Essa, Khamis Essa Ali (2011)
Ph.D. thesis, University of Birmingham.
This thesis presents new insights into gaps in the knowledge of conventional spinning and single point incremental forming (SPIF) processes through numerical modelling of their deformation mechanics. The deformation mechanics of conventional spinning is investigated by constructing finite element (FE) models of a cylindrical cup using both single and dual roller passes. A design of experiments (DOE) technique is used to generate an experimental plan based on all the relevant process parameters, followed by an analysis of variance (ANOVA) approach which is then used to determine the most critical parameters. The results indicated that the area in which most of the plastic deformation is taking place changes during the subsequent passes. The deformation mechanics of SPIF is investigated by constructing a novel dual-level finite element model of the forming of a truncated cone. The first-level FE model is validated against experimental data and the second level FE model is used to investigate the deformation modes through the sheet thickness. DOE and ANOVA techniques are used to investigate the influence of the different process parameters on the predicted through-thickness shear. Simple strategies are applied to reduce the geometrical errors without affecting the process flexibility. The results of the second-level FE model indicated that through-thickness shear is an important component in the deformation mechanism in SPIF.
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