In high temperature design, the accumulation of creep strain during the primary stage has to be considered since most of the allowable design strain occurs in this stage. In this work, assuming that the creep rate in the transient regime can be given as a fraction of the steady state creep rate and function of the internal stress, a mechanism based model for primary creep has been derived. Taking into account that the apparent activation energy varies with the internal stress, which evolves with creep strain, an exponential form of the creep rate versus creep strain has been obtained. The proposed model for primary creep requires the identification of two material parameters only which are shown to be function of the applied stress and independent of temperature. The proposed model has been validated for high chromium steel P91.
Primary Creep Modeling Based on the Dependence of the Activation Energy on the Internal Stress
Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNALOF PRESSURE VESSEL TECHNOLOGY. Manuscript received February 24, 2011; final manuscript received April 24, 2012; published online October 17, 2012. Assoc. Editor: Osamu Watanabe.
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Esposito, L., and Bonora, N. (October 17, 2012). "Primary Creep Modeling Based on the Dependence of the Activation Energy on the Internal Stress." ASME. J. Pressure Vessel Technol. December 2012; 134(6): 061401. https://doi.org/10.1115/1.4006856
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