Role of Acoustic Softening Effects in Ultrasonic Spot Welded Dissimilar Materials

Ultrasonic spot welding (USW) is a rapid solid-state welding process in which thin sheets are joined under the influence of high-frequency ultrasonic vibration and pressure. USW has several advantages over conventional fusion welding processes such as less energy consumption, no use of flux or filler material and generation of temperature below the melting point of parent materials. Experimental results have confirmed that USW is a combination of both thermal and acoustic softening effects. These two facts are essential for plastic deformation and bond formation during the welding process. In the present work, an attempt has been made to develop a novel thermomechanical model to characterize thermal and acoustic softening in AA1100 sheets. Experimental temperatures and increment in a width of the sheet are considered to quantify the amount of acoustic softening for different surface conditions. Acoustic softening confers a maximum reduction of 93.98% in yield strength of AA1100 sheets. This model provides a new approach to understand this complex bonding process in a very effective way.