In a linear analysis for brake squeal, an unwanted type of sound in the kHz-range produced during the braking process of vehicles, usually only the stability of the system is examined. However, with the appearance of additional stochastic excitation, the vibration of a linear system with subcritical self-excitation, i.e. having self-excitation but ...
A discrete-element based model of elastic-plastic materials with non-ideal plasticity and with an account of both cohesive and adhesive interactions inside the material is developed and verified. Based on this model, a detailed study of factors controlling the modes of adhesive wear is performed. Depending on the material and loading parameters, we...
Gedruckt erschienen im Unviversitätsverlag der TU Berlin, ISBN 978-3-7983-3139-6 (ISSN 0174-4003) / Aufgrund der deutlich unterschiedlichen Verarbeitungsbereiche von Polyhydroxybutyrat (PHB) und Polyamid 6 (PA 6) ist die gemeinsame Verarbeitung der beiden Polymere eine verfahrenstechnische Herausforderung. Um die Verträglichkeit und Prozessfähigkei...
The main focus of this thesis is on metal oxide layers and their possible implementation as carrier selective contacts in silicon heterojunction (SHJ) solar cells. The dominant topics in this work are the development of deposition processes for such metal oxide layers and their further analysis, covering layer composition, layer properties and thei...
In this work, effective methods for monitoring friction and wear of journal bearings integrated in future UltraFan® jet engines containing a gearbox are presented. These methods are based on machine learning algorithms applied to Acoustic Emission (AE) signals. The three friction states: dry (boundary), mixed, and fluid friction of journal bearings...
Improving the thermal insulation properties of cement-based materials is the key to reducing energy loss and consumption in buildings. Lightweight cement-based composites can be used efficiently for this purpose, as a structural material with load bearing ability or as a non-structural one for thermal insulation. In this research, lightweight cemen...
Despite the omnipresence of household refrigeration appliances, there is still a lack of knowledge about their age-related efficiency loss over time. Past studies provide basic evidence for increasing electricity consumption of cooling appliances with ageing but fail to investigate the associated technical wear. Concentrating on the degradation of ...
Im ersten Teil der vorliegenden Arbeit wird die Entwicklung und der Versuchsbetrieb einer Organic Rankine Cycle (ORC) Anlage zur Nutzung von Abwärme auf unterschiedlichen Temperaturniveaus beschrieben. Als Wärmequelle dient das Abgas und die Motorwärme eines mit Biogas betriebenen Blockheizkraftwerks. Es wird eine Kreislaufarchitektur mit einem Hoc...
Monolithic [Cs0.05(MA0.17FA0.83)0.95]Pb(I0.83Br0.17)3/Cu(In,Ga)Se2 (perovskite/CIGS) tandem solar cells promise high performance and can be processed on flexible substrates, enabling cost-efficient and ultra-lightweight space photovoltaics with power-to-weight and power-to-cost ratios surpassing those of state-of-the-art III-V semiconductor-based m...
Van der Waals forces between solids in vacuum are always attractive and are considered as the main source of adhesion. However, in the presence of an intermediate medium, they can also be repelling (Dzyaloshinskii et al., 1961) which means that the “work of adhesion” becomes negative. Similarly to the case of adhesion, the interaction range of thes...
