This investigation is focused on the understanding of mechanical and chemical reaction behaviors of stoichiometric mixtures of nano- and micro-scale aluminum and hematite (Fe2O3) powders dispersed in epoxy. Epoxy-cast Al+Fe2O3 thermite composites are an example of a structural energetic material that can simultaneously release energy while providing structural strength. The structural and energetic response of this material system is investigated by characterizing the mechanical behavior under high-strain rate and shock loading conditions. The mechanical response and reaction behavior are closely interlinked through deformation characteristics. It is, therefore, desirable to understand the deformation behavior up to and beyond failure and establish the necessary stress and strain states required for initiating chemical reactions. The composite s behavior has been altered by changing two main processing parameters; the reactants particle size and the relative volume fraction of the epoxy matrix. This study also establishes processing techniques necessary for incorporating nanometric-scale reactants into energetic material systems. The mechanochemical behavior of epoxy-cast Al+Fe2O3 composites and the influence of epoxy volume fraction have been evaluated for a variety of loading conditions over a broad range of strain rates, which include low-strain rate or quasistatic loading experiments (10-4 to 10-2 1/s), medium-strain rate Charpy and Taylor impacts (103 to 104 1/s), and high-strain rate parallel-plate impacts (105 to 106 1/s). In general, structural strength and toughness have been observed to improve as the volume fraction of epoxy decreases, regardless of the loading strain rate regime explored. Hugoniot experiments show damage occurring at approximately the same critical impact stress for compositions prepared with significantly different volume fractions of the epoxy binder phase. Additionally, Taylor impact experiments have indicated evidence for strain-induced chemical reactions, which subject the composite to large shear accompanied by temperature increase and associated softening, preceding these reactions. Overall, the work aims to establish an understanding of the microstructural influence on mechanical behavior and chemical reactivity exhibited by epoxy-cast Al+Fe2O3 materials when exposed to high stress and high-strain loading conditions. The understanding of fundamental aspects and the results of impact experiment measurements provide information needed for the design of structural energetic materials.

The aluminothermic (AT) process utilises a self-propagating high-temperature synthesis (SHS) type reaction for producing primarily thermite steel and alumina slag at high temperatures during the welding of rails. In this work, an investigation on the early stages of the aluminothermic process, the separation of AT reaction products and mould filling has been carried out, using both experimental and computational methods to predict the time duration of a complete separation and to obtain a better understanding of the internal multiphase flow within the crucible and mould. The decomposition of AT reaction products after the combustion and the subsequent mould filling by thermite steel and alumina slag have been simulated numerically, using a diffusive phase field and volume-of-fluid model. However, to minimize numerical errors on the input parameters of the high- temperature multiphase flow, a careful review on transport properties has been made. Missing data, e.g. the contact angle of thermite steel on waterglass-bonded mould and crucible wall material has been investigated experimentally. Being further necessary for the prediction of the separation time of AT reaction products in compacted thermite, results on the propagation front velocity show a decreasing trend with increasing initial compact temperature. Further, the combustion front velocity is used for a subsequent analysis of the separation time, which is obtained from the phase distribution of thermite steel, alumina slag and intermetallic compounds, using a combustion front quenching (CFQ) methodology. Moreover, geometric modifications on the crucible and mould have been developed for a reduction in changeover time, as well as an optimized multiphase flow field. Their performance during crucible discharge and mould filling has been verified numerically. Furthermore, alumina slag inclusions have been tracked within the mould using a volume-of-fluid approach with their final positions being verified through an authentic welding. / Während des aluminothermischen (AT) Prozesses findet eine SHS-Reaktion Anwendung, um primär Thermitstahl und Aluminiumoxidschlacke bei hohen Temperaturen für das Verschweißen von Bahnschienen herzustellen. In dieser Arbeit wurden Anfangsstadien, welche die Separation der AT-Reaktionsprodukte sowie das Füllen der Gießform einbeziehen, unter Anwendung von sowohl experimentellen als auch numerischen Verfahren untersucht. Damit konnte die Zeitdauer einer kompletten Separation ermittelt und ein genaueres Verständnis der Mehrphasenströmung in Tiegel und Gießform erlangt werden. Die Separation der AT-Reaktionsprodukte nach der aluminothermischen Reaktion und die anschließende Formfüllung wurden mit einem diffusen Phasenfeld und einem Volume-of-Fluid-Modell numerisch berechnet. Für die Minimierung numerischer Fehler in den Eingangsgrößen dieser Hochtemperatur-Mehrphasenströmungen wurde eine intensive Literaturrecherche durchgeführt und fehlende Parameter, wie zum Beispiel die Kontaktwinkel von Thermitstahl auf Wasserglas gebundenem Form- und Tiegelmaterial, wurden experimentell ermittelt. Messungen der Reaktionsfrontgeschwindigkeit in gepresstem Thermit sind notwendig für eine Vorhersage der Separationszeit der AT-Reaktionsprodukte, und die Ergebnisse zeigen einen linear abfallenden Trend mit zunehmender Anfangstemperatur des verdichteten Materials. In dieser Arbeit wurde die Geschwindigkeit der Reaktionsfront verwendet, um aus der Phasenverteilung von Thermitstahl, Aluminiumoxidschlacke und intermetallischen Verbindungen als Ergebnis des CFQ-Experimentes die Separationszeit in verdichtetem Thermit zu approximieren. Es wurden Modifikationen an Tiegel und Gießform erprobt, die für eine Verbesserung der internen Strömungsführung sowie für die Reduzierung der Umrüstzeit sorgen sollen. Die Effizienz dieser Veränderungen wurde anschließend mit numerischen Methoden überprüft. Des Weiteren konnten durch eine Realschweißung die numerisch vorhergesagten finalen Positionen von Schlackeeinschlüssen innerhalb der Gießform verifiziert werden.

Rail is a very expensive component of the railway track. Therefore, research methods extending rail life have great economic importance. During the past thirty years and, particularly during the past ten years there has been an increasing awareness throughout most rail networks in the world of the need to introduce improved design criteria, better construction techniques and higher standard track generally. This implies that quality control at all levels is mandatory if these objectives are to be achieved. With the improved understanding of degradation of track, a more complete comprehension of the costs associated with different operating and infrastructure conditions should also be developed, aiding in the determination of efficient maintenance costs and their contribution to access charges. Track and structures together account for 60% of maintenance costs, with 50% of the total being track. The UIC has done a lot of work on comparative performance indicators, and these show what potential savings much be out there for the taking, just by adopting current best practice. The old wisdom is that it's not enough o do things rights; we have to make sure that we do the right things. These developments have largely resulted from the demand for higher speeds particularly in passenger services and the demand to accept heavier axle loads of freight traffic. Whilst the conventional railway track structure is not likely to change significantly over the next ten years there will be a requirement over that period for better quality track infrastructure. This means less rail surface defects, less internal defects and less wheels irregularities. The presence of rail surface defects generally increases the roughness of the track leading to a poor passenger ride and increased safety risk with freight traffic. In addition, rail surface defects will generally increase the degradation rate of other track components; however, not all defects will produce visible track deterioration. Dynamic impacts produced by the rollingstock running over rail surface defects, such as poor welds, will, over time, create continuous rail defects, loosening of fastenings, abrasion and skewing of sleepers, crushing of ballast and loss of formation geometry. It is only in the recent years that the importance of poor welds in track has been identified. Dips and peaks must be recognised as a severe track irregularity that needs to be addressed and removed. Current maintenance activities have little effect on removing misaligned welds in track and the improvement obtained after the maintenance works is generally short lived. On the other hand, straightening operations have proven to solve the problem and maintain the results following 7 months of traffic. As part of this project, a six kilometre test section was selected on the Mt Isa Line and all welds located in this region were monitored for over 9 months to increase the understanding of the effect of individual maintenance activities on the track roughness. Three 2km Divisions were established; each Division had different maintenance activities and levels of intervention completed over the duration of the project. Over 15,000 readings were recorded and analysed. The following conclusions were drawn. The effect of cycle tamping was clearly identified when comparing the means of weld located in Division 1, 2 to the mean of welds in Division 3. Cycle tamping showed to have a significant positive effect on the dipped welds geometry and an increase in severity of peaked welds prior to their correction. Straightening operations completed in Division 1 and 2 reduced the overall mean of weld misalignments. These Divisions were subjected to different levels of straightening intervention however they produced similar results. Division 1 all dips were straightened and Division 2 only dips &gt0.3mm were straightened. This means that no additional benefit, in terms of overall misalignment of welds, can be gained when straightening operations target dips with a misalignment smaller than 0.3mm. Cycle grinding proved to have little effect on the removal of both dips and peaks. In fact, due to the configuration of the grinding machine, grinding operation produced a slight worsening of the dips misalignments and only a minor improvement of peaks. Although long term monitoring of the site may show minor variations in weld geometry performance, after approximately 3.9 Mgt of traffic the mean of dipped welds in Division 1 and 2 appeared to remain unaltered, as Division 3 showed a minor worsening. Furthermore, the mean of peaked welds in Division 1 and 2 appeared to remain unaltered, as Division 3 showed a minor worsening.