PSI - Issue 71

K.M.K. Chowdary et al. / Procedia Structural Integrity 71 (2025) 188–195

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Fig.3 . Creep strain and strain rate curves for IN-RAFM steel at 240-260 MPa and 823 K.

A minimum in creep rate was observed at all the stress levels. The variation of minimum creep rate with applied stress is also shown in Fig.3 and Fig.4. The secondary stage is where a balance between hardening and recovery mechanisms leads to a steady-state/ minimum creep strain rate, ̇ .The Mcvetty minimum creep strain rate equation [ ̇ = ℎ ℎ ( ∕ ) ] was used to fit the non-linear bend from primary to secondary creep transition stage. The constants A (1/h) and (MPa) are the creep coefficient and secondary creep mechanism transition stress respectively. In the Sinh model, the constant controls the sigmoidal bend of primary to secondary creep transition.