Papers by Keyword: NC Bending

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Authors: Jie Xu, He Yang, Heng Li
Abstract: A multi-objective optimization method for thin-walled tube NC bending is presented. Firstly, a half-symmetry 3D elastic-plastic FEM model is established based on the initial design values, applying the dynamic explicit code ABAQUS/Explicit. Secondly, virtual orthogonal arrays are designed to optimize friction coefficients, with minimizing the maximum wall-thinning ratio, the maximum cross section distortion ratio and the maximum height of wrinkling waves as the multi-objectives. Lastly, the mandrel radius is optimized by sequential quadratic programming with approximate regressive models fit from uniform design values in the allowed range. Application is put forward for Ф50×1×100 (tube outside diameter ×tube wall thickness × central line bending radius) and Ф100×1.5×200 aluminum alloy tube bending. It is proved that the forming quality has been improved by the method.
Authors: Jun Fang, Shi Qiang Lu, Ke Lu Wang, Zheng Jun Yao
Abstract: Based on the nonlinear FE platform ABAQUS, an elastic plastic 3D-FE model of 0Cr21Ni6Mn9N stainless steel tube was established to simulate the whole process, and its reliability was validated by experiment. Using the model, the effect of bending speed on forming quality was studied and the influence laws of bending speed on wrinkling wave ratio, wall thinning, cross section deformation and springback angle were revealed. The results show that the wrinkling wave ratio and springback angle decrease with the increasing of bending speed, while the effect of bending speed on wall thinning and cross section deformation are not significant. The maximum cross section deformation degree presents in the vicinity of the bending angle 30° along the bending direction and its position is almost unchanged with the variation of bending speed.
Authors: Jun Fang, Chuang Liang, Shi Qiang Lu, Ke Lu Wang
Abstract: 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.
Authors: Jian Guang Wang, Mei Zhan, Tao Huang, He Yang
Abstract: The significant die unfittingness and springback, occuring during the numerically controlled (NC) bending process of large diameter thin-walled CT20 titanium alloy tube, has an obvious influence on the shape and the geometrical precision of the bent tube, furthermore on the assembly precision and the sealing capability. The changing rules of die fittingness and springback of large diameter thin-walled CT20 titanium alloy tube under different bending parameters were investigated and the mechanism was analysed using finite element method (FEM) in this paper. The result shows that the springback of large diameter thin-walled CT20 titanium alloy tube is more significant than that of aluminum alloy and stainless steel tubes with the same specification. The die fittingness has a connection with the tangent compressive stress on the intrados of the tube before springback, the larger the tangent compressive stress, the worse is the die fittingness.The results may provide a significant guide to the control of bending radius and bending angle for large diameter thin-walled titanium alloy tube NC bending.
Authors: Heng Li, He Yang, Mei Zhan, L.G. Guo, R.J. Gu
Abstract: A definition of forming limit is given with minimum centerline radius min R before wrinkling for NC bending process of thin-walled tube. Based on the developed FEM wrinkling prediction system TBWS-3D, an effective searching algorithm of wrinkling limit is proposed and forming limit can be obtained conveniently. Thus influence laws of main forming parameters on wrinkling limit are investigated and revealed. Measures to improve forming limit is put forward consequently. The achievements may help to both practice of thin-walled precise tube bending and research of plastic wrinkling.
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