基于DIC技术的爆炸应力波过异质界面应变场演化规律实验研究

采用氯仿粘结聚碳酸酯（polycarbonate, PC）板和聚甲基丙烯酸甲酯（polymethylmethacrylate, PMMA）板模拟含异质界面模型；在PC介质中布置柱状炮孔并与界面呈一定角度，根据炮孔端部与界面相对位置，分别于柱状炮孔两个端部设置起爆点，起爆点远离界面端部时定义为孔口起爆，靠近界面端部时定义为孔底起爆；借助数字图像相关实验系统，研究爆炸应力波通过异质界面后PMMA介质应变场演化过程及炮孔底部区域拉、压应变变化规律。实验结果表明，异质界面改变了爆炸应力波过界面后的传播形态。孔口起爆时，异质界面受爆破荷载作用后易形成应力集中区，界面处产生开裂，横向拉伸波作用是造成异质界面开裂的主要原因。起爆方式对过界面后介质PMMA的横/纵向拉、压应变场作用贡献不同，主要体现在应变场强度、拉/压应变场位置分布2个方面。在炮孔底部区域，起爆方式对应变场时程特性的影响主要体现在作用时效长短和应变强度2个方面。孔口起爆时，横/纵向应变体现出短时效、高强度的变化特征。就应变强度而言，起爆方式对横向压应变的影响显著强于其对纵向拉应变的影响。对空间分布特性影响主要体现在衰减程度，起爆方式对纵向应变衰减程度影响较大。无论采用何种起爆方式，爆炸应变场在PC介质中衰减速度较快，进入PMMA介质后衰减速度显著降低。

Experimental study on evolution of strain field of explosion stress wave passing through a heterogeneous interface based on the DIC method

Chloroform was used to bond a polycarbonate (PC) plate and a polymethylmethacrylate (PMMA) plate to fabricate a model with a heterogeneous cemented interface. A cylinder blasthole was set in the PC plate with a certain angle to the interface. Base on the locations between the interface and the explosive initiation points, two kinds of initiation methods were used in the experiment. The one is the top initiation method, in which the initiation point is settled far away from the interface; and the other is the bottom initiation method, in which the initiation point is close to the interface. The digital image correlation (DIC) method was used to study the evolution of the strain field during the passage of the blast waves in the medium with the heterogeneous interface. The results show that the propagation pattern of the blast stress wave varies significantly after it passes through the interface. In the top initiation, a stress concentration zone is formed on the interface under blast loadings, and induce a crack initiate at the interface. The transverse tensile wave is the main reason for the cracking of the interface. Besides, it can be found that the initiation methods have different contributions to both the magnitude and the locations of the tensile/compressive strain in both the transverse and longitudinal directions. Moreover, in the bottom area of the borehole, the influence of the initiation method on the time-related characteristics of the strain field mainly has two aspects, namely, the duration time and the strain magnitude. And it is found that the transverse/longitudinal strain is of "short duration, high magnitude" variation characteristic for the top initiation. In terms of the strain magnitude, the influence of the initiation method on the transverse strain is much greater than it on the longitudinal strain. In addition, the initiation method can significantly influence the attenuation characteristics of the strain field, which is more obvious for the longitudinal strain field. In terms of the attenuation rate, the magnitude blast stress waves attenuated faster in the PC plate, whereas the blast stress waves attenuated slowly when it passed through the interface and propagated in the PMMA plate regardless of the initiation method.