| Abstract: | An experimental study of the heating and bonding mechanisms in ultrasonic welding is described. Polystyrene specimens were joined under a variety of welding conditions while the temperatures at the interface and within the interior of these specimens were measured. The power input, amplitude of vibrations, and amount of deformation during welding were measured concurrently. In general, the rate of heating at the interface is greatest at the beginning of the weld cycle, but slows markedly after the interface temperature reaches approximately 250°C. The interface temperature peaks well before the weld is completed. Temperatures within the body increase most rapidly at temperatures near the glass transition temperature. Welded specimens were broken on a special testing apparatus under combined torsional and compressional loads to determine the weld strength. The results show that weld strength is dependent on the amount of energy input and the degree to which material flows out of the interface region. Possible mechanisms for heating and bonding during ultrasonic welding are discussed in light of the observed behavior. |
