Thesis (MEd)--PU vir CHO

Proefskrif--PU vir CHO

The objective of this study is to investigate the picture book as a form of communication. The investigation comprises both a theoretical and a practical approach. An extensive literature survey was undertaken, publishers interviewed and visits undertaken to process and printing houses to establish the methods and approaches that are currently employed to produce a picture book. The theoretical formulation forms the background and motivation to the practical aspect of the study. The practical component entails the actual conceptualization, design, illustration and publication of a picture book. The possibilities and constraints imposed on the illustrator, comprising all the elements that influence and shape the communication process, are presented and discussed - firstly in theory and then in direct reference to the picture book which is bei:1g illustrated. The theoretical and practical components of this study combine to show up the picture book as a unique art and literary form. The manner in which successful communication is achieved through the effective utilization of all the processes and elements that combine to form the picture book is demonstrated. This study emphasizes that the illustrator should get to know and use all possibilities and restrictions to their full advantage to create an effective, unique interpretation and expression in picture book form. / Thesis (MA (Beeldende Kunste))--PU for CHE

Thesis (MEd)--PU vir CHO

Proefskrif--PU vir CHO

Extrusion is a continuous solid state deformation process which is widely used in the aluminium industry. The demand for aluminium extrudates are growing and extruders are pressurized to extrude products as fast as possible without lowering the quality of the product. Important extrusion parameters and conditions are exit temperature, extrusion speed and alloy composition. It is widely accepted in extrusion industry that extrusion surface defects increase when the extrusion speed and exit temperature are increased for a constant alloy. One of the major surface defects is the so-called die pick-up and it is presently uncertain if increase with extrusion speed (from a low 25m/min) would result in an increase of the number of die pick-up defect.Die pick-up appears like a scratch mark or comet on the surface of the extrudate which damages the appearance. Previous research suggests that second phase particles, eutectic reactions (555°C - 600°C), extrusion process conditions and die conditions may influence the cause of die pick-up. However the influencing factors for die pick-up are not well established.The research started by determining the lowest melting temperature for AA6060 alloy as this temperature limit the highest temperature above which incipient melting starts. This temperature corresponds to the eutectic melting temperature for AA6060 alloy. Eutectic melting was only detected above 610°C and therefore the exit temperature could be increased to a maximum of 610°C. For an AA6xxx alloy system the lowest melting temperature is 555°C if Mg2Si and excess silicon were present. However as Mg2Si may have fully dissolved into the solid solution, no reaction can take place.A preliminary investigation was conducted to study the characteristics of the newly installed extrusion control and monitoring system. Through this study the relationship between the set extrusion speed and the actual extrusion speed was established. It was found that the actual extrusion speed was lower than the set extrusion speed and was further complicated by the capacity limit of the extrusion pressure. Exit temperature measurements were accurate, however it was measured about 1m away from the die exit. Experiments were carried out to estimate the exit temperature drop and hence the exit temperature measurements were corrected accordingly.Thus, the aim of the present research was to establish the relationship between die pick-up and extrusion conditions (extrusion speed, exit temperature and die condition) and to propose the likely formation mechanism for die pick-up.In this research AA6060 alloy was used and was extruded at 25m/min, 30m/min, 35m/min, 40m/min and 45m/min. The exit temperature was found to increases from 542°C to 567°C. Three types of die pick-up was identified which were named as normal pick-up, die line pick-up and lump pick-up. Normal pick-up occurred regardless of the extrusion speed and exit temperature; however the amount of normal pick-up did not increase when the extrusion speed was increased. Die line pick-up occurred when the extrusion speed was 45m/min and appeared only on the die lines. Lump pick-up is not significant since it was very rare.AA6060 (0.4%Mg and 0.5%Si) alloy has about 0.27% excess silicon and therefore at 555°C, Mg2Si particles react with aluminium and excess silicon to form liquid. However normal pick-up and die line pick-up still occurred at temperatures lower and higher than 555°C and therefore it confirms that eutectic reactions do not influence formation of pick-up. Therefore die pick-up is most likely to be caused due to a mechanical process rather than a metallurgical process.

Thesis (Ph.D.)--Tufts University 1999. / Submitted to the Interdisciplinary Program. Adviser: Howard M. Solomon. "Doctor of Philosophy in the Interdisciplinary Program." Includes bibliographical references (leaves 454-497). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Zugl.: Basel, Univ., Diss.

Univ., Diss.--München, 2000.

Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2007. / [A thesis submitted] for the degree of Doctor of Philosophy, Industrial Research Institute, Swinburne University of Technology - 2007. Typescript. Includes bibliographical references (p. 154-167).