Research on variation characteristic of stress and strain in NC bending of TA18 high strength titanium alloy tube

A finite element model for the whole NC bending process of TA18 high-strength titanium alloy tubes is established based on ABAQUS platform. The variation characteristics of axial stress and axial strain in the outer and inner zones of the bending and the neutral layer zone are studied. The results show that: During the bending process, the material in the neutral layer zone undergoes more complicated axial stress-strain history. The material locating on the intersection between the initial bending section and the inside wall of the neutral layer zone, undergoes a history of the axial stress varying from a small tension to a small compression. However, the material in other sections still on the inside wall of the neutral layer zone undergoes a history of the axial stress varying from a small compression to a large tension. The material on the outside wall of the neutral layer zone, undergoes the same axial stress history but with larger stress values. The material in the initial bending section of the neutral layer zone undergoes the same axial tensile strain history. The material in the midst section and the back section of the neutral layer zone undergoes a variation of the axial strain from a compression to a tension, however the values in the midst section are larger than the back. During unloading process, the material in the inside and outside walls of the inner and outer zones of the bending undergoes an unloading-reloading history, and the material in the initial bending section of outside wall of the outer zone just increases. However, the material in the inside and outside wall of the neutral layer zone only undergoes a simple unloading history.