Yasuhiro Ujimoto

Collection of Product Synthesized Using Extremely High Impulsive Pressure Generator

A new method has been developed to generate an extremely high impulsive pressure by using a metal jet that is discharged when a metal collides with another metal. The high pressure is used to synthesize a new material. When a metal plate was accelerated by the detonation of an explosive, it collides with the concentric circle of the conic surface of a conical concave metal block metal jets are discharged from all parts on the concentric circle. The metal jets fly toward the center while converging and collide with each other at the central axis. Because those collide at high-speed pressure becomes extremely high. The flight direction of the converged metal jet changes downward. The metal jet collides with the bottom of the block. A large hole is formed inside the bottom. The formation process of the hole was examined by the observation of the section of the block. A specimen powder that was rubbed to the conic surface is discharged with the metal jet and become the high pressure. The specimen powder is synthesized to a different material. The synthesized material is held inside the formed hole. The existence of cBN was confirmed by the X-ray diffraction of the synthesized material, in the case that BN was used as the specimen powder. Similarly, the existence of diamond was confirmed in the case of graphite powder.

OBSERVATION OF METAL JET IN EXTREMELY HIGH IMPULSIVE PRESSURE GENERATOR

A new technique has been developed to generate an extremely high impulsive pressure by using an explosive. A metal jet, typically observed in explosive welding is used in this technique. The behavior of metal jet is crucial to the design of pressure generator. The experimental observation was made by the collision of metal jet on a metal block surface. Many craters formed by the collision of metal jets on the surface of the metal block were observed. The craters were overlapped and distributed in a wide range. The diameter of the largest crater was 0.5 mm. The quantity of the discharged metal jets was found to be a function of the quantity of explosive. The total area of the craters is considered as proportional to the quantity of the discharged metal jets and the experimental conditions for the formation of large craters was investigated.

Numerical Simulation on Explosive Welding Process Using Reflected Underwater Shock Wave

The paper describes a numerically simulated result for the explosive welding using reflected underwater shock wave. Through the numerical simulation, the effective use of reflected underwater shock wave was clearly suggested and the method to improve the assembly was demonstrated.

A New Method of Explosive Welding Performed by Effective Application of Reflected Underwater Shock Wave

In this report, we propose a new explosive welding method, and the welding is performed at employing underwater shock pressure produced by the underwater explosion of an explosive placed at one side almost vertical to the specimen to be welded. In order to prevent the reduction of the shock pressure with the distance away from explosive, a steel reflector is placed over the area of the specimen. The effects of the reflector are investigated based on the experimental results and the process is numerically analyzed results.Copyright

Explosive Welding of Thin Plates Using Underwater Shock Wave for Surface Modification

This paper presents a new method of explosive welding using underwater shock waves. The method renders the possibility of accelerating a thin metal plate uniformly at a velocity above a few hundreds m/s to satisfy the explosive welding requirements. The welding of a thin titanium plate onto a stainless steel base and other welding experiments were performed underwater. The bonding strength at the interface is observed to be high because the materials are welded based on the mechanism of explosive welding. The experimental results are discussed to characterize the state of bonding.