Spot welding process due to its ability to create a qualitative connection between metal plates and the absence of restrictions on old welding methods such as the impossibility of welding metals by many differences in their melting point is considered as one of the fastest and most economical methods. In this method, an atomic bonding is created on the surface of plates due to high-velocity impact and metal plates are welded together. In the present study, a gas mixture detonation set up was used to perform the impact spot welding tests. Also, the steel plate with a thickness of 4mm was considered as a base plate and steel plates with 1, 2, and 3mm thickness were used as front layers. They were under direct contact with flat- and spherical-nosed metallic projectiles with a mass of 650 and 1300g, respectively. The diameter of the projectiles was 25mm and the average velocity was 600 meters per second. To study the morphology of the weld interface in impact spot welding, the interface of the welds was studied using scanning electron microscope (SEM). Also, the effect of flyer plate thickness and stand-off distance on the spot welding of plates due to projectile impact was studied. The results showed that by increasing the thickness of the flyer plate, the formation of a damaged central area will be decreased. The results also confirmed that when higher stand-off distance was utilized, the velocity of impact was not sufficient to create continuous weld.

In the present study, deformation pattern in impact spot welded plates with flat and spherical-nosed projectiles using gas mixture detonation set up has been investigated and compared with numerical simulations. The steel plate with a thickness of 4mm was considered as a base plate and steel plates with 1, 2, and 3mm thicknesses were selected as flyer plates and were under direct contact with flat- and spherical-nosed metallic projectiles with a mass of 650 and 1300 gram, respectively. The average velocity of the projectiles was 600 meters per second. The ABAQUS finite element software was used to investigate the high-velocity impact of projectiles on steel sheets. The Johnson-Cook (J-C) model was utilized to describe the behavior of metals. The deformation of plates during the impact spot welding process has been simulated. Comparing the plate deformation pattern in numerical simulation and experimental results found that the numerical model predicted well the deformation of plates during the projectile impact spot welding process. The stress wave propagation on the flyer plates also was studied numerically. The results show that the waves start from the center and progress to the corners of the plate. The values of the equivalent plastic strain (PEEQ) and shear stress pattern for flyers and target plates have investigated as a measure of the quality of welding.