微注塑成形中熔体充模流动分析及其数值模拟

Analysis and Numerical Simulation of Polymer Melt Filling in Micro Injection Molding

借鉴宏观熔体的流变学理论和建模技术,针对微尺度流道中的聚合物熔体流动特性,采用模型修正方法,建立反映微小通道中熔体流动特性的理论模型。同时,应用数值模拟方法,研究微尺度粘度、壁面滑移和熔体与模具间的表面传热系数对微小熔体流动的影响关系,并与相关试验数据进行比较。结果表明,微流道中的熔体粘度明显小于传统理论下的粘度值,且与微流道的特征尺寸成正比。随微流道特征尺寸减小,滑移系数也明显减小,壁面滑移速度则增大。考虑局部表面传热系数时微流道中的熔体温度分布具有尺寸效应。微尺度流道中的熔体流动行为与宏观熔体有许多不同。

The theoretical models of melt flowing characterictics in microscale channels are constructed by model modification method according to the macroscopic rheological theories and the modeling technology for polymeric melt. Moreover, the influences of microscale viscosity, wall slip and convection heat transfer coefficient between polymer melt and mold wall on micro melt flowing are investigated by using numerical simulation method and compared with the existing experimental data. The results indicate that the viscosities of polymeric melt flowing in microchannels are obviously lower than those calculated with the conventional viscosity model and are proportional to the characteristic dimensions of microchannel. With the decrease of the characteristic dimensions of microchannel, the slip coefficients are obviously reduced, while the slip velocities of polymeric melt on the wall are increased. In addition, considering the surface convection heat transfer coefficients the distribution of melt temperature in microchannels is subject to the size effect. The flowing behaviors of polymeric melt in microchannels are different from those in macrochannels in some aspects.