen Kunststoffen, wie dem Polyethylen, zur Bestimmung der Biegefestigkeit σfM. Dieser Ver-such besitzt den Nachteil, dass am Ort des maximalen Biegemoments in der Randschicht, wo auch die maximale Biegespannung erzeugt wird, zusätzlich der Biegestempel angreift. Die Messergebnisse haben gezeigt, dass die Druckprüfung nach DIN EN ISO 604 sich sehr gut zur Bewertung des mechanischen Verhaltens der Polyethylenformstoffe unter Druckbelastung (Stapeldruckprüfung der Verpackungen) eignet. KW - Gefahrgutverpackung KW - Polyethylen KW - Biegesteifigkeit KW - Biegefestigkeit KW - Druckkraft PY - 2017 DO - https://doi.org/10.3139/120.111025 SN - 0025-5300 VL - 59 IS - 5 SP - 466 EP - 471 PB - Carl Hanser Verlag GmbH & Co.KG CY - München AN - OPUS4-40145 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rodrigues, A.C.P. A1 - Österle, Werner A1 - Gradt, Thomas A1 - Azevedo, César Roberto de Farias T1 - Impact of copper nanoparticles on tribofilm formation determined by pin-on-disc tests with powder supply: Addition of artificial third body consisting of Fe3O4, Cu and graphite N2 - Copper, magnetite and graphite particles were mixed in order to observe their impact on the coefficient of friction (CoF) during pin-on-disc tests and on the tribofilm formation after testing. Pure magnetite powder provided a value of CoF of 0.4. Magnetite-copper mixtures tested at 400 °C revealed lower CoF values (~0.4) than those at room temperature (~0.6). Magnetite-graphite and magnetite-graphite-copper mixtures presented lower CoF values (~0.3). All systems formed a magnetite-based tribofilm and patches of metallic copper were found on the tribosurfaces of the mixtures containing copper. Carbon layers and graphite nanoinclusions were observed in the graphite mixtures. The incorporation of zirconia particles, a by-product of ball milling mixing, prevented the selective transfer of graphite and copper to the tribosurfaces of some of the samples. KW - Brake pad materials KW - Sliding friction KW - Transfer layer KW - Surface analysis KW - Model friction tests PY - 2017 DO - https://doi.org/10.1016/j.triboint.2017.02.014 SN - 0301-679X VL - 110 SP - 103 EP - 112 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-40104 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sproesser, G. A1 - Chang, Y.-J. A1 - Pittner, Andreas A1 - Finkbeiner, M. A1 - Rethmeier, Michael T1 - Environmental energy efficiency of single wire and tandem gas metal arc welding N2 - This paper investigates gas metal arc welding (GMAW) with respect to energy consumption and its associated environmental impacts. Different material transfer modes and power levels for single wire GMAW (SGMAW) and tandem GMAW (TGMAW) are evaluated by means of the indicator electrical deposition efficiency. Furthermore, the wall-plug efficiency of the equipment is measured in order to describe the total energy consumption from the electricity grid. The results show that the energy efficiency is highly affected by the respective process and can be significantly enhanced by a TGMAW process. The wall-plug efficiency of the equipment shows no significant dependency on the power range or the material transfer mode. Moreover, the method of life cycle assessment (LCA) is adopted in order to investigate the influences of energy efficient welding on the environmental impacts. In the comparative LCA study, the demand of electrical energy is reduced up to 24%. In consequence, the indicator values for global warming potential (100), acidification potential, eutrophication potential, and photochemical ozone creation potential are reduced up to 11%. KW - Energy input KW - Tandem welding KW - MAG welding KW - Environment KW - Lifetime PY - 2017 DO - https://doi.org/10.1007/s40194-017-0460-y SN - 0043-2288 SN - 1878-6669 VL - 61 IS - 4 SP - 733 EP - 743 PB - Springer CY - Heidelberg AN - OPUS4-39877 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hennig, C. A1 - Weiss, S. A1 - Kraus, Werner A1 - Kretzschmar, J. A1 - Scheinost, A.C. T1 - Solution species and crystal structure of Zr(IV) acetate N2 - Complex formation and the coordination of zirconium with acetic acid were investigated with Zr K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and single-crystal diffraction. Zr K-edge EXAFS spectra show that a stepwise increase of acetic acid in aqueous solution with 0.1 M Zr(IV) leads to a structural rearrangement from initial tetranuclear hydrolysis species [Zr4(OH)8(OH2)16]8+ to a hexanuclear acetate species Zr6(O)4(OH)4(CH3COO)12. The solution species Zr6(O)4(OH)4(CH3COO)12 was preserved in crystals by slow evaporation of the aqueous solution. Single-crystal diffraction reveals an uncharged hexanuclear cluster in solid Zr6(μ3-O)4(μ3-OH)4(CH3COO)12·8.5H2O. EXAFS measurements show that the structures of the hexanuclear zirconium acetate cluster in solution and the solid state are identical. KW - Complex formation KW - Crystal structure KW - Zr(iV) compounds PY - 2017 DO - https://doi.org/10.1021/acs.inorgchem.6b01624 SN - 0020-1669 SN - 1520-510X VL - 56 IS - 5 SP - 2473 EP - 2480 PB - ACS AN - OPUS4-39677 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Joseph, A. A1 - Bernardes, C. E. S. A1 - Druzhinina, A. I. A1 - Varushchenko, R. M. A1 - Nguyen, Thi Yen A1 - Emmerling, Franziska A1 - Yuan, L. A1 - Dupray, V. A1 - Coquerel, G. A1 - Minas da Piedade, M. E. T1 - Polymorphic phase transition in 4′-hydroxyacetophenone: Equilibrium temperature, kinetic barrier, and the relative stability of Z′=1 and Z′=2 forms N2 - Particularly relevant in the context of polymorphism is understanding how structural, thermodynamic, and kinetic factors dictate the stability domains of polymorphs, their tendency to interconvert through phase transitions, or their possibility to exist in metastable states. These three aspects were investigated here for two 4′-hydroxyacetophenone (HAP) polymorphs, differing in crystal system, space group, and number and conformation of molecules in the asymmetric unit. The results led to a ΔfGm°-T phase diagram highlighting the enantiotropic nature of the system and the fact that the Z′=1 polymorph is not necessarily more stable than its Z′=2 counterpart. It was also shown that the form II → form I transition is entropy driven and is likely to occur through a nucleation and growth mechanism, which does not involve intermediate phases, and is characterized by a high activation energy. Finally, although it has been noted that conflicts between hydrogen bond formation and close packing are usually behind exceptions from the hypothesis of Z′=1 forms being more stable than their higher Z′ analogues, in this case, the HAP polymorph with stronger hydrogen bonds (Z′=2) is also the one with higher density. KW - Polymorphism KW - Polymorphic transition KW - 4'-hydroxyacetophenone PY - 2017 DO - https://doi.org/10.1021/acs.cgd.6b01876 SN - 1528-7483 SN - 1528-7505 VL - 17 IS - 4 SP - 1918 EP - 1932 PB - ACS AN - OPUS4-40167 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Myrach, Philipp A1 - Jonietz, Florian A1 - Meinel, Dietmar A1 - Suwala, Hubert A1 - Ziegler, Mathias T1 - Calibration of thermographic spot weld testing with X-ray computed tomography N2 - The paper presents an attempt for the calibration of an active thermography method that is suitable for the non-destructive evaluation of spot welds. Nowadays, the quality of spot welds is commonly characterised by the application of random chisel tests, which are time consuming, expensive and destructive. Recently a non-destructive testing method by means of active thermography was proposed that relies on the fact that the mechanical connection formed by the spot weld also serves as a thermal bridge between the two steel sheets joined in the welding process. It is shown in this paper that this thermal bridge can be thermographically characterised by extracting a measure for the spot weld diameter and hence the quality of the spot weld. The determination of the absolute value of the diameter hereby relies on a calibration of the testing system, which is performed by means of X-ray computed tomography in this study. The experiments were carried out using different experimental approaches, namely transmission as well as reflection geometry wSetup in reflectionith laser illumination. A comprehensive evaluation of samples produced using different welding currents, hence different quality, was carried out in order to validate the thermographic results. KW - Thermography KW - Spot welds KW - Spot welding KW - Computed thomography KW - Non-destructive testing PY - 2017 DO - https://doi.org/10.1080/17686733.2017.1281554 SN - 1768-6733 SN - 2116-7176 VL - 14 IS - 1 SP - 122 EP - 131 PB - Taylor & Francis CY - London AN - OPUS4-40180 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -