The determination of the pressure distribution generated along the arc of contact between the rolls and workpiece during the rolling process has been a subject of interest to researchers for many years. Existing rolling theories make assumptions and include simplifications which are not often substantiated by direct measurement techniques in which pressure transducers are located within the roll surfaces. Such techniques are effective but prohibitively expensive since they render the rolls useless for rolling. A technique has been developed in which the pressure distribution and roll separating load are determined from consideration of the elastic deformation of the rolls during operation. By interrupting a rolling pass before completion, the shapes of the deformed rolls are imparted to the workpiece surface. Accurate measurement of the imparted profiles at several sections across the width of the workpiece allows the extent of the elastic deformation of the roll to be determined. An analytical solution based on solid body contact theory was used to determine the pressure distribution responsible for the elastic deformation along each section. The solution incorporates experimentally determined parameters and functions relating to specific mill-stands and schedules. Initial experimental work was undertaken in which the proposed technique was applied to the quasi-static indentation of flat and inclinedstrip specimens. Having established the basic features of the method relating to these modes of deformation the technique was then applied to the cold rolling process in the form of interrupted rolling passes. Tests were undertaken using a two-high laboratory rolling mill reducing the thickness of mild steel strip workpieces. Comparisons between the predicted pressure profiles using the technique developed and those determined by others using pressure transducers show close similarities. A comparison between the predicted roll separating loads and those determined experimentally show a reasonable correlation.

Friction StirWelding (FSW) has been researched for a number of years since its inception in 1991. The work thus far has been based on understanding the material and thermal flow using the standard fixed pin tool. The keyhole resulting during tool extraction in a FSW weld, is a disadvantage and a current limiting factor. Eliminating this effect from a weld using a movable pin tools would make FSW more commercially viable. This dissertation focuses on the design of a novel retractable pin tool, and highlights the problems encountered during the welding of Aluminum plates, Al2024 and Al5083. Previously studied techniques of material and thermal flow were used, to investigate the effect of the tool during extraction in a FSW weld. A prototype retractable tool was designed using parametric and axiomatic design theory, and implementing a pneumatic muscle actuation system. The resulting problems in the calibration of the retractable pin tool and the resulting welds are presented, these results confirming previous studies. The movable pin produced discrepancies the heat generation around the shoulder during a FSW weld. The failure of this tool to produce a reasonable weld showed that previous ideas into the workings of a retractable pin tool requires further investigation, furthermore a fresh approach to the interpretation and understanding of the FSW weld process needs consideration.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2007 / The rheological behaviour of non-Newtonian, highly concentrated and non-transparent fluids used in industry have so far been analysed using commercially available instruments, such as conventional rotational rheometers and tube viscometers. When dealing with the prediction of non-Newtonian flows in pipes, pipe fittings and open channels, most of the models used are empirical in nature. The fact that the fluids or slurries that are used normally are opaque, effectively narrows down the variety of applicable in-line rheometers even further, as these instruments are normally based on laser or visible light techniques, such as Laser Doppler Anemometry. Electrical Resistance Tomography is a non-invasive method used to look into opaque suspensions during pipe flow, but cannot be used to measure in-line rheometry. In this research, an Ultrasound Pulsed Echo Doppler Velocity Profile technique (UVP), in combination with a pressure difference (PD) was tested to provide in-line measurement of rheological parameters. The main objective ofthis research was to evaluate the capabilities of the UVP-PD technique for rheological characterisation of different concentrations of non-transparent non-Newtonian slurries. A unique pipe viscometer was designed and constructed. It consisted of four pipes, one of stainless steel and three of PVC, linked to an in-line mass-flow meter and equipped with two different ranges of pressure transducers on each pipe. The stainless steel pipe, with an inner diameter of 16 mm, was equipped with a specially designed flow adapter for in-line rheological characterisation using the UVP-PD method. The three PVC pipes with different diameters of 9 mm, 13 mm and 16 mm served as a tube viscometer for in-line rheological characterisation of mineral suspensions.

At present the effects of friction are not included in three-dimensional mechanism simulation packages because of the difficulty of determining a friction model for joints such as the spherical joint where the frictional resistance to motion depends not only upon the coefficient of friction and the magnitude of the loading on the joint but also on the pressure distribution within the joint resulting from that loading. Thus the basis of this thesis has been the development of a mathematical model of the effects of friction in a spherical joint which could then be incorporated into a mechanisms simulation program. The model developed has shown that the main factors determining the magnitudes and directions of the frictional effects produced in a spherical joint, apart from the coefficient of friction and the magnitude of the loading, are the extent of the contact area between the ball and the socket and the magnitude of the angle between the axis of rotation of the joint and the direction of the applied load. Experimental results were obtained using apparatus that enabled the frictional moment produced on the socket of a joint to be measured while allowing the angle between the axis of rotation of the ball and the direction of the applied load to be varied between measurements. These results, obtained for a range of values of the coefficient of friction, confirm that this angle is a significant factor in the model and that the model usefully determines the frictional effects produced in a spherical joint.

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The object of this research was to study the effect of initial surface -finish and finish mark orientation on intermetallic friction under unlubricated sliding contact conditions. The metal used was mild steel and the parameters investigated were sliding speed and load. Qualitative assessments of wear were also made. The basic apparatus consisted of a rotating disc and an elastically supported slider. The disc and slider each had the same-initial surface finish. Six different surface finishes were examined ranging in roughness from a peak to valley distance of 6.9 thousandths of an inch to 35 microinches R.M.S. Speed was varied from 1.25 to 60 inches per second and normal load from 1.025 to 3.075 pounds. No significant correlation was found, between the theory of Ernst and Merchant and the experimental results. Friction was more dependent on surface parameters affecting load concentration than, on the particular details of each surface asperity. The effects of finish mark orientation were only significant when they produced appreciable load concentration. Friction was found to increase as "wear-in" progressed and remain approximately constant once wear-in was complete. No relation between friction and velocity could be deduced. Wear-in was found to be influenced by initial surface geometry. The sufaces which gave high load concentration at sharp protuberances "wore-in" more quickly than those-with low load concentration. Smooth compatible surfaces which required little surface alteration also wore-in rapidly. Wear debris was found to influence both friction and wear-in. Evidence of mechanical working of debris between the surfaces was obtained. A quasi-harmonic oscillation of the slider supporting system was observed to result from wear-in. The frequency of vibration was a function of disc speed and load. The amplitude of the vibration increased linearly with disc speed up to a maximum value. The magnitude-of this maximum was dependent on normal load. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Certain surface-active media can considerably influence the flow and fracture properties of the .solids they wet. The effects of various lubricating media on the sliding friction behaviour of diamond on soda-lime glass were studied in the present research. An experimental apparatus was constructed to slide a hemispherical diamond linearly and at constant speed across the surface of a Corning type 2947 soda-lime glass microslide and to measure the resultant friction force. Tests were conducted in a variety of liquid and gaseous media at sliding speeds ranging from 0.001 cm/sec to 0.4 cm/sec. As a base for comparison initial tests were conducted in a high vacuum — 8 at 4 x 10 ⁻⁸. The results showed that all the media enhanced material displacement from that observed in high vacuum. In addition, the friction force was observed to rise with displaced material. A simple theory was used to predict with reasonable agreement the results obtained in in vacuum and air only. The greatest increase in displaced material was observed in heptyl alcohol. Scanning electron micrographs of the friction tracks suggest that heptyl; alcohol softened the surface of the glass. This is in agreement with previous work. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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