Development of a simple round bar horn for power ultrasonics using a friction-welded joint between dissimilar metals

Summary

Solid horns for power ultrasonics usually magnify the vibration amplitude by reducing the cross-sectional area along their axis. However, these horns are usually too heavy to handle easily, and their fatigue strength is reduced by the stress concentration induced by their profile. The authors have therefore attempted to develop a new type of horn based on a different magnification principle by connecting two simple round bars with different specific acoustic impedances. Vibration of the round bar horn has been analysed by longitudinal wave theory and FEM to achieve a practical design. New types of horn were fabricated and tested to confirm their displacement amplitude magnification capabilities. The analytical and experimental results showed that the simple round bar horn is satisfactory for practical use. On this basis, an attempt was made to fabricate a simple round bar horn using a friction-welded joint consisting of SUS304 stainless steel and 6061 aluminium alloy dissimilar metals. The vibration characteristics of the input-output displacement amplitude, frequency, elevated temperature, and fatigue fracture were respectively investigated for friction-welded simple round bar, step, and exponential horns consisting of SUS304 and A6061. The results obtained suggest that the simple round bar horn has better vibration characteristics than the others.