Filtern
Erscheinungsjahr
Dokumenttyp
Schlagworte
- SAXS (2)
- Terahertzsysteme (2)
- A549 (1)
- Agricultural mycology (1)
- Analytical methods (1)
- Anatase nanoparticles (1)
- Austenitic steel (1)
- Bayesian approach (1)
- Benchmark (1)
- Bildhafte Auswertetechnik (1)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (4)
- 8.0 Abteilungsleitung und andere (3)
- 4 Material und Umwelt (2)
- 7 Bauwerkssicherheit (2)
- 4.0 Abteilungsleitung und andere (1)
- 4.3 Schadstofftransfer und Umwelttechnologien (1)
- 7.2 Ingenieurbau (1)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (1)
- 8.6 Faseroptische Sensorik (1)
An assessment of the elastic-plastic buckling limit state for multi-strake wind turbine support towers poses a particular challenge for the modern finite element analyst, who must competently navigate numerous modelling choices related to the tug-of-war between meshing and computational cost, the use of solvers that are robust to highly nonlinear behaviour, the potential for multiple near-simultaneously critical failure locations, the complex issue of imperfection sensitivity and finally the interpretation of the data into a safe and economic design.
This paper reports on an international ‘round-robin’ exercise conducted in 2022 aiming to take stock of the computational shell buckling expertise around the world which attracted 29 submissions. Participants were asked to perform analyses of increasing complexity on a standardised benchmark of an 8-MW multi-strake steel wind turbine support tower segment, from a linear elastic stress analysis to a linear bifurcation analysis to a geometrically and materially nonlinear buckling analysis with imperfections. The results are a showcase of the significant shell buckling expertise now available in both industry and academia.
This paper is the first of a pair. The second paper presents a detailed reference solution to the benchmark, including an illustration of the Eurocode-compliant calibration of two important imperfection forms.
Stress is a normal part of life for fungi, which can survive in environments considered inhospitable or hostile for other organisms. Due to the ability of fungi to respond to, survive in, and transform the environment, even under severe stresses, many researchers are exploring the mechanisms that enable fungi to adapt to stress. The International Symposium on Fungal Stress (ISFUS) brings together leading scientists from around the world who research fungal stress. This article discusses presentations given at the third ISFUS, held in Sao Jose dos Campos, Sao Paulo, Brazil in 2019, thereby summarizing the state-of-the-art knowledge on fungal stress, a field that includes microbiology, agriculture, ecology, biotechnology, medicine, and astrobiology.
The present work shows results on elemental distribution analyses in Cu(In,Ga)Se2 thin films for solar cells performed by use of wavelength-dispersive and energy-dispersive X-ray spectrometry (EDX) in a scanning electron microscope, EDX in a transmission electron microscope, X-ray photoelectron, angle-dependent soft X-ray emission, secondary ion-mass (SIMS), time-of-flight SIMS, sputtered neutral mass, glow-discharge optical emission and glow-discharge mass, Auger electron, and Rutherford backscattering spectrometry, by use of scanning Auger electron microscopy, Raman depth profiling, and Raman mapping, as well as by use of elastic recoil detection analysis, grazing-incidence X-ray and electron backscatter diffraction, and grazing-incidence X-ray fluorescence analysis. The Cu(In,Ga)Se2 thin films used for the present comparison were produced during the same identical deposition run and exhibit thicknesses of about 2 µm. The analysis techniques were compared with respect to their spatial and depth resolutions, measuring speeds, availabilities, and detection limits.
The suitability of common analytical methods for the determination of active substances from wood preservatives in aged wood samples was investigated during an interlaboratory study. Permethrin, propiconazole and tebuconazole were quantified in 1.5 and 8 year-old wood samples by gas chromatography and liquid chromatography. Generally, the applied Methods yielded reliable results for these samples. However, wood components can coelute with propiconazole and tebuconazole during liquid chromatography. Optimization of separation might be required if UV detection is applied.
Hydrogen represents an important alternative to fossil fuels. Hydrogen storage is possible as a gas, at room temperature (RT) at about 20 MPa pressure, and in a liquefied form, at cryogenic temperatures of about 20 K. The latter form is particularly attractive due to the possibility of stocking a large quantity of hydrogen within a small volume. In moving parts (e.g. of transport vehicles) cryogenic temperature and the presence of hydrogen strongly enhance wear processes and subsequently component failure.
The present work deals with the deformation behaviour and the microstructural deterioration of austenitic CrNi- and CrMn high nitrogen-steels during friction in liquid hydrogen at 20 K. The modified microstructure within the wear scar is studied by scanning electron microscopy and X-ray diffraction methods. Diffraction studies of wear scars reveal the importance of twinning during deformation at 20 K. This increase of twinning can be attributed to a hydrogen-induced reduction of stacking fault energy (SFE) in the austenitic steels. Interactions between twin boundaries and planar dislocation structures along with locally increased stresses led to the formation of extensive crack networks. The amount of hydrogen-induced surface cracks depends on the alloy composition and is not necessarily correlated to the wear resistance of the austenitic steels.
Zusammenfassung
Bei der laufenden Instandhaltung der Schienenfahrzeuge werden die Radsätze auf Fehlerfreiheit geprüft. Dabei werden sowohl die Laufräder wie auch die Radsatzwellen einer zerstörungsfreien Prüfung mit Ultraschall unterzogen.
Im Werk Wittenberge der DB Regio AG wurde im Jahre 2001 die bisher eingesetzte Handprüfung bzw. eine teilmechanisierte Prüfung mit konventioneller Technik durch eine mechanisierte automatische Prüfung mit Ultraschall-Gruppenstrahlertechnik abgelöst. Die bisherige individuelle Befundbewertung durch A-Bilder wurde durch eine numerische Rekonstruktion der Prüfdaten mit bildhafter Darstellung ersetzt. Dabei konnte die Prüfaussage signifikant verbessert und die Prüfzeit von bisher bis zu 30 Minuten auf 5 Minuten reduziert werden.
Ziel bei der Prüfung von Radsatzvollwellen ist es, die Rad- und Bremsscheibensitze sowie sämtliche Querschnittsübergänge auf radiale Fehler, d.h. auf quer zur Längsachse liegende Risse, zu überprüfen. Die eingeschränkte Zugänglichkeit der Prüforte hätte beim Einsatz von konventioneller Technik eine Vielzahl von Winkelprüfköpfen erforderlich gemacht, was in der Praxis einen schwer zu bewältigenden Aufwand allein auf Seiten der Prüfmechanik mit sich gebracht hätte. Die Technik der laufzeitgesteuerten Gruppenstrahler ermöglicht es, sämtliche geforderten Prüfbereiche mit 4 Prüfköpfen zu erfassen.