Modelling of rolling contact fatigue for rail materials being subject to severe plastic deformation

Modern railway systems are a beneficial way of transport. However, the operation requires maintenance to compensate for rail degradations. Key issues of degradation regard severe plastic deformation and rolling contact fatigue, which lead to the formation of cracks. A better understanding contributes to improve maintenance and operations. Numerical simulations offer ways to predict these degradations. State of the art for the simulation of solid mechanics is the Finite Element Method. An inherent limitation, though, is the basic assumption that the material is a continuum. Discontinuities like cracks violate this assumption. Thus, alternatives like Discrete Element Method models and Peridynamics were developed recently. These methods describe the material by a modular assembly of elements. This arrangement allows for a better modelling of discontinuities. Though, modelling of rolling contacts is a case where compressive loads dominate. This fact challenges discrete modelling approaches due to the common assumption that the failure of an element implies its removal. Another challenge models of this type face regards the validation of rolling contact fatigue. The aim of this work was to develop a discrete element model, which is optimised for the rolling contact application. For this reason, it was called the "Discrete Element Rolling Contact" model. Based on a linear-elastic model, a fatigue capability was introduced. This capability was transferred to the set-up of the rolling contact, which highlighted the first limitation stated above. In order to address this issue, a solution was developed and validated to calibrate the model to crack closure. Experimental results indicate that the fatigue crack growth behaviour of rails is governed by the severe plastic deformation the materials are subject to. For this reason, data of undeformed and deformed materials was parameterised and validated. A method to interpolate materials of varying degrees of deformation was introduced. Further, a method to transfer the material parameters to other materials of similar strength was developed. The result was a material library which is available for the model. In order to transfer the fatigue parameters to the rolling contact condition, a set-up to model the behaviour of highly shear deformed material was introduced. In this way, a drawback of the adopted fatigue law was highlighted, which emphasised the requirement to weight the influence of compressive strains. Finally, a procedure for the validation of the rolling contact model was proposed. In this work, a novel rolling contact fatigue model and a procedure for validation are presented, that consider the anisotropy of severe plastic deformation. With regard to the validation of discrete rolling contact models, the proposed procedure delivers a contribution that addresses key aspects that are not matured yet. These aspects, however, are critical for the development of dependable discrete models to predict rolling contact fatigue

Modernisierung eines Gasturbinenprüfstandes

Der Inhalt dieser Arbeit umfasst einen von mehreren Modernisierungsschritten eines Kleingasturbinen-Prüfstandes. Bei der Kleingasturbine handelt es sich um eine ROVER 1S60 des Instituts Energietechnik und Thermodynamik der TU Wien. Bei der Modernisierung wurde die Messtechnik erneuert, und eine neue Leistungsbremse angeschlossen, was jedoch nur dokumentiert wurde, und nicht Teil der Arbeit ist. Weiters wurde ein Betriebsmanual erstellt, mit dem die Maschine sicher betrieben werden kann.The thesis is about the upgrade of a stationary gas turbine testbed used by the Vienna Technical University / Institute for Energy Technology and Thermodynamics. The testbed uses a ROVER 1S60 which was developed for low-power applications. In the diploma thesis the renewal of measurement instruments, and the influence on operation of the new eddy current brake are discussed. Further an operation manual is added to the thesis in order to operate the testbed in a correct and safe way.von Markus JanuschewskyAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersWien, Techn. Univ., Dipl.-Arb., 2009(VLID)160955

Upgrade of a gas turbine testbed

Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersDer Inhalt dieser Arbeit umfasst einen von mehreren Modernisierungsschritten eines Kleingasturbinen-Prüfstandes. Bei der Kleingasturbine handelt es sich um eine ROVER 1S60 des Instituts Energietechnik und Thermodynamik der TU Wien. Bei der Modernisierung wurde die Messtechnik erneuert, und eine neue Leistungsbremse angeschlossen, was jedoch nur dokumentiert wurde, und nicht Teil der Arbeit ist. Weiters wurde ein Betriebsmanual erstellt, mit dem die Maschine sicher betrieben werden kann.The thesis is about the upgrade of a stationary gas turbine testbed used by the Vienna Technical University / Institute for Energy Technology and Thermodynamics. The testbed uses a ROVER 1S60 which was developed for low-power applications. In the diploma thesis the renewal of measurement instruments, and the influence on operation of the new eddy current brake are discussed. Further an operation manual is added to the thesis in order to operate the testbed in a correct and safe way.8

Structural and Chemical Investigations of (La, Sr)CoO_3-δ Thin Film Electrodes Exhibiting Extremly Fast Oxygen Reduction Kinetics

Abstract not Available.</jats:p

Structural and Chemical Investigations of (La, Sr)CoO_3-δ Thin Film Electrodes Exhibiting Very Fast Oxygen Reduction Kinetics

The polarization resistance of La0.6Sr0.4CoO3-δ thin film electrodes prepared via pulsed laser deposition (PLD) is investigated by impedance spectroscopy for various film deposition temperatures. The electrodes were deposited on yttria stabilized zirconia (YSZ) single crystals and polycrystals and on polycrystalline gadolinia doped ceria (CGO). Structure-property relations emphasizing the correlation between crystallinity and performance are determined by additional XRD, SEM and TEM measurements. These experiments revealed that thin film electrodes of extraordinary low polarization resistance and little degradation may be produced on YSZ by optimizing the deposition conditions.</jats:p