目的 基于内支撑作用下三维自由弯曲成形过程中铝合金和不锈钢薄壁管起皱失稳等缺陷,通过理论推导、有限元仿真、物理模拟试验相结合的方式,进行基于芯棒内支撑的管材自由弯曲起皱失稳特性预测研究。方法 首先,基于失稳起皱能量预测模型,构建内支撑作用下管材失稳起皱的能量预测模型;其次,构建了纯弯和轴向压缩条件下的几何微缺陷,通过能量最小原理,合理选取了几何微缺陷的形式、屈曲模态及缩放系数;再次,基于AA5052和SS304管材力学性能实验及有限元物理模拟实验验证有限元模拟的准确性;最后,探讨管材失稳起皱特性的预测方法,结合0.618搜索方法研究管材起皱敏感区的变化规律。结果 实现了管材自由弯曲成形过程失稳起皱的高效准确预测,揭示了管材自由弯曲失稳起皱特性。结论 AA5052管最大起皱因子所对应的起皱敏感区越大,与直线段相比,弯曲段的起皱可能性越大;随着弯曲角度的增加,弯曲段的起皱敏感区越大,管材抵抗起皱的能力越低。当成形比为100%时,SS304管材直线段敏感区的长度最短;随着管材弯曲成形的进行,管材最大轴向压应力在成形比为70%时达到最大,当成形比达到70%后,最大轴向压应力减小,从而使起皱发生的可能性降低,并趋于稳定。
Abstract
The work aims to predict the wrinkling and instability characteristics of thin-walled aluminum alloy and stainless steel tubes during the three-dimensional free bending forming process under the action of internal support, through a combination of theoretical deduction, finite element simulation and physical simulation tests. Firstly, an energy prediction model for instability wrinkling under internal support was established based on the instability wrinkling energy prediction model. Secondly, geometric micro-defects under pure bending and axial compression conditions were constructed, and by applying the principle of minimum energy, the form of geometric micro-defects, buckling modes, and scaling factors were appropriately selected. Then, the accuracy of finite element simulations was validated through mechanical performance experiments on AA5052 and SS304 tubes and finite element physical simulation experiments. Finally, prediction methods for tube instability wrinkling characteristics were explored. The research combined the 0.618 search method to study the changing pattern of tubes' wrinkle sensitive areas, thereby achieving efficient and accurate prediction of instability wrinkling during the free bending forming process of the tubes, revealing the characteristics of free bending instability wrinkling. In conclusion, for AA5052 tubes, the larger the wrinkle sensitive area corresponding to the maximum wrinkling factor, the greater the likelihood of wrinkling in the bent section compared with the straight section. As the bending angle increases, the larger the sensitive area in the bend, the lower the tube's ability to resist wrinkling, and simultaneously, the greater the bending work of the tube. For SS304 tubes, at a forming ratio of 100%, the straight segment's sensitive zone is the shortest. As the tube bending process continues, the maximum axial compressive stress of the tube reaches its peak at a forming ratio of 70%, and following that, the maximum axial compressive stress decreases, thereby reducing the likelihood of wrinkling and approaching stability.
关键词
金属薄壁管 /
自由弯曲 /
几何微缺陷 /
起皱预测
Key words
thin-walled metal tube /
free bending /
geometric micro-defects /
wrinkling prediction
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基金
国家自然科学基金（52105360, 52175328）
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