室温变形镁合金多轴循环塑性本构宏微观研究

The goal of the proposed research is to enhance the predictive capabilities in order to obtain a fundamental understanding of the cyclic plastic properties of the deformed magnesium alloys of ZK60 and GW83K under multiaxial loading at room temperature. Based on the measurements of stress and strain distributions under the monotonic and cyclic loadings, the macro-scale multiaxial cyclic plasticity constitutive is approached for the strong texture as well as the week texture magnesium alloy. The anisotropy, the asymmetric yield, the nonproportional hardening, and the different hardening laws for slips, twins, and detwins are considered in the constitutive. Furthermore, the traditional crystal plasticity finite element method (CPFEM) is improved on the observation of the shape of micro-texture in the magnesium alloys. The interaction as well as the combined action from slips, twins (detwins) and secondary slips (twins), the hardening modulus for slips and twins, the multiaxial nonporpotional hardening with consideration of the hardening matrix are contributed in the new CPFEM for multiaxial cyclic load. Finally, the bridge connected the macroscopic multiaxial cyclic plasticity and the new CPFEM is constructed with the sub-model technology in finite element analysis. The proposed research is to establish a theoretical elementary for the prediction of fatigue failure of the magnesium alloys under complicated cyclic loading at room temperature.

以室温下强织构ZK60和弱织构GW83K两种变形镁合金为研究对象，在单轴、多轴循环荷载下变形镁合金力学性能实验数据分析的基础上，通过对各向异性、非对称屈服应力、非比例硬化以及滑移、孪生（去孪）不同的硬化规律等进行合理的描述，建立适用强/弱织构变形镁合金材料的宏观循环塑性本构；从微观组织结构观察入手，发展传统的晶体塑性有限元理论，考虑晶体的滑移、孪生（去孪）以及二次孪生和滑移等既共同作用又相互影响，引入滑移和孪生（去孪）不同形式的硬化模量，通过硬化矩阵实现多轴非比例硬化的影响等，建立包含滑移、孪晶和去孪等微观织构演化的镁合金微观多轴晶体循环塑性有限元模型；通过子模型方法建立宏观与微观本构之间的联系，发展宏微观结合的变形镁合金多轴循环本构建模方法。为室温下变形镁合金在承受多轴交变载荷作用下的疲劳性能预测奠定理论基础和提供可供量化的参考指标。

变形镁合金具有高强度、高延展性和多样化的力学性能，其宏观循环塑性特性和微观组织演化之间有着密切的关系。本项目采用理论分析、多尺度数值模拟和宏微观实验观察相结合的方法来研究两种典型变形镁合金循环塑性力学行为。通过微观实验观察得到晶体滑移、孪生以及去孪等微观组织的演化规律。建立了微观组织和宏观循环塑性性能之间的关系。采用宏微观循环塑性本构理论，发展了宏微观结合的变形镁合金多轴循环本构模型和数值方法。本项目的开展为室温下变形镁合金在承受交变载荷作用下的疲劳性能预测奠定理论基础，对镁合金材料以及器件设计、使用提供重要的指导意义。