铸态高强铝合金筒形件多道次强力热反旋损伤破裂机制与调控

Crack mechanism and control of cast high-strength aluminium alloy tubes in multi-pass hot power backward spinning have become the key basic problems urgently be solved for developing the power backward spinning technology of thin-walled cast high-strength aluminium alloy tubes, realizing crack predicted and controlled, and meeting the requirements of lightweight, high performance and high reliability. In this project, the ductile fracture criterion considering the effects of temperature, anisotropy, strain rate and stress triaxiality is proposed, and a 3D coupled thermo-mechanical finite element (FE) model and the method of the spinning process for crack prediction are established using FE numerical simulation method combined with theoretical analysis and experimental study. Based on the model, the crack behavior and its evolution mechanism are revealed. Then, the factors affecting crack and its associating mechanical model are revealed. The action mechanism and regularity of multi-field, multi-pass and multi-factors on crack, and coupling relationship among them are revealed. And the relational model between key factors and crack is proposed. Then optimum design method, theory and control method of crack for the process acted by multiple factors are developed. These achievements of the investigation have real significance in improving the advanced precision forming theory and technology of hot power backward spinning of thin-walled tubes with lightweight, high-strength materials for urgent necessity of missile, rocket and rocket in aviation, aerospace, weapons etc.

铸态高强铝合金筒形件多道次强力热反旋成形损伤破裂机制与调控，是发展铸态高强铝合金薄壁筒形件强力旋压成形技术，实现对该成形过程中开裂的预测与控制，使之满足轻量化、高性能和高可靠性要求，迫切需要解决的关键基础问题。本项目综合采用理论、实验、计算机仿真方法，建立能够反映铸态高强铝合金热反旋过程中损伤发展特点的考虑各向异性、温度效应、应变速率和应力三轴度影响的破裂准则及破裂预测仿真模型与方法；探明该成形过程中破裂的产生、发展和演化机理，揭示开裂的主要影响因素和关联的力学模型；揭示多场多因素及其耦合作用对该成形过程中损伤破裂的影响规律与作用机制；建立关键因素与损伤开裂的关联模型；研究建立多因素作用下铸态高强铝合金薄壁筒形件多道次强力热反旋全过程优化设计与开裂控制的方法与理论。对发展导弹、火箭和鱼雷壳体等航空、航天领域迫切需求的轻质、高强材料薄壁筒形件强力热反旋精确成形理论与技术具有重要的科学意义。

高强铝合金薄壁筒形件由于具有重量轻、比强度高和耐腐蚀性好等优点广泛应用于航空、航天和兵器等高技术领域。“铸筒+多道次强力热反旋”工艺是制造此类薄壁件的有效方法之一。然而，多道次强力热反旋是一个具有多道次、多参数、多场耦合等特点的复杂成形过程，旋压过程中材料经历了尤为复杂的不均匀塑性变形和组织演变历程。如果成形参数选择不当，热旋过程中就容易产生开裂、起皮和鼓包等缺陷。特别是开裂是决定其成形质量和成形极限提高的关键因素之一，已成为发展此类轻质、高强、难变形材料薄壁筒形件强力旋压精确成形技术迫切需要研究解决的关键基础问题。因此，本项目采用以有限元仿真为主并有机结合理论和实验研究的方法，对铸态高强铝合金筒形件多道次强力热反旋成形损伤破裂的预测与控制进行系统深入的研究。分析了铸态高强铝合金高温多道次加载不均匀塑性变形和损伤破裂行为，建立了铸态7075铝合金高温变形时弹性模量随温度变化的关系模型；揭示了损伤破裂与材料的各向异性性能、成形温度、应变速率和应力三轴度的关联关系；建立了考虑各向异性、温度效应、应变速率和应力三轴度影响的符合铸态7075铝合金筒形件多道次强力热反旋损伤发展特点的韧性断裂准则和损伤破裂预测有限元仿真模型；探明了铸态高强铝合金筒形件多道次强力热反旋成形过程中损伤开裂的产生、发展和演化的机制；研究获得了筒形件预热温度、减薄率、进给率和摩擦等成形参数对损伤破裂的影响规律，揭示了成形参数对损伤影响机制，探明了成形参数与损伤值的关联关系；获得了不同道次旋压成形过程中应力三轴度沿筒形件周向和轴向的分布特征及其对断裂应变的影响规律，揭示了其对断裂应变的影响机制；建立了应力三轴度、工艺参数与损伤开裂的关联关系模型；研究建立了铸态7075高强铝合金筒形件强力热反旋基于开裂的成形工艺极限预测模型和基于开裂的工艺极限图；构建了基于损伤破裂的铸态7075铝合金筒形件多道次强力热反旋全过程优化设计与调控的方法与理论。