Geometrical properties of strip produced by plasto-hydrodynamic drawing.

A detailed investigation is carried out for the novel process of Plasto-hydrodynamically produced wide strip. In this process the conventional die is replaced by a pressure head with a rectangular hole. The internal geometry of the hole is shaped such that a convergent fluid flow is produced. This flow causes the production of hydrodynamic forces within the pressure head, namely hydrodynamic pressure and surface shear stresses. These forces are of sufficient magnitude that plastic deformation is induced within the working material. An in-depth theoretical analysis has been undertaken to establish the relevance of the geometrical parameters of the pressure head for the control of deformation performance. An extensive study of the solution algorithm for this type of plasto-hydrodynamic problem is made and modifications introduced to improve die dynamic response of the model. A new non-Newtonian model of the process has been developed using a power law type constitutive equation for the fluid behaviour. The modifications to the solution algorithm were also included in this new model. The plasto-hydrodynamic models developed during this work were subjected to numerical optimisation. The non-linear pattern search algorithm was utilised for this purpose. Correlations between the optimum geometrical form for the pressure head and process velocity were established. A study was made of the effect of varying the non-Newtonian parameters and the optimum pressure head geometry. A Computational Fluid Dynamic (CFD) analysis was made of the Hydrostatic assumption. This assumption allows major simplifications during the derivation of the models of the process. Its validity is established along with the impact of side leakage on the pressure field. An experimental programme was undertaken to provide data to establish a correlation between the predictions of process performance and an analysis of the output form of the strip produced by the process. The material used for the study was commercially available soft copper strip. The maximum reduction in area produced was 12% approximately.