基于数字图像相关法的熔融沉积聚乳酸材料动态力学性能测试

为研究熔融沉积聚乳酸（PLA）材料动态的力学性能，利用分离式霍普金森压杆（SHPB）装置对PLA材料进行了加载应变率分别为880、1 230、1 650、2 230 s^-1的动态压缩实验，通过高帧率图像采集设备获得了不同应变率下PLA材料的变形图像，结合数字图像相关（DIC）法分析得到PLA试样表面沿加载方向的应变场，并对应变率进行了分析。结果表明，熔融沉积PLA材料在动态载荷作用下的变形过程存在弹性阶段、塑性阶段和卸载阶段；随着应变率的增加，PLA材料在塑性阶段出现了显著的塑性流动区域；PLA材料的压缩强度和最大应变均随应变率增大而增大；利用DIC法测得在整个动态冲击实验过程中，应变在试样中分布基本均匀，应变范围随应变率增大而增大，应变率在整个加载过程中基本保持恒定；DIC法测得的应变与SHPB实验基本一致，应变率误差均小于3 %，表明本研究使用的DIC法能够应用于SHPB实验。

Dynamic Mechanical Property Test of Melt Deposited PLA Based on Digital Image Correlation Method

To study the dynamic mechanical properties of melt deposited poly（lactic acid）（PLA） materials， their dynamic compression experiments were carried out using a split Hopkinson pressure bar （SHPB） experimental device with loading strain rates of 880， 1 230， 1 650 and 2 230 s^-1. The deformation images of PLA materials were obtained under different strain rates using a high frame rate image acquisition instrument. A digital image correlation （DIC） method was adopted to analyze the strain field along the loading direction， and the strain rate analysis was carried out. The results indicated that the melt deposited PLA present elastic， plastic and unloading stages in the deformation process under a dynamic loading. With an increase in strain rate， a significant plastic flow region appears in the plastic stage of PLA， and the compressive strength and maximum strain also tended to increase. The strain distribution in the sample was almost uniform over the whole dynamic impact experiment， and the strain range increased with an increase in strain rate. The strain rate kept almost a constant value during the whole loading process. According to the SHPB experiment， the strain rate error measured by the DIC method was less than 3 %. This indicates that the DIC method can be applied to the SHPB experiment.