Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1935. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed June 9, 2010) Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 80-83).

No description available.

A detailed investigation is carried out for a novel process of die-less strip drawing, in which conventional reduction dies have been replaced by a die-less reduction unit having a rectangular hole of stepped configuration. The smallest hole dimensions are larger than those of the incoming strip, thus eliminating direct metal to metal contact and hence the problem of die-friction and consequential die wear. The strip is plastically deformed by means of the combined effect of the hydrodynamic pressure and drag force generated in the unit due to the motion of the strip through a polymer melt. An extensive experimental study has been undertaken, which showed that higher reductions were achieved at slower drawing speeds with gradual decrease in reduction at higher drawing speeds. The maximum reduction in area of the strip noted was, about 12%. Various parameters were changed to examine their effects on the performance of the process. Theoretical analyses have been developed considering Newtonian and non-Newtonian characteristics of the pressure medium. These analyses enable the predictions to be made of the pressure distribution , within the reduction unit, on-set of plastic yielding of the strip marerial, shear and axial stresses, and the percentage reduction in strip size. The analyses incorporate critical shear stress limit of the polymer melt, the strain hardening and the strain rate sensitivity of the strip material. The predicted results for the percentage reduction in strip size appear to under-estimate the experimental values at the slow drawing speed and over-estimate them at the higher drawing speed.

A new technique for tube sinking has been developed which should, in a number of ways, help to solve the problems associated with conventional tube sinking processes, eg die wear and the need for a swaged down leading end for easy insertion through the die. The conventional reduction die is altogether replaced by a die-less reduction unit of stepped bore configuration. The deformation is induced by means of hydrodynamic pressure and drag force generated in the unit due to the motion of the tube through the viscous fluid medium (polymer melt). The dimensions of the die-less reduction unit are such that the smallest bore size is dimensionally greater than the nominal diameter of the undeformed tube, thus metal to metal contact and hence wear, should no longer be a problem. As no conventional reduction die is used, the need for a reduced diameter leading end is also eliminated. Experimental results show that greater reduction in tube diameter and the coating thickness were obtained at slower drawing speeds (about 0.1 m/s). The maximum reduction in diameter noted was about 7 per cent. Analytical models have been developed, assuming with Newtonian and non-Newtonian characteristics of the pressure medium, which enabled prediction of the length of the deformation zone, percentage reduction in diameter and drawing stress. In the non-Newtonian analysis account was taken of the pressure coefficient of viscosity, derived from the available data; the limiting shear stress, which manifests itself as slip in the polymer melt and the strain hardening and the strain rate sensitivity of the tube material. The percentage reduction in diameter predicted using the Newtonian analyses appear to differ considerably from the experimental results both in trend and magnitude. Non-Newtonian analysis predicted theoretical results which are much closer to the ones observed experimentally.

No description available.

No description available.

The parallel surface thrust bearing has been studied both theoretically and experimentally. The general equations governing the laminar flow of a Newtonian fluid are presented and suitably reduced to describe the flow of lubricant through a plain collar bearing. A computer solution of the resulting equations has been obtained in which the variations, of density and viscosity with temperature are accommodated and the circumferential leakage of oil from the bearing is recognised. The resulting performance curves indicate that useful load carrying capacities, produced by a 'thermal wedge' effect, are possible with parallel surface thrust bearings. A series of tests was carried out on a three inch diameter bearing operating at speeds ranging from 15,000 to 19,000 r.p.m. The results confirm that hydrodynamic lubrication may be achieved with a parallel surface thrust bearing. The experimental values obtained for the load carrying capacity and the coefficient of friction were both less than the theoretical predictions. The discrepancies appear to be caused, for the most part, by an increase in the oil temperature resulting from entrainment of the lubricant in the bearing. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The static friction of steel under boundary lubricated conditions was investigated both experimentally and theoretically. The theoretical model was developed using the assumption that during the application of a tangential load to a friction couple, the real area of contact grows in a viscoelastic manner until a critical shear stress is reached. Using this model, it was possible to distinguish the effect of static and dynamic contact time on area growth and thus to show why the traditional "time dependence of static friction" theories have limited validity. The model predicts that µs, the static friction coefficient, is a function of the rate parameter θ, and that a relaxation time can be assigned to a given interface. Subsequent experimental work using steel surfaces in vacuum as well as steel surfaces lubricated by various surface films showed that surface conditions play a large role in determining the exact µs - θ relationship for a given friction couple. Over the range of θ investigated the static friction coefficient of steel is constant if certain surface films are present; for other films the static friction coefficient vs θ curve shows an upper and lower asymptote. In the latter case a relaxation time was assigned to each boundary lubricant. For given asymptotes these relaxation times can be used to predict whether the film will be a useful lubricant at a particular θ. A subsequent investigation showed that the relaxation times are strongly affected by temperature. Since raising the substratum temperature results in smaller relaxation times, it is obvious that a particular lubricant may become ineffective as the substratum temperature changes. Both the experimental and theoretical work clearly demonstrate that the static friction of steel can be significantly modified by the application of appropriate boundary lubricants. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

No description available.