Study on surface quality and tool life in ultrasonic vibration countersinking of titanium alloys (Ti6Al4V).

Titanium alloys (Ti6Al4V) have been widely applied in modern aerospace industry as structural components due to their superior mechanical and physical properties. Meanwhile, the countersinking technology of fastener hole is indispensable to the fastener assembly of countersunk screw. However, the conventional drilling and conventional countersinking (CC) process of Ti6Al4V hole will be difficult due to its low thermal conductivity, high chemical reactivity with many cutting tool materials, and high strength, which can easily cause the rapid tool wear, premature tool failure, unstable cutting process with chatter, and poor machining quality of hole surface. This has attracted wide attention of researchers. In recent years, the rotary ultrasonic vibration machining (RUVM) technology, as a novel machining method, has been found to be very effective in the machining process of difficult-to-cut materials like nickel alloys and Ti6Al4V. This paper first employed the RUVM technology to carry out the ultrasonic vibration countersinking (UVC) of Ti6Al4V, which was a new application of RUVM, and first presented a study on surface quality and tool life in UVC of Ti6Al4V. The experimental results indicated that compared with CC of Ti6Al4V, in UVC process, the maximum value of cutting force Fx and Fy as well as the thrust force Fz and torque Mz decreased by 56.5% and 35.2% as well as 20.6% and 12.8% respectively, the surface roughness of countersunk hole decreased by 41.2 to 42.3%, and the tool life of countersunk drill increased by three times; the cutting chatter of countersinking process was effectively suppressed, and the excellent surface integrity of countersunk hole was obtained in UVC. Moreover, the experimental results also proved that the UVC technology of Ti6Al4V was feasible and effective as well as the cutting effects of UVC were superior. [ABSTRACT FROM AUTHOR]