共查询到19条相似文献,搜索用时 515 毫秒
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以超高分子量聚乙烯的圆形轴对称气辅口模挤出为研究对象,采用Polyflow软件对气辅口模挤出时的等温流动进行数值模拟,并对挤出口模内的速度、压力、剪切速率等场量分布进行分析. 相似文献
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异型材口模挤出三维流动计算机模拟系统 总被引:5,自引:1,他引:5
建立了异型材口模挤出三维流动计算机模拟系统的基本框架,介绍了其结构和功能,该系统主要包括前置处理,有限元分析和后置处理三大模块,有限元分析模块又包括对口模内幂律流动的分析模块,粘弹性PTT流体流动的分析模块以及粘弹性PTTI充体三维挤出胀大的分析模块,后置处理主要包括速度场和应力场的后置处理。该系统目前只是一个雏形,经过不断发展和完善,有望成为异型材口模挤出过程模拟的通用分析软件。 相似文献
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以超高分子量聚乙烯的圆形轴对称气辅口模挤出为研究对象,在采用Polyflow软件对气辅口模挤出时的等温流动进行数值模拟之后,就入口流率、松弛时间以及零剪切黏度等物性和工艺参数对挤出胀大、速度分布、口模压降和熔体外表面上剪切速率的影响进行了数值模拟和分析。分析表明:气辅挤出是克服超高分子量聚乙烯传统挤出时面临一系列困难的有效加工方式。 相似文献
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介绍了一种基于横截面法的异型材挤出成型中熔体在模头内流动压力降的数值计算方法,可用于预测截面复杂的异型材挤出模头的压力降:并通过算例说明了数值计算结果的可靠性和用途。 相似文献
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聚合物熔体在异型材三维动态挤出口模内的停留时间分布 总被引:1,自引:1,他引:1
利用ANSYS软件对受口模入口处周期性振动的压力驱动的聚合物熔体在“Y”形和“L”形异型材挤出口模内的停留时间分布进行了数值模拟。设熔体流动为三维等温广义牛顿幂律流动,在求得速度场后,应用路线示踪法跟踪流场中任一粒子的流动轨迹,进而求得熔体在口模中的停留时间分布。通过改变振动参数再重复计算,总结出振动参数对停留时间分布的影响规律。结果表明:压力的振动能有效地缩短熔体在口模内的停留时间,振幅和频率越高则停留时间越短,而且在靠近口模流道壁面处停留时间的缩短最明显,表明振动的引入可以降低壁面附近的流动阻力,使截面上的流速更平稳,从而改善挤出制品的表观质量。 相似文献
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针对聚合物双腔微管直角挤出模具非对称流道结构,基于聚合物流动平衡原理,建立了直角挤出模具非对称流道结构参数关系。在直角挤出模具的挤出成型方向上,采用反向流道的方法计算流道长度,并对反向流道的终点进行拟合,基于拟合偏差构建了目标函数,对模具非对称流道结构进行了优化设计。根据优化结果设计制造了双腔微管直角挤出模具,并且进行了挤出成型实验。实验结果表明挤出模具非对称流道设计是合理的,证明了聚合物双腔微管直角挤出模具非对称流动平衡设计方法的正确性和有效性。 相似文献
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塑料异型材的挤出胀大及其引起的不规则挤出形变,是异型材挤出制品尺寸控制的难点所在。针对此类问题,采用有限元方法研究了典型异型材口模构型要素如T型口模分支立臂位置、90°夹角L型口模过渡区域转角、L型口模两臂夹角等对挤出形变和模流平衡的影响。结果表明,随T型口模分支立臂由挤出中心位置向右偏移,挤出后的型材挤出中心位置发生偏移,立臂顶端向右上变形,从而使得挤出形变加剧,需要在模具设计时将立臂顶端向挤出中心方向进行补偿。在90°夹角L型口模内外转角处设置过渡圆角,有助于模具出口处的模流平衡。L型异型材两臂夹角在挤出后变大,且初始设计夹角为60°和90°时变化较大,需要根据相关实验找出其初始设计夹角与挤出后的实际夹角对应关系,以便在模具设计过程中进行参照。上述研究结果对逆向挤出问题的求解、异型材挤出模具的设计和口模构型的确定有着一定的参考意义。 相似文献
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Naret Intawong Chatchawan Kantala Watit Lotaisong Narongrit Sombatsompop 《应用聚合物科学杂志》2011,120(2):1006-1016
A die‐rotating system was proposed in this work for moderations of extrusion forces and entrance pressure drop for molten polypropylene (PP) and wood/polypropylene (WPP) composites in a capillary rheometer and a single screw extruder. The effects of processing conditions and wood loading in PP were of our interests. The extrusion force and entrance pressure drop with and without the die rotating system were monitored in real‐time. This was the first time that the die‐rotating system was used for processing of highly viscous wood/polymer composite materials. It was found that the flow properties of the molten PP and WPP composites obeyed pseudoplastic non‐Newtonian behavior. The behavior was more obvious at wood contents of above 6 wt % and in the capillary rheometer. The rotation of the die could moderate the extrusion load by 60% and entrance pressure drop by 20% in the capillary rheometer, and the entrance pressure drop by 30% in the single screw extruder, especially at the conditions where the viscosities of the WPP and the extrusion rate were high. Greater fluctuations in entrance pressure drop caused by die rotation were observed in the single screw extruder. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120:1006–1016, 2011 相似文献
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A pulse pressure was superimposed on the melt flow in extrusion, called vibration extrusion. A die (L/D = 17.5) was attached to this device to study the rheological properties of an amorphous polymer (ABS) and semicrystalline polymer (PP, HDPE), prepared in the vibration field, and the conventional extrusion were studied for comparison. Results show that the melt vibration technique is an effective processing tool for improving the polymer melt flow behavior for both crystalline and amorphous polymers. The enhanced melt rheological property is also explained in terms of shear thinning criteria. Increasing with vibration frequency, extruded at constant vibration pressure amplitude, the viscosity decreases sharply, and so does when increasing vibration pressure amplitude at a constant vibrational frequency. The effect of vibrational field on melt rheological behavior depends greatly on the melt temperature, and the great decrease in viscosity is obtained at low temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5292–5296, 2006 相似文献
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塑料熔体在挤出模中的流动状态分析是挤出模设计的基础。尽管塑料异型材的成型模具种类繁多、形状各异,但都可视为圆环和孔隙的组合。分析了模头流道结构和熔体在圆环型材挤出模中的流量,为环类型材挤出模设计提供了依据。 相似文献
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塑料异型材挤出成型的流动平衡分析 总被引:2,自引:0,他引:2
介绍了一种基于横截面法和流动路径法混合的异型材挤出成型中熔体流动平衡的分析方法,可用于确定具有多个分支流道、截面复杂的异型材挤出模头出口处物料的平均流速,帮助设计者判断模头流道设计是否合理,且计算量较小,适于工程应用。 相似文献
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The aim of this work is to investigate the effect of finite element formulation and element type on the accuracy of 3D modeling of generalized Newtonian fluid flow in complex domains. Computer models based on three finite element solution schemes (mixed, continuous, and discrete penalty), and two element types (hexahedral and tetrahedral) in a 3D framework were developed. The well‐known Carreau model was used to reflect the rheological behavior of the fluid. To determine the validity of the developed computer simulations, the flow of two high‐density polyethylene (HDPE) melts with different viscosities through an extrusion die was simulated and compared with experimentally measured data. Comparison showed that the three methods produced nearly the same results with the hexahedral elements. However, continuous penalty method using tetrahedral elements demonstrated an extreme discrepancy from the experimental data. Discrete penalty method was unable to predict secondary variable (pressure) accurately using tetrahedral elements. The best results were obtained by the use of mixed method in conjunction with tetrahedral elements. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献