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How experimental and computational methods allow us to design negative thermal expansion materials
No full textCombined experimental and computational methods allow comprehensive understanding, design, and tailoring of material properties. We focus on a well-known negative thermal expansion (NTE) material, zirconium vanadate (ZrV2O7), and address synthesis, characterisation and validation of results with computational simulations. Experimental and computational X-ray diffraction and Raman spectroscopy data highlighted differences between phase-pure and multiphase ceramics. These techniques allowed us to distinguish subtle differences in the structure of the material. Based on ab initio simulated phonon data, unaffected by impurities or instrumental errors, we could interpret the Raman spectra and visualise Raman active atom vibrations. These computational models allowed better insight and further experimental improvement while high-quality experimental data granted the validation and improvement of computational simulation strategy
A statistical assessment of the laser energy absorption and keyhole stability in high-power laser welding
No full textThe behavior of the molten pool and final weld qualities in high-power laser welding are significantly influenced by laser absorption and keyhole stability. However, the dynamic features involved make the in-depth analyses challenging. This study addresses the challenges by conducting a thorough statistical evaluation of the effects of key welding parameters on laser absorption and keyhole fluctuations, using experimental investigations and a robustly validated multi-physics model. From a statistical aspect, the laser energy distribution and the keyhole collapse, commonly considered to be highly time-varying, show certain regularities, for example, three distinct regions of the temporally averaged energy distribution and a universal normal distribution of the keyhole collapse positions. Further discussion is performed to clarify the greater potential of the statistical data in revealing some well-known, industry-related but unclearly explained findings, such as the saturation of the weld penetration with increasing heat input and the physical basis of the contributions of different welding parameters in the porosity reduction
Investigations on the Thermochemical Degradation of PFAS in Flue Gas from Laboratory and Pilot Plant Facilities
No full textPer- and polyfluoroalkyl substances – abbreviated as PFAS - are compounds that enter the environment through industrial material cycles. Their chemically stable carbon-fluorine bonds provide valuable technical properties for industrial applications, but also render them resistant and environmentally persistent. Consequently, PFAS accumulate in various biological systems and organisms, and can now be detected in numerous samples, including drinking water, human blood, and soil. This accumulation is concerning due to the documented harmful and/or carcinogenic properties of many PFAS compounds [1,2]. For this reason, it is important to understand the pathways of these compounds from industrial processes into the environment. Combustion processes, such as those in waste incineration, are of particular interest to ensure that no PFAS are released into the environment. In this project, various combustion processes at laboratory and pilot plant scales will be examined to determine the optimal parameters for the reduction of PFAS in different materials.
Depending on the definition applied, the range of PFAS spans from ~4,700 to ~14,000 individual compounds, which can vary significantly in their chemical properties. This, combined with a variety of complex matrices, makes PFAS analysis particularly challenging [1,2]. Due to the complexity of PFAS, the analysis of fluorine sum parameters has become established in recent years. The application of High Resolution Continuum Source Graphite Furnace Molecular Absorption Spectroscopy (HR-CS-GFMAS) has seen increased usage [3]. However, such a methodology has not yet been established for gas analysis. Although OTM 45 was published in 2021, allowing the quantification of 50 individual PFAS, it is unclear whether this is representative of the entire class of substances [4].
Therefore, the aim of this project is to improve the analysis of PFAS in flue gas from laboratory and pilot plant facilities, thereby contributing to the understanding of their thermochemical degradation and the optimization of combustion parameters. In initial experiments, a suitable sampling apparatus consisting of impigners, a coil condenser, and gas washing bottles was tested and optimized. Cuttings, partially spiked with PFOA, and sewage sludge served as reference materials. For the measurement of sum parameters, an HR-CS-GFMAS method was developed and validated
Spannstahlbrücken der Vergangenheit in der Zukunft richtig bewerten
No full textSpannstahlbrücken die in der Vergangenheit mir vergüteten Spannstählen errichtet worden sind können unter ungünstigen Gegebenheiten bei deren Erstellung signifikante Probleme hinsichtlich der Tragfähigkeit bekommen. Im Speziellen kann die wasserstoffinduzierte Spannungsrisskorrosion hier bei der Errichtung der Brückenbauwerke Anrisse an den Spanndrähten erzeugt haben die Jahre später zum Versagen der Brücke führen können. Die Präsentation im Speziellen behandelt den Teileinsturz der Carolabrücke in Dresden
Wechselwirkung zwischen Nahtgestaltung und Ermüdungsfestigkeit in LTT-geschweißten Längssteifen
No full textSchweißzusätze mit niedriger Martensitstarttemperatur (Low Transformation Temperature, LTT) induzieren während der Abkühlphase infolge einer volumeninduzierten Martensitumwandlung Druckeigenspannungen in der Schweißnaht sowie in der angrenzenden Wärmeeinflusszone (WEZ). Diese Spannungen können zu einer signifikanten Erhöhung der Ermüdungsfestigkeit führen. Zur quantitativen Bewertung des Potenzials dieser innovativen Werkstoffe wurden konventionelle Längssteifen als Versuchsproben herangezogen, bei denen an den Stirnseiten Schweißnähte unter Verwendung von LTT-Zusatzwerkstoffen appliziert wurden. Durch gezielte Variation der Schweißparameter konnten unterschiedliche Nahtgeometrien realisiert werden. In Abhängigkeit von der Nahtausführung zeigte sich bei einer Belastungszahl von 2 Millionen Zyklen eine Steigerung der Ermüdungsfestigkeit im Bereich von 64 MPa bis 100 MPa im Vergleich zu Referenzproben mit herkömmlichen Schweißzusätzen. Die Ergebnisse belegen, dass der Einsatz von LTT-Schweißzusätzen grundsätzlich geeignet ist, die Ermüdungsfestigkeit geschweißter Strukturen zu verbessern
Fire resistance of existing steel structures with aged intumescent coating based on an in situ test method
No full textIntumescent coatings are commonly used in civil engineering to increase the fire resistance of steel structures. Exposed to fire, the intumescent coating reacts and forms a thermal protective char around the steel member. Thus, the heating of the steel is significantly slowed down and the fire resistance can be improved. Information regarding the scope of application and the durability of intumescent coatings are given in national approvals or European Technical Assessment documents. Due to the environmental conditions, intumescent coatings are subjected to ageing effects, which can reduce the durability and their thermal protection performance. To predict the durability for several years, during the approval procedure the behaviour of intumescent coatings is predominantly extrapolated based on accelerated artificial ageing. The established German and European assessment procedures to test and assess durability assume a working life of at least 10 years. Additional evidence may be required for longer periods. However, at present there is no method of verifying the thermal performance of existing structural members on site. For this reason, BAM is conducting the research project "INSIST" [1] to develop a minimally invasive in situ test method to determine the fire resistance of existing steel structures with applied intumescent coating. The investigation includes the development of a mobile prototype furnace. The paper describes the test setup, the developed prototype furnace, and the results of the performed test programme on uncoated and coated steel specimens. Based on this, recommendations for the test procedure are given
Condition monitoring for lifetime extension of interim storage facilities
No full textThe German interim nuclear storage facilities are designed for a 50 year service life and 40-year operating period. They will be needed much longer, as a final repository will not be available until 2050 at the earliest.
The objective of ZuMoBau-ZL is to develop a suitable condition assessment and monitoring concept suitable for the structures in interim storage facilities, including life prediction models, with which the remaining service life can be predicted, verified, and monitored as realistically as possible
Herausforderungen des modernen Holzbaus: Erste statistische Erkenntnisse aus realen Gebäudebränden in Holzbauweise
No full textHinsichtlich des Brandschutzes zeigt der durch die Bundesregierung geförderte Holzbau Herausforderungen gegenüber Massivbauweisen. Diese spiegeln sich in Erfahrungen von Feuerwehren wider, aber nun auch in statistischen Untersuchungen der Brandschadenstatistik der Vereinigung zur Förderung des deutschen Brandschutzes sowie der Arbeitsgemeinschaft der Leiterinnen und Leiter der Berufsfeuerwehren (AGBF) und des Deutschen Feuerwehrverbands (DFV). Im Zeitraum von 2013 bis 2017 wurden in der vfdb-Brandschadenstatistik Daten zu 5016 Alarmierungen bei Gebäudebränden in Deutschland systematisch mit einem einheitlichen Erfassungsbogen erfasst und seit 2016 „bemerkenswerte Brandeinsätze“ durch einen Evaluierungsbogen zu Maßnahmen des vorbeugenden Brand- und Gefahrenschutzes von AGBF/DFV. Grundlage des vorliegenden Beitrags sind die Auswertung und der Vergleich beider statistischer Datensätze hinsichtlich der Brände in Gebäuden in Holzbauweise. Es zeigt sich, dass der Holzbau mit brandschutztechnischen Herausforderungen verbunden ist
A brief journey through the world of standardization of fireworks of the last decade and into the future
No full textThis paper aims at giving an overview about this entire standardization process, explaining the main differences of the EN versions from 2015 and 2022, outlining the practical implications for the stakeholders applying these ENs and giving a cautious look into the future requirements for fireworks in Europe
Facile Fluorometric Detection of Faecal Pigments: Challenges and Solutions Concerning Water Quality Testing
No full textAbstractDetection and monitoring of faecal contaminants in water is an important component of water quality testing protocol worldwide. However, a systematic overview of the faecal indicator paradigm, including its fundamentals and challenges in analytical applications, is missing. In particular, with respect to the advantages of using faecal indication pigments (FIP) over faecal indication bacteria (FIB). This discussion is based on two FIPs, Urobilin (UB) and Stercobilin (SB), which can enable rapid and real‐time indication of faecal contaminants in ground/surface water. Novel strategies for enhancing sensitive fluorescence‐based techniques for trace concentration detection have been discussed in detail, with specific reference to understanding their physicochemical properties, photophysics, metal‐ligand complexation, molecular aggregations, thermodynamics, fluorescence response and matrix interferences in aqueous media or environmental samples. The insights provided in this perspective article could inspire procedures by avoiding ambiguities and misinterpretations