Modeling of temperature distribution in ultrasonic welding of thermoplastics for various joint designs

Use of engineering plastics in structural and non-structural applications is rapidly increasing. As the demand for plastics increases so does the requirements for joining. Of the many techniques that are available for joining of thermoplastics, ultrasonic welding is one of the preferred processes. Thermoplastic polymers are categorized according to their molecular structure as amorphous and semi-crystalline. Ultrasonic welding of these two types of thermoplastics is expected to be quite different. As heating is confined to the interface area, quality of weld mainly depends on temperature at the interface. So study on temperature distribution during welding is very important to predict the quality of weld. Viscoelastic heating is most critical to ultrasonic welding of thermoplastics because it is the main mechanism by which heat is developed at the interface. Heat developed due to viscoelastic heating depends on applied frequency, square of amplitude and loss modulus. In this study, modeling of temperature distribution for various joint designs of thermoplastics as practised by industry is attempted and simulation is done in ANSYS. Model is validated by measurement of temperature during welding.