基于数字图像相关性方法的脆性材料拉氏反分析实验技术

A Lagrangian inverse analysis technique for studying dynamic mechanical properites of brittle materials based on digital image correlation

利用分离式Hopkinson压杆作为加载系统,借助超高速数字图像相关性分析方法,发展了长杆试件拉氏反分析实验技术,并用于研究脆性材料在小变形条件下的动态本构特性。通过超高速相机实时拍摄冲击加载下长杆试件变形的散斑图像,再对散斑图像进行数字图像相关性(digital image correlation,DIC)分析,获得长杆试件表面速度场和应变场。随后,以脆性材料PMMA(polymethyl methacrylate)为例,从DIC分析得到的速度场中提取出不同拉格朗日位置上质点速度时程曲线,构建路径线连接整个速度场,再结合零初始条件,数值求解得到了试件中的应力时程曲线,消去时间参数后,获得了脆性材料PMMA的动态应力-应变曲线,并与Hopkinson压杆实验和准静态压缩实验的结果进行了对比,揭示了PMMA材料在小应变条件下的黏弹性本构响应特征。

Based on the Hopkinson pressure bar and digital image correlation(DIC)techniques,a new Lagrangian inverse analysis experimental method was proposed to study the dynamic constitutive relation of brittle materials.A series of speckle images of long specimen deformation were recorded by an ultra-high-speed camera.The speckle images were processed by DIC to derive the velocity fields and strain fields on the surface of a long specimen.Based on the multi-particles velocity history curves measured by DIC,the whole velocity fields were constructed by many path lines.Then,a Lagrangian inverse analysis method was established for the dynamic constitutive relation of brittle rate-dependent PMMA materials by numerical solution.The results were compared with those of Hopkinson pressure bar test and quasi-static compression test,which display the characteristics of viscoelastic constitutive response of PMMA under the condition of small strain.