An iterative penalty finite element model is developed for the analysis of three-dimensional coupled incompressible fluid flow and heat transfer problems. The pressure is calculated by solving the momentum equation using known values of velocities, velocity gradients, and flow stresses from previous iteration. An iterative solution algorithm which employs the element-by-element data structure of the finite element equations is used to solve large systems of algebraic equations resulting from finite element models of real world problems. Three different iterative methods (ORTHOMIN, ORTHORES and GMRES) are implemented and tested to determine the efficiency of each algorithm terms of CPU time and storage requirements. Jacobi/Diagonal preconditioning is used to scale the system of equations and improve the convergence of the iterative solvers. The developed iterative penalty finite element model is extended to analyse three-dimensional manufacturing processes such as casting, extrusion and forming of metals. For numerical simulation of extrusion and forming, flow formulation is used since these operations involve large deformations. The viscosity of the metal at elevated temperatures is calculated from the flow stress. The formulation uses the enthalpy method to account for the transfer of latent heat during phase change. The fluid inside the mushy region (between liquid and solid regions) is assumed to obey D’Arcy’s law for flow through porous materials. The permeability of the material is determined as a function of liquid fraction. This forces the velocities in the solid region to zero. In the finite element model, the effects of convection during phase change of the material are included. A method for calculation of the movement of liquid metal-air interface during mold filling process is presented. The developed model predicts the location of the interface (defined by a pseudo-concentration value) by solving for its movement due to forced convection. Also during filling analysis, only the filled and interface elements are used for flow field calculations. / Ph. D.

This research project is partnership project involving industrial, university and government collaborators. The overall objective is to develop and enhance tools for use in Resin Transfer Moulding (RTM) design technology in order to re-design existing metallic parts using composite materials. / The specific objective of this work is to present preliminary research findings of the development of an optimized design of a leading edge slat (horizontal stabilizer component) from the Bell Model 407 Helicopter. The results presented here focus on the static stress analysis and the structure design aspects. The findings will serve as a basis for future design optimization as well as further developments in the use of RTM technology in re-designing metallic aeronautic components and can be considered to be "semi-optimized". / This research is based on extensive finite element analysis (FEA) of several composite material configurations, with a comparison made with the original metallic design. Different key criteria of the part design such as ply lay-up, bracket geometry, angle and configuration are tested using FEA technology with the objective of selecting the design which is minimizing stress concentrations. The influence of the modification of model-related parameters was also studied. / Preliminary comparative studies show that the slat configuration with half brackets opened towards the inside with an angle of 70 degrees (angle between the top of the airfoil and the side of the bracket) is the best option according to minimum stress concentration and structural flexibility. This choice is confirmed by other factors such as material savings and ease of processing.

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Molding is a simple manufacturing process whereby fluid fills a master tool and then solidifies in the shape of the tool cavity. The precise nature of material flow during molding has long allowed fabrication of plastic components with sizes 1 mm 1 m. Polymer molding with precise critical dimension control could enable scalable, inexpensive production of micro- and nanostructures for functional or lithographic use. This dissertation reports experiments and simulations on molding of polymer micro- and nanostructures at length scales 1 nm 1 mm. The research investigates two main areas: 1) mass transport during micromolding and 2) polymer mechanical properties during nanomolding at length scales 100 nm. Measurements and simulations of molding features of size 100 nm 1 mm show local mold geometry modulates location and rate of polymer shear and determines fill time. Dimensionless ratios of mold geometry, polymer thickness, and bulk material and process properties can predict flow by viscous or capillary forces, shape of polymer deformation, and mold fill time. Measurements and simulations of molding at length scales 100 nm show the importance of nanoscale physical processes distinct from bulk during mechanical processing. Continuum simulations of atomic force microscope nanoindentation accurately model sub-continuum polymer mechanical response but highlight the need for nanoscale material property measurements to accurately model deformation shape. The development of temperature-controlled nanoindentation enables characterization of nanoscale material properties. Nanoscale uniaxial compression and squeeze flow measurements of glassy and viscoelastic polymer show film thickness determines polymer entanglement with cooperative polymer motions distinct from those observed in bulk. This research allows predictive design of molding processes and highlights the importance of nanoscale mechanical properties that could aid understanding of polymer physics.