Tool wear mechanism and its relation to material removal in ultrasonic machining

As a particular important factor in UltraSonic Machining (USM), the tool wear largely affects the material removal process and accordingly influences the machining performance. Although a number of experiments were conducted to monitor and measure the tool wear during USM in previous works, the nature of the tool wear mechanism and its relation to material removal have not been totally understood. Therefore, both simulations and experiments were conducted for studying the influence of tool wear on material removal in this work. Three different tool materials i.e. 304 stainless steel, 1045 carbon steel, and tungsten carbide were used. A numerical simulation model utilizing both Smoothed Particle Hydrodynamics (SPH) meshfree method and Finite Element Method (FEM) was built first to predict tool deformation and fractures of workpiece and abrasive particles. Experiments were then conducted to verify the simulation results. It was found that using tool materials possessing a high flexibility such as 304 stainless steel can slow down the wear of abrasive particles and improve the material removal efficiency. Additionally, work hardening was confirmed to occur in 304 stainless steel and accordingly suppressed the tool wear. On the other hand, when using tungsten carbide as the tool material, even though the tool wear was small due to the high hardness, the abrasive particles were abraded seriously and the material removal efficiency was lowest. Finally, the relation between the material removal and the tool wear was discussed based on these results.