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Lebensdauerberechnung von Aluminium-Radialverdichterrädern unter Berücksichtigung der Werkstoffalterung

Computational methods for the lifetime-evaluation of aluminum compressor wheels with consideration of material ageing
: Rockenhäuser, C.; Hartrott, P. von; Metzger, M.; Schriever, S.; Augenstein, E.; Karlin, J.; Piesker, B.; Schweizer, C.; Skrotzki, B.

Forschungsvereinigung Verbrennungskraftmaschinen -FVV-, Frankfurt/Main:
Abschluss- und Zwischenberichte der Forschungsstellen Turbomaschinen : Frühjahrstagung 2018, Tagungsband, 22.-23. März 2018, Bad Neuenahr
Frankfurt a.M.: FVV, 2018 (Forschungsvereinigung Verbrennungskraftmaschinen 583)
Forschungsvereinigung Verbrennungskraftmaschinen (FVV Frühjahrstagung) <2018, Bad Neuenahr>
Bundesministerium fur Wirtschaft und Energie BMWi (Deutschland)
IGF; 17734 N
Conference Paper
Fraunhofer IWM ()
aluminium; degradation; S-phase

In this project, a procedure was developed to improve the lifetime assessment precision of exhaust turbo charger radial compressor wheels made from the age hardenable aluminum alloy EN AW-2618A. This comprises particularly the consideration of material aging, which has to be anticipated during operation of such components under relevant service conditions (temperature, time, stress). First of all, a solid experimental database was established for the investigated material. This includes a mechanical as well as a microstructural characterization of the as-received state (T61) and after aging up to 25,000 h at relevant service temperatures (160 °C, 180 °C, 190 °C). The microstructural investigations focused on the development of the radii of the cylindrical hardening phase, which coarsens during aging. The relation between aging temperature, time and mechanical load (if applicable) was established for the first time to this extent. An interrelationship to describe the coarsening was established. The effect of aging on hardness, strength, creep behavior and fatigue lifetime (LCF, TMF) was studied and a correlation to the microstructure was established. The results of the creep tests were used to calibrate a modified hyperbolic sine creep model. A time and temperature dependent deformation model according to Chaboche, which describes the relevant phenomena of high temperature deformation and cyclic plasticity, was extended. It now considers material aging by describing the strength not only as a function of temperature but also as a function of aging, i.e. of the mean radius of the precipitates. A similar procedure was applied to extend the model in order to assess the fatigue lifetime. The calculated lifetimes of LCF and TMF tests completed during this project match well with the experimental results. Only one LCF test with a hold time of 900 s in tension deviates clearly from the mean value and shows the limits of the time independent damage model. Tests with shorter hold times of 60 s are within the scatter band, likewise the different aging conditions. A damage accumulation model additionally describing the progressive aging during lifetime was developed and implemented. Besides considering aging in the deformation and lifetime assessment, it is also possible to judge complex loading cycles in a postprocessing by rain flow classification of typical complex loading cycles. The methodology and the models were implemented into the Finite-Element software Abaqus and Ansys and are available for numerical assessment of components.