Thermomechanical Analysis of an Ultrasonic Rapid Manufacturing (URM) System

Ultrasonic rapid manufacturing (URM), a low-temperature solid freeform fabrication method capable of producing high-strength functional solid metal parts and multi-material composites, is based on ultrasonic welding (USW) of metals. The quality of the weld, a critical aspect of the URM process, depends on (a) the amount of mechanical energy applied, through an appropriate combination of welding parameters: vertical pressure, horizontal vibration frequency, amplitude, and welding time, (b) the resulting heat generation, and (c) temperature rise. This paper investigates the thermomechanical process aspects and provides insight into the heat generation and transient-temperature profile during a single weld cycle under the special welding conditions developed in this article and validated in the laboratory. The finite element model analysis of two layers of aluminum foil subjected to these welding conditions-with surface contact resistance calibrated by experiments-reveals a moderate temperature rise but one that is sufficient for metal bonding via vacancy diffusion.