Pillinger, Ian (1984)
Ph.D. thesis, University of Birmingham.
A knowledge of the flow occuring in metal-forming processes is of great industrial importance, and the finite-element technique is the only form of deformation analysis which can predict the flow of the material. The examination of forging operations requires a full elasticplastic treatment to be used. This thesis is concerned with an elastic-plastic, finite-element program which has been developed to investigate three-dimensional examples of this process. The fundamental theory of the finite-element method is first introduced, and then the finite-element program is described in detail. The deformation, and distributions of hardness and die-interface pressure, predicted by this technique for the unlubricated upsetting of a rectangular block are compared with experimental results, and found to be in broad agreement, the differences being attributed to the incorrect imposition of very high friction by the friction-layer technique used in the analysis. With a corrected form of the friction technique, the finiteelement program predicts results for the axisymmetric friction-ring test and a new three-dimensional friction test which are in good agreement with experimental findings up to deformations of approximately 30%; the friction-layer technique used successfully in previous axisymmetric treatments appears to be unsuitable for threedimensional formulations when large deformations are considered. The finite-element program developed here is shown to be capable of modelling an example of a more complicated three-dimensional forging, that of an automobile connnecting rod. The experimental measurements of cteformation and hardness for an aluminium con rod forged using graphite lubrication are found to be in good agreement with the finite-element predictions obtained assuming sticking friction conditions but not with the results of a zero-friction idealisation. Finally, suggestions are made for the future development of this technique.
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