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@PHDTHESIS{Paysan:1012234,
author = {Paysan, Florian},
othercontributors = {Requena, Guillermo Carlos and Münstermann, Sebastian},
title = {Über die bruchmechanische {C}harakterisierung
mikroskopischer {E}rmüdungsrissphänomene in {AA}2024-{T}3
mittels {R}oboter-gestützter {HR}-{DIC} {M}ikroskopie},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2025-04934},
pages = {XVI, 167 Seiten : Illustrationen},
year = {2025},
note = {Dissertation, Rheinisch-Westfälische Technische Hochschule
Aachen, 2025},
abstract = {The aluminum alloy AA2024-T3 is employed in the outer skin
of aircraft fuselages. Despite decades of research, the
damage tolerance and fatigue crack behavior of AA2024-T3 in
thin sheets is not yet fully understood. For a deterministic
life prediction of aviation components, it is imperative to
understand the underlying fatigue crack phenomena throughout
the entire crack growth process and their interaction with
the material microstructure. This is complicated due to the
microscopic scale of the phenomena. Furthermore, phenomena
such as crack branching, crack deflection, or crack closure
occur in a time-limited manner and can thus only be studied
in terms of their impact on crack progression behavior or
correlated to the da/dN − ∆K curve through time-series
data. This work introduces an innovative method for
conducting crack propagation experiments utilizing an
automated, robot-assisted, high-resolution digital image
correlation (HR-DIC) measurement system. A robotic arm moves
a microscope across the sample surface to collect precise
DIC data during crack growth. With this experimental setup,
the crack propagation behavior of AA2024-T3 under various
load ratios R ∈ {0.1, 0.3, 0.5} is investigated. Each
experiment generates approximately 350 GB of data—a
significant advancement over the conventional method
according to ASTM E647-15, which is limited to the a − N
curve. Analysing the extensive data sets requires the
adoption of new, advanced data- and algorithmbased
evaluation methods. In this context, the study develops
novel HR-DIC-based crack propagation curves, which relate
the crack growth rate (da/dN) to the cyclic crack tip stress
intensity (∆Kcp). The stress intensity factor ∆Kcp is
determined using the interaction integral J(a,b) based on
HR-DIC displacement field data. Here, influencing factors
that affect the results of the line integral, especially
with HR-DIC data, are identified. Moreover, the work
characterizes local crack closure behavior and compares the
experimental results to those from 3D finite element (FE)
crack propagation simulations. The excellent agreement
enables the identification of plasticity-induced crack
closure as the dominant crack closure mechanism and the
derivation of new evaluation strategies for characterizing
crack closure. Finally, the study demonstrates that fatigue
crack growth in L-T orientation progresses slower than in
T-L orientation, attributable to a higher frequency of crack
deflections and branching in L-T orientation. The effect of
crack deflections or branching can be correlated to
characteristics in the HR-DIC-based crack growth curves,
elucidating the link between multi-scale data. Consequently,
this work makes a significant contribution to the
digitalization of fracture mechanics.},
cin = {521420 / 520000},
ddc = {620},
cid = {$I:(DE-82)521420_20160125$ / $I:(DE-82)520000_20140620$},
typ = {PUB:(DE-HGF)11},
url = {https://publications.rwth-aachen.de/record/1012234},
}
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