钛合金航空薄壁构件热冲压回弹预测与控制方法研究

A novel hot stamping technology for titanium alloy thin-walled aviation components is developed to overcome the disadvantage of conventional isothermal forming in the aspects of efficiency, cost and energy consumption. The study on prediction and control for springback during hot stamping process of titanium alloy sheet is carried out focusing on the thermal-mechanical-phase transformation coupled mechanism under drastic mechanical and thermal stress gradient. Considering the coupling effect between phase transformation and plastic deformation at elevated temperature of titanium alloy, a novel tension-compression asymmetric yielding and hardening model under drastic thermal gradient condition is constructed, which fills the gap in asymmetric yielding theory under thermal loading path of drastic temperature gradient. This yielding model provides accurate description on constitutive behavior for springback simulation during hot stamping. The accurate model of mechanical-thermal coupled stress during hot stamping process is established to provide exact constraint conditions for springback prediction. The conventional approach of springback investigation which emphasizing constitutive behavior yet ignoring thermal constraints is broken up in this project. The stress-based thermal-mechanical coupled springback control method is proposed. The novel thermal administration technology and die structure innovation are implemented from the point of constraint regulation during hot stamping, which breaks through the limitation of pure geometrical compensation for springback and meets the demands for precise and cost-efficient manufacture of titanium alloy thin-walled aviation components.

针对钛合金航空薄壁构件传统低速等温热成形在效率、能耗和成本方面的不足，开发钛合金新型热冲压工艺。围绕“钛合金薄壁构件在机械与变温热应力复合作用下的热-力-相变耦合机理”这一科学问题，开展高温钛合金冷模热冲压回弹精确预测与控制研究。针对钛合金热冲压成形高温相变和变形耦合以及HCP非对称特征，建立高温变温路径下拉-压不对称屈服和硬化的热-力-相变耦合新模型，为钛合金热冲压回弹预测提供精确的材料本构，并填补高温变温路径下钛合金非对称屈服模型的空白；提出机械和变温热应力叠加的复合应力精确预测方法，为钛合金薄壁构件热机械耦合回弹变形的精确预测提供准确的热力约束条件；改变传统回弹研究“重本构、轻约束”的思路，提出基于应力补偿的热力耦合回弹控制新方法，从约束调控角度开发模具热管理技术和模、件同步收缩创新模具结构，突破单一几何补偿对热力耦合回弹控制的局限，满足钛合金航空薄壁构件精确、高效、低成本制造需求。

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