To manufacture a high precision component, the aircraft industry in particular, employs computer numerical control machining to produce the aircraft components. However, it has often been found that problems of distortion occur when thin and slender components are manufactured this way. It is believed that the distortion arises due to the re-distribution of the residual stress field that was present in the original component in addition to the effects of cutting forces and temperatures that were induced during the machining process. At present, the process to produce a component with acceptable tolerance limits is one of trial and error. This often consumes a lot of time and produces considerable material wastage. The finite element method has been used to develop a methodology to model the actual machining process that produced the aircraft component. The finite element model that has been developed so far was able to demonstrate the effects of redistribution of the residual stresses on the distortion of the final machined component. It was found that the final component distorted differently when the materials were simply removed from a solid billet with different material removal sequences. A preliminary investigation on the effects of cutting temperature and forces has also been made. The investigation showed that such effects could not be totally ignored as they significantly affect the distortion of the final component. In addition to modelling the machining process, a methodology has also been developed to introduce and simulate the clamps and machine worktable that are part of the machining process. Although there is a considerable amount of work relating to modelling machining processes, there has not been any previous attempt to address the problem as a whole as described in this thesis. It is hope that the work undertaken here would be able to provide a stepping-stone to such attempts in future. However, further experimental data would be required to complement a more refined model in the attempt to accurately predict the distortion in machined components. It is believed that it would be possible to then extend the developed methodology to minimise the distortion by changing the machining sequence and the shape of the material to be removed. This would reduce the timescales involved to correct the problems of distortion and eliminate material wastage.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:365964 |
| Date | January 2001 |
| Creators | Yeow, Jee Leong |
| Publisher | University of Salford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://usir.salford.ac.uk/43017/ |
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