Experimental investigation on the combined effects of mechano-chemical and ultrasonic vibration in titanium alloy grinding

The machining of titanium alloy has attracted much research attention due to its wide application demand and, however, the low material machinability. The mechanochemical effect and ultrasonic tool vibration are regarded as efficient approaches to improving the machining performance of titanium alloy. This study proposes to combine the above two approaches to obtain synergetic benefits in titanium alloy grinding: use the mechanochemical effect to enlarge the brittleness of the chip and simultaneously use the ultrasonic tool vibration to promote crack propagation on the chip. Finite element analysis (FEA) of cutting is first carried out to demonstrate the process principle. Scratching experiments using a single-edge tool are conducted to explore the synergetic process effects by observing the micro/nano morphology of the chip. Fractured chips are generated due to the synergy of mechanochemical effects and ultrasonic tool vibration. Finally, ultrasonic face and side grinding experiments of titanium alloy are performed, respectively. The results show that the mechanochemical effects can further reduce the surface roughness and cutting force in ultrasonic face grinding. The reduction rate of cutting force increases with the increasing ultrasonic amplitude, and the proportion of cutting force reduction has increased from 18 % to 25 %, indicating the existence of a strong synergetic process effect. However, this synergetic process effect is not found in ultrasonic side grinding. Moreover, it has been proved that the benefits of surface active medium (SAM) in ultrasonic face grinding are not caused by lubrication effects.