The interpretation of experimental observation date for the development of mechanisms based creep damage constitutive equations for high chromium steel

Abstract

It is very important to design a safe factor or estimating the remain lifetime for electric power plant components of steam pipes which mostly manufacture by high chromium steels and work at high temperature and low stress level. The author will develop the mechanisms based on creep damage constitutive equations for high chromium steel under lows stress in initial stage: (1) Creep cavities mostly formed attaching with the precipitation of Laves phase or on grain boundary for high chromium steel under low stress. The Laves phase should play an active role in the nucleation of creep cavities and suggest to explore the function between cavity nucleation and the evolution of Laves phase; (2) The dominant cavity nucleation mechanism is adapted to high chromium steels under low stress level;(3) Brittle intergranluar model is appropriate for high chromium steels at high temperature under low stress level; (4) High density number of cavity of crept test high chromium steel at high temperature under low stress could be as fracture criterion.

Recent progress on the modelling of the minimum creep strain rate and the creep cavitation damage and fracture

“…The development of a set of creep damage constitutive equations suitable for long term service is one of the key research activities and it has been very active, for example [5][6]. Within this context, the authors initiated and carried out research work on the development of a set of creep damage constitutive equations for high Cr creep resistant steel suitable for long-term service [7][8]. Here, the long-term service in time and lower stress in load is interchangeable.…”

“…During research [8], three major sub-tasks were identified as: 1. The relationship of the minimum creep strain rate and a wider stress level; 2.…”

“…These three sub-tasks were resolved [8], respectively, by: 1. The application of the modified hyperbolic sine law [8][9]; 2.…”

“…These three sub-tasks were resolved [8], respectively, by: 1. The application of the modified hyperbolic sine law [8][9]; 2. The calibrating the cavity nucleation model and cavity growth model using the cavity histogram [8][9]; and 3.…”

“…The application of the modified hyperbolic sine law [8][9]; 2. The calibrating the cavity nucleation model and cavity growth model using the cavity histogram [8][9]; and 3. Retaining a separate variable to depict the effect of cavity on the creep deformation as the conventional creep damage mechanics does [8,10].…”