铝合金双壁间隙管绕弯调控不均匀变形抑制成形缺陷机制

Due to the special-shaped structure of double-walled clearance and the introduction of filling medium, severe uneven deformation occurs easily in the rotary draw bending (RDB) of aluminum alloy double-walled clearance tube with multi-die and multi-interface constraints, which results in forming defects, such as cross-sectional deformation and wrinkling. These defects severely restrict the improvement of bending forming precision of double-walled tube with clearance. By using the numerical simulation method combined with theory and experiment in this project, taking thin-walled 6061-T4 aluminum alloy double-walled clearance tubes with different specifications as the research objects, whose diameter of the inner tube is more than 30mm and the gap is less than 10mm. A 3D finite element model of rotary draw bending for double-walled tube with clearance considering the anisotropy and ductile fracture of aluminum alloy tube and the viscoelasto-plastic constitutive of filling medium is developed. The reasonable filling medium materials and structures, which are suitable for double-walled tubes with different clearances are determined, and the mechanism of the filling medium to coordinate the uneven deformation of the double-walled tube with clearance is revealed. And the key factors and their influence laws affecting the uneven deformation and forming defects are discovered. The relationship between uneven deformation and forming defects is established, and then the characteristics of the uneven deformation and the mechanism of its effect on the forming defects are studied systematically so as to reveal the mechanism of forming defects. In order to control uneven deformation and restrict the forming defects, the method of multi-objective parameters optimization for RDB considering the coupling effect of multiple defects is studied. This research is of great scientific significance and broad application prospect for promoting the development of pipeline system in the aerospace field to high performance, light weight, high efficiency, low loss and high safety performance.

双壁间隙的特殊结构及填充介质的引入,使得多模具多界面约束下铝合金双壁间隙管绕弯过程极易产生剧烈的难以协调的不均匀变形，由此引发截面变形和起皱等成形缺陷，严重制约了管件绕弯成形精度的提高。本项目拟采用数值模拟与理论和试验相结合的方法，以内管外径≥30mm、间隙≤10mm的不同规格薄壁6061-T4铝合金双壁间隙管为研究对象，建立考虑管坯各向异性与韧性断裂和高分子填充介质粘弹塑性本构的双壁间隙管绕弯有限元模型；确定适用于不同内外管间隙的合理填充介质材料和结构，揭示填充介质对协调双壁间隙管不均匀变形的作用机制；建立不均匀变形和成形缺陷间的关联关系，探明不均匀变形诱发成形缺陷机理；考虑多缺陷的耦合，研究通过调控内外管不均匀变形以实现成形缺陷控制的绕弯过程多目标优化设计方法。该研究对推动航空航天等领域管路系统向高性能、轻量化、高功效、低损耗与高安全性能方向发展，具有重要的科学意义和广阔的应用前景。

多模具多界面约束下铝合金双壁间隙管绕弯成形极易产生剧烈的难以协调的不均匀变形，由此引发截面变形和起皱等成形缺陷，严重制约了管件绕弯成形精度的提高。在该项目的资助下建立了不同规格6061-T4铝合金管以及不同高分子填充材料的本构模型，在此基础上，建立了高分子填充材料辅助铝合金双壁间隙管绕弯成形三维有限元模型。确定了适用于双壁间隙管绕弯过程的填充介质材料和结构，揭示了填充介质对协调双壁间隙管不均匀变形的作用机制。获得了填充介质几何参数、填充介质材料种类与结构、内外管与填充介质装配关系、模具几何参数等对铝合金双壁间隙管绕弯成形过程的起皱、壁厚减薄、截面畸变和回弹等缺陷的影响规律，以及工艺参数对双壁间隙管绕弯成形缺陷的显著性影响规律，研究成果对推动航空航天等领域管路系统向高性能、轻量化、高功效、低损耗与高安全性能方向发展，具有重要的科学意义和广阔的应用前景。.在该项目的资助下，在IJMS等国际著名学术期刊发表论文3篇，全被SCI收录。在国际会议发表论文2篇，在国内相关领域会议发表论文2篇。在国际会议The 13th Asian Workshop on Micro/Nano Forming Technology and The 3rd Asian Pacific Symposium on Technology of Plasticity宣读论文，获得优秀报告奖（仅有6人）。授权国家发明专利3项，实用新型专利1项。培养博士生2人，1人即将毕业，1人在读；培养硕士生6人，4人已毕业，1人即将答辩，1人在读。基于上述成果，获得2022陕西高等学校科学技术研究优秀成果奖特等奖以及陕西省技术发明一等奖各一项。

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