注塑成型熔接线性能的实验研究和数值模拟

【作者】 肖长江；

【导师】 申长雨； 刘春太；

【作者基本信息】 郑州大学 ， 材料加工工程， 2003， 硕士

【摘要】 注射成型是生产塑料制件的一种很重要的成型方法之一，大多数热塑性塑料和许多热固性塑料都可以用此法成型，然而，注射成型仍然存在一些没有解决的问题，熔体前沿的汇合形成的熔接线是其中之一，熔接线的形成是由于在模腔中存在嵌件、空洞、几何因素的突然变化或多浇口而引起熔体在流动的分开。因为熔接线的存在显著地减少注射制件的力学性能，因此，近些年来，对注塑制品熔接线的分析得到了普遍的关注，这一方面是由于大型复杂制件的逐渐增多，另一方面是人们对制品的外观和内在性能要求越来越高，如何提高制品熔接线区域的性能成为研究的重点。本文主要从实验上和数值模拟上来对熔接线的性能的优化，具体工作如下： (1)理论上分析熔接线的形成原因、形成机理，形态结构和对制品性能的影响，讨论了影响熔接线的各种因素如材料、工艺条件(熔体温度、模具温度、注射压力、保压压力、保压时间、注射速度)等，以及提高熔接线的制件性能的途径。 (2)实验研究熔体温度变化对Zytel 70G33L(PA66加33％玻纤)的有熔接线和没有熔接线的制件的影响，实验表明，随着熔体温度的升高，有熔接线和没有熔接线的制件的拉伸强度增加，但拉伸应变下降。在没有熔接线的情况下，拉伸强度的变化非常缓慢，而有熔接线的制件的拉伸强度变化要剧烈得多，这主要是由制品中的纤维取向结构和分子运动所决定。 (3)利用Taguchi方法分别对Zytel 70G33L和ABS的各种工艺条件的组合(熔体温度、注射压力、保压压力、注射速度)进行了实验和实验分析，经过方差分析，得到有熔接线和没有熔接线的制件的最佳的工艺组合，和每个因子的影响程度，找出影响最大的因子。 (4)实验研究了Zytel 70G33L不同的流动形态(制件中不同直径圆嵌件和不同形状嵌件即圆、正方形、菱形)对有熔接线的制件的影响，实验表明，嵌件的尺寸越小，熔接线的影响越小；嵌件的形状为菱形时的影响最小。并运用CAE技术模拟了各种情况的熔接过程。 (5)针对材料Zytel 70G33L、ABS，比较热熔接和冷熔接所形成的熔接线对制件性能的影响。更多还原

【Abstract】 Injection molding is one of the most important processing methods for producing plastic parts, However, there are still several unresolved problems that confound the overall success of the injection molding process . The forming of weldline wherever polymer flow front meet is one of them. Weldlines form because of the presence of inserts, cores, abrupt change in geometry along the flow path and multiple gates that divide the polymer melt during flow in the mold. It has been observed that the presence of weldlines significantly reduces the mechanical property of injection molded parts . Therefore, in recent years, the analysis on injection molded parts with weldline obtains global concerns, this is. on the one hand , due to large-scale complex parts gradually manifold , on the other hand, the people desires on the appearance and internal performance of parts are increasing high , how to enhance the performance on the weldlind area becomes investigative emphasis . on the basis of the experiments and the numerical simulations , the paper optimized the mechanical property in the weldline area of injection molded parts , the details of paper are as following :(1) Theoretically, I analysed the forming cause. forming mechanism .morphological structure of weldline and its effect on the mechanical property of injection molded parts; discussed the different kinds of factor that affect weldline. such as material, processing condition (melt temperature, mould temperature, injection pressure, packing pressure, packing time, injection speed ), and the measures for enhancing the mechanical property of injection molded parts with weldline;(2) By experiment, that the change of melt temperature affects the Zytel 70G33L parts with weldline and non-weldline has been studied. Experiment shows: along with melt temperature increasing, the tensile strength of parts with weldline and non-weldline both enhance, whereas the stretching strain of ones both fall, on the condition of the parts without weldline, the variance of tensile strength is at a very slow speed, but it is intensify ten times on the parts with weldline, the difference is mostly decided by the fiber orientation structure and the molecular motion.(3) Using Taguchi method ,respectively experimented and the combination of different kinds of processing condition (melt temperature , injection pressure ,packing pressure, injection speed) on Zytel 70G33L and ABS , by analysis of variance, obtained the optimal processing condition combination of parts with weldline and non-weldline , and the affecting level of each factor, found out the one that affect maximally ; simulated the flowing process on ABS by using CAE technology.(4) By experiments, studied that the different flow patters(the inserts in parts have different sizes, namely, the diameters of circular inserts are different and the shape of inserts are circle, square, diamond) of Zytel 70G33L affecting the mechanical property of injection molded parts with weldline. Experiment shows: the samller insert size is, the lighter the damage of weldline is ; on the condition of the diamond insert ,the damage is least; and simulated the melt process of different kinds flowing pattens by using CAE technology .(5) Aiming at Zytel 70G33L and ABS , compared the different effect of weldline on the parts of both at the cold melt and at the hot melto更多还原