Ultrasonic flexible bulging process of spherical caps array as surface texturing using aluminum alloy 5052 ultra-thin sheet

Ultrasonic flexible bulging process based Ethylene-vinyl acetate (EVA) soft medium is presented for fabricating the surface texturing with 3 dimensional shape using ultra-thin metallic sheet of 50 μm in thickness. Advantages of ultrasonic vibration and flexible forming are both utilized to guarantee the forming quality of big area surface texturing, i.e. spherical caps. Effects of ultrasonic vibration, such as amplitude and duration time, were investigated, and compared between flexible and rigid punch. Experimental results show that the ultrasonic flexible bulging can improve the surface quality and increase the height of bulged cap and length of intersection edge. Analysis and discussion of ultrasonic flexible bulging mechanism are carried out from the viewpoint of stress states of ultra-thin sheet in bulging process by considering the acoustic softening effects and abilities of EVA soft medium in uniformly transmitting pressure. The results reveal that the proposed process is suitable to manufacture the complex surface texture of ultra-thin metallic sheet with high quality.