Modelling long term creep lifetime and extrapolation method

Description

Accurate prediction of long-term creep lifetime remains a major challenge for the safe operation of high-temperature components because of stress-dependent mechanism changes and the limited availability of very long-term experimental data. This work develops two complementary approaches for creep lifetime modelling and extrapolation. First, the classical Monkman-Grant relationship is extended through a modified hyperbolic-sine formulation of the minimum creep strain rate, enabling creep-life prediction over a wider stress range and across multiple temperatures. The proposed formulation is calibrated and validated against NIMS creep data and demonstrates good agreement with experimental rupture-life data, providing improved extrapolation capability compared with conventional approaches.

Second, a physics-based creep rupture model is established from grain-boundary cavitation mechanisms. By employing cavity nucleation and growth laws together with experimentally measured cavity-size distributions, an analytical relationship between cavitation evolution and rupture lifetime is derived. The model is calibrated using cavitation data for P91 and E911 steels and subsequently applied to creep rupture prediction for P92 steel over a wide stress range. The predicted rupture curves show good consistency with experimental observations.

The originality of this work lies in: (i) the development of a novel modified sinh-law formulation for minimum creep strain rate modelling; (ii) the integration of deformation-rate-based and cavitation-based lifetime descriptions within a unified predictive framework; and (iii) the establishment of mechanism-informed extrapolation methods capable of linking creep deformation, cavity evolution, and long-term rupture life. The methodology provides a promising route towards more reliable long-term creep life assessment, extrapolation, and future extension to multiaxial creep-damage modelling.

Period	24 Jun 2025
Event title	MIMA-4 International Conference: Decarbonisation of Power Generation
Event type	Conference
Conference number	4
Location	London, United KingdomShow on map
Degree of Recognition	International