Uncertainty of lifetime evaluation for cafe creep damage model

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Uncertainty of lifetime evaluation for cafe creep damage model

Krzysztof Nowak

Politechnika Krakowska, ul. Warszawska 24, 31-155 Kraków, Poland.

DOI:

https://doi.org/10.7494/cmms.2011.2.0349

Abstract:

In the paper the influence of material microstructure randomness upon statistically observed scatter of experimental results on macroscopic level is searched through. It is well known that a lot of random factors influence the lifetime of engineering structures working under elevated temperatures, like variations of loading and temperature. Although they can be controlled in laboratory conditions the scatter of experimental results of creep tests is still very large. Remaining variability is mainly due to randomness of material structure. Not only lifetime of structure, set here as the time to first macroscopic defect, but also other parameters like strain to failure or steady-state strain rate are of random characters. Macroscopically the scatter of creep test results can be modelled by some probabilistic distribution of material parameters used in macroscopic equations. But this approach cannot explain the reasons of this scatter. To reflect the importance of material structure the multiscale model has been built where the influence of polycrystalline grains pattern on damage development process is modelled by cellular automata simulation described in previous author’s papers. Material structure is homogenous as all grain properties, including mean grain diameter over Representative Volume Element remain constant. Macroscopic results obtained by the model are statistically analysed. Proposed model predicts the scatter of time to failure in range of scatter of experimental results for intergranular failure mode.

Cite as:

Nowak, K. (2011). Uncertainty of lifetime evaluation for cafe creep damage model. Computer Methods in Materials Science, 11(2), 315 – 323. https://doi.org/10.7494/cmms.2011.2.0349

Article (PDF):

Keywords:

Randomness of creep failure data, Creep fracture, Damage mechanics, Cellular Automata, CAFE

References: