基于高速冲击异质惯性场的金属各向异性动态力学属性虚场表征法

Identification method for anisotropic and high strain rate plasticity of sheet metals based on heterogeneous highspeed inertial impact and principle of virtual work

2024变形铝合金等轻质高强金属板材作为重要结构材料广泛应用于航空航天工业领域,其轧制生产过程引起的塑性各向异性和冲击载荷下表现出的应变率相关性显著影响着板材的变形行为,加大结构部件精确成形和极端工况服役行为准确预测的难度。当前,材料动态力学属性表征主要依赖于经典霍普金森压力杆法,该方法基于均匀变形和一维应力波假设前提,对于宽应变率范围各向异性动态力学属性,存在试验数量大、耦合效应表征难、部分参数难提取等缺点。针对此,提出一种基于高速冲击异形件诱导异质惯性场的金属各向异性-率相关塑性参数虚场同步表征新方法。通过设计开展双缺口异形试件高速冲击虚拟试验,实现试件非均匀应力应变状态调控,获取其惯性加速阶段的异质状态应变场、应变率场及加速度场;基于虚功原理构建动态本构参数识别算法,分析不同边界条件、冲击加载模式等状态条件变量对参数表征精度的影响规律,从单次冲击异质惯性场数据中实现试件动态各向异性-率相关塑性属性多参数一次准确表征,最大程度减少试验数量,简化测试过程,突破常规动态测试方法所受条件限制。

High-strength lightweight alloy sheets.such as 2024 wrought aluminum alloy sheets,are widely applied in aeronautic and astronautic industries as essential structural materials.The anisotropic plasticity induced by the rolling process and the strain rate sensitivity under impact loadings significantly affect their dynamic deformation behaviors,which make it difficult to accurately predict the material response during complex forming process or under extreme service conditions.Currently,the characterization of dynamic mechanical properties of materials mainly relies on the classical split Hopkinson pressure bar.It is based on the assumption of uniform deformation and one-dimensional stress wave propagation,which lead to the shortcomings of large number of required tests for comprehensive anisotropic plasticity,difficulty in characterizing coupling effect as well as in extracting parameters at early yielding stage.In this paper,a new method for the simultaneous characterization of the anisotropic and strain rate-related plasticity parameters is proposed based on the heterogeneous inertial fields obtained from the highspeed impact of a nonuniform specimen and the virtual fields method.Specifically,by designing and conducting the virtual highspeed impact test of a double-notched specimen,the comprehensive stress-strain state of the specimen can be manipulated and the simulated heterogeneous strain,strain rate and acceleration field data at the inertial acceleration stage obtained.Then,the dynamic constitutive parameter identification algorithm is developed based on the principle of virtual work,using which the multiple anisotropic and strain rate-related dynamic plasticity parameters of the specimen are accurately characterized at the same time from the single virtual heterogeneous impact test.Also,the influence of the state variables such as the boundary conditions,impact loading modes on the identification accuracy is analyzed.The proposed method shows its merits in minimizing the required tests for identifying such comprehensive constitutive models and releasing the limitations suffered by conventional dynamic testing methods.