A study of the utilization of generated energies in hydro-spark forming and explosive forming

Abstract

In hydro-spark forming and explosive forming, it is necessary to transform effectively any generated energy into energy for the plastic working of a blank. This paper describes the mechanism of energy transmission involved in plastic deformation and the utilization of generated energies. A high-speed camera was frequently employed to observe conditions under water. The main points in this paper are as follows: 1. (1) In the free forming of a circular blank, the polar deflection varies with the stand-off distance and the distance between the water surface and the charge. A result of observation is that the behaviour of the gas bubble greatly influences the deflection of the blank. 2. (2) By adopting the forming method that uses an air-bag over a blank, the efficiency of energy utilization for deformation is improved remarkably. In this case, the primary shock wave has little effect on the deformation, and the kinetic energy of the water which is taken up from the gas bubble energy is responsible for the deformation. 3. (3) When both the pressure pulse and water hammer act together, the deformed shape of a blank becomes round. The character of the deforming process in this case is such as to establish a round profile at an early stage. 4. (4) The high pressure whose duration is of the order of a millisecond is created by the water hammer, which is generated by the water jet and a rapid gas expansion. 5. (5) Generally, the primary shock wave is not essential for deformation, but the pressure pulse as a shock wave can form a circular blank into a conical shape.