Effects of high-pressure coolant on cooling mechanism in high-speed ultrasonic vibration cutting interfaces

Cutting temperature can be effectively reduced by high-pressure coolant (HPC) method. When using HPC on high-speed ultrasonic vibration cutting (HUVC), the precision machining cutting speed on titanium alloys could reach to 400 m/min due to the significant cutting temperature reduction resulted from HPC and ultrasonic vi-bration. However, when the cutting speed continued to increase, the advantages of HUVC with HPC were vanished rapidly. Therefore, it was necessary to figure out the effect of HPC on the cooling mechanism of HUVC for further improvement in high-speed machining. In this paper, computational fluid dynamics (CFD) method and experiments on tool life were applied. The results demonstrated that even though the effect of ultrasonic vibration (Nusselt Number) was reduced sharply by HPC from 158,368 to 78296, the high coolant inlet velocity and large temperature gradient caused by the thinned stable-thermal boundary layer (S-TBL) in the cases of applied HPC would in one side cover the loss of the benefits of ultrasonic vibration and in the other side furtherly enhance the heat transfer ability from 26,158 to 46830 J/m2 s. Thus, the tool life had been significantly pro-longated more than 10 times. After revealing the cooling mechanism from the aspect of HPC transient state within ultrasonic vibration interfaces, the theory foundation of how to further improve the machinability of difficult-to-cut materials by HUVC was developed.