EXTRAPOLATION OF SHORT TERM CREEP DATA INTO LONG TERM RUPTURE TIME PREDICTIONS VIA CAVITY NUCLEATION MEASUREMENTS

ABSTRACT

Due to the demand, especially by the power generation and the aerospace industries, for materials withstanding prolonged high temperatures – and relatively high stresses – it has become imperative to make long-term (>100,000 hrs) creep rupture time predictions using short-term/practical experiments. The current standard – based on numerical curve-fitting of data rather than natural law, and thus having limited success – is to start with accelerated experiments, i.e. tests under modified stress-temperature conditions so that rupture can occur in realistic experimental time scales, and then extrapolate the results ‘indefinitely’. In the present work, the phenomenon of creep cavity nucleation is exploited in order to propose a novel methodology for creep rupture time predictions via interrupted/short-term experiments – measuring cavity nucleation rates – conducted under true operating conditions; utilising the interrelation between creep cavity nucleation rates and minimum strain rates, and the coupling of the latter with rupture times via the Monkman-Grant ductility.

Graphical abstract

KEYWORDS:

• Creep cavity nucleation
• creep lifing methodology
• rupture time prediction

Disclosure statement

No potential conflict of interest was reported by the author.