Plasto-hydrodynamic pressure in a simple tapered and combined geometry units for drawing and coating wires
Nwir, Mohamed Abubaker (1994) Plasto-hydrodynamic pressure in a simple tapered and combined geometry units for drawing and coating wires. PhD thesis, Dublin City University.
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In plasto-hydrodynamic die-less wire drawing process, the conventional reduction die is replaced by a pressure unit of certain internal geometry. The deformation is induced by the combined effect of hydro-dynamic pressure and stress generated in the unit due to the motion of the wire and the viscous action of the polymer melt. The dimensions of the unit are such that the smallest bore size is greater than the incoming wire diameter. In this system, larger magnitude of the hydro-dynamic pressure is advantageous in obtaining greater deformation. In the present study, theoretical models have been developed for both the combined parallel and tapered geometry and simple taper bore pressure units, assuming non-Newtonian characteristics of the pressure medium, which enabled prediction of the maximum pressure and drawing stress, which gives better indication about the unit and it’s performance. The pressure and the viscosity coefficients were derived from the available data in the literature. Experimental work was undertaken with borosiloxane polymer at 110 °C melt temperature and using combined geometry and simple tapered bore pressure units. A number of parameters in terms of gap ratios and wire materials were changed for drawing speed of up to 0.7 m/sec.
The whole work was mainly devoted to assessing the performance of the unit and to establish the way it is affected by the unit geometry, the drawing speed, the working temperature. The optimum working dimensions were investigated and the theoretical results seem to be reasonably close to the experimental ones.
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