Performance of ultrasonic vibration tools with different longitudinal-torsional ratios in extrusion tapping of Ti-6Al-4V

Longitudinal torsional ultrasonic vibrations with different longitudinal torsional ratios <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> were introduced into the extrusion tapping process to explore the effects of ultrasonic vibrations in different vibration directions on extrusion tapping of small blind holes in Ti-6Al-4V. First, the motion trajectory model of longitudinal torsional ultrasonic vibration extrusion tapping (LT-UVET) was established, and the intermittent extrusion separation characteristics of edge teeth during the LT-UVET process were analyzed. In addition, finite element simulation was used to analyze the stress and torque of the LT-UVET process with different <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> . The simulation results show that the effective stress and torque of LT-UVET at different <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> are reduced compared with conventional extrusion tapping (CET). When the ultrasonic vibration direction coincided with the thread direction ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> = 0.08), the effective stress and torque were the lowest. A tapping experiment platform was built and two ultrasonic tools with different aspect ratios were used to conduct tapping experiments. Experimental results show that the torque of LT-UVET is significantly lower than that of CET. Among them, when <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> = 0.08, the effect on torque reduction is more obvious. In addition, LT-UVET can also promote metal flow forming, reduce material accumulation, and improve thread surface integrity.