The first part of the thesis covers the development of a high-end GA, with arguements being made for and against a variety of evolutionary principles adopted in this field, as well as some innovations. A gradient based optimiser is also discussed which is used for comparison purposes thoughout the thesis. The GA is benchmarked against a variety of difficult, highly non-linear functions to ascertain its effectiveness, and then applied to the optimisation of 2D & 3D trusses under static and free vibration conditions. The aim of this is to provide a test-bed of benchmark examples and allow for experimentation of the more innovative features of the GA. Fairly basic sizing optimisation of trusses is first considered, moving on to more involved multi-load case, combined size & shape optimisation problems. After covering various splines typically used for shape definition, a mesh generation preprocessor algorithm, and allocation of size/shape design information for prismatic structures, the benefits of using Fourier series for the solution of simply supported beams is clarified. Extending from this 1D method to 2D curved Mindlin-Reissner finite strips, a variety of static prismatic structural problems are compared against known solutions to verify the formulation. The final chapter in this field reviews and compares the higher precision and rate of convergence of GAs against more traditional SQP based optimisation algorithms when applied to prismatic structures. Subsequently the work has progressed to the simulation of slit dies for the extrusion of polymer sheets. An in-depth investigation of the methodologies used for modelling flow and die deflection are made, including the significance of die body deflection on flowrate. The final section of this thesis considers the optimisation of exit flowrate uniformity employing the coupled flow simulation and deflection analyses mentioned in earlier chapters. Two optimisation methods are employed to determine the best possible exit flow uniformity within the movement capabilities of the choker bar. Three materials with differing shear thinning properties are selected, and simulated under high & low pressure conditions. The effect of shear thinning on the effectiveness of the choker bar optimisation is also discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637848 |
| Date | January 2003 |
| Creators | Langley, D. S. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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