Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017. / Space limitation in ships and the complex pipe layouts in chemical, mineral and food processing plants lead to the employment of closely spaced bends. The limited information regarding the head loss coefficient of pipe bends orientated as bend-spacer-bend has led pipeline designers to treat them as isolated bends with the same loss coefficient. Thus, to calculate the head loss in the piping system would simply involve summing the head loss coefficient of bends and neglecting their configuration. This practice causes inaccurate computation of head losses in the system. In this study a computational model is developed for the head loss coefficient of closely spaced pipe bends. This is then supported by experimental verification. A more accurate but still simple and easy to use empirical correlation is derived. The empirical correlation is established and the data presented under isothermal conditions for turbulent flows in a range 7.3x104 ≤ Re ≤ 5.8x105 and a spacing ratio of 1D ≤ L/d ≤ 10Dand curvature ratio of 3 ≤ rc/d ≤ 5. Using ANSYS® CFX® 11, a commercial computational fluid dynamics (CFD) package, the fluid domain representing two 900 smooth pipe bends separated by a short pipe was solved and the mechanisms causing the head loss coefficient were explored by using the CFD results to visualise the fluid flow structure/pattern. The computational model was validated by comparing the head loss coefficient of a single bend and the model was found to be sound. The experiments conducted in the built test facility using smooth pipes showed similarities in the trends between the CFD work and the published data and they were to be found have a similar trend. The experiment had shown results that agree to the findings from literature.

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Unlike most instabilities, which are non-synchronous in nature, the Morton Effect is a synchronous phenomenon. This thermal instability occurs primarily in overhung rotors that are supported by fluid film bearings and is caused by differential viscous shearing within the bearing lubricant. The Morton Effect has also gained much attention within the last decade. Prior studies of the Morton Effect have used complex analysis in the frequency domain to model this instability. However, such an approach makes it difficult to develop a user-friendly design tool for engineers. The current research employs a steady-state analysis to predict the onset of the Morton Effect, and it uses an instability criterion which is based on a threshold unbalance caused by a force equal to 15% of the weight of the rotor. It is hoped that this method will provide a more easily adaptable platform for design and analytical purposes. The current model has demonstrated good agreement with other theoretical models and experimental data. This agreement applies to rotors that are supported by either plain or tilting pad journal bearings and it was found that a worse case scenario for the Morton Effect would involve centered, circular and large-amplitude bearing orbits. A test rotor was also designed and built. Initial experimental data revealed an unusual instability that might have been caused by the Morton Effect. / Ph. D.

This research investigates the effect that knots in close proximity have on strength properties of southern pine lumber. The project involved specimens of 2×4 dimension southern yellow pine lumber exhibiting multiple knots in close proximity. Knot dimensions were measured to determine the knot diameter (KD) parallel to the cross-section of the specimen, knot area (KA), and clear wood (CW). In addition, the density (D) using the entire specimen weight by volume was determined. A third-point bending test was used in a flatwise orientation to quantify the modulus of rupture (MOR) and modulus of elasticity (MOE). The relationships between the simple correlation coefficients showed significant correlation. Multiple regression analysis with one dependent variable, MOR, and three independent variables, KD, MOE, and D resulted in a coefficient of determination value (r2) of 0.702 as contrasted with 0.564 obtained by using MOE alone to predict MOR.

No / Convenient exact closed-form expressions are derived for calculating the bending stiffness of and stresses within loaded cylindrical bonded rubber blocks of circular cross-section. The particular solutions for simple bending, cantilever loading and apparent shear situations are deduced and studied in detail. The shapes of the deformed profiles are discussed and confirmation is provided that the previously adopted assumption of parabolic profiles of the deformed lateral curved surface is only valid for blocks of very small aspect ratio. In simple bending a relationship which is more realistic than those hitherto suggested is derived for the couple required to maintain a specified rotation of the loaded end of the block. In apparent shear an exact expression for the ratio of the true to the apparent shear modulus is derived, and compared with the experimental data. An improved approximate relation is deduced.

Crosslinked polymers or elastomers are examples of soft, synthetic material that can bend, crease, snap, wrinkle in response to external stimulus like pH, humidity, electric field or swelling. If a droplet of favorable solvent is placed on top of a thin, elastomer beam, it bends drastically to accommodate the excessive swelling stress. Keeping the solvent and its volume constant if we just increase the thickness of the beam, microscopic surface creases appear on the top surface. In this thesis, we experimentally characterize this transition between global bending to surface creasing. Closing of Venus flytrap leaves is a classic example of well known snap-through instability. A knowledge of the timescale of snapping is crucial in designing advanced functional materials. We perform the simplest experiment of poking an soft, elastomer arch at its apex till it snaps. Combining our experiments with analytical model we are able to predict the purely geometric nature of the snapping timescale. We also develop a simple scaling law that captures the dynamics of jumping toy poppers. / Master of Science

The bottleneck of forming small radius tube is that traditional processing methods can¡¦t effectively produce smaller bend radius tube in domestic industry now. First, this study will propose methods without mandrel, based on traditional bending way of rotary draw bending to form small bending radius tubes. This paper investigate results of traditional bending mode without mandrel in second part. By using finite element analysis, find the effects on wall-thinning, wall-thickening and ovility with different processing parameters. Also using the research results to obtain forming ranges. Through heating tubes we explore the possibility of hot forming of parameters and to find the impacts on bending tubes which heating under different parameters. We use the results above to find out the hot forming ranges. In heating and quenching of rotary draw bending experiments, we found that heating tubes under the same processing parameter can effectively enhance the formability and successfully derive better products of small radius bending tubes, to accomplish non-mandrel rotary bending process of small bending radius.

The aim of this master´s thesis is the design, proposal and production of a functional jig for technological testing of metal sheet by bending in the pre-production stage to the limit bend radius of the steel sheet up to a thickness of 2 mm, or in case of non-ferrous metal to a thickness of 3 mm. The required bending angle is in the range from zero to ninety degrees. The functionality of the jig will be verified by a practical testing of springing. The proposal will be supported by technological and economic calculations and technical - economic evaluation.

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In this thesis we review and build on the common methods used to analyze null geodesics in Schwarzschild de Sitter space. We present a general technique which allows finding measurable intersection angles of null trajectories analytically, and as one of its applications we establish a general relativistic aberration relationship. The tools presented are used to analyze some standard setups of gravitational deflection of light and gain a clear understanding of the role that the cosmological constant, Λ, plays in gravitational lensing phenomena. Through reviewing some recent papers on the topic with the present results in mind, we attempt to explain the major sources of disagreement in the ongoing debate on the subject, which started with Rindler and Ishak’s original paper, regarding the influence of Λ on lensing phenomena. To avoid ambiguities and room for misunderstanding we present clear definitions of the quantities used in the present analysis as well as in other papers we discuss. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-09-30 21:18:26.762