Abstract
The heat generation mechanism in ultrasonic welding by a torsional vibrator is discussed based on a simple theory of viscoelasticity. It is concluded that the principal heat source in ultrasonic torsion welding is friction loss at the interface, not viscous dissipation. However, near the resonant frequency, which is much higher than practical frequencies, viscous dissipation becomes the main cause of the heat generation. Optimum welding conditions are also discussed. A loose interface and non-slip conditions at the anvil are preferable for welding. The present discussions will contribute to a further development of the ultrasonic welding technology.
