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Aufsatz
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
On the Effect of Quenching on Postweld Heat Treatment of Friction-Stir-Welded Aluminum 7075 Alloy
(2019)
This work focuses on the effect of postweld heat treatment (PWHT) on the mechanical properties and microstructural evolution of aluminum 7075 alloy processed via friction stir welding (FSW). FSW is known to be capable of grain refinement in the nugget zone (NZ). Two different quench media (water and air) were employed for PWHT. Regardless of the quench media, the PWHT led to the occurrence of grain growth in the NZ of the FSWed aluminum 7075 alloy. Abnormal grain growth occurred in the water quenched specimen. It is ...
Aufsatz
Cyclic Deformation Response of Ultra-fine Grained Titanium at Elevated Temperatures
(2019)
This study focuses on the high-temperature cyclic deformation response (CDR) of ultra-fine grained (UFG) titanium of commercial purity (grade 4) processed via equal channel angular extrusion as a severe plastic deformation method. Low-cycle fatigue experiments were conducted at elevated temperatures up to 600 °C and at strain amplitudes ranging from 0.2% to 0.6%. Besides temperature and strain amplitude, the influence of two processing routes (8BC and 8E) on the fatigue characteristics of UFG Ti was examined. It is ...
Aufsatz
Effect of grain size on the very high cycle fatigue behavior and notch sensitivity of titanium
(2019)
The very high-cycle fatigue performances of coarse-grained and ultrafine-grained titanium samples with different geometries at ambient temperature and various stress amplitudes were investigated. Severe plastic deformation improves monotonic strength of titanium at the cost of a loss in ductility. Ultrafine-grained titanium demonstrates a superior fatigue performance compared to that of coarse-grained counterparts in the high-cycle fatigue regime, however, suffers notch sensitivity. Furthermore, in the very high-cycle ...
Aufsatz
Energy Resolved Residual Stress Analysis with Laboratory X-Ray Sources
(2017-04-17)
It is well known that existing residual stress fields play an important role for strength and lifetime of components. Consequently there is a great interest in the availability of fast, reliable and possibly nondestructive methods for their determination. In this context, X-ray diffraction methods play an important role in technical practice as well as in scientific research. They are based on the determination of lattice strains from which residual stresses are determined applying Hooke's law with appropriate elastic ...
Aufsatz
Prozessintegration von induktiver Wärmebehandlung und Festwalzen – sichere und zuverlässige Komponenten mit hoher Schwingfestigkeit
(2017-02-08)
Mechanische Oberflächenbehandlungen, beispielsweise das Festwalzen, spielen in der technischen Praxis eine bedeutende Rolle und tragen wesentlich zur Steigerung der Zuverlässigkeit hochbeanspruchter Komponenten bei. In einer Reihe von Fällen wurde gezeigt, dass eine Erhöhung der Prozesstemperatur die Wirksamkeit der Verfahren noch steigert, weil dies zu einer besseren Stabilisierung der eingebrachten Druckeigenspannungen führt. Eine wesentliche Voraussetzung zur Einführung dieser Verfahren in die Praxis ist allerdings, ...
Aufsatz
Effect of nanometric γ´-particles on the stress-induced martensitic transformation in ⟨001⟩-oriented Co49Ni21Ga30 shape memory alloy single crystals
(2019)
The effect of finely dispersed particles on the functional properties and morphology of thermally induced martensite in Co-Ni-Ga shape memory alloys has been already reported in literature, however, still important aspects are not fully understood. The current study focuses on the stress-induced martensitic transformation of solution-annealed, i.e. precipitate-free, and aged 〈001〉-oriented single crystals. In situ optical microscopy and neutron diffraction experiments show a significant influence of γ′-particles on ...
Aufsatz
Wood-Polypropylene Composites: Influence of Processing on the Particle Shape and Size in Correlation with the Mechanical Properties Using Dynamic Image Analysis
(2018-11-16)
The particle size and shape are of momentous significance for the mechanical properties of plastic composites. However, natural fillers, like wood, are not consistent in these attributes. In order to investigate the shared traits between these characteristics, WPCs were produced using polypropylene, hardwood and softwood fillers with different particle sizes and a coupling agent. Afterwards, specimens were processed using an injection molding machine. The filler sizes and shapes were measured using dynamic image ...
Aufsatz
Characterization of wood-based multi-material systems under dynamic impact stress
(2018)
Due to its naturally grown properties, wood has played a rather subordinate role as a material for technical applications up to now. In this paper, multi-material systems based on veneers of beech (Fagus sylvatica) with different reinforcing variants were investigated. In addition to the influence of different adhesive systems (urea formaldehyde and polyurethane), the effect of reinforcing by aramid fiber fabric and stainless steel foil in different climates was examined. At the center of the investigations were ...