Recent Advances In the Ultrasonic Additive Manufacturing (UAM) Process

The ultrasonic additive manufacturing (UAM) process has found applications that include injection molding dies, thermal management, armor and embedded sensors.  EWI, in cooperation with Solidica, several industry, agency, and academic partners, and with the support of the State of Ohio’s Wright Program, has developed a “Very High-Power Ultrasonic Additive Manufacturing System” (VHP UAM), now operational, that is expanding the uses of the prior UAM technology, permitting it to deal with advanced materials, large part sizes and increased production speeds.  A key part of the development is the design of a 9.0-kW ultrasonic welding module able to produce sound welds in advanced materials.  This was first demonstrated on a VHP Test Bed, where welding of materials such as Ti 6-4, 316SS, 1100 Cu, and Al7075 was done.  The higher ultrasonic power levels are permitting welding of thicker metal tapes at higher production speeds and for larger parts than had been achieved with prior equipment.  Thus, the VHP system is capable of fabricating metal parts having lineal dimensions of up to 1.5 × 1.5 × 0.6 m.  An essential part of this technology advancement has been research on the ultrasonic bonding process that is the basis for UAM.  Recent studies have shown that bonding between tapes is accomplished by the occurrence of dynamic recrystallization of grains across the interface. This is a direct consequence of dynamic shearing of asperities at the interface inducing adiabatic plastic deformation heating and a concurrent localized temperature rise. The increased vibration amplitudes available in the VHP UAM machine together with higher force levels enhance these effects, resulting in improved bond quality.   Several applications of the technology will be reviewed including solid metal parts with embedded channels for thermal management, metal matrix composites (MMC) for structural materials, embedded shape memory alloys (SMA) for active stiffness control and composite-to-metal transition parts, and solid-state cladding for petro-chemical applications.