Fracture mechanism of steel plate loaded by explosive-induced shock waves

The fracture mechanism of in-plane notched steel plate were experimentally investigated under the loading of the triangle shock waves. A series of 20 mm thick steel plates were loaded by explosive charges with different weights and the steel plates were notched in the load surface and free surface. The explosives cut the central part of the plate along the notches and the recovered specimens were processed and analyzed by the scanning electron microscope (SEM). It was found that the explosive charges and the notch properties had a significant effect on the notch fracture and the spall observed in the experiments. Thick explosive charge plate generated deeper, smaller and more dimples on the spall fracture surface which means the ductile of the fracture was increased and the crack extension resistibility was strengthened. This led to a step-like morphology on the spall surface. Moreover, the fractures of two sides of the notch were different. The shear fracture emerged on the loading side and the tensile fracture appeared to the free surface side. However, when there was no notch in the loading surface, the shear fracture appeared to the free surface side and extended to the loading surface. At the same time, the spall and notch fractures interrelated near the notch. Based on the experimental results, a new damage level function was proposed considering the statistic of crack length instead of the void volume. The theoretical analyses of spalls under all six loadings were performed and compared with the experimental results. The comparison showed a good agreement and the reliability of the proposed model was verified. The fracture behavior and mechanism obtained from the experiments provided a good foundation for the further theoretical investigations and the improved damage model was applicable in engineering analysis.