铝合金弹-塑性蠕变时效形性演变建模分析

Modelling and analysis of evolution for deformation and property in elastic-plastic creep ageing of aluminium alloy

大尺寸复杂薄壁结构精确成形、成性要求传统蠕变时效成形工艺从弹性加载扩展至弹-塑性加载,为了研究此弹-塑性加载状态对材料与结构蠕变变形及时效强化的影响,开展从应力松驰时效特性表征、跨尺度本构建模到典型带筋壁板蠕变时效成形仿真与试验分析的系列研究。考虑弹、塑性加载下不同初始位错特性建立的基于蠕变背应力演变的跨尺度材料模型,可有效实现弹-塑性蠕变时效特性模拟与预测。典型带筋壁板类结构的蠕变时效成形试验与仿真结果表明,加载过程中产生的塑性应变会大幅降低试验件的回弹率,最大加载等效总应变为1.62%和0.46%的试验件,其回弹率分别为13.8%和31.0%。试验件筋条及蒙皮区域的屈服强度均得到提高,且成形后筋条的屈服强度略高于蒙皮。

The traditional creep age forming process is required to extend from elastically loading to elastic-plastically loading for achieving the precise formability and property of large thin-walled structures with complex shapes.To investigate the effect of elastic-plastically loading state on the creep deformation and age hardening of materials and structures,a series of studies were conducted,including the characterisation of stress relaxation ageing,building of cross-scale constitutive model,and the simulation and experimental analysis for creep age forming of typical stiffened panels.The cross-scale material model based on the variation of creep threshold stress,which considers the different initial dislocation characteristis under elastic-plastically loading,can effectively realize the simulation and prediction of the elastic-plastic creep ageing characterisation.The experimental and simulation results of creep age forming for typical stiffened panel structures show that the plastic strain produced in the loading process significantly reduces the springback percentage of specimens.For the specimens with the maximum loading total equivalent strains of 1.62%and 0.46%,the springback percentages are 13.8%and 31.0%,respectively.The yield strength of stiffeners and skin areas of the experimental specimen is improved,and the yield strength of stiffener is slightly higher than that of skin after forming.