Effect of Pre-Notch on Deformation of Aluminium Square Plate under Free Blast Loading

In this paper the deformation and response of the Al square plate with pre-notch under free blasting loading were investigated. The blast loading process is a complex phenomenon, and accurate modeling, the prediction of deformation during this condition of loading is difficult, numerous investigations have carried out on the permanent deformation and the failure of various materials subjected to the blast; however, the transient deformation of plate subjected to the such intensely loaded has been difficult to measure due to the experimental difficulties. Recently, High speed imaging and 3D digital image correlation (3D DIC) have enabled the reliable none-contact measurement of the deformation and strain in various applications. In this research, 3D DIC method is used to study the effects of pre-notches on the dynamic deformation and rupture of thin Al square plates. The displacement and strain fields during the deformation were analyzed by this method. The Al square plate with the thickness of 3 mm and with different notch geometries were tested under the free blast loading by 20 gr of TNT. Two synchronized high-speed cameras were used to capture the response of the plate with an inter frame rate of 35000 frame/s. The result of test shows that the 3D DIC is a precise method to measure the full-field dynamic deformation of plate. The pre-notch possesses a direct effect on the maximum and final deformation of plate. Based on the result, the deformation occurs in the two stages; in the first one, the plate is deformed due to the shock impulse and all particles are forced to move out-of-plane and provided with initial velocities, and in the second one, pressure wave is vanished and deformation is occurred due to the imparted momentum.