On the origin, physical basis and numerical stability of creep life equations

ABSTRACT

In this paper several aspects of single line minimum creep rate and time to rupture models are examined that have not been discussed previously in the literature – the origin and boundary condition behaviour of some models; and the existence and relevance (for industrial applications) of temperature turnback. It is found that some published time to rupture models will predict very finite times to rupture at zero stress and temperatures of industrial use of the alloys, and that temperature turnback is mathematically possible even with physics-based models, but unlike stress turnback, the conditions at which temperature turnback would occur are usually of no physical or industrial relevance.

KEYWORDS:

• Creep
• creep life equations
• Monkman Grant equation
• stress and temperature turnback
• boundary conditions of creep life equations

Acknowledgments

The author would like to thank Joel Burdette (NETL site support contractor) for his assistance in preparing the graphs and formatting of the equations in this manuscript.

Disclosure statement

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

Disclaimer

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favouring by the United States Government or any agency thereof. The views and opinions of authors expressed therein do not necessarily state or reflect those of the United States Government or any agency thereof.

Additional information

Funding

Formatting of the manuscript and preparation of graphs were funded by the National Energy Technology Laboratory under the Mission Execution contract (23CFE000074) for support services.