FY17 Status Report on the Micromechanical Finite Element Modeling of Creep Fracture of Grade 91 Steel

Messner, Mark C.; Truster, Timothy J.; Cochran, Kristine B.; Parks, David M.; Sham, T.-L.

doi:10.2172/1401966

Cited by 6 publications

(20 citation statements)

References 56 publications

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“…The above-mentioned grain boundary cavitation model is a classical one. Recently, Messner et al [ 43 ] and Zhang et al [ 44 , 45 ] employed it to model creep fracture of creep-resistant ferritic steels, showing its computing capability of predicting the effects of microstructure, stress and temperature on creep damage.…”

Section: Modelmentioning

confidence: 99%

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Creep-Fatigue Crack Initiation Simulation of a Modified 12% Cr Steel Based on Grain Boundary Cavitation and Plastic Slip Accumulation

et al. 2021

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High-temperature components in power plants may fail due to creep and fatigue. Creep damage is usually accompanied by the nucleation, growth, and coalescence of grain boundary cavities, while fatigue damage is caused by excessive accumulated plastic deformation due to the local stress concentration. This paper proposes a multiscale numerical framework combining the crystal plastic frame with the meso-damage mechanisms. Not only can it better describe the deformation mechanism dominated by creep from a microscopic viewpoint, but also reflects the local damage of materials caused by irreversible microstructure changes in the process of creep-fatigue deformation to some extent. In this paper, the creep-fatigue crack initiation analysis of a modified 12%Cr steel (X12CrMoWvNBN10-1-1) is carried out for a given notch specimen. It is found that creep cracks usually initiate at the triple grain boundary junctions or at the grain boundaries approximately perpendicular to the loading direction, while fatigue cracks always initiate from the notch surface where stress is concentrated. In addition to this, the crack initiation life can be quantitatively described, which is affected by the average grain size, initial notch size, stress range and holding time.

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Section: Modelmentioning

confidence: 99%

“…The damage model parameters of grain boundary cavity coalescence are mainly obtained by Wen et al [ 13 , 41 ] and Messner et al [ 43 ]. All the parameters are listed in Table 2 .…”

Section: Finite Element Implementationmentioning

confidence: 99%

Creep-Fatigue Crack Initiation Simulation of a Modified 12% Cr Steel Based on Grain Boundary Cavitation and Plastic Slip Accumulation

et al. 2021

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“…The prior austenite grain (PAG) model and the grain boundary cavitation (GBC) model. Previous work calibrated the PAG and GBC models to fit the deterministic average of a set of Grade 91 experimental [3,12,22,23]. However, a deterministic model cannot capture the experimentally observed variability in creep-rupture life.…”

Section: Grain Boundary Cavitation Modelmentioning

confidence: 99%

Identify the influence of microstructure on mesoscale creep and fatigue damage

Rovinelli

Messner

2020

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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.

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“…The modeling approach employs initially zero-thickness 2D interface elements on the boundaries of 3D PAG, as shown in figure 5(b), with an associated traction-separation (cohesive) model. The cohesive model for cavity nucleation, growth, coalescence and viscous grain boundary sliding derives from multiple decades of effort starting with Ashby and co-workers [42,43,72] on spherical cavities, and more recently by Sham and co-workers [73,74]. Our efforts are the first to extend the model to 3D grain boundaries that enables far more realistic (geometrical) representations of the surfaces connecting grains.…”

Section: Pagb Constitutive Modelmentioning

confidence: 99%

Combined crystal plasticity and grain boundary modeling of creep in ferritic-martensitic steels: I. Theory and implementation

Nassif

Truster

et al. 2019

Modelling Simul. Mater. Sci. Eng.

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This paper presents a physically-based microstructural model for creep rupture at 600 °C for Grade 91 steel. The model includes constitutive equations that reflect various observed phenomena in Grade 91, and it is incorporated into a mesoscale finite element model with explicit geometry for the prior austenite grains and grain boundaries. Creep within the grains is represented using crystal plasticity for dislocation motion and recovery along with linear viscous diffusional creep for point defect diffusion. The grain boundary models include physics-based models for cavity growth and nucleation that accurately capture tertiary creep and creep rupture. Simulations of creep at 100 MPa are performed, and the contribution of each mechanism is analyzed. The overarching goal is to gain a mechanistic understanding of the material to improve the prediction of creep rupture for long service lives in elevated temperature operating conditions. The creep response of the material at different stress levels, stress states, and temperatures is studied in Part 2 of this paper in order to determine the implications of the simulations on high temperature design practice. Furthermore, the second part explores the effect of triaxial stress states on the creep response and finds a transition from notch-strengthening behavior at high stress to notch-weakening behavior at lower stresses.

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FY17 Status Report on the Micromechanical Finite Element Modeling of Creep Fracture of Grade 91 Steel

Cited by 6 publications

References 56 publications

Creep-Fatigue Crack Initiation Simulation of a Modified 12% Cr Steel Based on Grain Boundary Cavitation and Plastic Slip Accumulation

Creep-Fatigue Crack Initiation Simulation of a Modified 12% Cr Steel Based on Grain Boundary Cavitation and Plastic Slip Accumulation

Identify the influence of microstructure on mesoscale creep and fatigue damage

Combined crystal plasticity and grain boundary modeling of creep in ferritic-martensitic steels: I. Theory and implementation

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