The aim of this thesis was to improve the understanding of microstructure in single crystal ferroelectrics. This was achieved through macroscopic testing of Lead Magnesium Niobate – Lead Titanate (PMN-PT) and microscopic observations of Barium Titanate (BT) single crystals. Multi-axial polarization rotation tests on PMN-PT showed a gradual increase in the change in dielectric displacement due to ferroelectric switching as the electric field is applied at increasing angles to the initial polarization direction. A relatively high remnant polarization for loading angle near to 90° suggested that PMN-PT is more polarizable in certain directions. Strains measured in two directions, parallel to the electric field and perpendicular to the electric field, showed a noticeable variation on two opposite faces of the specimen suggesting an effect of local domain configurations on macroscopic behaviour. A micromechanical model gave an insight into the switching systems operating in the crystal during the polarization rotation test. Domain structure in BT was mapped using synchrotron X-ray reflection topography. By making use of the angular separation of the diffracted reflections and specimen rocking, different domain types could be unambiguously identified, along with the relative tilts between adjacent domains. Fine needle domains (width ≈ 10μm) were successfully mapped providing a composite topograph directly comparable with optical micrograph. The domain structure was confirmed using other techniques such as piezoresponse force microscopy and atomic force microscopy/scanning electron microscopy and optical observations on the etched crystal. Results show that combined use of multiple techniques is necessary to gain a consistent interpretation of the microstructure. Finally, domain evolution in BT under compressive mechanical loading was observed in-situ using optical and X-ray diffraction techniques providing a series of images that show ferroelastic transition. The domain configurations influence the switching behaviour and constitutive models that can account for such effects need to be developed. Quantitative and qualitative data presented in this thesis can assist model development and validation.

Thesis (D.Tech.: Mechanical Engineering)-Dept. of Mechanical Engineering, Durban University of Technology, 2007 xxx, 190 leaves, Annexures A-D / A composite material comprises two or more materials with properties that are superior to those of the individual constituents. Composites have become important engineering materials, especially in the fields of chemical plant, automotive, aerospace and marine engineering. The development of more advanced materials and manufacturing techniques in composites has grown from humble beginnings in the 1930s to a recognized and well-respected engineering discipline, providing solutions to conventional and challenging applications. At present, fibre-reinforced composites (FRCs) are amongst the most common types of composites used. They are produced in various forms with different structural properties, and designers, specifiers and end-users can choose from an almost endless list of these materials, providing design flexibility as well as low manufacturing and maintenance cost. Many suggest that composites have revolutionised the chemical and petro-chemical industries. Examples of applications include tanks and chemical reactor vessels that contains many hundreds of litres of hazardous chemicals, reinforced pipes measuring up to several meters in diameter conveying dangerous gases and so on. The South Africa Coal, Oil and Gas Corporation Limited (SASOL) was established in September 1950. From a small start-up, the company has grown to be a world leader in the commercial production of liquid fuels and chemicals from coal and crude oil. Sasol manufactures more than 200 fuel and chemical products at its main plants in Sasolburg and Secunda in South Africa as well as at several other plants abroad. Its products are exported to more than 90 countries around the world. The use of composites in general, and fibre reinforced composites in particular has received little support in Sasol through the years. Some sporadic use of these materials in the construction of process equipment, e.g. tanks, vessels and piping has taken place with varying degrees of success. While the use of equipment fabricated with fibre-reinforced composites has proven extremely successful in the chlorine producing facility in Sasolburg, catastrophic failures have taken place in Secunda in critical fire water systems made of these materials. The history of correct use and application of fibre-reinforced equipment has shown that the cost of ownership of such equipment is significantly lower than similar metallic equipment, therefore reducing costs and safety risks. However, even though this technology brings a company like Sasol closer to the realisation of the vast number of advantages and solutions offered by these materials, the reality is that most engineering personnel are still applying traditional (viz. steel and wood) technology as used by our predecessors. The work presented here attempts to indicate the relevance of fibre-reinforced composites for Sasol, and to detail efforts aimed at the raising of awareness amongst appropriate personnel at Sasol to increase the use of these materials in major capital projects and day-to-day maintenance contracts, therefore taking advantage of the superior performance of fibre-reinforced composites in demanding applications. In support of this drive, part of the work presented indicates the status as well as progress of the composites industry in the last few years. This project was therefore aimed at identifying the level of utilization of fibre-reinforced composites at Sasol, and the possible improvement in benefits of using these technologies. A methodology was developed, using engineering as well as marketing principles, to reach the engineering personnel in various divisions and seniority levels of Sasol to increase the awareness of the capabilities of composites materials, specifically regarding fibre-reinforced composites. Questionnaires were used to gauge the level of awareness while various methods, e.g. one-on-one meetings, seminars, conferences, electronic media, etc were used to upgrade the target groups’ knowledge. The results of the initial survey to determine the status of various dimensions in the company are indicated as well as the outcomes at the end of the research period. In support of the process in Sasol, the development, interaction and cross-pollination of international and national role-players in the fibre-reinforcement industry with respect to chemical containment and Sasol are indicated. The importance of this two-legged process is demonstrated: it ensures a professional national support framework for companies like Sasol. Results are indicated, compared and discussed to give future direction in this ongoing process. As important to this process was the development of appropriate technical resources (like design standards and codes) to enable their use within the group. It was recognised early on that raising the level of awareness of the target groups was not enough and that these resources had to be in-place down the line so that those who chose to could start to implement these material technologies with the aid of the resources. The development of the necessary resources is also discussed. Finally, it will be shown that significant growth has taken place regarding the awareness within the group over the course of implementation of this project. Specifically, about 20% of the target groups have moved from a stage of no knowledge to higher levels of confidence. In terms of use of these materials, significant growth has also taken place judging by the number of plant requests, activity on major capital projects and so on. In fact, from almost nothing in 1999, over the last 5 years in excess of R137 Million has been spent on capital equipment manufactured from composite materials, with the majority in the last 2 years.

Predictive models of structures containing frictional joints presently suffer from poor descriptions of interface behaviour at the joints. This thesis aims to address this shortfall by furthering the physical understanding of parameters affecting interface behaviour such as friction and contact stiffness. Aspects of friction and contact stiffness relevant to the characterisation of fretting joints are investigated by a combined modelling and experimental approach. Friction and wear behaviour in gross-slip fretting are investigated by in-line and rotational fretting tests. New 3D topography parameters are found to be useful in the analysis of surfaces during fretting. Wear-scar shape is found to be dependent on material. A phenomenon whereby friction increases during the gross-slip phase of individual cycles is found to be due to wear-scar interaction primarily through the interference of local features distributed over the contact area. These features are similar in size to the applied fretting stroke. A simple model to explain the behaviour is put forward which shows that wear-scar shape determines the form of the friction variation. A finite-element (FE) model of the interaction of an elastic-plastic asperity junction is used to predict sliding friction coefficients. The modelling differs from previous work by: permitting greater asperity overlaps, enforcing an interface shear strength, and allowing material failure. The results are also used to predict friction coefficients for a stochastic rough surface. The magnitudes of the predicted friction coefficients are generally representative of experimental measurements. Results suggest that friction arises from both plasticity and tangential interface adhesion. Contact stiffness is studied for both fretting and non-fretting. A technique to isolate the true interface stiffness from results derived from load-deflection data is developed by comparing experimental and FE results. In the fretting wear case, comparison of tangential contact stiffness results in the literature with FE results reveals an interface whose compliance dominates the response to the extent that stiffness is proportional to contact area. In fretting tests such as this, wear debris is thought to be a factor contributing to high interface compliance. Non-fretting experiments performed here show that, at higher pressures, interface domination is reduced as the contact approaches the smooth case. Experiments are performed where contact stiffness is measured simultaneously by both ultrasound and digital image correlation. The effect of normal and tangential loading upon the contact stiffness (normal and tangential) is investigated. Experimental evidence showing that ultrasound measures an ‘unloading’ stiffness while DIC measures a ‘loading’ stiffness is obtained for the case of tangential loading where the ‘DIC stiffness’ decreases with increasing tangential load whereas the ‘ultrasound stiffness’ remains approximately constant. On average, ultrasound gives magnitudes 3.5 and 2.5 times stiffer than the DIC results for the normal and tangential stiffness cases, respectively. The difference in magnitudes can largely be physically explained, and is relatively small considering the significant differences between the techniques. Therefore, both methods can claim to give valid measurements of contact stiffness – though each has its own limitations which are outlined herein.

The primary aim of this research was to develop and improve the experimental method and data interpretation for strain measurements using diffraction methods to gain a better understanding of micromechanical deformation and anisotropy of lattice strain response. Substantial part of the research was devoted to the development of the laboratory high energy X-ray diffractometer (HEXameter) for bulk residual strain evaluation. White beam energy dispersive X-ray diffraction was chosen as the principal diffraction mode due to its extreme efficiency in utilising X-ray flux and its ability to capture large segments of diffraction patterns. The specimens that have been examined were real engineering components, mechanically deformed specimens and thermally treated specimens, ranging from dynamic in-situ measurements to ex-situ materials engineering. For the real engineering components, a wedge coupon from the trailing edge of a Ti64 wide fan blade and a turbine combustion casing were examined. Among the mechanically deformed specimens that have been measured were shot-peened steel plates, elasto-plastically bent bars of Mg alloy and cold expanded Al disks. Amongst the thermally deformed specimens, laser-formed steel plates, thermal spray coatings, a manual inert gas weld of Al plates, a friction stir weld of Al plates and Ni tubes and a quenched Ni superalloy cylinder used for strain tomography were studied. In-situ loading experiments have also been carried out, such as experiments on pointwise mapping of grain orientation and strain using the 3DXRD microscope at the ESRF and in-situ loading experiments on titanium alloy, rheo-diecast and high pressure diecast Mg alloy, IN718 Ni-base superalloy and Al2024 aluminium alloy. Experimental results from X-Ray diffraction and strain tomography were used to achieve a better understanding of the material properties. Some results were compared with polycrystal Finite Element model predictions. Amongst the most prominent research achievements are the development on the HEXameter laboratory instrument, including: (i) the development of special collimation systems for the detectors and the source tube; (ii) the development of a twin-detector setup (that allows for simultaneous determination of strain in two mutually orthogonal directions); (iii) improved alignment procedures for better performance; and (iv) the adaptation of instrumentation for efficient scanning of both large and small components, that included choosing and adapting translation devices, programming of the translation system and designing sample mounting procedures. In this research several approaches to data treatment were investigated. Quantitative phase analysis, single peak fitting (using custom Matlab routines and GSAS) and full pattern fitting (with individual pattern data refined by GSAS and batch refinement done by invoking GSAS via a Matlab routine) were applied. Different Matlab routines were written for specific experimental setups; and various analysis methods were selected and used for refinement depending on the requirements of the measurement results interpretation. 16 papers were published, ensuring that the results of this thesis are readily available to other researchers in the field.

Es wurde ein plattenförmiges Qualitätshalbzeug aus Spezialholzwerkstoffen für den konstruktiven Einsatz im Maschinebau, mit dem Schwerpunkt Fördertechnik entwickelt. Mit diesem Halbzeug sind ökologisch vorteilhafte Konstruktionen möglich. Entwicklungsschwerpunkte waren: einstellbare, hohe absolute und spezifische mechanische Eigenschaften mit kleinen Streuungen. Die Entwicklung wurde durch verschiedene Werkstoffprüfungen von Labor- und Industriewerkstoffen begleitet und deren Ergebnisse mittels speziell erarbeitetet Bewertungskriterien evaluiert. Weiterhin wurde das Werkstoffverhalten von diversen Holzwerkstoffen unter dynamischer Belastung klassifiziert. / A panel-shaped high quality semi-finished product made of special wood-based materials for structural applications in mechanical engineering, with a focus on materials handling technology, was developed. With said semi-finished product ecologically advantageous constructions are possible. Development priorities were: adjustable, high absolute and specific mechanical properties with little variation. The development was accompanied by various materials tests of laboratory and industrially manufactured materials, and their results were evaluated by specially developed evaluation criteria. Furthermore, the material behaviour of various woodbased materials under dynamic loading was classified.

Indiana University-Purdue University Indianapolis (IUPUI) / This paper presents a novel approach of particulate material (soot) measurement in a Diesel particulate filter using Electrical Capacitance Tomography. Modern Diesel Engines are equipped with Diesel Particulate Filters (DPF), as well as on-board technologies to evaluate the status of DPF because complete knowledge of DPF soot loading is very critical for robust efficient operation of the engine exhaust after treatment system. Emission regulations imposed upon all internal combustion engines including Diesel engines on gaseous as well as particulates (soot) emissions by Environment Regulatory Agencies. In course of time, soot will be deposited inside the DPFs which tend to clog the filter and hence generate a back pressure in the exhaust system, negatively impacting the fuel efficiency. To remove the soot build-up, regeneration of the DPF must be done as an engine exhaust after treatment process at pre-determined time intervals. Passive regeneration use exhaust heat and catalyst to burn the deposited soot but active regeneration use external energy in such as injection of diesel into an upstream DOC to burn the soot. Since the regeneration process consume fuel, a robust and efficient operation based on accurate knowledge of the particulate matter deposit (or soot load)becomes essential in order to keep the fuel consumption at a minimum. In this paper, we propose a sensing method for a DPF that can accurately measure in-situ soot load using Electrical Capacitance Tomography (ECT). Simulation results show that the proposed method offers an effective way to accurately estimate the soot load in DPF. The proposed method is expected to have a profound impact in improving overall PM filtering efficiency (and thereby fuel efficiency), and durability of a Diesel Particulate Filter (DPF) through appropriate closed loop regeneration operation.

In der vorliegenden Arbeit wird ein spanloses und umformendes Verfahren zur Erzeugung von Durchgangslöchern mit einer lokalen Dichteerhöhung untersucht. Der Ansatz beruht auf dem Fließlochformen aus der Metalltechnik. Im Bereich der Holztechnik findet dieser Ansatz noch keine Anwendung. Im Umfang der Arbeit werden für den Prozess relevante Grundlagen erläutert sowie die Prozesseinflussfaktoren für das Verfahren aufgedeckt und angepasst. Es werden Berechnungsansätze u. a. für die Abschätzung der auftretenden Axialkraft und der vom Dorn wirkenden Kräfte auf den Werkstoff aufgestellt. Es erfolgen Untersuchungen in statischen Versuchen ohne rotierenden Dorn und dynamische Versuche mit rotierendem Dorn. Untersuchte Einflüsse sind z. B. die Axialkraft, der Spitzenwinkel, die Rauheit, der Dorndurchmesser, der Einfluss des verdrängten Volumens, die Temperatur, die Dorndrehzahl und die Prozesszeit. Die aufgedeckten Einflüsse werden sukzessiv nacheinander untersucht und positive Einflussgrößen für die nachfolgenden Untersuchungen übernommen. Ebenso werden ausgewählte Auswirkungen in der praktischen Anwendung aufgezeigt.:Bibliografische Beschreibung 3 Kurzzeichenverzeichnis 9 Anmerkungen zur Arbeit 15 1 Einführung 17 1.1 Einleitung 17 1.2 Ausgangssituation 18 1.3 Zielstellung 20 1.4 Lösungsweg 21 1.5 Abgrenzung der Arbeit 21 2 Holztechnologische Grundlagen 23 2.1 Aufbau und Anatomie 23 2.1.1 Makroskopischer Aufbau 23 2.1.2 Mikroskopischer Aufbau 25 2.1.3 Chemischer Aufbau 27 2.2 Technische Begrifflichkeiten 28 2.2.1 Anisotropie und Inhomogenität 28 2.2.2 Feuchte- und Wassergehalt 29 2.2.3 Quellen und Schwinden 30 2.2.4 Spaltfestigkeit 30 2.2.5 Nagelfestigkeit 31 2.2.6 Lochleibungsfestigkeit von Nagelverbindungen 31 2.2.7 Platten und Scheibenbeanspruchung 32 2.2.8 Druckfestigkeit und Verdichtung 33 2.2.9 Faser-Last-Winkel 33 2.2.10 Dichte 35 2.2.11 Holzhärte 37 2.2.12 Thermische Eigenschaften 41 2.2.13 Rheologische Eigenschaften 43 2.3 Furnierwerkstoffe 45 3 Stand der Technik 51 3.1 WVC in technischen Anwendungen 51 3.2 Verbindungen in der Holztechnik als WVC-Anwendung 52 3.3 Umformende Prozesse bei Holzwerkstoffen 56 3.4 Bohren bei Holzwerkstoffen 58 3.5 Fließlochformen 60 3.5.1 Fließlochformwerkzeug 60 3.5.2 Prozess des Thermofließlochformens 62 3.5.3 Wärmeübergang und Materialverhalten 64 3.5.4 Thermomechanisches Ausformfügen 65 4 Auswertungsmethodik und statistische Betrachtung 67 5 Fließlochformen in Holzwerkstoffe 71 5.1 Verfahrensansatz 71 5.2 Plattenmodelle 72 5.3 Dornmodell 78 5.4 Rechnerisches Modell 87 5.5 Dorndurchmesser 91 5.6 Vorbohrung 91 5.7 Dornzieldrehzahl 91 5.8 Einflussfaktoren auf den Fließlochformprozess 92 5.8.1 Werkzeug 93 5.8.2 Temperatur 93 5.8.3 Feuchtigkeit 94 5.8.4 Verdrängtes Volumen 95 5.8.5 Werkstoff 95 6 Versuchswerkstoff 97 6.1 Furnierwerkstoff 97 6.2 Dimension 98 6.3 Konditionierung 98 6.4 Feuchtegehalt 99 6.5 Rohdichte 100 7 Druckversuche 101 7.1 Vorbetrachtung 101 7.2 Durchführung 102 7.3 Ergebnisse 103 8 Statische Versuche 105 8.1 Vorbetrachtung 105 8.2 Durchführung 108 8.3 Auswertung 110 8.3.1 Spitzenwinkel 110 8.3.2 Rauheit 113 8.3.3 Durchmesser 113 8.3.4 Verdrängtes Volumen 114 8.3.5 Temperatur 116 8.3.6 Lochrückformung 118 8.3.7 Dichtebestimmung der Messreihen 119 8.3.8 Gewichtsdifferenz 120 8.3.9 Beidseitiges Eindringen 120 8.4 Mikroskopische Analyse 122 8.5 Modell und Versuch 124 8.6 Fazit 126 9 Dynamische Versuche 127 9.1 Ablauf 127 9.2 Vorversuche 127 9.3 Fließlochformautomat 129 9.4 Werkzeuge 131 9.5 Auswertung 132 9.5.1 Drehzahl 132 9.5.2 Axialkraft 133 9.5.3 Hubzahl 136 9.5.4 Prozesszeit 136 9.5.5 Abstand 137 9.5.6 Werkstoffeinfluss 139 9.5.7 Lochrückformung 141 9.5.8 Dichte 142 9.5.9 Gewichtsdifferenz 142 9.5.10 Maßhaltigkeitsuntersuchung 142 9.6 Mikroskopische Analyse 144 9.7 Modell und Versuch 147 10 Auswirkung auf die Praxis 149 10.1 Vorspannkraftabfall 149 10.2 Muffenauszugskraft 153 10.3 Fließlochformen in der Praxis 154 11 Fazit 157 12 Ausblick 161 13 Quellenverzeichnis 163 14 Abbildungsverzeichnis 169 15 Tabellenverzeichnis 175 Anlagen 177 / In the present work, a non-cutting and forming process for the production of through holes with a local density increase is investigated. The approach is based on flow drill technology from metal technology. This approach is not yet applied in the field of wood technology. In the scope of the work, fundamentals relevant to the process are explained, and process influencing factors for the process are uncovered and adjusted. Calculation approaches are used, e. g. for estimating the occurring axial force and the forces acting on the material from the mandrel. Static tests without rotating mandrel and dynamic tests with rotating mandrel are carried out. Influences investigated include axial force, point angle, roughness, mandrel diameter, influence of displaced volume, temperature, mandrel speed and process time. The revealed influences are successively investigated one by one and positive influence variables are adopted for the subsequent investigations. Likewise, selected effects in practical application are shown.:Bibliografische Beschreibung 3 Kurzzeichenverzeichnis 9 Anmerkungen zur Arbeit 15 1 Einführung 17 1.1 Einleitung 17 1.2 Ausgangssituation 18 1.3 Zielstellung 20 1.4 Lösungsweg 21 1.5 Abgrenzung der Arbeit 21 2 Holztechnologische Grundlagen 23 2.1 Aufbau und Anatomie 23 2.1.1 Makroskopischer Aufbau 23 2.1.2 Mikroskopischer Aufbau 25 2.1.3 Chemischer Aufbau 27 2.2 Technische Begrifflichkeiten 28 2.2.1 Anisotropie und Inhomogenität 28 2.2.2 Feuchte- und Wassergehalt 29 2.2.3 Quellen und Schwinden 30 2.2.4 Spaltfestigkeit 30 2.2.5 Nagelfestigkeit 31 2.2.6 Lochleibungsfestigkeit von Nagelverbindungen 31 2.2.7 Platten und Scheibenbeanspruchung 32 2.2.8 Druckfestigkeit und Verdichtung 33 2.2.9 Faser-Last-Winkel 33 2.2.10 Dichte 35 2.2.11 Holzhärte 37 2.2.12 Thermische Eigenschaften 41 2.2.13 Rheologische Eigenschaften 43 2.3 Furnierwerkstoffe 45 3 Stand der Technik 51 3.1 WVC in technischen Anwendungen 51 3.2 Verbindungen in der Holztechnik als WVC-Anwendung 52 3.3 Umformende Prozesse bei Holzwerkstoffen 56 3.4 Bohren bei Holzwerkstoffen 58 3.5 Fließlochformen 60 3.5.1 Fließlochformwerkzeug 60 3.5.2 Prozess des Thermofließlochformens 62 3.5.3 Wärmeübergang und Materialverhalten 64 3.5.4 Thermomechanisches Ausformfügen 65 4 Auswertungsmethodik und statistische Betrachtung 67 5 Fließlochformen in Holzwerkstoffe 71 5.1 Verfahrensansatz 71 5.2 Plattenmodelle 72 5.3 Dornmodell 78 5.4 Rechnerisches Modell 87 5.5 Dorndurchmesser 91 5.6 Vorbohrung 91 5.7 Dornzieldrehzahl 91 5.8 Einflussfaktoren auf den Fließlochformprozess 92 5.8.1 Werkzeug 93 5.8.2 Temperatur 93 5.8.3 Feuchtigkeit 94 5.8.4 Verdrängtes Volumen 95 5.8.5 Werkstoff 95 6 Versuchswerkstoff 97 6.1 Furnierwerkstoff 97 6.2 Dimension 98 6.3 Konditionierung 98 6.4 Feuchtegehalt 99 6.5 Rohdichte 100 7 Druckversuche 101 7.1 Vorbetrachtung 101 7.2 Durchführung 102 7.3 Ergebnisse 103 8 Statische Versuche 105 8.1 Vorbetrachtung 105 8.2 Durchführung 108 8.3 Auswertung 110 8.3.1 Spitzenwinkel 110 8.3.2 Rauheit 113 8.3.3 Durchmesser 113 8.3.4 Verdrängtes Volumen 114 8.3.5 Temperatur 116 8.3.6 Lochrückformung 118 8.3.7 Dichtebestimmung der Messreihen 119 8.3.8 Gewichtsdifferenz 120 8.3.9 Beidseitiges Eindringen 120 8.4 Mikroskopische Analyse 122 8.5 Modell und Versuch 124 8.6 Fazit 126 9 Dynamische Versuche 127 9.1 Ablauf 127 9.2 Vorversuche 127 9.3 Fließlochformautomat 129 9.4 Werkzeuge 131 9.5 Auswertung 132 9.5.1 Drehzahl 132 9.5.2 Axialkraft 133 9.5.3 Hubzahl 136 9.5.4 Prozesszeit 136 9.5.5 Abstand 137 9.5.6 Werkstoffeinfluss 139 9.5.7 Lochrückformung 141 9.5.8 Dichte 142 9.5.9 Gewichtsdifferenz 142 9.5.10 Maßhaltigkeitsuntersuchung 142 9.6 Mikroskopische Analyse 144 9.7 Modell und Versuch 147 10 Auswirkung auf die Praxis 149 10.1 Vorspannkraftabfall 149 10.2 Muffenauszugskraft 153 10.3 Fließlochformen in der Praxis 154 11 Fazit 157 12 Ausblick 161 13 Quellenverzeichnis 163 14 Abbildungsverzeichnis 169 15 Tabellenverzeichnis 175 Anlagen 177