Wu Wangqing, Zou Yang, Wei Guomeng, Jiang Bingyan
State Key Laboratory of High Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
Polymers (Basel). 2022 Mar 8;14(6):1073. doi: 10.3390/polym14061073.
The acoustic melt stream velocity field, total force, and trajectory of fluorescent particles in the plasticizing chamber were analyzed using finite element simulation to investigate the acoustic streaming and mixing characteristics in ultrasonic plasticization micro-injection molding (UPMIM). The fluorescence intensity of ultrasonic plasticized samples containing thermoplastic polymer powders and fluorescent particles was used to determine the correlation between UPMIM process parameters and melt mixing characteristics. The results confirm that the acoustic streaming driven mixing occurs in ultrasonic plasticization and could provide similar shear stirring performance as the screw in traditional extrusion/injection molding. It was found that ultrasonic vibrations can cause several melt vortices to develop in the plasticizing chamber, with the melt rotating around the center of the vortex. With increasing ultrasonic amplitude, the melt stream velocity was shown to increase while retaining the trace, which could be altered by modulating other parameters. The fluorescent particles are subjected to a two-order-of-magnitude stronger Stokes drag force than the acoustic radiation force. The average fluorescence intensity was found to be adversely related to the distance from the sonotrodes' end surface, and fluorescence particles were more equally distributed at higher parameter levels.
利用有限元模拟分析了塑化腔内的声熔体流场、总力和荧光颗粒轨迹，以研究超声塑化微注塑成型（UPMIM）中的声流和混合特性。含有热塑性聚合物粉末和荧光颗粒的超声塑化样品的荧光强度用于确定UPMIM工艺参数与熔体混合特性之间的相关性。结果证实，超声塑化过程中发生了声流驱动的混合，并且可以提供与传统挤出/注塑成型中的螺杆类似的剪切搅拌性能。研究发现，超声振动会导致塑化腔内形成多个熔体涡旋，熔体围绕涡旋中心旋转。随着超声振幅的增加，熔体流速度显示出增加，同时保留轨迹，这可以通过调节其他参数来改变。荧光颗粒受到的斯托克斯阻力比声辐射力强两个数量级。发现平均荧光强度与距超声换能器端面的距离呈负相关，并且荧光颗粒在较高参数水平下分布更均匀。
