Geoffrey Taber

In situ velocity measurements of very high power ultrasonic additive manufacturing using a photonic Doppler velocimeter

Abstract To understand the dynamic structural movements of very high power ultrasonic additive manufacturing, simultaneous in situ velocity measurements of the sonotrode, welding foil and substrate during consolidation were made using a photonic Doppler velocimeter. During consolidation in which the welding foil was successfully bonded to the substrate, the welding foil and substrate had similar vibration phase angles which came into and then out of phase of the sonotrode; in addition to having large changes in relative velocity as the normal force from the sonotrode was applied and then removed. A consolidation pass in which no bonding occurred, consisted of relatively constant velocity amplitude for all structures. The welding foil and sonotrode remained fully coupled and in phase, but was out of phase of the substrate during the entire welding pass. Therefore, by examining velocity and phase data, bonding versus non-bonding conditions can be determined in situ using the photonic Doppler velocimeter system.

An electromagnetically driven metalworking press

A small press operated by electromagnetic repulsion and driven by a pulse power supply was constructed at The Ohio State University. This design that applies kinetic energy rather than static force to do work on materials is much lighter and potentially much less expensive than traditional hydraulic, mechanical or servo presses. Performance of the kinetic press is compared to traditional presses in the applications of powder compaction and forming. The results tend to indicate that modest impact speeds of 3 to 18 m/s can improve performance in these manufacturing operations as compared to traditional low-speed machines.

Vaporizing Foil Actuator: a Tool for Creating High‐Pressure Impulses for Metalworking

Impulse based metalworking has significant advantages, in that short time scales change the fundamental nature of the forming process and short duration impulses can be used with much lighter and more agile equipment because large static forces do not need to be resisted. Electrically vaporized thin conductors, termed as Vaporizing Foil Actuators (VFA), can be used to develop significantly high driving pressures over short time scales. The driving pressures can be a few GPa’s, and have been used to launch sheet metal workpieces to velocities in excess of 1 km/s. Applications include, but are not limited to, impact welding, forming, embossing, shearing, tube joining, and powder compaction.