Investigation of Indentation Zone on K9 Glass under Ultrasonic Vibration Condition Using an Equivalent Mean Contact Pressure

Abstract

Ultrasonic vibration-assisted grinding (UVAG) is a promising processing method for parts made of hard-brittle material, as a green machining. The material removal mechanism of hard-brittle material in UVAG is not yet fully understood. The mean contact pressure in the mechanical model of material deformation/fracture that is induced by abrasive grit reveals the deformation/fracture level during the material removal of the indentation of hard-brittle material. To investigate the material removal mechanism of K9 glass in UVAG, a new variable, namely, the equivalent mean contact pressure (EMCP) of glass indentation under ultrasonic vibration was proposed as a corresponding variable for mean contact pressure. A series of indentation experiments with/without ultrasonic vibration was carried out to analyze the material fracture of glass as induced by single random-shaped diamond grits. To obtain the EMCP, an equivalent characteristic size of ultrasonic vibration indentation of K9 glass was defined and measured in the experiments. The vertical load, EMCP and the profile features of the indentation zone, such as the equivalent characteristic size and indentation depth, were investigated in the indentation experiments. Subsurface damage of the K9 glass was also investigated by using UVAG and traditional grinding experiments to analyze the significance of the EMCP on material fracture during machining. The experimental results show the EMCP correlated better with the subsurface damage from UVAG than vertical load. Therefore, compared with the load, the EMCP is a better variable to reveal the difference of material removal mechanism between the UVAG and traditional grinding of glasses.