Predicting the long-term behaviour of present-day ice sheets is hampered by the short timescales of our observations and restricted knowledge of the subglacial environment. Studying palaeoice sheets can help by revealing the nature and amplitude of past centennial- to millennial-scale ice sheet change. This thesis uses glacial sediments and landforms to examine the evolution of the partly marine-based British-Irish Ice Sheet (BIIS) and its bed, in western Scotland. Three zones of the former BIIS are considered: ranging from a mountain ice cap, to a core area of the ice sheet, to a peripheral marine-terminating sector. The topography of the subglacial landscape was an important in uence on the location of dynamic and stable components of the ice sheet. At an ice cap scale, zones of glacier inception and retreat were linked to catchment elevation and size. At the ice sheet scale, the migration of ice divides and thermal boundaries were focused through corridors of low relief subglacial topography. The main west-east ice divide of the BIIS in central Scotland migrated by 60 km, 10% of the ice sheet's width, through one such corridor during the glacial cycle. A major change in the ow regime of the BIIS in western Scotland accompanied the development of a marine-based sector on the Malin Shelf. As the BIIS advanced to the shelf edge, ice ow was drawn westwards { orthogonal to the earlier, geologically controlled, ow pattern. Retreat of the BIIS from the shelf edge occurred at an average rate of 10 m a-1, but was punctuated by at least one episode of accelerated retreat at 100 m a-1. In each zone of the BIIS examined, a rich palimpsest landscape is preserved and the role of earlier glaciations in conditioning or priming the landscape is highlighted. Western Scotland in particular is dominated by features relating to a 'restricted' mountain ice sheet, suggested to have been the prevailing ice sheet mode during the Early and Middle Quaternary. Where the last BIIS was underlain by soft sediments, glacier movement at the bed was facilitated by a combination of basal sliding and a localised mosaic of shallow deforming spots, allowing landform and sediment preservation. In places, till deposition was focused over permeable substrates acting to seal the bed, promote lower e ective pressures, and enhance motion by basal sliding. The modern land surface in western Scotland provides an approximation for the relief of the former glacier bed, and can be used for conceptual palaeoglaciological reconstructions. Areas of focused postglacial deposition have, however, obscured parts of the ice sheet bed, with demonstrable implications for quantitative palaeoglaciological analyses. Methods to improve the representation of former ice sheet bed in these areas are discussed and may be pertinent to future palaeo-ice sheet modelling exercises.

The relationship between some mechanical properties (tensile, creep and thermal fatigue behaviour) and microstructure has been investigated for lead sheet containing <0.06 wt % Cu (the eutectic composition), made either by a conventional milling (rolling) process, or by continuous casting (Direct Method). Milled lead sheet exhibits a recrystallised microstructure, the grain size of which decreases with increasing copper content; copper is present as particles of ≃1-5 μm long, formed from the initial needles or plates of the cast billet by spheroidisation, or by particle break-up during rolling. A comparison of materials produced by several manufacturers indicates that the copper distribution and final grain size are dependent on the thermo-mechanical history of the sheet. Direct Method (DM) sheet exhibits a cast cellular structure within grains which usually extend through the full thickness of the cast sheet; copper is present as a fine dispersion (particles ≃0.5 μm diameter) at cell boundaries. The copper distribution in both materials is stable to prolonged heating (100 hours at 200<SUP>o</SUP>C), but some grain growth occurred in the milled sheet. It was not possible to obtain a fully dispersed eutectic microstructure at the eutectic composition; primary lead dendrites (or cells) were always present. This is thought to be due to the difficulty of nucleating a copper particle at the very low copper concentrations used in this work. The tensile behaviour of specimens was investigated at various strain rates and temperatures. DM sheet exhibits an increase in UTS both with increasing copper content at each strain rate, and with increasing strain rate for each copper content; no systematic variation of strain with copper content was observed. The UTS of milled lead sheet (at ambient temperature and slow strain rates) was a maximum at 0.02 - 0.03 % copper. A steady increase in UTS with increasing copper content was obtained at higher strain rates (2.67 min<SUP>-1</SUP> and above) and low temperatures (≃200 K) and indicated that a time and temperature dependent softening process is active at ambient temperature and slower strain rates (up to 1.33 min^-1) which is thought to be grain boundary sliding, although no evidence for this has been detected in the recrystallised microstructure. Values of the work-hardening coefficient (n) and the strain-rate sensitivity (m) were determined for milled and DM sheet, and were found in all cases to be high. DM sheet exhibits good creep resistance, which increases with increasing copper content, owing to the large grains and stable grain boundaries at ≃90' to the direction of stress. Milled lead sheet was less creep resistant, exhibiting maximum creep resistance at 0.03% copper; this is thought to be due to competing processes of strengthening by copper (which pins grain boundaries to some extent) and grain boundary sliding, which increases with the corresponding decrease in grain size. Thermal fatigue tests have been conducted externally, using lead flashing lengths fixed to an outside wall, and in the laboratory using specially developed apparatus. The development of the apparatus, specimen shape and test cycle length is described. Cracking is usually multiple and intergranular; examination of the fracture surface indicates a combination of intergranular fatigue, creep processes (cavitation) and regions of ductile failure. The use of acetate replicas to trace crack growth has shown the migration of grain boundaries to directions of high stress in milled lead, and in 0.01% copper DM sheet. Grain boundary migration was not observed in the more stable DM microstructures of higher copper content.

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Ng Yiu Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 110-114). / Abstracts in English and Chinese. / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Diagnosis concept based on thermal energy distribution --- p.6 / Chapter 1.1.1 --- A cup drawing example --- p.8 / Chapter 1.2 --- Need for 3D infrared thermal distribution measurement --- p.10 / Chapter 1.3 --- Outline of the Thesis --- p.11 / Chapter 2. --- Approach --- p.15 / Chapter 2.1 --- Similarity and extreme temperature analysis --- p.15 / Chapter 2.2 --- Thermodynamics for FEA in sheet metal stamping --- p.17 / Chapter 2.3 --- Acquisition of 3D thermal distribution --- p.20 / Chapter 3. --- Implementation of the Diagnosis System --- p.23 / Chapter 3.1 --- Thermograph acquisition --- p.23 / Chapter 3.2 --- Diagnosis system setup --- p.24 / Chapter 3.3 --- Perspective camera model --- p.25 / Chapter 3.4 --- System calibration --- p.27 / Chapter 3.4.1 --- LEDs calibration board --- p.27 / Chapter 3.4.2 --- Net-and-board calibration box --- p.29 / Chapter 3.5 --- Reconstruction algorithm --- p.33 / Chapter 3.6 --- Summary --- p.37 / Chapter 4. --- Consistency from Different Viewpoints --- p.38 / Chapter 4.1 --- Summary --- p.42 / Chapter 5. --- Visual Reconstruction of Objects --- p.44 / Chapter 5.1 --- Visual camera calibration --- p.45 / Chapter 5.2 --- Results --- p.49 / Chapter 5.2.1 --- "Cartoon model ""SiuSun""" --- p.49 / Chapter 5.2.2 --- Stamping disc --- p.51 / Chapter 5.3 --- Summary --- p.53 / Chapter 6. --- Thermal Distribution Reconstruction of Stamping Workpieces --- p.54 / Chapter 6.1 --- Infrared camera calibration --- p.54 / Chapter 6.2 --- Results --- p.57 / Chapter 6.2.1 --- Air conditioner cap --- p.57 / Chapter 6.2.2 --- Deep drawing cup --- p.59 / Chapter 6.2.3 --- Stamping cylinder from KS Factory --- p.61 / Chapter 6.3 --- Summary --- p.65 / Chapter 7. --- Infrared Camera on a Robotic Arm --- p.66 / Chapter 7.1 --- Robotic arm system setup --- p.67 / Chapter 7.2 --- System calibration --- p.68 / Chapter 7.3 --- Results --- p.77 / Chapter 7.3.1 --- Image sequence from horizontal viewpoints --- p.77 / Chapter 7.3.2 --- Image sequence from inclined viewpoints --- p.80 / Chapter 7.3.3 --- Image sequence from arbitrary viewpoints --- p.83 / Chapter 7.4 --- Comparison of the three different viewpoints --- p.85 / Chapter 7.5 --- Summary --- p.87 / Chapter 8. --- Compensation of Temperature Fade-out Problem --- p.88 / Chapter 8.1 --- Causes of temperature fade-out --- p.88 / Chapter 8.2 --- Solutions --- p.90 / Chapter 8.3 --- Summary --- p.91 / Chapter 9. --- Other Applications --- p.92 / Chapter 9.1 --- Automotive industry --- p.92 / Chapter 9.1.1 --- Background --- p.93 / Chapter 9.1.2 --- Experiment and result --- p.94 / Chapter 9.2 --- General heat transfer analysis --- p.97 / Chapter 9.3 --- Summary --- p.98 / Chapter 10. --- Conclusions --- p.99 / Chapter 10.1 --- Summary --- p.99 / Chapter 10.2 --- Future work --- p.104 / Chapter A. --- Transformation Matrices of the System --- p.106 / Bibliography --- p.110

In order to ensure the desirable performance of the machine, dynamic analysis of the machine is necessary. The analysis is conducted by the mean of computer simulation in consideration of applying a large impulsive force. This study validates the machine stability and accuracy. / In order to verify the new mechanics model, numerical and experimental studies are conducted using the new incremental punching system. The final shape and thickness distributions of parts are compared to verify the mechanics model. It is found that the model prediction fits the experiment result well. Forming parameters are also investigated. / In this research, a new incremental forming system based on incremental punching is designed and built. The system consists of a 3-axes CNC platform, a high speed hydraulic cylinder with a hemispherical forming tool, and a PC-based CNC control system. The hydraulic system provides the forming force to deform the sheet metal with constant stokes, while the CNC system positions the part. When forming a part, the forming tool punches the sheet metal along the given contour of the part punch by punch; when one layer of the part is completed, the forming tool moves down to the next layer; and the process is finished till all layers are completed. The CNC control system works with standard NC code, and hence, is easy to use. / ISMF uses a small generic tool to apply a sequence of operations along the given path to deform the sheet incrementally. These small deformations accumulate to form the final shape of the part. As a result, different parts can be made by the same setup. Despite of some 30 years of research and development, however, ISMF technology is still premature for industrial applications due to the following reasons: The accuracy of the part is limited; the surface roughness is poor; and the productivity is low. This motivates the presented research. / One of the keys to successful application of sheet metal forming is to be able to predict the deformation and the strain/stress of the part incurred during the forming process. Because of the complexity of the ISMF process, it is not possible to derive an analytical method. The alternative is to use Finite Element Analysis (FEA). However, based on our experience, it takes about one week to solve a simple case. A mechanics model is therefore developed. It consists of two steps. The first step is to computer the final shape: the initial geometric surface is obtained using the punch positions; then using the minimum energy principle, the virtual forces drive the nodes of geometric surface to their lowest energy positions, which gives the final shape of the forming part. The second step is to predict the strain and stress distributions. This is done using the inverse Finite Element Modeling (FEM). An in-house computer software is developed using MATLABRTM. / Stamping is one of the most commonly used manufacturing processes. Everyday, millions of parts are formed by this process. The conventional stamping is to form a part in one or several operations with a press machine and a set/sets of dies. It is very efficient but is not cost effective for small batch production parts and prototypes as the dies are expensive and time consuming to make. Recently, with the increasing demands for low-volume and customer-made products, a die-less forming method, Incremental Sheet Metal Forming (ISMF), has become one of the leading R&D topics in the industry. / To evaluate the capability of the presented ISMF process, the formability is studied by the means of theory and experiment. A modified M-K model is proposed for predicting the forming limit of the formed part which is undergoing a very complicated strain path. The maximum forming angle is also investigated by experiments. / Luo, Yuanxin. / Adviser: Ruxu Du. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 121-133). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

There is a strong desire among automobile manufacturers to reduce the fuel consumption and greenhouse gas emissions of their current vehicles. Reducing the overall weight of a vehicle represents the most practical opportunity to reduce fuel consumption. Replacing the current steel sheet structures with lightweight alternatives, such as aluminum, offers an excellent solution. Much of the attention in North America has been focused on copper-containing Al-Mg-Si aluminum alloys (6xxx series), such as AA6111. These alloys offer an excellent combination of good formability and precipitation-strengthening ability.<p> In this study, the effect of solute concentration on the strength and strain aging behavior of a proprietary Al-Mg-Si-(Cu) alloy was evaluated. The experimental design used was a 26 full factorial design, with the primary factors being the solute concentrations of magnesium, silicon, and copper, as well as the effects of applied strain (cold work), and natural and artificial aging heat treatments (e.g., a simulated paint bake process). The primary investigative techniques employed included tensile testing, microhardness measurements, and optical metallography.<p> The results show that cold work and artificial aging produce the most substantial strengthening in the alloys. The occurrence of natural aging prior to forming and artificial aging reduced strengthening. The highest strength levels in the naturally aged and paint baked condition, which most closely resembles what is found in industry, were achieved at a combination of low magnesium levels (i.e., 0.5 wt.%) and high silicon and copper levels (i.e., 0.9 and 0.3 wt.%, respectively).