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Dissertation
The Fatigue and Corrosion Fatigue Behavior of Austenitic Stainless Steel AISI 304 after Deep Rolling at Various Temperatures
(2019-09)
The austenitic stainless steel AISI 304 was deep rolled at 20 °C (RTDR), -195 °C (CTDR), and 550 °C (HTDR). The deep rolling pressures used for each deep rolling temperature were 1.0, 1.7, and 2.4 bar. From microstructural investigation, the largest compressive residual stress field was found in RTDR, and the highest amount of martensitic content and plastic deformation were found in CTDR. The strain aging effect was only found in HTDR.
In the rotating bending fatigue tests, the strain aging effect after HTDR is ...
Aufsatz
On data-driven nonlinear uncertainty modeling: Methods and application for control-oriented surface condition prediction in hard turning
(2020-10-16)
In this article, two data-driven modeling approaches are investigated, which allow an explicit modeling of uncertainty. For this purpose, parametric Takagi-Sugeno multi-models with bounded-error parameter estimation and nonparametric Gaussian process regression are applied and compared. These models can for instance be used for robust model-based control design. As an application, the prediction of residual stresses during hard turning depending on the machining parameters and the initial hardness is considered.
Aufsatz
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Innovative Materials for Novel Concepts for Internal Heat Exchangers
(2018-07-27)
Internal heat exchangers are often employed in solar thermal applications as well as in many other applications that involve heat, and, for the most part, consist of metallic materials (copper, stainless steel). Corrugated stainless steel tubes are easy to assemble, and are commonly used in various storage geometries. In order to significantly reduce costs, alternative materials, such as plastics, can function as excellent substitutes. Alternative heat exchangers for the following examinations using various materials ...
Aufsatz
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Influence of the Miniaturisation Effect on the Effective Stiffness of Lattice Structures in Additive Manufacturing
(2020-10-29)
Thin-walled and cellular structures are characterised by superior lightweight potential due to their advantageous stiffness to weight ratio. They find particular interest in the field of additive manufacturing due to robust and reproducible manufacturability. However, the mechanical performance of such structures strongly depends on the manufacturing process and resultant geometrical imperfections such as porosity, deviations in strut thickness or surface roughness, for which an understanding of their influence is ...
Aufsatz
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Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques
(2020-01-06)
By means of electron beam powder bed fusion (E-PBF), highly complex lightweight structures can be manufactured within short process times. Due to the increasing complexity of producible components and the entangled interplay of damage mechanisms, common bulk material properties such as ultimate tensile or fatigue strength are not sufficient to guarantee safe and reliable use in demanding applications. Within this work, the damage tolerance of E-PBF-manufactured Ni-based alloy Inconel 718 (IN 718) strut geometries ...
Aufsatz
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Determination and Validation of Residual Stresses in CFRP/Metal Hybrid Components Using the Incremental Hole Drilling Method
(2020-09-21)
Lightweight materials contribute to an efficient decrease in fuel consumption in the automotive and aircraft industries. Hybrid components made of metal and carbon fiber-reinforced plastics (CFRP) have a high potential in lightweight applications due to their high strength-to-weight ratio. For cost-effective processing of hybrid materials, advanced manufacturing processes such as the prepreg-press-technology have been developed, in which the bonding between a metallic component and a fiber compound is exclusively ...
Aufsatz
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The Manufacture of Hot-Compacted Layered Composite Systems Made of Oriented Semifinished PP-Films
(2014-03-04)
Monoaxial stretched PP-films are used for the manufacture of hot-compacted layered composites. These are layered with stretched co-extruded coupling agent films, and are consolidated to laminates by means of a hot-compaction process, which employs pressure and temperature. This paper aims to examine the influence of the process settings on the properties of the composites during the hot-compaction process. For this purpose, the mechanical values will be determined by means of tensile testing variously compacted and ...
Dissertation
Oberflächennahe Schädigung von Superlegierungen unter Hochtemperatur
(2020-02)
In der vorliegenden Arbeit wird die Alterung von Nickelbasislegierungen in Oberflächennähe betrachtet. Dabei wird der Einfluss von Temperatur und Zeit in Zusammenhang mit der Oberflächenrauheit, Deformation und der Konzentration von Natriumsulfat an der Probenoberfläche untersucht. Zur Quantifizierung der Schädigung kommen rasterelektronenmikroskopische Methoden wie EBSD und EDX zum Einsatz.
Es wird gezeigt, dass die analysierten Verarmungs- und Vergröberungsprozesse der Gamma'-Ausscheidungen eine deutliche ...
Buch
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Thermo-mechanische Gradierung eigenverstärkter Polypropylen-Composite
(kassel university press, 2015)
Eigenverstärkte Polypropylen-Composite weisen ein enormes Leichtbaupotential und überdurchschnittliche mechanische Grundeigenschaften auf. Das Eigenschaftsspektrum lässt sich auf die makromolekulare Orientierung oder sog. Eigenverstärkung der eingesetzten textilen Faser- und Bändchenhalbzeuge zurückführen, welche die Ausgangsbasis der Schichtverbunde bilden. Über eine gezielte Prozessführung kann die Eigenverstärkung bis ins heißkompaktierte Bauteil hinein kontrolliert und erhalten werden, wobei sich das Eigenschaftsspektrum ...
Buch
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Rotatives Vibrationsschweißen
(kassel university press, 2017)
Schweißversuche mit den von dem Schweißmaschinenhersteller Fischer Kunststoff-Schweißtechnik GmbH entwickelten Prototypenmaschinen für das neuartige Rotative Vibrationsschweißen zeigen eine vergleichbare erforderliche Prozessführung und die bereits bekannten Ausprägungen der vier Schweißprozessphasen anderer Vibrationsschweißverfahren. Unter Verwendung unterschiedlicher Werkstoffe und Probekörpergeometrien zeigt sich, dass sich die Fügenahteigenschaften von mit dem Rotativen Vibrationsschweißverfahren gefügten ...