基于虚场法的铝合金各向异性屈服及硬化属性参数同步表征

变形铝合金板材因轻质、高比强和比模量等优点广泛应用于航空航天工业中，其轧制生产过程引起的塑性各向异性可显著影响板材的变形行为，加大零部件成形精度控制和服役行为数值模拟预测的难度。针对目前常规测试方法表征材料各向异性屈服及各向异性塑性硬化属性所需试验数量多、种类复杂、限制条件多的现状，结合全场变形测量和虚场法，通过一种桥型试件的循环拉伸-压缩试验，首次实现2024铝合金板材各向异性屈服与塑性硬化本构参数的同步表征，大幅减少试验数量，简化试验过程。研究表明，采用当前的加载构型，在参数优化目标函数中结合材料0°和90°两个拉伸加载方向的试验数据，并配合多虚场约束，可以在不同参数表征初始猜测值下产生稳定的Hill1948各向异性屈服参数表征结果，保证解的准确性；对于非线性运动硬化模型，采用单材料方向加载和单虚场的目标函数即可获得对应材料方向稳定可靠的非线性运动硬化参数表征结果。研究成果可为铝合金板材成形工艺分析提供理论依据、数据参考和便捷的测试技术支持。

Identification of the Anisotropic Yield and Hardening Constitutive Parameters for Aluminum Alloys Using the Virtual Fields Method

Wrought aluminum alloy sheets are widely applied in aeronautic and astronautic industries thanks to their lightweight, high specific strength and high specific rigidity. They exhibit notable anisotropic plasticity due to the rolling fabrication process, which can significantly influence the mechanical behavior of the sheets, but also bring complexity to the analytical and numerical study of various forming processes. Currently, the conventional identification methods for the anisotropic yield and hardening properties usually involve multiple homogeneous tests and complex testing machines. They are also constrained by various limitations. In order to simplify the identification procedures, the full-field deformation measurement and the virtual fields method are coupled to identify the anisotropic yield and hardening constitutive parameters simultaneously from the same cyclic tension-compression tests on the bridge-like 2024 aluminum alloy sheet specimens. The results show that using the current test configuration the Hill1948 anisotropic yield parameters can be identified successfully with stable results when the two tension stages in the rolling and the transverse directions are combined and the multiple virtual fields constraints applied. As for the nonlinear kinematic hardening parameters, loading in a single material direction and a single set of virtual fields can guarantee a reliable identification result. The current work provides useful material information and a convenient identification tool for the aluminum sheet metal forming industry.