LAUSR

ABSTRACT Uniaxial creep life data is still used to estimate long-term creep strength and maximum allowable design stresses for structural materials. Many ‘single-line’ equations have been developed to correlate uniaxial creep life data, such as the Larson-Miller Parameter (LMP) and Wilshire (WS) equations; few are derived from the physics of creep. Some forms of these equations can be mathematically inconsistent with the behaviour of metals at high temperatures, making them potentially unreliable predictors of long-term life. Two modified hyperbolic sine minimum creep rate equations combined with the Monkman-Grant equation were used to correlate uniaxial creep life data of Sanicro 25 and HR6W, and then calculate their long-term creep strength. A modified hyperbolic sine equation was selected because it has a physical basis in dislocation creep and is numerically stable. It was found that the modified hyperbolic sine equations fit the experimental data as well as the LMP and WS equations.