Naslov
Lifetime Prediction for Metallic Materials in the Creep-Fatigue Interaction Regime Based on the Constitutive Modelling of Material Behaviour

Autori
Rubeša, Domagoj

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Inst. für Metallkunde und Werkstoffprüfung & Inst. für Struktur- und Funktionskeramik

Mjesto
Leoben

Datum
12.05

Godina
1995

Stranica
148

Mentor
Danzer, Robert

Ključne riječi
lifetime prediction; creep-fatigue interaction; linear accumulation of damage; strain rate modified rule; creep damage; constitutive modelling; Chaboche's viscoplastic model; IN 738 LC superalloy

Sažetak
The aim of the present work was to explain and point out a general need for constitutive modelling in conjunction with life time prediction and to investigate the application of a particular, potentially very powerful method of lifetime prediction in the creep-fatigue interaction regime, based on the principle of linear accumulation of strain rate modified (SRM) creep damage. The SRM rule of damage accumulation has been coupled with Chaboche's viscoplastic model and built into the computer programme. The proposed method has been verified on the example of nickel-base superalloy IN 738 LC at 850 °C under invariable cyclic loading. The procedure of the calibration of the method to a specific material and practical application have been shown in detail. The application of the SRM method supported by Chaboche's model to IN 738 LC gave good and reliable life predictions in the whole range of cyclic creep and creep- fatigue interaction. The deviations of the predicted from experimentally observed cycles to failure approximately correspond to the inherent data scatter. It would be superfluous to require a prediction that is more certain than the phenomenon is by its nature, and any method, at least for this example, can hardly be better. Two definite advantages of the SRM method over its rivals came into view: its suitability for the extrapolation of life predictions to various load cycling conditions other than those of the small number of fatigue tests required for its calibration and a fairly well defined inherent criterion of validity of a given prediction. By supporting the SRM method in its original form with the suitable constitutive model the amount of necessary experimental details considerably further reduced compared to that needed for the application of the previously existing modified method. Furthermore, the application is not limited to special cases of cyclic loading and, being computer-assisted, it is significantly simplified. The verified computer implementation of Chaboche's viscoplastic constitutive model complemented with the SRM rule of damage accumulation, both calibrated to IN 738 LC superalloy, can serve as a practical tool for the analysis of both the uniaxial deformation behaviour and the evolution of damage, and for the prediction of life time of IN 738 LC under any possible loading sequence given by the prescribed stress or strain time-variations in isothermal conditions.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo, Temeljne tehničke znanosti

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