Transactions of the Canadian Society for Mechanical Engineering

Volume 32 (2008), Issue 1

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In this paper, the hardness prediction and microstructures of MSI 4340 high strength alloy under different cooling conditions are studied. The heat-transfer coefficient of specimens quenched in water, oil, and air are very different. These different conditions were used in a code to obtain cooling curves. Through the superimposition of the cooling curves on CCT diagrams, the microstructural features and hardness were predicted. The results show that the microstructure and hardness of the steel are significantly affected by quenching media. The existent phases and hardness obtained from both the experiments and the modeling are in good agreement. Finally, the cracking is reported, during water rapid cooling condition.

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The purpose of this work is to modelize the rheological behaviour of crude oil using threshold stress Bingham and Herschel-Bulkley models. This is allowed us to highlight that the Herschel-Bulldey model represents a better rheological behaviour of the crude oil than the Bingham model. We had also modelized the rheological behaviour using Cross, Krieger and Dougherty, and Quemada models. The obtained results with these models were validated and we therefore confirmed the non newtonian properties of the crude oil. It is this complex character, due to the solid-fluid interaction which does not allow us to use these traditional models that consider fluids as homogeneous. To bypass this difficulty, we have used the Model of Phan-Thien and Tanner (MPTT) which is based on the description of the fluid microstructure and which seems very plausible to modelize such a flow.

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A combined nodeless variable finite element method and the flux-based formulation is developed for solving the two-dimensional Poisson's equation. The nodeless variable finite element employs quadratic interpolation functions to provide higher solution accuracy without requiring additional actual nodes. The flux-based formulation is applied to reduce the complexity in deriving the finite element equations as compared to the conventional finite element method. The solution accuracy is further improved by implementing an adaptive meshing technique to generate finite element mesh that can adapt automatically with the solution behavior. The accuracy of the combined procedure is evaluated by several problems that have exact solutions.

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Due to the high levels of noise into the modern launchers, the structural-acoustic coupling problem is an important subject in the area of vibro-acoustic analysis. In this paper, analytical study is conducted on oblique plane wave incident upon a flexible orthotropic double-walled thin cylindrical shell to understand the characteristic of sound transmission. External and internal fluid media surround the shells and there is fluid (air) in the annular space between them. A uniform flow moves with a constant velocity in the external fluid medium. The wave equations represent the fluid media and the Sanders equations describe the motions of the two shells. On the internal and external shell surfaces, the equations of fluid-structure interaction are considered. An exact solution is obtained by solving the classical shell equations and acoustic wave equations simultaneously. As, the pressure and displacement terms are expressed in infinite series form, an iterative procedure is constructed in each frequency. This convergence algorithm presents the advantage of best accuracy. Transmission losses (TLs) obtained from numerical solution are compared with those of other authors. Eventually, the numerical results are used to show the effects of, orthotropy ratio, geometrical properties, air gap specifications, Mach number, material and fluid properties.

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The image quality of an optical system is limited not only by its inherent design aberrations, but also by the fabrication and assembly errors of its elements. Any small decentration error of an optical lens has a significant effect on the quality of the image it produces. In this paper, a simple method which employs skew ray tracing is described for calculating the decentration error resulting from the surface tilt of a measured optical lens by using transmission optical centering device. We address two important topics: (1) the decentration error and the spot circle radius are related by a linear approximation when the decentration error is small; and (2) an approximate value of the decentration error can be obtained by taking the first-order differentiation of the mathematical expression for the decentration error when the surface angle of tilt is small.

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To achieve a particular property, it is possible to mix two or more materials to form composites. In this study, to obtain superior characteristics, new composites are made with multi-components reinforcement. In order to improve the interface properties and brittleness of Glass/Polyester composites, glass woven fabrics are modified by using more elastic yams of polyester. Polyester yarns are located either parallel to glass yarns or perpendicular to them. In this way, a new fabric made of Glass and Polyester fibers is manufactured. Fabrics are manufactured in the form of cross-plies or unidirectional plies in order to make superior hybrid laminated composites. A Comparison between the buckling behaviour of hybrid composites with glass woven composites shows that under similar conditions, the use of hybrid fabrics increases the buckling strength. Also, high resilience of polyester yarns in hybrid fabric composites returns the sample, after failure, nearly to its original shape.

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This paper discusses the importance of turbulent heat flux modeling in predicting an impinging flow. A higher order version of the generalized gradient diffusion hypothesis (HOGGDH) is employed for the simulation of turbulent heat flux in impingement heat transfer. The flow field is modeled with both high and low Reynolds second moment closure turbulence models. For the high Reynolds second moment closure both GGDH and HOGGDH are not capable of capturing the shape of local Nusselt number profile in the impingement region. Combination of the low Reynolds second moment closure with either GGDH or HOGGDH models can reasonably predict the local Nusselt number distribution in comparison with the available experimental data. Results show that the HOGGDH over-predicts the turbulent heat transfer and the local Nusselt number particularly in the impingement zone.

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In this work, conventional (non-coherent), coherent jet, and high pressure coolant delivery systems are compared for profile creep-feed grinding, under non-continuous dressing conditions. To facilitate this comparison, an analytical method of determining the available flow (coolant that hits the wheel or workpiece) was presented. The coolant delivery systems were compared for five different feed rates. At each feed rate the form error was measured using a coordinate measuring machine at five cross sections along the workpiece. The high-pressure coolant delivery system had the lowest form error and had an available flow of only 1.7 L/min. The non-coherent jet had the second best form error and had an available flow of 17 L/min. The coherent jet had the highest form error with an available flow of 39 L/min.