金属板材面内扭转实验研究

Study on in-plane torsion experiment for sheet metal

以5182铝合金为研究对象,对双桥剪切试样进行了面内扭转实验,引入数字图像相关技术(DIC)实现了对扭转角的精确测量,得到了基于DIC方法的扭矩-扭转角曲线,与通过理论角速度计算的扭转角曲线相比,DIC方法显著减小了对扭转角的测量误差。通过引入有限元模型更新技术(FEMU),在大变形条件下对应变硬化曲线进行了参数标定,并与正向计算得到的曲线进行了比较。经过FEMU技术优化后的硬化曲线与单轴拉伸状态下的曲线更加接近,获得的应变范围更大。进行了剪切断裂实验,得到了扭转实验过程中剪切带中心位置的应变路径,验证了面内扭转实验过程中试样剪切带中心位置处于理想简单剪切状态,完成了理想简单剪切状态下的断裂应变测量。并进行了循环剪切加载实验,通过正向计算得到了循环加载应力-应变曲线,观察到了材料的包申格效应。

Taking 5182 aluminum alloy as the research object,in-plane torsion experiment was conducted on twin-bridge shear specimens.Digital image correlation(DIC)technology was introduced to realize the accurate measurement of torsion angle,and the torquetorsion angle curves based on DIC method were obtained.Compared with the curves obtained by theoretical angular velocity calculation,DIC method dramatically reduces the measurement error of torsion angle.By introducing the finite element model updating(FEMU)technology,the parameter calibration of strain hardening curve was carried out under large deformation condition,and the curves were compared with that obtained by forward calculation.The hardening curve optimized by FEMU is closer to the curve under uniaxial tensile state and strain range is larger.Shear fracture experiment was carried out,and the strain path at the center of shear band during the torsion experiment was obtained.It is verified that the center position of shear band of sample during the torsion experiment is at ideal simple shear state.The fracture strain measurement at ideal simple shear state was completed.Cyclic shear loading experiments were also carried out,the cyclic loading stress-strain curves were obtained by forward calculation,and the Bauschinger effect of the material was observed.