Wall thinning behaviors of high strength 0Cr21Ni6Mn9N tube in numerical control bending considering variation of elastic modulus

Wall thinning, as one of the key defects in tube bending determined the forming quality and limit, is more easily to occur due to the specific properties of high strength 0Cr21Ni6Mn9N stainless steel tube (0Cr21Ni6Mn9N-HS tube). To achieve tube accuracy numerical control (NC) bending forming, the wall thinning characteristics of the 0Cr21Ni6Mn9N-HS tube should be clarified. An analytical model was proposed to reveal the essential relation between tube parameters and wall thickness distribution. Considering the varied elastic modulus, a finite element (FE) model was applied to explore the wall thinning under different geometrical and process parameters. Using the modified multi-parameter sensitivity analysis method combined with FE simulation, the sensitivity of the wall thinning to geometrical and process parameters was carried out. The experiments of NC tube bending were conducted to validate the analytical and simulate results. The results show that the varied elastic modulus can enhance the wall thinning degree, but has no obvious effect on wall thinning characteristics. The wall thinning characteristics under different geometrical and process parameters are revealed and the reasonable parameters ranges for the 0Cr21Ni6Mn9N-HS tube in NC bending are obtained. The most sensitive parameter on wall thinning is the relative bending radius, while the bending angle is the least one.

Springback Behavior of High Strength Titanium Tube after Bending under Variations of Material Property Parameters

In order to reveal the springback behavior of high strength TA18 tube after numerical control (NC) bending under the variations of material property parameters, the finite element (FE) model of the whole process for the high strength TA18 tube during NC bending was established under ABAQUS code and its stability was evaluated. Then, using the model, the springback behavior after tube bending under the variations of material property parameters was studied, and the significance of material property parameters on springback was revealed. The results show that the springback angle decreases with the increase of the Young’s modulus, hardening exponent and thickness anisotropy exponent or with the decrease of the strength coefficient and yield stress. The significance of material property parameters on springback of the high strength TA18 tube after NC bending from high to low are the yield stress, Young’s modulus, strength coefficient, thickness anisotropy exponent and hardening exponent.

Effect of Boosting Velocity on Forming Quality of High-Strength TA18 Titanium Alloy Tubes in Numerical Control Bending

In order to reveal the effect laws of boosting velocity on forming quality of tube bending. A three dimensional (3D) elastic plastic finite element (FE) model of whole process of high-strength TA18 tubes in numerical control (NC) bending was established based on the FE code of ABAQUS, and its reliability was validated by using the experimental results in literature. Then, the effect laws of boosting velocity on deformation behaviors of high-strength TA18 tubes in NC bending were explored with respect to multiple defects such as wall thinning, wall thickening, cross section deformation and springback. The results show that wall thinning ratio decreases with the increasing of boosting velocity; wall thickening ratio increases with the increasing of boosting velocity; cross section deformation ratio decreases with the increasing of boosting velocity; springback decreases slightly with the increasing of boosting velocity.