Abstract Tests are reported into the bulging of copper tubes by internal pressurisation within a closed die, using urethane rods of different hardnesses and under different conditions of lubrication. The component explored was ‘bottle shaped’, the ‘neck’ being the original diameter of the tube, i.e., 38.1 mm, and the body being expanded under the action of the urethane to a diameter of 60 mm. It is found that by varying the frictional conditions, three different but repeatable modes of deformation formation are encountered. The axial pressures required to be applied to the urethane rod for different lengths and stiffnesses of rod were measured and compared with those predicted by an approximate theory, good agreement being found. Measurement of the strains of the bulged tubes indicates that higher axial compressive stress on the tube - obtained by securing higher levels of friction between the urethane rod and the tube - leads to less thinning of the tube wall, under the resultant axial feeding of tube material into the deformation zone.
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