Determination of process parameters for the NC bending of a TA18 tube

Determining appropriate process parameters is key to obtain qualified TA18 (Ti–3Al–2.5V, ASTM Gr. 9) titanium alloy tubes with medium strength by numerically controlled (NC) bending at low cost. This paper focuses on the variations in wall thickness and cross-section under various operating parameters and mandrel parameters for the NC bending of TA18 tubes. We put forward a method for quickly determining the range of the axial mandrel feed. The method is based on the principle of an equivalent mandrel supporting radius for a given bending radius but employing some mandrels with varying diameters and the principle of an equivalent mandrel supporting angle for various bending radii but employing the same diameter mandrel. The finite element analysis and the experimental verification results show that the bending speed should be less than 0.5 rad/s and the pressure die velocity should be approximately equal to or slightly higher than the bending speed, and that the method for determining the range of the axial mandrel feed is feasible. Considering the effects of an equivalent mandrel supporting radius and equivalent mandrel supporting angle, the mandrel diameter and axial feed should be chosen in a compatible range.