Ultrasonic plastics welding is a widely employed joining technique for thermoplastic polymer assembly nowadays. As one fusion joining method, the ultrasonic welding quality is mainly dependent on the interfacial temperature which is affected by many process factors, such as welding time, welding pressure, and vibration amplitude, as well as material properties. Many attempts have been made to understand the mechanism of creation of an ultrasonic weld but limited by the complexity of the welding process. The current study developed a novel approach to process modeling for ultrasonic plastics welding. The thermoplastic materials were characterized with time domain viscoelastic model. The energy dissipation by the viscoelasticity was converted into the heating source which caused the temperature rose. The temperature change affected the material and structure responses and eventually the dissipated energy. As such, a fully coupled thermal-stress finite element (FE) model was established to simulate the performances of the ultrasonic welding. With the fully coupled model, the temperature distribution and displacement could be solved accurately and simultaneously. Meanwhile, the interfacial temperature was experimentally measured under the different process parameters. The simulation model was further validated by the measured temperature. With this novel approach, the ultrasonic plastics welding process can be completely simulated and the process parameters can be optimized numerically.

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