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Aufsatz
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Simultaneous impact modified and chain extended glass fiber reinforced poly(lactic acid) composites: Mechanical, thermal, crystallization, and dynamic mechanical performance
(2021-02-05)
Herein, glass fiber (GF) reinforced binary, ternary, and quaternary poly(lactic acid) (PLA) composites were prepared. Toughening, and chain extension of PLA was achieved through the incorporation of impact modifier and chain extender and their concurrent effects on the spectroscopic, crystallization, mechanical, thermal, and thermomechanical properties of the composites were investigated. High mechanical properties of GF influenced the mechanical performance of the composites. However, GF alone could not restrict the ...
Aufsatz
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A Novel Approach to Robustly Determine Residual Stress in Additively Manufactured Microstructures Using Synchrotron Radiation
(2021-07-29)
In recent decades additive manufacturing (AM) for years has been in focus of academia and industry as its underlying production principle allows for the realization of designs of unprecedented geometrical complexity. However, often such structures are not realized due to the lack of understanding of structural and mechanical properties, this fact amongst others related to the unique microstructures established by the related processes. In this context, residual stresses, highly affected by the scan strategy and process ...
Aufsatz
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On the Influence of Microstructure on the Corrosion Behavior of Fe–Mn–Al–Ni Shape Memory Alloy in 5.0 wt% NaCl Solution
(2020-10-03)
Herein the corrosion behavior of Fe–Mn–Al–Ni shape memory alloys characterized by different microstructures in a 5.0 wt% NaCl solution is investigated. Open circuit potential and potentiodynamic polarisation tests are conducted. Generally, Fe–Mn–Al–Ni shows corrosion properties being similar to pure iron. However, the polarization curves of single crystals indicate the presence of an unstable passive system. The corrosion damage is analyzed by means of optical microscopy and electron microscopy. It is revealed that ...
Aufsatz
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Investigation of residual stresses in polypropylene using hot plate welding
(2020-08-05)
During the cooling process of the molten material, residual stresses appear because the reduced volume of the cooled material cannot fully fill the space formerly occupied by the molten material. The morphology in and around the weld is formed by different factors depending on the material and process parameters. Different morphological structures relate to different mechanical properties. The process parameters and the welding results including morphology and residual stress are linked together. In this article, ...
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 ...
Aufsatz
Influence of the degree of crystallinity and the surface free energy on the adhesion properties of different PLA/PBS blends in multicomponent injection molding
(2020-01-10)
Biocomposites made of biodegradable polymers have grown in interest due to their environmentally friendliness, considering that non-biodegradable polymers waste conduces to pollution, displaying high environmental impact in climatic changes. Therefore, in the presented study, biodegradable Poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) were investigated as a series of PLA/PBS melt-blending compounds with the weight ratios of 50/50, 60/40, 70/30, 80/20 and 90/10. In a two-component injection molding ...
Aufsatz
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On the Influence of Surface Hardening Treatments on Microstructure Evolution and Residual Stress in Microalloyed Medium Carbon Steel
(2020-06-09)
Tailoring surface properties is a key to superior performance of components subjected to fatigue loadings in application. Process–microstructure–property relationships have to be established to allow for optimization of techniques employed for surface treatments such as deep rolling and induction hardening. Although both techniques are employed widely in industrial application, studies examining microstructure evolution and residual stress states for a single material in a comparative manner are missing. Amongst ...
Dissertation
Simulationen und Experimente im Schwellenwertbereich zur Aufklärung der Risswachstumsmechanismen in einer Aluminiumlegierung
(2020)
Lange Risse, die bei Belastungen nahe des Schwellenwerts wachsen, können Ausbreitungscharakteristika zeigen, welche denen kurzer Stadium I-Risse ähneln. Neben einer lokalen Blockade der Rissfront durch Teilchen einer zweiten Phase ist ein schubspannungsgesteuerter Rissfortschritt ein interessanter Effekt, der bei diesen Belastungsbedingungen auftritt. Das berichtete Verhalten wird im Rahmen dieser Arbeit auf das Rissspitzenfeld zurückgeführt. Zu diesem Zweck wurden Risswachstumsexperimente mit angerissenen Flachproben ...
Konferenzveröffentlichung
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The Effect of Injection Molding Parameters on Microcellular Foam Morphology
(2021)
Microcellular foam injection molding with physical blowing agent (MuCell®) delivers monetary benefits, processing advantages and freedom of product design by reducing shrinkage. In conjunction with an advanced mold technology, so-called Pull and Foam method, there is great potential in controlling the foam structure of the component locally. In this study, Polycarbonate (PC) components were produced with nearly compact outer skin and a closed cellular core. To understand the relation between processing parameters and ...
Aufsatz
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Effect of Compositional Variation Induced by EBM Processing on Deformation Behavior and Phase Stability of Austenitic Cr-Mn-Ni TRIP Steel
(2020-01-24)
Electron beam melting (EBM) is an established powder bed-based additive manufacturing process for the fabrication of complex-shaped metallic components. For metastable austenitic Cr-Mn-Ni TRIP steel, the formation of a homogeneous fine-grained microstructure and outstanding damage tolerance have been reported. However, depending on the process parameters, a certain fraction of Mn evaporates. This can have a significant impact on deformation mechanisms as well as kinetics, as was previously shown for as-cast material. ...