复杂应力状态下高强铝合金变形-损伤耦合本构模型及断裂机制研究

The plasticity of high strength aluminum alloy is low at room temperature. The damage theory and fracture problem are more complicated because it is under the multi-axis stress states in the plastic processing. Currently, it is mainly studied through macro- and meso-approaches, respectively. The constitutive model cannot describe the damage and fracture behavior from multiscale. In order to solve these problems, the deformation-damage coupled constitutive model of high strength aluminum alloy under macro-meso-micro scale is established based on the damage variables. Diatomic model, void evolution model and micro-indentation dimensional analysis methods are applied in the study. On this basis, combined with numerical simulation and experimental research, the finite element subroutine module embedded deformation-damage and ductile-brittle transition parameters is developed. The deformation-damage mode, crack initiation and crack type of high strength aluminum alloy under the complex stress states are studied. The influences of stress field on plastic deformation and damage of high strength aluminum alloy during crack initiation and propagation are discussed. Damage and fracture mechanism of high strength aluminum alloy under complex loading conditions are revealed. The accurate predictions of bearing characteristics of high strength aluminum alloy components after plastic deformation are realized. Verifications and applications are carried out using plastic forming processes, such as bulging and hole cold expansion. The results of the project will provide the theoretical foundation and engineering value for avoiding the forming defects and improving the service life of the high strength aluminum alloy components for aviation.

高强铝合金室温塑性低，在塑性加工过程中由于受多轴应力状态，其损伤理论与断裂问题较为复杂。目前主要从宏观和细观两个角度单独的进行研究，所建立的本构模型无法从多尺度描述其损伤与断裂行为。因此，本项目以损伤变量为研究基础，借助双原子模型、空穴演化模型及微压痕量纲分析构建宏-细-微观尺度下的高强铝合金变形-损伤耦合本构模型。在此基础上，结合数值模拟与实验研究，开发镶嵌变形损伤与韧脆性转换参数的有限元子程序模块，研究复杂应力状态下高强铝合金变形损伤的萌生方式、起裂位置和裂纹类型，探讨裂纹萌生和扩展过程中应力场对高强铝合金塑性变形和损伤的影响规律，揭示高强铝合金在复杂加载条件下的损伤机理与断裂机制，实现塑性变形后高强铝合金构件承载特性的精准预测，并采用胀形及孔挤压强化塑性成形工艺进行模型验证与应用。项目研究成果可为航空用高强铝合金构件避免成形缺陷、提高使用寿命奠定理论基础与工程应用依据。

针对高强铝合金室温塑性低，在塑性加工过程中由于受多轴应力状态，其损伤理论与断裂问题较为复杂，目前建立的本构模型无法从多尺度描述其损伤与断裂行为问题。本项目以损伤表征为基础，构建了宏-细-微观多尺度变形-损伤耦合分析模型，用于铝合金材料塑性损伤演化过程、损伤萌生机理及断裂特性的研究，同时基于能量释放原理，将高强铝合金的受载变形与微裂纹萌生、扩展联系起来，研究了复杂应力状态下铝合金变形损伤的萌生机制及裂纹类型与扩展等特征，结合数值模拟与实验研究，开发了镶嵌变形损伤与韧脆性断裂准则的有限元子程序模块，应用于铝合金薄板件胀形、航空孔板结构件挤压强化工艺分析，预测了复杂应力状态塑性变形后高强铝合金构件的承载特性及疲劳寿命。项目研究成果可为航空用高强铝合金构件避免成形缺陷、提高使用寿命奠定理论基础与工程应用依据。