In recent years, many studies for increased productivity of metal forming have been performed. In these fields,
it is important to decrease production cost make lower. However, in general a very expensive metal die is necessary
for metal forming. Consequently, it is difficult to decrease the cost by excluding the metal die. We have been
developing a technique for metal forming without using the metal die as a novel method for lowering costs.
We have considered the free forming by explosives using underwater shock wave generated by detonation of explosives
placed in water. This technique uses only a metal die with circular edges, it does not use an expensive metal die
with the same shape as the product. We investigated varying the pressure condition acted on the metal plate
by changing the set position of the explosive. We have also been trying to establish metal pipe forming using
an underwater shock wave. In this technique the cross section becomes a desired shape using the underwater shock
wave by detonation of explosive in water.
In this paper, we present some experiments of these methods (free metal forming and metal pipe forming) and some
simulation results by FDM (Finite Difference Method). This numerical simulation can express the detonation process of
explosive, the propagation of the underwater shock wave and the deformation process of a metal plate or a pipe.