Identify the influence of microstructure on mesoscale creep and fatigue damage

Abstract

This report describes the development of a microstructural model that can quantify the uncertainty in the observed rupture life of Grade 91 steel. The model is microstructural, meaning it relates microstructural characteristics of the material to the resulting material response. As such, one of the uses of this model is to identify the key microstructural parameters controlling the development of damage in Grade 91 operating at elevated temperatures. The report describes two veins of work: improvements to the crystal plasticity model required to run the uncertainty quantification analysis and the results of that UQ analysis. For creep, the model identifies the grain boundary diffusivity as the critical parameter controlling the rupture life of the material. The report demonstrates that a reasonable microstructural distribution of grain boundary diffusivity can account for the observed macroscale variation in rupture life at fixed temperature and load.

Initial framework for engineering-scale statistical creep-fatigue modeling

“…Figure 1.1 shows an example simulation of this type. Previous research at ANL developed the basic capabilities to perform simulations of this kind in a separate MOOSE app called DEER [1]. These simulations consist of three main modules 1.…”

“…Past work at ANL developed the theory behind these modules [1][2][3][4][5][6]. The main objective of this develop work was to improve the underlying implementations and integrate the system into the mainline MOOSE.…”

“…The new mechanics system integrates into a subsystem for imposing cell-average strain or stress constraints over periodic simulation domains. Our previous report [1] describes the system in detail. This section summarizes the theory and its implementation into the new mechanics system.…”

“…A previous ANL technical report [1] outlines much of the theory underlying these modifications. The following chapter summarizes the important aspects of new solid mechanics system, focusing on the new elements not described our previous report.…”

Efficient Failure Probability Calculations and Modeling Interface Debonding in TRISO Particles with BISON

“…Such experimental evidence highlights the importance of developing a capability in Bison to model TRISO layer interface debonding. Cohesive zone modeling (CZM) is a powerful tool for predicting delamination in adhesively bonded structures, and its framework was implemented in MOOSE [14]. This section summarizes new code development for the CZM and demonstrates several numerical examples of TRISO debonding.…”