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Thesis (MScEng (Industrial Engineering))--Stellenbosch University, 2008. / There is a growing global demand for titanium. The aircraft industry is the driving force behind the demand for titanium. The reason for this is that titanium has attractive properties that justify its use both economically and environmentally. Titanium alloys have superior strength-to-weight ratios. This implies that by substituting components manufactured from other metals in the aircraft with titanium components, a substantial reduction in structural weight can be achieved. From an economical point of view a lower mass implies lower fuel consumption. From an environmental point of view lower fuel consumption implies less harmful greenhouse emissions. Ti6Al4V components are the most widely used titanium alloy products in aircraft components. Ti6Al4V is known as a difficult-to-machine material. This is due to its low thermal conductivity and small contact area between the tool and the chips causing higher temperatures to be generated closer to the cutting edge of the insert. This will subsequently increase the rate at which the cutting tool wears. For this reason relatively low cutting speeds and feed rates are employed for the machining of Ti6Al4V compared to the machining of steels. Ti6Al4V is an exceptionally high cost material. The low cutting speeds and feed rates used in Ti6Al4V machining raises the machining cost of parts and contributes to an increase in the price of Ti6Al4V parts. By employing higher cutting speeds and feed rates machining times on Ti6Al4V products could be decreased, subsequently lowering the price for Ti6Al4V components. An increase in cutting speeds and feed rates will subsequently cause an increase in generated cutting temperatures, resulting in an increase in tool wear. This stresses the importance of controlling the cutting temperature during machining of Ti6Al4V in order to prolong tool life. The focus of this work was to investigate different lubrication strategies for polycrystalline diamond (PCD) and tungsten carbide inserts for Ti6Al4V milling operations in the quest to develop improved feasible cutting parameters. The results of this study showed that flood lubrication should be utilized for PCD inserts, while a “softer” 60 bar high pressure through spindle lubrication worked best for the tungsten carbide inserts. By utilizing these lubrication strategies, cutting speeds of 100 m/min and feeds per tooth of 0.05 mm/rev for both the PCD and tungsten carbide grades could be attained with satisfactory tool life.

The geotechnical aspects of a hazardous waste disposal site located in Piney River, Nelson County, Virginia, were investigated. The waste material consisted primarily of a by-product of the production of titanium known as copperas which is highly acidic. The investigatory program consisted of field and laboratory work. Objectives included delineating the pit geometry and liner system, assessing the characteristics of the natural soils at the site as well as the wastes, and evaluating the degree of contamination of the natural subsoils around the pit. The field investigation findings show a more complex geometry for the pit than that suggested in the design documents. While shown on the plans, the presence of the bottom clay liner is questionable. Large depressions and numerous cracks were found in the waste area. Acid contamination of the groundwater and the subsoils exists to a considerable depth. Laboratory tests illustrated the susceptibility of the copperas to dissolution under water seepage. This could have caused the large settlements. Remedial actions could include grading the top of the pit for better drainage. Other actions could include redepositing the waste in a burial pit which has a leachate collection system and properly compacted clay liners which include an impervious fabric. Perhaps the waste could be treated chemically prior to final disposition. In any case, some level of continual maintenance will be necessary. / M. S.