Abstract:The springback mechanism for a large-diameter thin-walled CT20 titanium alloy tube with an outside diameter of 85 mm and a wall thickness of 2.5 mm (denoted as D85 mm×t2.5 mm) was investigated using numerical simulation. The results show that the areas among the crest lines and the neutral layer unload significantly, whereas the areas adjacent to the neutral layer unload indistinctively. These differences lead to a reverse loading in certain areas of bent tube and an obvious tensile-compressive stress concentration in the area adjacent to the neutral layer after springback. The variation rules of springback angle and springback radius with bending radius and bending angle were studied. These data were used to propose a springback compensation method, which was verified to be effective in an example study.

Key words: CT20 titanium alloy; large-diameter thin-walled tube; numerically controlled (NC) bending; springback; springback compensation