The development of advanced creep constitutive equations for high chromium alloy steel (P91) at transition stress range

Creep damage is a time-dependent deformation in metals under a constant stress at high temperature condition. Since the 1980s, high chromium alloy steel P91 (9%Cr-1%Mo-0.25%V) is highly demanded in high temperature industries (Saha, 2003). Continuum damage mechanism is becoming a generic life assessment tool to predict the lifetime of materials at creep condition. The consitutive equations were proposed to predict the lifetime and creep behaviours of materials. The most widely used constitutive equations are simply called Kachanov-Rabotnov-Hayhurst (KRH) in the current research.
The lifetime of high chromium alloy steel P91 has been overestimated by the extrapolation method from short-term creep tests (high stress) to long-term creep tests (lower stress). The definition of stress ranges depends on different materials and temperatures. The current researcher classifies the stress ranges into high stress range, transition stress range and low stress range with stress exponent