【作者】 朱文娜；

【导师】 王利霞； 申长雨；

【作者基本信息】 郑州大学 ， 材料加工工程， 2009， 硕士

【摘要】 伴随着微机电系统技术而发展的微注塑成型技术,目前已在微机械、微电子、微光学及生物医学等领域获得了较广泛的应用。然而,由于微型塑件的结构尺寸与体积极其微小,在微注塑成型充填过程中,高聚物熔体流过微小通道时的流变特性与传统注塑成型时有许多不同,因而影响微型塑件成型质量与传统大尺寸塑件成型质量的关键因素有所不同。微注塑成型中,聚合物熔体充填过程直接影响着微塑件的成型质量和生产效率,是成型中最重要的阶段。因此,对微尺度型腔内熔体充填流动行为,尤其对微尺度效应进行深入研究,建立描述微注塑成型的数学模型及高效的数值方法,实现对微注射成型过程的数值模拟,对优化设计微注塑模具、合理设置成型工艺参数和提高微型塑件质量都具有重要的理论意义和实用价值。本文结合微注塑成型的特点,对微注塑成型充填过程进行了数值模拟,主要工作和结论如下:1.借鉴宏观熔体充填流动理论,比较了微型注塑成型技术与传统注塑成型技术的差异。对微注塑成型熔体充填过程中的影响因素进行了系统的分析,并引入了Eringen-Okada微观粘度模型和Rosenbaum-Hatzikiriakos壁面滑移速度模型。2.针对狭缝微流道中高聚物熔体的稳态流动进行了分析,分别考虑了微观粘度、壁面滑移对稳态流动的影响及二者的共同作用对稳态流动的影响,通过算例分析了微观粘度和壁面滑移对微流道中熔体流动的影响规律及重要性。3.从粘性流体力学的基本方程出发,结合微注塑成型过程的流动特点,进行合理简化和假设,并引入微观粘度模型和壁面滑移模型,建立熔体在狭缝微型腔内充填的数学模型;采用混合有限元/有限差分/控制体积法实现微注塑充填过程的数值模拟;通过算例分析讨论了微观粘度和壁面滑移对高聚物熔体在微型腔内充填过程的粘度、速度、压力等参数变化的影响。模拟结果表明,微观粘度有阻碍熔体流动的趋势,而壁面滑移有促进熔体流动的趋势。两者的综合作用决定了微注塑成型充填过程中熔体的流动。更多还原

【Abstract】 With the development of the Micro Electro Mechanical System (MEMS), micro-injection molding technology is developed and widely used in the micro-mechanical, micro-electronics, micro-optics , biomedical and many other fields now. However, because of the very small size and volume of micro-plastic parts, the flow behavior of polymer in the filling stage of micro-injection molding has many differences compared with that of the traditional injection molding, Therefore, the key factors affecting the qualities of micro-parts are different with that the factors in the traditional injection molding.The filling stage is the most important stage in the micro-injection molding process and influences the part quality and production efficiency of micro-injection molding directly. Therefore, it has great theoretical and practical significance for designing micro-injection mould, setting processing parameters reasonably and improving micro-plastic parts quality to investigate the melt flow behavior in the filling stage in the micro-scale cavity, especially the micro-scale effect on the flow behavior, build mathematical model and efficient numerical method, and implement the numerical simulation of filling stage in micro-injection molding.The objective of the paper is to analysis the main factors and to simulate the filling stage of the micro-injection molding process. The works and achievements are as following:1. The differences of the process characteristic between micro-injection molding and traditional injection molding were compared. The influence factors in the micro-injection process were analyzed systematically and the micro viscosity model and wall slip velocity model were introduced.2. The steady-state flow of polymer in slit cavity was analyzed. The effects of the micro-viscosity and wall slip and the comprehensively effect of two factors on steady-state flow were investigated, and the influence laws of the micro-viscosity and wall slip on the steady-state flow were analyzed.3. Based on the viscous fluid mechanics and the flow characteristics of micro-injection molding process, the reasonable simplification and hypothesis were introduced, the micro-scale viscosity model based on Eringen and Okada theory and the power-law wall slip model were adapted, and the mathematical model of the filling stage in slit micro-cavity was built. Numerical simulation of the filling stage of micro-injection molding was implemented using hybrid Finite Element/ Finite Difference/Control Volume method. The effects of the micro-viscosity and wall slip on the viscosity, velocity and pressure field of the melt in the cavity in filling stage were investigated. The simulation results indicate that the micro-viscosity has the effect of hindering the melt flow and wall slip has the effect of promoting the melt flow. The melt flow condition in the filling stage of micro-injection molding is determined by the combined effects of micro-viscosity and wall slip.更多还原