Force Determination of Bimetal Tube Drawing on a Mandrel or Floating Plug

Abstract

This investigation was prompted by the absence of published work on the drawing of bimetal tube with a mandrel and the drawing of bimetal with a floating plug whilst these tubes are being produced and used in Industry. Initially, an equilibrium approach was used to analyse the bimetal tube mandrel drawing process. The proposed theory assumed that the tube-die interface and the clad-matrix interface converge towards an arbitrary intersection point. With this assumption, the accuracy of the theory is dependent on the accuracy of the final clad and matrix thicknesses used in the calculations. When final clad and matrix thicknesses, which were obtained from experiment were used, the theoretical solutions for draw load were in good agreement with the experimental results. It is also possible to obtain the die pressure, interfacial shear stress and stresses acting on the clad and matrix using the proposed theory. When the assumption was made that the proportion of clad thickness remains the same after a pass as that before, the theoretical predictions gave reasonably good estimations of the experimental draw loads. The die rotation method was used to obtain the coefficients of friction at the tube-tool interfaces. Velocity fields were proposed for the two bimetal tube drawing processes in separate theoretical analyses of the processes. Separate computer programmes were written to optimise for minimum stress ratio, ox/Ye. The upper bound solutions for both processes were in reasonably good agreement with the experimental results. The final clad and matrix thicknesses predicted by the separate computer solutions gave good estimations when compared with the clad and matrix thicknesses obtained from the experiments.