Effect of surface electroplating on fragment deformation behavior subjected to contact explosion

Abstract

Abstract Prefabricated fragments can deform or even fracture subjected to contact explosion. Thus, the surface of the prefabricated fragment was electroplated with Ni, in order to change the fragment deformation behavior. The effect of surface electroplating on the fragment deformation behavior under contact explosion was analyzed. Firstly, explosion recovery experiments were carried out on uncoated and coated fragments, and different lining thicknesses were set for comparison. By observing the recovered samples, the deformation behavior of two kinds of samples was found to change after contact explosion: the uncoated fragments were fractured, while the coated fragments maintained integrity. The lining did not change the fragment deformation behavior but could change the degree of deformation. As the thickness of the lining decreased, the degree of fragmentation compression increased. To study this phenomenon, detonation wave theory and shock wave transmission theory in solids were used to calculate the pressure amplitude variation at the far-exploding surface of the fragments. The pressure amplitude of the uncoated samples instantly dropped to zero after the shock wave passed through the far-exploding surface, which resulted in the formation of tensile zone. But the pressure amplitude of the coated samples increased, which transformed the tensile zone into the compression zone, thereby preventing the fracture of the fragment near the far-exploding surface, which was consistent with the test results. Then, microscopic observation of the circumferential direction of the recovered samples showed that the coatings were better than the lining in preventing "weld melting" and fracture phenomena in the radial direction of the fragments. The test results and theories show that the coating can change the deformation behavior of the fragment and prevent the fracture phenomenon of the fragment. The coating also has better protection performance than the lining against contact explosion.