Welding Research

APRIL 2004 -S 140 ABSTRACT. This article analyzes the mechanics of the metal ultrasonic welding process as a basis for a new solid free-form fabrication technology. Three-dimensional prototypes are constructed by ultrasonic welding of overlaid metal foil laminations, followed by contour cutting of the 2-D layers. This was implemented in the laboratory by a computer-automated ultrasonic welding station, and the normal compression, ultrasonic vibration, and process time for a single weld were experimentally optimized. The layered prototypes from aluminum foil exhibit density and stiffness comparable to solid specimens. Using strain gauge measurements on the prototype surface, the friction conditions at the foil-substrate interface were characterized via a simple analytical model of the elastic stress field and used to calibrate a full numerical simulation of the ultrasonic welding mechanics in order to relate the propagation of plastic deformation to the bond development. Besides solid metal and multi-material composites, “cold” ultrasonic welding enables integration of prefabricated components into intelligent structures, yielding active prototypes with internal functionality.