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Eingeladener Vortrag
- nein (1102)
Konventionelle und innovative Hochtemperaturwerkstoffe sind im technischen Betrieb einer Vielzahl an Belastungen ausgesetzt. Neben mechanischen Beanspruchungen stellt die chemische Belastung durch das Vorhandensein von aggressiven und korrosiven Medien (SO2, CO2, O2, H2O…) bei hoher Temperatur einen Schlüsselfaktor dar, der die Langlebigkeit der Materialien im Einsatz beeinflusst. Neben konventionellen, mikroskopischen Analyseverfahren bieten röntgenbasierte Techniken Möglichkeiten, die Grenzflächenreaktionen zwischen dem Werkstoff und den Medien während der chemischen Belastung (in situ) zu untersuchen. Neuartige Einblicke in die zugrunde liegenden Prozesse der Schädigungsmechanismen werden anhand von klassischen ferritischen Legierungen beschrieben. Das Verständnis von Schlüsselfaktoren zur Induzierung eines Schutzmechanismus ist insbesondere für die Entwicklung von neuartigen Materialklassen wie Hochentropie- und chemisch komplexe Legierungen notwendig. Erste Einblicke in Schädigungsmechanismen durch Gaskorrosion dieser innovativen Materialsysteme werden vorgestellt.
Rail inspection performed by ultrasonic rail inspection trains is a complex and challenging process. A large number of variables and parameters given by the environment, the track and the testing-system have an influence on the overall performance of the inspection and the inspection result. Typically the parameter vary in a combination depending on the track condition.
To evaluate the individual influence of each relevant variable, simulation tools can be used. Therefore the entire inspection process has to be transferred into a model using combined modelling techniques.
The goal of this work is to model an instrumented ultrasonic test run with a rail inspection train with the parameters varied by a script over a virtually driven distance.
Der Implant-Test nach ISO 17642-3 gehört zur Gruppe der fremdbeanspruchten Kaltrisstests, bei dem eine äußere Beanspruchung auf einen zylindrischen Stab (Implant-Probe) definiert aufgebracht wird. Mit dieser Kaltrissprüfung wurde vergleichende Analysen zur Kaltrissempfindlichkeit der modernen hochfesten Feinkornbaustähle S960MC und S960QL durchgeführt.
Asymmetrical laser-induced plasmas were investigated by a tomography approach based on the inverse Radon transform. Two distinct sources of asymmetricity were investigated: double-pulsed laser-induced plasmas in the orthogonal configuration and single-pulsed laser-induced plasmas under an inclined incidence angle. Both cases were observed at various delay times. The optical thinness of the laser-induced plasmas was achieved by appropriately adjusting the pulse energies. High temporal resolution is achieved by a gated intensified charge-coupled-device camera. The asymmetrical laser-induced plasmas are investigated in terms of their total emissivity, spectrally resolved emissivity, and temperature. The latter is obtained by the Saha–Boltzmann plot method. The images required for the inverse Radon transform technique were obtained with a high angular accuracy and reproducibility provided by mounting the spectrometer on a high-precision nano-positioning rotary stage. The plasmas were induced in the center of rotation of the stage. This arrangement allows the reconstruction of emissivity, which is integrated over a full spectral range (200-800 nm) or over a desired spectral range selected by a bandpass filter (~10 nm). It also allows for the reconstruction of spectrally-resolved emissivity in each cross sectional plasma slice by scanning the plasma across a spectrometer slit. The 3D maps of temperature and electron density are thus obtained for different types of asymmetric plasmas.
CEQAT-DGHS Interlaboratory tests for method validation and measurement uncertainty determination
(2019)
An explosion in a chemical plant or a fire on a dangerous goods vessel - the reason for such accidents can be numerous. Prevention starts in the laboratory where chemicals are tested for their hazardous properties in order to be able to assess the risks involved in their handling. For this purpose, test methods have been developed and published. They are applied globally nowadays. Safety experts, manufacturers, suppliers, importers, employers or consumers must be able to rely on the validity of safety-related test methods and on correct test results and assessments in the laboratory.
Interlaboratory tests play a decisive role in assessing the reliability of test results. Participation in interlaboratory tests is not only a crucial element of the quality assurance of laboratories; as such it is explicitly recommended in DIN EN ISO/IEC 17025. In addition, interlaboratory tests are also used to develop and validate test methods and can be used for the determination of the measurement uncertainty.
Interlaboratory tests on different test methods have been performed by Bundesanstalt für Materialforschung und –prüfung (BAM) and Physikalisch-Technische Bundesanstalt (PTB) in collaboration with the QuoData GmbH during the last 10 years. Significant differences between the results of the participating laboratories were observed in all interlaboratory tests. The deviations of the test results were not caused only by laboratory faults but also by deficiencies of the test method (see interlaboratory test reports of the CEQAT-DGHS Centre for quality assurance for testing of dangerous goods and hazardous substances: www.ceqat-dghs.bam.de).
In view of the interlaboratory test results the following conclusions can be drawn:
• To avoid any discrepancy on classification and labelling of chemicals it should become state of the art to use validated test methods and the results accompanied by the measurement uncertainty.
• A need for improvement is demonstrated for all examined test methods. Thus, interlaboratory tests shall initially aim at the development, improvement and validation of the test methods (including the determination of the measurement uncertainty) and not on proficiency tests.
• The laboratory management and the practical execution of the tests need to be improved in many laboratories.
• The term "experience of the examiner" must be seen critically: A "long experience with many tests" is not necessarily a guarantee for correct results.
Chemical compositions of the welds have significant effect on weld quality. Current inspection methods for the weld seams employ mostly post factum methods and cannot prevent weld defects.Elemental burn offs may significantly affect solidification leading to embrittlement or cracking. Control of weld chemical compositions insures a controlled solidification and resistance to related weld defects.
In situ ED XRD und Radiographie während eines Zugversuchs an wasserstoffbeladenem Supermartensit
(2019)
Die Ergebnisse von in-situ Experimenten am Berliner Elektronenspeicherring (BESSY II) werden vorgestellt. Es wurden Zugversuche an wasserstoffbeladenen und wasserstofffreien supermartensitischen Proben durchgeführt und Diffraktionsspektren und radiographische Bilder aufgenommen. Die energiedispersive Röntgendiffraktion ermöglichte dabei die dehnungsinduzierte Phasenumwandlung von Restaustenit zu Martensit in-situ zu beobachten. Die Radiographiebilder der zerreisenden Probe gaben Einblicke in das Bruchverhalten in Abhängigkeit vom Wasserstoffgehalt des Supermartensits.
aRTist is an easy-to-use and practical simulation tool to generate realistic radiographic images from CAD objects. A dedicated add-on module makes CT simulation easy (virtual computer tomography). Just choose the number of projections.
Unlike in the practice, simulation can separately image the primary and scatter radiation. This allows studying the scattering artefacts in CT (gray-level variations in regions of homogeneous material).