Abstract: Based on physical visualized technology, a new visualization device is developed to understand polymer melts flowing behavior in ultrasonic vibration assisted injection molding. The impact of ultrasonic vibration on polyethylene (PP) melts flowing velocity distribution is studied. Combined with tracer particles marking and Kringing interpolation method，a new method is proposed to analyze melts flowing velocity field during injection molding process as well. The results show that the distribution of PP melts flow velocity tends to be high in the middle and near the entrance of the cavity, while low on both sides and the end of cavity. Thermoplastic melts flow is promoted by ultrasonic vibration in mold cavity, and the gradient of melts flow velocity is decreased along melts flow direction as well. Meanwhile, ultrasonic vibration has a benefit on reducing melts viscosity. But, the reduction of melts viscosity goes against to the generation of shear heat. So it is not true that the higher the ultrasonic power is, the greater the speed of melts velocity is. At the same time, the performance of polymer material is changed by the ascent of ultrasonic power which influences the final quality of parts. On the condition of this research, there is a noticeable effect on PP melts shaping when ultrasonic power is between 200 W and 400 W.

Key words: injection molding, rheological properties, ultrasonic vibration, velocity distribution, visualization