A comparison of hyperbolic sine creep life equations and data correlation methods for these equations

ABSTRACT

Hyperbolic sine (HS) minimum creep rate equations combined with the Monkman-Grant equation are attractive for correlating time to rupture data because of their physical basis in dislocation creep theory, numerical stability, and conformance to physical boundary conditions at zero and infinite stress. In this study, uniaxial creep life data of Sanicro 25 and HR6W alloys were correlated to two recently published HS creep life equations with three commonly used objective functions. For each alloy, the correlation results (fit to the data and predicted strength at 100,000 h time to rupture) were essentially the same using either HS equation. Multiple equivalent solutions (same goodness of fit but different values of the fitting constants) were obtained with the HR6W data set. A discussion on obtaining initial estimates of fitting constants is provided as an Appendix.

KEYWORDS:

• Creep
• creep rupture
• Monkman-Grant equation
• Garofalo and Xu hyperbolic sine minimum strain rate equations
• Excel Solver
• Python SciPy
• Sanicro 25
• HR6W

Disclosure statement

No potential conflict of interest was reported by the author(s).

Disclaimer

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Additional information

Funding

NETL site support contractors’ contributions to this work were funded by the National Energy Technology Laboratory under the Mission Execution contract (23CFE000074) for support services.