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Aufsatz
Predicting Flow Stress Behavior of an AA7075 Alloy Using Machine Learning Methods
(2022-09-09)
The present work focuses on the prediction of the hot deformation behavior of thermo-mechanically processed precipitation hardenable aluminum alloy AA7075. The data considered focus on a novel hot forming process at different tool temperatures ranging from 24°C to 350°C to set different cooling rates after solution heat-treatment. Isothermal uniaxial tensile tests in the temperature range of 200°C to 400°C and at strain rates ranging from 0.001 s-¹ to 0.1 s-¹ were carried out on four different material conditions. ...
Aufsatz
Effects of Aging under Stress on Mechanical Properties and Microstructure of EN AW 7075 Alloy
(2021-07-20)
In the present study, microstructural and mechanical properties of EN AW 7075 following stress-aging were assessed. For this purpose, properties of stress-aged samples were compared with values obtained for conventionally aged counterparts. It is revealed that the strength and hardness of EN AW 7075 can be increased by the presence of external stresses during aging. Precipitation kinetics were found to be accelerated. The effects of conventional and stress-aging on the microstructure were analyzed using synergetic ...
Aufsatz
Effect of Friction Stir Processing on Microstructural, Mechanical, and Corrosion Properties of Al-Si12 Additive Manufactured Components
(2020-01-03)
Additive manufacturing (AM) is an advanced manufacturing process that provides the opportunity to build geometrically complex and highly individualized lightweight structures. Despite its many advantages, additively manufactured components suffer from poor surface quality. To
locally improve the surface quality and homogenize the microstructure, friction stir processing (FSP) technique was applied on Al-Si12 components produced by selective laser melting (SLM) using two different working media. The effect of FSP on ...
Aufsatz
Effect of Cell Morphology on Flexural Behavior of Injection-Molded Microcellular Polycarbonate
(2022-05-19)
The quantitative study of the structure and properties relationship in cellular materials is mostly limited to cell diameter, cell density, skin layer thickness, and cell size distribution. In addition, the investigation of the morphology is generally carried out in two dimensions. Therefore, the
interrelation between morphological properties and mechanical characteristics of the foam structure has remained in an uncertain state. In this study, during the physical foaming process, a foam morphology is locally created ...
Aufsatz
Thermal Properties of Plasticized Cellulose Acetate and Its β-Relaxation Phenomenon
(2021-04-21)
Cellulose acetate (CA), an organic ester, is a biobased polymer which exhibits good mechanical properties (e.g., high Young’s modulus and tensile strength). In recent decades, there has been significant work done to verify the thermal and thermomechanical behaviors of raw and plasticized cellulose acetate. In this study, the thermomechanical properties of plasticized cellulose acetate—especially its β-relaxation and activation energy—were investigated. The general thermal behavior was analyzed and compared with ...
Aufsatz
Baumwolle als Faserverstärkung
(2023)
Jedes Jahr landen große Mengen Textilen auf Deponien oder in der thermischen Verwertung. Ein Teil dieser Abfälle könnte allerdings auch als Rohstoffe für Verbundwerkstoffe dienen. Baumwollfasern eignen sich etwa als Verstärkungsfasern, die die mechanischen Eigenschaften von biobasierten Kunststoffen steigern. Durch die Nutzung solcher Abfallströme können in Zukunft kostengünstig und biobasiert Materialien verstärkt werden.
Aufsatz
Additive manufacturing of Co-Ni-Ga high-temperature shape memory alloy - Processability 3 and phase transformation behavior
(2019)
Co-Ni-Ga high-temperature shape memory alloy is additively processed by selective laser melting for the first time. Reversiblemartensitic transformation of the as-built material is proven by differential scanning calorimetry. Microstructural analysis reveals a columnar-grained microstructure due to epitaxial solidification. Columnar-grained microstructures are characterized by a very low degree of constraints being beneficial for superior functional performance in numerous shape memory alloys. However, process-induced ...
Aufsatz
Microstructure of an additively manufactured Ti-Ta-Al alloy using novel pre-alloyed powder feedstock material
(2023-05-01)
Binary Ti-Ta and ternary Ti-Ta-Al alloys attracted considerable attention as new potential biomaterials and/or high-temperature shape memory alloys. However, conventional forming and manufacturing technologies of refractory based titanium alloys are difficult and cost-intensive, especially when complex shapes are required. Recently, additive manufacturing (AM) emerged as a suitable alternative and several studies exploited elemental powder mixing approaches to obtain a desired alloy and subsequently use it for complex ...
Dissertation
Zur Verbesserung des Ermüdungsverhaltens des austenitischen Stahls X5CrNi18-10 im Temperaturbereich 25-600°C durch mechanische Randschichtverfestigungsverfahren
(2007-11-16)
Die technischen Oberflächen werden oft als Bauteilversagungsorte definiert. Deswegen ist eine optimale Ausnutzung der Werkstoffeigenschaften ohne mechanische Oberflächenbehandlungsverfahren nicht mehr wegzudenken. Mechanische Randschichtoptimierungsverfahren sind vergleichsweise einfach, Kosten sparend und hocheffektiv. Gerade das Festwalzen wird wegen seiner günstigen Auswirkungen wie die exzellente Oberflächengüte, die hohen Druckeigenspannungen sowie die hohe Oberflächenverfestigung zunehmend an Bedeutung gewinnen. ...
Aufsatz
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, ...