Fine Particle Peening (FPP) is one of the cold working process to improve fatigue strength. FPP is used in a wide range of industries such as automobiles and aircraft. FPP is a process which shots collide with specimen. Work hardening increases the hardness of the specimen surface and improves the fatigue strength of the specimen. In FPP, the shots are released from the nozzle by the airflow. Outside of the nozzle, depending on the spread of the airflow, there is also a spread in shots flight. After shots bounce off the specimen, the bounced shots collide with flying shots. However, there are few studies that have described the spread and bounce of the shots.
Herein, the purpose of this research is to optimize the conditions of FPP process by analyzing the series of shot flight by simulation. By simulating the spread of shots and the bounce of shots, we can optimize the FPP processing conditions, such as the processing speed.
Moving Particle Simulation Method (MPS) was used to simulate the spread and bounce of the shots during processing. For the airflow, the velocity data obtained from the finite element simulation was transferred to the particle method software, and we analyze the flight of the shot under the airflow inside and outside the nozzle. The parameters used in the analysis were the nozzle outlet diameter, nozzle inlet pressure, and the distance between the nozzle outlet and the specimen.
We investigated airflow velocity inside and outside the nozzle. As the inlet pressure of the nozzle increased and the nozzle outlet diameter decreased, the velocity of the airflow near the nozzle outlet increased, and the region of high velocity also increased. We also investigated the flight of shot in the airflow. As the diameter of the shot decreased, the velocity of the shot increased. In front of the specimen, the bounce of the airflow off the specimen decreased the velocity of the shot.
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