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@PHDTHESIS{Schwinn:755550,
author = {Schwinn, Julian},
othercontributors = {Reh, Stefan and Münstermann, Sebastian},
title = {{E}rmüdungsrissverhalten von {T}ailored {W}elded {B}lanks
unter {B}erücksichtigung der {E}igenspannungen und der
{G}eometrie eines {D}ickenübergangs},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2019-01904},
pages = {XIII, 131 Seiten : Illustrationen, Diagramme},
year = {2018},
note = {Dissertation, Rheinisch-Westfälische Technische Hochschule
Aachen, 2018},
abstract = {Scope of past and current research and development in
aviation is the reduction of the aircraft’s weight in
order to reduce fuel consumption as well as to raise payload
and range. A potential joining technology to replace the
riveting (state of the art) of fuselage parts is friction
stir welding (FSW), because riveting is expensive and raises
the aircraft’s weight. FSW enables to weld high strength
aluminium alloys that are used in aircraft manufacturing
without drastic loss of mechanical properties. Furthermore,
it is possible to produce load optimized structures by
joining sheets with different thickness (Tailored Welded
Blanks, TWB). In the present work, an Al-Mg-Sc alloy was
investigated. Al-Mg-Sc alloys offer good corrosion and
damage tolerance properties and can be processed by creep
forming, which allows to produce double curvature parts.The
process of FSW introduces macroscopic residual stresses,
which influences the fatigue crack growth behavior
significantly. Additionally, the crack arresting capability
of riveted structures does not apply to welded structures
due to the material’s bond. The fatigue crack growth
behavior is essential for the engineering design approach of
damage tolerance. Thus, the aim of the present work is to
investigate and quantify the crack growth behavior of FSWed
structures of the Al-Mg-Sc alloy AA5028-H116.To achieve this
aim, experimental and evaluation procedures were advanced.
With the help of finite element simulation with fracture
mechanics analysis and 3D digital image correlation
experimental dependent geometry functions were determined in
order to provide stress intensity factors for the cyclic
fatigue crack growth experiments on welded specimens. By
this means, crack growth curves for rather large specimens
could be determined with high accuracy. In order to be able
to investigate residual stresses and their influence on the
crack growth, the cut-compliance-method was applied. Finite
element simulations were used to cover the geometrical
influence of the thickness transition for the determination
of the residual stresses by means of the
cut-compliance-method. Crack growth behavior and residual
stresses were determined for specimens with and without
thickness transition with the crack growing perpendicular to
the weld as well as growing along the weld.Macroscopic
residual stresses and their influence on the crack growth
were determined for the residual stress affected specimens.
Thereby, residual stress affected crack growth curves could
be corrected and thus attributed to the base material’s
crack growth behavior. For this reason, a correction for the
mean stress regarding the cyclic stress intensity factor was
specified. It became apparent that the changes in crack
growth rate were affected prevailingly by the residual
stress. Major effects due to the microstructural changes
inside the weld were not observed. The crack growth behavior
of the highly distorted specimens with thickness transition
could not be explained by solely considering the residual
stress. Thus, further investigations of the crack mouth
opening displacement were included.},
cin = {521110 / 520000},
ddc = {620},
cid = {$I:(DE-82)521110_20140620$ / $I:(DE-82)520000_20140620$},
typ = {PUB:(DE-HGF)11},
url = {https://publications.rwth-aachen.de/record/755550},
}
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