Investigations on the effects of ultrasonic vibrations in the extrusion process

Ultrasonic vibrations can be applied on the die during the extrusion process. Numerical and experimental analyses have been already performed in the literature on the application of ultrasonic vibrations on the wire drawing, deep drawing, upsetting and rolling processes. No attempts have been made to investigate on the effects of ultrasonic vibrations on the forward extrusion process, yet. A detailed analysis and understanding of the mechanism of improvement is not possible on the basis of conventional experimental observations because ultrasonic vibration processing phenomenon occur at high speeds. Hence, in order to progress the perceptive of the mechanism of ultrasonic vibration extrusion, the finite element analysis was performed by using the explicit analysis procedure. The results were compared with conventional cold forward extrusion. Simulations were performed for various extrusion speeds, vibration amplitudes and frequencies, friction factors and reductions. The effects of the ultrasonic vibrations on the material flow stress, the equivalent plastic strain distributions and the extrusion force were considered. The results show that the extrusion force and the material flow stress would be reduced by applying the ultrasonic vibrations if the extrusion speed was below the critical speed. In addition, it was found that applying the ultrasonic vibrations had no significant affect on the equivalent plastic strain of the material. A larger reduction in average extrusion force was obtained by either reducing the extrusion speed or increasing the amplitude of vibrations. (c) 2006 Elsevier B.V. All rights reserved.