Papers by Author: Naotake Mohri

Abstract: In electrical discharge machining (EDM), an electrical discharge occurs between a tool electrode and a work-piece, and removal of materials is carried out by vaporized explosion between the electrode and the work-piece. However, the mechanism of material removal in EDM is not well understood. In order to clarify this issue, the acoustic emission (AE) method has been applied to examine the force of explosion, and the Schlieren visualization method has been applied to observe the explosion. In this study, we investigate the effect of discharge current behavior on the occurrence of the AE waves by means of an optical fiber vibration sensor.

Abstract: In this study, we investigate the effect of discharge current on the occurrence of burst AE wave caused by microsecond discharge. Electrical discharge duration was changed from about 1µs to 8µs by using condenser circuit. Effect of current behavior was estimated by comparing with experimental signal and simulation one. AE wave was detected by optical fiber vibration sensor. The optical fiber vibration sensor is located on an aluminum work-piece (cathode) plate. Simulation was carried out with MSC. Marc. As the results, it was found that AE wave was occurred by a force depending on electrical current behavior. The force direction was machining direction. The force has been occurred during microsecond discharge.

Abstract: In this study, the possibility of electrical discharge pulse sound for new inspection technologies instead of hammering test was investigated. Electrical discharge pulse sound was applied for hammering sound and sensor by using sound detection was applied for the optical fiber vibration sensor. Elastic wave was detected by optical fiber vibration sensor during electrical discharge. The plate thickness was changed from 0.5mm to 10mm. On the assumption that generation factor of elastic wave was only depending on a force, numerical analysis by using the finite element method (FEM) was adapted. The numerical analysis result using the FEM and the experimental result along with the electrical discharge were compared. The plate thickness was estimated by comparing with experimental signal and simulation one. It was found that plate thickness was able to estimate from comparing with experimental signal and simulation one. Moreover, a quasi-defect was created the plate by comparing with experimental results and simulation one. It was found that the defect shape was able to estimate by comparing with experimental results and simulation one.