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获得同时满足起皱、过度减薄和扁化质量要求的大直径铝合金薄壁管的弯曲成形极限即最小弯曲半径,已成为提高大直径铝合金薄壁管弯曲成形潜力的关键问题.本研究基于不同加载条件下的铝合金大直径薄壁管弯曲过程动力显式三维弹塑性有限元模型以及管材起皱能量预测模型,提出了管材最小弯曲半径的搜索算法,该算法有效考虑了模具、摩擦等工艺参数对小弯曲半径弯管成形的影响.在此基础上,获得了不同直径铝合金薄壁管的最小弯曲半径,并揭示了几何参数对管最小弯曲半径的影响,以及工艺参数组合对实现最小弯曲半径弯管成形的作用.结果表明:(1)在满足小弯曲半径弯管成形质量要求的模具和摩擦参数组合的合理范围内,减小芯棒球头厚度和直径,并施加轴向压缩载荷能够实现管材的极限弯曲成形;(2)若忽略几何尺寸对管材本构关系的影响,对于直径小于80mm的管材,管材的最小弯曲半径将取决于临界减薄;对于直径大于80mm的管材,管材的最小弯曲半径将取决于起皱.与解析预测结果相比,采用本文方法获得的管材最小弯曲半径最大相对减小了57.39%;(3)工艺参数组合促进实现最小弯曲半径弯管成形的效用,得到了实验的验证.
It has become a key issue to improve the bending forming ability of large-diameter aluminum alloy thin-walled tube by obtaining the bending forming limit, that is, the minimum bending radius, of the large-diameter aluminum alloy thin-walled tube that meets the requirements of creping, excessive thinning and flattening simultaneously. Based on the dynamic explicit three-dimensional elasto-plastic finite element model of aluminum alloy large-diameter thin-walled tube under different loading conditions and the prediction model of tube wrinkling energy, a search algorithm of the minimum bending radius of the tube is proposed. The algorithm takes into account the effects of die, And other process parameters on the small bending radius elbow forming.Based on this, the minimum bending radius of the aluminum alloy thin-walled tubes with different diameters was obtained and the influence of the geometric parameters on the minimum bending radius of the tube was revealed, The results show that: (1) The thickness and diameter of core ball joint are reduced within the reasonable range of the combination of mold and friction parameters which meet the requirements of forming quality of small bend radius elbow, and the axial Compressive load can achieve the ultimate bending of the pipe forming; (2) If you ignore the geometry of the pipe constitutive relationship, for the diameter For a pipe of 80 mm, the minimum bend radius of the pipe will depend on the critical thinning; for pipes larger than 80 mm in diameter, the minimum bend radius of the pipe will depend on the crepe. Compared with the analytical prediction, the minimum bend of the pipe obtained by this method The maximum radius of the relative reduction of 57.39%; (3) the combination of process parameters to promote the formation of the smallest bending radius of the effectiveness of the tube has been experimentally verified.