高强度大直径铆钉自激励式电磁铆接动态塑性变形行为及成形质量控制

To improve the carrying capacity, forming of large diameter rivet with high strength and its riveting quality control has received widely attentions in the aerospace industries. Electromagnetic riveting (EMR) provides an effective method for riveting of difficult-to-deformation materials. However, traditional induction electromagnetic riveting exhibits low energy-utilization efficiency, relatively small driving force and less controllable riveting quality. A novel riveting method, namely self-excitation electromagnetic riveting (SE-EMR), is therefore proposed in this project for the large diameter rivet with high strength. The present project plans to establish the mathematic model of the driving force and perform a full coupling numerical analysis of electromagnetism-mechanic-heat multi-physical fields in the SE-EMR process to study the dynamic plastic forming behavior, via combining theoretical analysis, numerical simulation, and experiments with measuring test. Effects of processing parameters on the deformation behavior, the microstructure evolution of adiabatic shearing band and its deformation mechanism are investigated. The range of the loading rate for different materials is identified to establish the processing window. The riveting quality control is focused on by the establishment of the relationship between the processing, the structure and the mechanical properties and the in-depth understanding of the coordinate deformation between the rivet head and shank. The results could advance the in-depth understanding of the SE-EMR technology and make progress on the riveting forming-and-quality integrated control. In addition, the research could lay the theoretical foundation and provide a technique support for riveting of the large diameter rivet with high strength used in aeronautics and astronautics devices.

为提高结构承载能力,高强度大直径铆钉成形与铆接质量控制备受航空航天领域的关注与重视。电磁铆接为难变形材料铆钉成形提供了一种有效方式。但传统感应式电磁铆接能量利用率低，驱动力偏小，成形质量可控性较差。为此，本项目针对高强度大直径铆钉提出自激励式电磁铆接方法，拟通过理论分析、数值模拟、试验和分析检测等手段，建立铆接驱动力数学模型；实现自激励式电磁铆接电磁-力-热全耦合数值模拟，研究铆接动态塑性变形行为；掌握工艺参数对铆接变形的影响规律，探讨绝热剪切微观组织演变规律，揭示绝热剪切变形机理；确定材料加载速率范围和工艺窗口；建立工艺参数-微观组织-力学性能关联性；揭示镦头与钉杆协调变形机制，实现铆接成形质量控制。研究结果对于全面认识自激励式电磁铆接方法，实现铆钉“成形-成性”一体化控制具有重要意义，同时将为航空航天飞行器中高强度大直径铆钉成形奠定理论基础和提供技术支撑。

为实现轻量化，高强度铝合金和钛合金已成为目前航空航天装备的首选材料。同时，为提高结构承载能力，高强度大直径铆钉被广泛用于飞行器铆接部段。围绕高强度大直径铆钉的成形和质量控制难题，本项目提出自激励式电磁铆接方法。采用理论分析、数值模拟、试验和分析检测等手段，开展自激励式电磁铆接驱动力、铆接动态变形行为、绝热剪切微观组织演变和铆接成形质量控制等内容的研究。根据能量守恒原理，建立了自激励式电磁铆接驱动力数学模型，获得了各参数对铆接驱动力的影响规律，实现了对铆接驱动力的主动控制，为铆接驱动力的产生引入了新方式。建立了2A10和7050铆钉材料的动态本构关系，材料呈现应变、应变速率硬化及温度软化效应，随着应变、应变速率增加，材料屈服强度增加；随着温度升高，其屈服强度减小。建立了自激励式电磁铆接电磁-力-热全耦合数值模拟模型，分析了自激励式电磁铆接过程磁场时空分布特性和动态塑性变形行为，系统地研究了各参数对铆钉镦头和钉杆变形的影响，获得了镦头与钉杆协调变形关系，揭示了自激励式电磁铆接动态塑性变形规律。自激励式电磁铆接铆钉以绝热剪切的方式变形，探讨了绝热剪切微观组织演变规律，揭示了铆钉的绝热剪切变形机理；在平头铆模作用下，2A10铆钉随着变形量的增加，绝热剪切带由在镦头对角处的萌生向镦头中心处不断扩展，最后呈类圆锥形；2A10铆钉绝热剪切带内和过度区均发现再结晶晶粒，其再结晶机制为旋转动态再结晶。通过解耦法实现了电磁铆接加载速率的主动调节，满足不同材料对铆接驱动力和加载速率的要求；建立了工艺参数-微观组织-力学性能的关联性，实现了高强度大直径铆钉铆接成形质量控制。研究结果对于全面认识自激励式电磁铆接方法，实现铆钉“成形-成性”一体化控制具有重要意义，同时将为航空航天飞行器中高强度大直径铆钉成形奠定理论基础和提供技术支撑。