Werkstoffmodelldatenbank

FKM 2007 Issue No. 296 Project No. 264
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Final report
Abstract:

The increased operating requirements of modern power plants increasingly require the consideration of more complex operating modes and more complicated component geometries with regard to the design and fatigue calculation of highly stressed components. In recent years, material laws that can be implemented in finite element calculations have been increasingly developed for this purpose, which, due to their formulation, allow not only elastic-plastic material behavior and viscoplastic behavior, but also the description of the interactions necessary for creep fatigue loading, for example. The practical application of these models usually requires the complex determination of a relatively large number of material-specific parameters. The often quite complex material laws also lead to complex calculations. The aim of this project carried out by the MPA Stuttgart, the company EnChip Nürnberg and the TU Dresden was to determine the advantages and disadvantages of the individual models and to simplify their application. For this purpose, a model database was created in which the structure and application as well as the software required for use are compiled. The approaches behind the models are explained. The existing material models are described with regard to the possible areas of application, the application limits, the required computing time and the parameters used, and tools for parameter optimization are developed. Sensitivity analyses are used to check the application of the models for material groups. Extensive experimental results from tests with practical stresses for power plant components were available to evaluate the models. In order to compare the simulation results obtained with the different models, uniaxial tests (creep rupture tests, LCF tests) and multiaxial creep fatigue tests were simulated on thick-walled hollow cylinder specimens and compared with the experimental results. This showed that the most complex modelling, a complex material law based on the Chaboche model, can achieve very good approximations with correspondingly good parameterization. Good approximations can also be achieved with the structural model, but the effort for the formulation and parameter adjustment then also increases. The creep behavior can be described very well using the modified Graham-Walles model and the TMF model. It could be shown that useful approximations can also be determined for creep fatigue stresses where creep is the dominant stress. This also applies to the simulated tests with creep fatigue loading. The material model database provides a tool that can be extended with regard to models, but above all with regard to material-specific adaptations, which supports manufacturers and operators of high-temperature systems in the selection and application of adequate models for simulating the material behavior of components under stress cases of varying complexity.

Scope of report:
61 pages, 35 figures, 4 tables, 18 pages of appendix

Start of work:
01.01.2003

End of work:
30.06.2005
Funding body:
AVIF-No. A 201

Research centers:
Materialprüfungsanstalt Universität Stuttgart (MPA)

Head:
Prof. Dr.-Ing. habil. Eberhard Roos EnChip GmbH, Frankenstr. 140, 90461 Nuremberg, Germany

Author:
Dipl.-Ing. O. Steiling, Dipl.-Ing. K .Schmidt, Dr.-Ing. Andreas Klenk, Materialprüfungsanstalt Universität Stuttgart Dr.-Ing. E.Götzfried, EnChip GmbH, Dr.-Ing.J. Raddatz, TU Dresden

Chairman of the working group:
Dr.-Ing. Roland Mücke, Alstom Power, CH - Baden

Chairman of the board:
Dipl.-Ing. W.Siepmann, Stahl-Armaturen PERSTA GmbH , Warstein