“…Therefore, the enhancement of the material flow during the process is required. As an approach to enhance the material deformation, ultrasonic vibration has been applied to the microforming processes such as micro-extrusion (Bunget and Ngaile, 2011), micro-upsetting (Hung and Tsai, 2013and Yao, et al, 2012, micro-forging (Kosuge and Yang, 2012), micro-deep drawing (Huang, et al, 2014). In particular, Hung et al (2013) demonstrated that the reduction of flow stress by ultrasonic vibration becomes more significant with decreasing the process dimensions.…”