局部加载控制不均匀变形与精确塑性成形研究进展

局部加载控制不均匀变形与精确塑性成形关键理论与技术研究,既是先进塑性成形学科前沿领域中的关键和挑战性课题,又是航空航天高技术发展的迫切需求。文章以局部不均匀加载实现通常极难的板面内弯曲成形为切入点,发展了控制不均匀变形以实现精确塑性成形的理论与技术,为我国先进飞机发展面临的大型复杂整体钛框成形制造难题的解决,提供了启示。建立了薄壁管数控弯曲失稳起皱、回弹、截面畸变预测和成形极限分析的模型、过程仿真和优化设计的方法;揭示了其关键影响因素和影响规律;实现了难度很大的薄壁管小弯曲半径数控弯曲精确成形。建立了多道次普旋、曲母线和带内筋件强旋等复杂过程三维仿真模型,提出了解决不均匀变形导致的复杂成形缺陷和旋轮轨迹优化设计难题的方法。解决了大型铝型材先进等温挤压中迫切需要解决的多场耦合作用下温度与速度效应和控制的重大难题。发展了复杂环件辗扩过程和控制仿真的三维有限元模型以及临界摩擦系数确定的解析-数值方法;总结了冷辗扩3种塑性变形行为及多因素耦合对辗扩过程的影响;提出了率相关晶体塑性模型在有限元中实现的稳健算法,实现了冷辗扩宏观变形行为的细观响应描述。

Advances in control of unequal deformation by locally loading and theories related to precision plastic forming

Research on control of unequal deformation and theories related to precision plastic forming is not only one of the key and challenging subjects in frontiers of advanced plastic forming, but also the urgently needs of the development of aercrspace high technology. In this project, beginning with realizing in-plane bending under local unequal loading, which is difficult to form using conventional methods, the theory and technology is developed for realizing precision plastic forming processes by controlling unequal deformation, which provides an important inspiration for solving difficult problems of forming and manufacturing large scale complex integral components of titanium alloy. Numerical models are established for predicting wrinkling onset, spring- back, cross section distortion, and for analyzing and determining forming limit in NC thin-walled tube bending processes, and methods are developed for process simulation and optimization design; effect laws of key factors on the process are revealed. 3D-FE process simulation models are established for multi-pass conventional spinning, curved thin-walled shell spinning, power spinning with hoop inner rib. Methods are proposed for solving complex forming defects produced by unequal deformation and roller-trace optimization design. The effects of temperature and velocity and their controls under coupled thermo-mechanical effects with multi-factors and multi-physical fields are solved in isothermal extrusion processes for large-size aluminium profiles, which are important and difficult problems to be urgently solved in the research and development of advanced isothermal extrusion theory and technology. 3D-FE simulation models are developed for complex cold ring rolling process, and an analytic-numerical method for ascertaining the critical friction coefficient for stable rolling process; three kinds of plastic deformation behaviors dur ing cold ring rolling process and effects of multi factors on the process are found; a robust integration algorithm for implementing rate dependent crystal plasticity into explicit FEM are proposed and Macro-deformation are described by Micro-reflect in cold ring rolling process. The achievements of this study are of significance to developing advanced theory and technology of precision plas tic forming for thin walled and large-scale complex components.