基于局部高速率增塑效应的高强钢板复杂件精确成形及变形协调控制

Aiming to the problem of traditional stamping in manufacturing large complex parts of high-strength steel sheets for its poor formability at room temperature, and based on the research foundation of the applicant, the new technologies are explored for manufacturing high-strength steel sheets based on the hyperplasiticity effect of high-speed electromagnetic forming, and the idea of local high-speed loading-based electromagnetically assisted sheet metal forming is proposed. In this project, by using the methods of combining theoretical analysis, experiments, numerical simulation and micro-analysis, studies are conducted on precision forming and deformation coordinated control of complex high-strength steel parts based on the hyperplastic effect of local high-speed forming. Accordingly, materials responses of high-strength steel under complex high-speed loading paths are measured, the plastic forming mechanisms of high-strength steel are revealed under the cross-scale strain rate loadings, and the deformation coordinated regulation of sheets resulting form local high-speed loading are investigated. The research results can be applied to develop the theory and method in regulating the room-temperature formability of high-strength steel by using local high-speed loading. By this project, the stable foundation will be established for the deep theory and experiment investigations of electromagnetically assisted sheet metal forming of high-strength steels, which has not only marked science value but also economical and strategic significance.

针对因高强钢板等轻质高钢板材室温成形性差而导致其大型板材复杂构件传统冲压成形难以实现的问题，申请人在多年研究的基础上，探索基于电磁成形高速率增塑性效应的高强钢板材成形新工艺，提出了基于局部高速率加载的磁脉冲辅助板材成形新思路。采用理论分析、工艺试验与数值模拟的研究方法，运用宏观与微观分析相结合的手段，进行基于局部高速率增塑效应的高强钢板复杂件精确成形及变形协调控制研究，探明高强钢板在高应变率复杂路径加载下的材料响应规律，揭示应变率跨尺度加载时高强钢板坯的塑性变形机制，掌握局部高速率加载板坯变形协调控制规律，寻求高速率局部加载调控高强钢板室温成形性的理论与方法。项目的实施为高强钢板材磁脉冲辅助成形理论和工艺应用的深入研究奠定坚实的理论和实验基础，不仅具有重要的学术价值，而且还具有十分重要的经济和战略意义。

结构和材料的轻量化趋势使得在汽车和航空航天等先进制造领域以高强钢板等为代表的轻质结构材料的应用日益广泛，而此类板材的低室温成形性成为制约传统冲压工艺应用的关键。鉴于此，项目探索基于电磁成形高速率增塑性效应的高强钢板材复合成形新工艺。以典型车身用DP780高强钢板材为研究对象，探索高强钢板在高应变率复杂路径加载下的材料响应规律，揭示应变率跨尺度加载时高强钢板坯的塑性变形机制，掌握局部高速率加载板坯变形协调控制规律，寻求高速率局部加载调控高强钢板室温成形性的理论与方法。研究表明：（1）DP780板材的室温力学行为表现出较强的应变路径和应变速率相关性。高应变率时，材料的应变速率敏感性增强，形变强化和应变率强化共存；预变形的引入显著影响材料的本构特征，提高动态变形时材料的流变应力阈值，且随着预变形程度的提高，应变强化效应增强，而应变速率敏感系数下降，板坯表现出更好的冲压性能。（2）准静态变形条件下，DP780板材塑性变形以位错滑移机制为主；而动态变形时，应变速率的增加对位错的交滑移和多系滑移表现出较大的抑制作用，且由于冲击载荷的作用，位错密度显著增加，微观特征组织有诱发形变孪晶的趋势。准静态预变形的存在对于板坯的动态再变形过程起到积极的协调作用，从而使得材料表现出较高的塑性。（3）准静态-动态复合变形模式下，预变形特征对复合加载板坯的最终成形效果会产生较大影响，有利于提高板坯的整体变形水平，局部高速率柔性加载的变形模式更有利于复杂构件的变形协调控制。项目研究为高强钢板材磁脉冲辅助成形技术的工程化应用奠定坚实的理论和实验基础，具有重要的理论意义和工程应用价值。