Filtern
Erscheinungsjahr
Dokumenttyp
Schlagworte
- P92 (5)
- Stress relaxation (3)
- Tempered martensite-ferritic steel (3)
- Creep (2)
- Creep-fatigue (2)
- Low Cycle Fatigue (2)
- Ontology (2)
- P91 (2)
- TMF (2)
- Tempered Martensite Ferritic Steels (2)
Organisationseinheit der BAM
- 5 Werkstofftechnik (15)
- 5.2 Metallische Hochtemperaturwerkstoffe (15)
- 5.5 Materialmodellierung (4)
- 5.1 Mikrostruktur Design und Degradation (3)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.3 Instrumentelle Analytik (1)
- 6 Materialchemie (1)
- 6.4 Materialinformatik (1)
- 7 Bauwerkssicherheit (1)
- 7.7 Modellierung und Simulation (1)
- 8 Zerstörungsfreie Prüfung (1)
- 8.0 Abteilungsleitung und andere (1)
- VP Vizepräsident (1)
- VP.1 eScience (1)
Components in the Aerospace, Power and Automotive engineering sectors are frequently subjected to cyclic stresses induced by thermal fluctuations and mechanical loads. For the design of such components, reliable material property data are required which need to be acquired using well accepted and reproducible test procedures for thermo-mechanical fatigue (TMF) loading. There is limited availability of proven TMF data indicating there is need for further research and testing. The TMF behaviour of materials is often desired to be simulated in models which describe the cyclic stress-strain behaviour, the fatigue life and the cyclic crack growth behaviour. There is a continuous need for the development and amendment of such models. Models can be validated by using materials in industrial applications which are subjected to TMF loading.
The 3rd Workshop on Thermo-Mechanical Fatigue was held on 27–29 April 2016 at BAM, Berlin, Germany. The workshop was attended by 90 attendees coming from 17 countries in the world. 38 presentations including five poster presentations were held.
The following topics were covered by the workshop:
– TMF of materials coated with Thermal Barrier Coatings.
– Thermal Gradient Mechanical Fatigue.
– TMF crack growth.
– TMF + High Cycle Fatigue.
– TMF Modelling and Lifetime Prediction.
– TMF Properties of steels, cast iron, Al-, Mg- and Ni-alloys
– Advanced TMF Testing Techniques.
– Industrial Applications.
A panel discussion was held regarding the present state of TMF testing standards (ISO and ASTM) and their potential for improvement. The discussion and contributions were summarized and forwarded to the standard committees. The 3rd TMF-Workshop ensured the continuation of international exchange of knowledge providing a forum to present and discuss all recent developments in the field of thermo-mechanical fatigue.
The current special issue publishes eleven selected papers of the 3rd TMF-Workshop 2016. The papers were peer reviewed by a number of experts in the Thermo-Mechanical Fatigue sector. I hope you will enjoy reading papers of this special issue.
The current competitive situation on electricity markets forces power plants into cyclic operation regimes with frequent load shifts and starts/shutdowns. In the present work, the cyclic mechanical behavior of ferritic-martensitic 9-12 % Cr steels under isothermal and thermomechanical loading was investigated for the example of grade P92 material. A continuous softening was observed under all loading conditions. The introduction of hold periods to the applied cycles reduced material lifetime, with most prominent effects at technologically relevant small strain levels. The microstructural characterization reveals a coarsening of the original “martensitic” lath-type microstructure to a structure with polygonal subgrains and reduced dislocation density. The microstructural data forms the input for a physically-based modelling approach.
A miniature specimen geometry is presented that allows to extract small samples for tensile creep tests directly from critical components of steam generators in power plants like e.g. superheater tubes. In this way, material can be tested which has been subjected to the full processing chain of the component. The specimens then exhibit all microstructural modifications that are present in the component after the shaping process and heat treatment, and representative mechanical properties are determined. Similarly, specimens can be extracted from pre-corroded test pieces or used components after service to determine the impact of complex aging/loading/oxidation conditions during service on the mechanical properties of the material. The applicability of the miniature specimen test method is demonstrated in a comparative creep study involving standard and miniature specimens of P91 tempered martensite ferritic steel. Test results indicate satisfactory accuracy/repeatability of the method. Comparison with large scale specimen data reveals an influence of specimen size on the obtained creep behavior. These size effects need to be considered for a correct interpretation of results from miniature specimen creep tests.
The use of miniaturized specimen geometries in mechanical testing allows extracting the sample material directly from critical components of power plants like e.g. headers and pipes. In this way, both the impacts of the manufacture of the component (including all shaping and tempering influences) and of the complex aging/loading/oxidation conditions during Service can be analyzed and representative mechanical properties are obtained. In the present study, example results of a comparative creep and creep rupture study on P91 tempered martensite ferritic Steel, involving Standard and miniature specimens that were all taken from one batch of material, are presented.
Cylindrical creep specimens with a minimum gauge length diameter of 3 mm were used, representing the smallest recommended test geometry of ISO 204. The test results of miniature specimens exhibit all characteristic creep features of tempered martensite ferritic steels, and analysis of the stress and temperature dependence of creep results in values that correspond well to literature data for P91. However, direct comparison with large scale specimen data reveals small but systematic variations in minimum creep rates, elongations at fracture and times to rupture. In our contribution, these differences are discussed in the light of literature findings on specimen size influences in other heat resistant alloys. Size effects need to be considered for a correct interpretation of results from miniature specimen creep tests.
Charakterisierung des Kriechverhaltens hochwarmfester Stähle durch Versuche an Miniaturproben
(2014)
Die Einsatzbedingungen der Bauteile von fossil befeuerten Kraftwerken unterliegen derzeit durch aktuelle Entwicklungen des Energiesektors (Stichwort „Energiewende“) erheblichen Veränderungen. Während das Interesse an einer weiteren Steigerung der Wirkungsgrade und den damit verbundenen Erhöhung der Prozessdrücke und -temperaturen prinzipiell anhält, werden parallel neue Verbrennungsprozesse wie z. B. die Oxyfuelverbrennung diskutiert und die Einsatzmöglichkeiten von Ersatzbrennstoffen wie Biomasse und hochkalorischen Müllfraktionen werden untersucht.
Während diese Maßnahmen über veränderte Rauchgaszusammensetzungen ggf. zu einem generell verstärkten Hochtemperaturkorrosions-Angriff der Bauteile führen, zwingt der Ausbau der Stromerzeugung auf Basis von Wind- und Sonnenenergie die Anlagenbetreiber gleichzeitig zu einer lastflexiblen Anlagenfahrweise mit häufigen Warm- und Kaltstarts bei möglichst hohen Lastgradienten.
Diese veränderten Betriebsbedingungen stellen eine Herausforderung für die Überwachung und Instandhaltung bestehender Kraftwerke sowie für die Konstruktion neuer Anlagen und Komponenten dar.
Size effects in miniature specimen creep testing of heat resistant ferritic-martensitic steels
(2015)
The use of miniaturized specimen geometries in mechanical testing allows extracting the sample material directly from the sidewall of critical components of power plants, like e.g. headers and steam pipes. In this way, both the impacts of the processing of the component (including all shaping and tempering influences) and of the exposure to the complex aging/loading/oxidation conditions in the plant (in case of post-Service tests) can be analyzed and representative mechanical properties are obtained.
The continuing increase of steam parameters of fossil fuelled high efficiency power plants and new combustion concepts for the capture and storage of carbon dioxide lead to harsher service conditions for the components and structural materials of such facilities. The present work introduces a test concept that allows testing of candidate materials under simultaneous mechanical and corrosive loading. The material's reaction can be directly investigated under simulated temperature, load and corrosion conditions of modern installations. First results obtained for different heat resistant steels suggest a strong influence of the environmental medium on the fatigue and creep behaviour. Such findings complement the data that is available from the classical qualification process of the materials and may support the material selection for new power plant installations.
Mechanical properties of superheater materials after ageing and corrosion in CO2 rich flue gases
(2010)
Das hochaktuelle Thema der Integration und Wiederverwendung von Wissen und Daten aus Herstellung, Bearbeitung und Charakterisierung von Materialien ('Digitalisierung von Materialien') wird in den Projekten Innovationsplattform MaterialDigital (PMD, materialdigital.de) und Materials-open-Lab (Mat-o-Lab, matolab.org) adressiert. In diesem Beitrag werden die Weiterentwicklungen in diesen Projekten hinsichtlich der Speicherung von Zugversuchsdaten gemäß einer normenkonformen (DIN EN ISO 6892-1:2019-11) ontologischen Repräsentation vorgestellt. Das umfasst den Weg von der Entwicklung einer Ontologie nach Norm, der Konvertierung von Daten aus Standardtests in das interoperable RDF-Format bis hin zur Verknüpfung von Ontologie und Daten. Letztendlich können die entsprechenden Daten in einem Triple Store abgelegt und abgefragt werden.
Performing mechanical tests at high temperatures is a nontrivial issue: Compared to room temperature testing, additional phenomena like time-dependent Deformation processes and oxidation effects raise the complexity of the material’s response, while more sophisticated test setups and additional control parameters increase the number of potential sources of error. To a large extent, these complications can be overcome by carefully following all recommendations given in the respective high temperature testing standards, but more comprehensive background information helps to identify points of specific importance in particular test campaigns. In this chapter, an overview is given on general high temperature testing issues like the appropriate choice of experimental equipment and key aspects of temperature measurement. In subsequent sections, the major static and dynamic high temperature test methods are reviewed and their Special features, as compared to testing at room temperature, are highlighted based on example data sets. Influences of specimen size and environmental effects are shortly outlined in a concluding section. In the whole chapter, a focus is set on testing of “classical” metallic high temperature materials, but many considerations are equally valid for testing of intermetallics, composites, and high temperature ceramics.