航天高强铝合金拉锻式摩擦塞焊成形控制机制与接头强度评价

Aiming at the urgent need for the development of big/heavy rockets in China, this project will study the related fundamental problems for weld forming control mechanism and the joint strength evaluation in friction pull plug welding for the aerospace high strength aluminum alloy. The key scientific problem will around the coupling mechanism of heat generation, heat transfer and plastic material flow, the high accuracy and fast response control mechanism of the welding process driven by big data and knowledge, and the scale problem for the joint strength evaluation. The main contents will include the thermal process and material plastic flow behavior of aluminum alloy during friction pull plug welding, the high accuracy and fast response control strategy for welding process, the optimization of the welding process and control the performance, and method for the evaluation of the joint strength. We focus on to make up the short board of the friction pull plug welding technology for the rocket storage, to improve the process stability, welding quality, and joint properties, and to establish the evaluation method for the joint strength. The results will provide important theoretical basis and technical support for developing the friction pull plug welding for the tank in big/heavy rockets.

项目拟针对我国大/重型火箭发展的迫切需要，研究航天高强铝合金拉锻式摩擦塞焊成形控制机制与接头强度评价相关基础问题。围绕“火箭贮箱铝合金拉锻式摩擦塞焊的产热/传热与材料流动的耦合作用机理、大数据及知识驱动焊接过程高精度快响应控制机制、焊接接头强度评价的尺度问题"三个关键科学问题，重点研究铝合金拉锻式摩擦塞焊热过程与材料塑性流动行为、焊接过程的高精度快响应控制策略、焊接工艺优化及组织性能调控、焊接头强度评价方法相关内容。主要目的是：弥补我国火箭贮箱拉锻式摩擦塞焊技术短板，提高焊接工艺稳定性、焊接质量和接头性能，建立合理的接头强度评价方法，为我国大/重型火箭铝合金贮箱摩擦塞焊提供理论依据和技术支撑。

针对大/重型火箭铝合金贮箱一体化全位置固相焊接工艺中亟待解决的原位拉锻式摩擦塞焊技术，本项目研究了航天高强铝合金拉锻式摩擦塞焊接头成形控制机制和接头强度评价等相关问题。具体实施以建立可靠的多场耦合数值模型为切入点，获得了拉锻式摩擦塞焊接头附近区域热场、应力场以及流场分布特征，揭示了摩擦塞焊过程中摩擦产热和热塑性材料流动的耦合作用机理。采用数值模拟和工艺试验相结合的方法，掌握了接头几何尺寸及焊接工艺参数对焊接缺陷产生和接头成形质量的影响，大幅提升了接头成形质量和力学性能，接头抗拉强度最高可达376.5 MPa。阐明了摩擦塞焊接头附近组织的软化机理，发现动态再结晶过程是塞焊接头实现冶金结合的关键。由于液压系统关键控制参量对不同焊接阶段焊接工艺参数的动态响应精度和速度不同，采用了模糊PID控制策略和前馈控制策略对焊接转速、轴向拉力等关键焊接参数进行闭环控制。最终建立了拉锻式摩擦塞焊高精度快响应智能化控制机制。进行了摩擦塞焊焊缝+不同方向搅拌摩擦焊缝的混合接头的宽板拉伸试验，借助DIC方法确定了搅拌摩擦焊缝与塞焊焊缝结合位处为接头最薄弱位置。建立了铝合金拉锻式摩擦塞焊接头宽板拉伸试验方法，揭示了宽板拉伸试样尺寸对接头抗拉强度，断裂特征等结果的影响。相关成果可为我国大/重型火箭贮箱一体化全位置固相焊接战略提供理论指导和技术支持。