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@PHDTHESIS{Wang:755595,
author = {Wang, Ding},
othercontributors = {Raabe, Dierk and Svendsen, Bob},
title = {{D}amage and strain patterning simulation of structural
heterogeneity},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2019-01925},
pages = {1 Online-Ressource (v, 131 Seiten) : Illustrationen,
Diagramme},
year = {2019},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2019},
abstract = {Structural heterogeneities arise in most metallic materials
on the microscopic scale prior or after deformation. On the
one hand such heterogeneities have great potential to
achieve specific properties for high strength and
lightweight applications, but on the other hand the
ductility and toughness of materials could be critically
reduced by damage initiation which is promoted by such
heterogeneities. In this thesis, the effect of individual
microstructure features and underlying dislocation
interactions on mechanical and/or damage responses of
materials were investigated by systematic simulation
studies. Crystal plasticity Fast Fourier transformation
simulations were conducted to gain deep insights into the
complex interactions between individual microstructural and
micromechanical mechanisms in heterogeneous structures. Two
subjects were studied in this thesis: the first is the
particle-induced damage in Fe - TiB2 metal matrix composites
steels and the second is the formation of laminate
deformation patterning in nickel single crystal. Fe - TiB2
metal matrix composites, termed high modulus steels due to
their high specific stiffness, have great potential for
lightweight design applications. However, the toughness of
these steels is critically reduced by the presence of the
brittle TiB2 particles. Due to the multitude of parameters
affecting microstructural damage, experimental studies are
complex and inefficient to identify the impact of particle
microstructure on fracture toughness. In this thesis, a
computational simulation approach to derive guidelines for
optimizing the mechanical properties of high modulus steels
was conducted. Key microstructural parameters such as
particle clustering degree, size and volume fraction were
investigated. Model geometries were statistically and
systematically generated with varied particle configurations
from random to clustered distributions. Simulations were
then performed using a crystal plasticity Fast Fourier
Transformation simulation method coupled with a novel phase
field damage model. The effect of individual particle
parameters on particle damage revealed that microstructures
with homogeneous particle distributions of $7~15\%$ volume
fraction TiB2 devoid of large primary TiB2 particles (the
primary precipitates for hypo-eutectic composition), are
most favorable for obtaining high modulus steels with
increased toughness. Deformation patterning in the form of
deformation bands is observed in single crystals under
suitable loading conditions. In this thesis, the reasons for
this severe deformation patterning were investigated through
crystal plasticity simulations. An f.c.c nickel single
crystal with initial near-Copper orientation was deformed in
plane strain compression boundary conditions. It was found
the resulting strain partitioning in the form of alternating
parallel bands initiates at a very early loading stage and
sharpens with ongoing deformation. It revealed that the
microstructure lamination is the result of a complex
interplay between available deformation systems, strain
hardening, kinematics, and deformation energetics: (i) the
dislocation collinear interaction plays an essential role in
the formation of the deformation bands under the imposed
boundary conditions; (ii) the laminate patterning case
minimizes the energy contribution due to strong collinear
interaction strength by selecting a locally prevalent slip
system. This behaviour is explained by the lower global
deformation energy in comparison to a homogeneous double
slip behaviour. It also demonstrated that only interaction
strength values in the range predicted by discrete
dislocation dynamic simulations result in deformation bands.
Altogether, the effectiveness and possibilities of
systematic crystal plasticity simulations were presented and
discussed in this thesis. The complex interactions between
individual microstructural and micromechanical mechanisms in
structure heterogeneities were identified. Based on the
effect of individual microstructural factors, the optimized
microstructure or damage tolerant microstructures can be
derived, and deeper insights can be gained for the
underlying deformation and damage mechanisms.},
cin = {523110 / 520000},
ddc = {620},
cid = {$I:(DE-82)523110_20140620$ / $I:(DE-82)520000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2019-01925},
url = {https://publications.rwth-aachen.de/record/755595},
}
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