Coupling crystal plasticity and continuum damage mechanics for creep assessment in Cr-based power-plant steel

Abstract

To improve the design and safety of power plant components, long-term hightemperature creep behaviour of a power-plant material, such as Cr-based alloy, should be assessed. Prior studies indicate that power-plant components undergo material degradation and premature failure by nucleation, growth and coalescence of microvoids as a result of creep damage. In classical crystal-plasticity-based models, a flow rule and a hardening law do not account for global stiffness degradation of materials due to evolving microvoids, having a significant influence on material behaviour, especially under large deformations. In this study, a crystal-plasticity scheme coupled with an appropriate continuum damage model is developed to capture the anisotropic creep-damage effect on the overall deformation behaviour of Cr-based power-plant steel. Numerical simulations show that the developed approach can characterize creep deformation of the material exposed to a range of stress levels and temperatures under consideration of stiffness degradation under large deformation.

Characterization of Multi-layer Weld Metal and Creep–Rupture Behavior of Modified 10Cr–1Mo Welded Joint

“…10a. In addition, a high density of free dislocations can be found around M 23 C 6 phases, which is beneficial to microstructure stability [16]. There are two types of precipitates found along grain boundaries in Fig.…”

“…In order to save costs and improve production efficiency, large components are usually manufactured by the multi-layer welding method [15]. Creep damage of the welded joint is considered to be one of the most serious failure modes for critical components in fossil fuel-fired power plants in service [16]. Type IV failure is deemed as the main failure form during the creep process under lower-stress and higher-temperature conditions, which occurs from fine-grain heat-affected zone (FGHAZ) toward the outer edge of the heat-affected zone (HAZ) [17][18][19].…”

An initial framework for the rapid qualification of long-term creep rupture strength via microstructural modeling

“…The CPFE model includes a grain interface-cohesive model [9][10][11][12][13] to represent grain boundary sliding and diffusion assisted creep-cavitation and eventual grain boundary failure. The authors and others have used similar models to accurately predict creep deformation and failure in a variety of materials [14][15][16]. Physics-based models can be more accurate in predicting long-term material behavior outside the test database.…”

Microstructural Model for Creep-Fatigue Interaction in Grade 91 Steel

“…There are numerous crystal plasticity models incorporating damage mechanics concepts (c.f. [28][29][30]), though comparatively few aimed at simulating fatigue and none, to our knowledge, examining creep-fatigue interaction. The reason for this comparative lack of interest may be the downsides of the continuum damage approach:…”