Solid-state welding has been around for many centuries, developing and modernizing as time progresses. It is a process where two metals are joined by heating (without melting) and/or pressure that cause the surfaces to deform. Forge welding, resistance welding, and roll bonding have either adapted or given way to friction stir welding, ultrasonic welding, and explosive welding to name a few. This process had been the hidden but to a few skilled craftsmen. Today, however, those sufficiently skilled to operate machinery can perfect the process of welding. One particular solid- state welding process, which was largely developed in the 1960's, is explosive welding. The explosive welding process allows one to join dissimilar materials of varying sizes with the aid of explosives. Explosives are ignited and propel one sheet into another at a unique angle that allows a jetting effect to occur, which aids in bonding. This process creates a strong weld without typical problems such as heat-affected zones and deleterious intermediate phases. Drawbacks include: the need to store large amounts of explosives, the difficulty in handling the large amounts of energy released upon discharge, and the difficulty in welding complex surfaces and small structures within a larger whole.
The High Rate Forming Group at The Ohio State University has recently found a similar solid-state welding process that can be developed using a high velocity projectile to impact two thin sheets of aluminum against a constrained die of a unique geometry. Impact spot welding is a dynamic, high-speed process where the weld is created in a fraction of a second and, unlike numerous welding processes, has no adverse effects from temperature and is not burdened by large and bulky equipment. Metallurgical bonding has been observed in two separate regions where the sheets slide and/or extend past each other under large normal pressures. Strengths comparable to aluminum spot welds have been attained. The present work represents the first attempt to optimize this spot impact welding process by experimentation guided by some complementary numerical modeling.