Effects of ultrasonic vibration on the deformation behavior of copper in micro-coining.

Ultrasonic-assisted forming technology has great potential in micro-coining. In this paper, ultrasonic-assisted micro-coining experiments comparing different ultrasonic frequencies, amplitudes, action times and other parameters were conducted. The experimental results were analyzed by numerical simulation. It was shown that ultrasonic duration was the main factor determining micro-cylinder height. The micro-cylinder height increased rapidly when ultrasonic duration time was less than 10 s, but longer ultrasonic treatment provided little extra gain micro-cylinder growth. The ultrasonic frequency and amplitude also played an important role in micro-coining. Ultrasonic frequency closest to natural frequency of tools and larger ultrasonic amplitude could provide more ultrasonic energy to specimens, thus leading to higher micro-cylinders. When the ultrasonic frequency and amplitude were 20 kHz and 8.6 μm, respectively, the micro-cylinder height increased the most, nearly five times higher than that achieved without ultrasound. Numerical simulation showed that the surface effect of ultrasonic played a major role in micro-coining by effectively reducing the friction coefficient between tools and specimens, contributing >90% of the increase of micro-cylinder height. Conversely, the contribution of ultrasonic volume effect was <10%. Finally, ultrasonic vibration assistance was applied to the fabrication of micro-cylinder arrays, and effectively improved their height and surface quality, demonstrating that ultrasonic-assisted micro-coining has broad applicability in practical production. [ABSTRACT FROM AUTHOR]