Accurate modelling and prediction of both statistical trends in damage formation and damage site initiation
is critical in both the design, microstructure optimization and lifetime management of components and
welded joints for nuclear power stations. This paper presents a coupling between a strain-gradient based
crystal plasticity formulation and a phase field fracture model to predict damage initiation sites, damage
propagation and void initiation statistics that match electron microscopy experimental results for grain
boundary damage from a 316H stainless steel creep test specimen. The interplay between the grain
misorientation and the presence of carbides at the grain boundaries is investigated. A range of novel
variations are incorporated into this approach that can isolate damage from varying mechanisms, including
slip, creep, and contributions from plastic or elastic deformation within the simulated microstructure. The
local effect of carbides, forming on specific grain boundary types, on void cavitation is included by using
a misorientation-dependent critical energy release rate. The direct comparison with electron backscatter
diffraction experiments clarifies what the most important damage mechanisms are and the quantitative
fracture energy reduction as a function of carbide density. The extension of this model to ferritic steel
microstructures is also explored.
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Accurate modeling of fracture in polymer nano-composites entails the consideration of numerous complex phenomena including the branching and coalescence of multiple cracks. This contribution employs a graded interphase enhanced phase-field fracture approach (PFF-GI) to capture a wide spectrum of experimentally observed fracture behaviors including particle debonding. Herein the overall fracture response of the composite material is controlled via the degree of grading, i.e. continuous variation in material properties, within an interphase region of finite thickness around the filler particle.
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The poker-chip experiments of Gent and Lindley (1959) – in which they bonded thin disks of elastomers to metal plates at two ends and applied tension – jump-started investigations into the phenomenon of cavitation. Despite their importance, these experiments and other similar experiments have yet to be fully explained. One likely reason for their elusiveness is that it had long been mistakenly presumed that cavitation in elastomers could be explained on the basis of an elastic instability. Another reason is that a unified nucleation and propagation fracture theory in large deformations to explain cavitation as a fracture phenomenon had not existed. Recently, Kumar, Francfort, and Lopez-Pamies (2018) have introduced a comprehensive macroscopic phase-field theory for the nucleation and propagation of fracture in elastomers undergoing arbitrarily large quasistatic deformations. In this work, we quantitatively analyze the poker-chip experiments using this theory and showcase the theory’s ability to model nucleation and propagation in a unified manner.
EXTENDED ABSTRACT

The dynamic aspect of crack propagation is a topic of deep interest in material science. The phase field fracture modeling has shown encouraging results in a dynamic framework but remains challenging in terms of the time discretization resolution. Though the implicit time integration methods are mainly used in the literature, they become limiting in nonlinear problems due to the resolution of the system of equations required. Thus, explicit time integration schemes are an alternative to avoid these massive matrix operations. This paper presents the approaches set up to adapt the coupled formulation to a full explicit time integration for both equations.
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