{"references": ["Gao lin. Research of high-energy USP technology in sheet metal forming (D). Nanjing University of Aeronautics and Astronautics, 2012", "Liu Hai-ying. Research of the mechanism of Ultrasonic shot peening (D). Taiyuan University of technology, 2008", "V.O. Abramova, O.V. Abramov. Surface hardening of metals by ultrasonically accelerated small metal balls (J). Ultrasonics, Vol. 36(1998),p.1013\u20131019", "A. Sand\u00e1, V. Garc\u00eda Navas, O. Gonzalo. Surface state of Inconel 718 ultrasonic shot peened: Effect of processing time,material and quantity of shot balls and distance from radiating surface to sample (J). Materials and Design, Vol. 32(2011), p. 2213\u20132220", "Bohdan N. Mordyuk. Ultrasonic impact peening for the surface properties management (J). Journal of Sound and Vibration, Vol. 308(2007), p. 855 \u2013 866", "Miao hong, Zuo Dun-wen. Effect of shot peening on surface properties of NAK80 steel (J). Journal of Jilin University (Engineering Science), Vol.41 (2011), p.1290-1294"]}

Ultrasonic shot peening (USP) on AALY12 sheet was studied. Several parameters (arc heights, surface roughness, surface topography and micro hardness) with different USP process parameters were measured. The research proposes that radius of curvature of shot peened sheet increases with time and electric current decreasing, while increases with pin diameter increasing, and radius of curvature reaches a saturation level after a specific processing time and electric current. An empirical model of the relationship between radius of curvature and pin diameter, electric current, time was also obtained. The research shows that the increment of surface and vertical micro hardness of material is more obvious with longer time and higher value of electric current, which can be up to 20% and 28% respectively.