Additive Manufacturing Technologies by Ian Gibson David W. Rosen & Brent Stucker

Author:Ian Gibson, David W. Rosen & Brent Stucker
Language: eng
Format: epub
Publisher: Springer US, Boston, MA

8.4.3 UC Process Parameters and Process Optimization

The important controllable process parameters of UC are: (a) oscillation amplitude, (b) normal force, (c) travel speed, and (d) temperature. It has been found that the quality of bonding in UC is significantly affected by each of these process parameters. A brief discussion of each of these parameters and how they affect bonding in UC follows.

8.4.3.1 Oscillation Amplitude

Energy input directly affects the degree of elastic/plastic deformation between mating metal interfaces, and consequently affects bond formation. For a given material combination, oscillation amplitude and frequency of the sonotrode determines the amount of ultrasonic energy available for bond formation. In commercial UC machines, the frequency of oscillation is not adjustable, as it is preset based on sonotrode geometry, transducer and booster hardware and the machine power supply. In UC, the directly controllable parameter for ultrasonic energy input is oscillation amplitude.

Generally speaking, the higher the oscillation amplitude, the greater the ultrasonic energy delivered. Consequently, for greater energy, more elastic/plastic deformation occurs at the mating metal interface and therefore better welding quality is achieved. However, there is an optimum oscillation amplitude level for a particular foil thickness, geometry, and material combination. A sufficient amount of ultrasonic energy input is needed to achieve plastic deformation, to help fill the voids due to surface roughness that are inherently present at the interface. However, when the energy input exceeds a critical level, bonding deteriorates as excess plastic deformation can damage previously formed bonds at the welding interface due to excessive states of stress and/or fatigue.

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