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:
Belloni, G., Bernasconi, G., Piatti, G., 1977, Creep damage and rupture in A1SI 310 austenitic steel, Meccanica, 12, 84-96.
Bodnar, A., Chrzanowski, M., Nowak, K., Latus, P. , 2008, Influence of small variations of initial defects upon crack paths in creeping plates – Continuum Damage Mechanics description, Eng. Fract. Mech., 75, 526-533.
Boettner, R.C., Robertson, W.D., 1961, A Study of the Grow of Voids in Copper During the Creep Process by Mes urement of the Accompanying Change in Dens* Trans. Metall. Soc. AIME, 221, 613-622.
Chrzanowski, M., 1972, On the Possibility of Describing Complete Process of Metallic Creep, Bull. Ac. PoL J Ser. Sc. Techn.,XX, 75-81.
Chrzanowski, M., Nowak, K., 2009, On Multiscale Modelhajp Creep Damage by Means of Cellular Automata, J. Aftrf-tiscale Modelling, 1, 389-402.
Cocks, A.C.F., Ashby, M. F., 1982, On creep fracture by void growth, Prog. Mater. Sci., 27, 189-244.
Das, S., Palmiere, E. J., Howard, I.C., 2001, CAFE: a new ap¬proach to the modelling of multipass hot rolling, Proc Modelling of Metal Rolling Processes Symposium II -Through Process Modelling, The Institute of Materials. London, 33-40.
Delph, T.J., Yukich, J.E., 1992, A finite element method for tte probabilistic creep of solids, Int. J. Numer. Meth. Eng, 35, 1171-1182.
Dyson, B.F., 1976, Constraints on diffusional cavity growik rates, Metal Sci., 10, 349-353.
Evans, M., 1995, Statistical properties of the failure time distri¬bution for 0.5Cr 0.5Mo 0.25V steels, J. Mater. Process. Tech., 54, 171-180.
Farris, J.P., Lee, J. D., Harlow, D. G., Delph T.J., 1990, On Ike scatter in creep rupture times, Metall. Mater. Trans. 21 A, 345-352.
Feltham, P., Meakin, J.D., 1959, Creep in Face-Centred Cuba: Metals with Special Reference to Copper, Acta ML … 7, 614-627.
Giessen, E. van der Onck, P., van der Burg, M.W.D., 1997,Some effects of random microstructural variations creep rupture, Eng. Fract. Mech., 57, 205-226.
Harlow, D. G., Delph, T.J., 2000, Creep Deformation and Failure: Effects of Randomness and Scatter, J. Eng. Mater. Tech.-T. ASME, 122, 342-347.
Hayhurst, D.R., 1974, The effects of test variables on scatter in high-temperature tensile creep-rupture data, Int. J. Mech. Sci., 16, 829-841.
Matic, P., Geltmacher, A.B., 2001, A cellular automaton-based technique for modeling mesoscale damage evolution, Comp. Mat. Sci., 20, 120-141.
Monkman, F.C., Grant, N.J., 1956, An Empirical Relationship between Rupture Life and Minimum Creep Rate Creep-Rupture Test, Proc. ASTM, 56, 593-620.
Nowak, K., 2007, Modelling of Brittle Damage Nucleation by Means of CA, Computer Methods in Materials Science.,7, 150-155.
Nowak, K., 2009, Micro- versus macro- modelling of creep damage, Computer Methods in Materials Science, % 249-255.
Raabe, D., 2002, Cellular Automata in Materials Science WT& Particular Reference to Recrystallization Simulation. Ann. Review of Materials Research, 32, 53-76.
Riedel, H. , 1987, Fracture at High Temperatures, Springer-Verlag, Berlin, Heidelberg, New York, London, Paris. Tokyo.
Roy, N, Bose, S.C., Ghosh, R.N., 2010, Stochastic aspects of evolution of creep damage in austenitic stainless steeL Mater. Sci. Eng., 527A, 4810-4817.
Wilshire, B., Battenbough, A.J., 2007, Creep and creep fracture of polycrystalline copper, Mater. Sci. Eng., 443A, 156-166