塑料异型材挤出模头稳定性设计的数值方法

根据挤出模头设计的最小横向流动理论，运用ANSYS有限元分析软件，模拟分析了两副模头分流段流道的三维非牛顿流场，讨论了分流段流道设计对模头稳定挤出的影响；指出分流段流道设计满足流动平衡条件时，流道横向流动最小，模头的稳定性能较好；并通过两副实际使用的挤出模具，验证了理论分析与实际的一致性，从而给出了塑料异型材挤出模头稳定性设计的数值方法。     

不等壁厚塑料异型材挤出模头稳定性的研究

针对塑料门窗发展中对不等壁厚异型材的需要,通过对不同结构的不等壁厚流道中熔体流动过程的数值模拟,展现出流道结构设计对模头挤出稳定性的影响,指出了合理的阻流块设计是对模头挤出稳定性更有利的出口平均流速调节方法,为不等壁厚异型材挤出模头的合理设计提供了依据。     

圆环型材挤出模塑料熔体流量分析与结构设计

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。     

异型材挤出模头压力降的数值计算

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。     

异型材挤出模头压力降的数值计算

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。     

应用Flow 2000软件分析功能块成型结构的设计

利用Flow 2000软件，从3个方面对塑料异型材挤出模头中功能块成型结构的设计进行了分析，即进行部分功能块的结构改进、流道中功能块局部流速过慢的处理、流道中功能块局部流速过快的处理。从而确保成型区上功能块的流道截面图形设计及平直段长度的设计满足挤出模头流道设计的基本要求，提高了挤出模具的设计水平，缩小了与国外设计上的差距。     

塑料异型材挤出模具中内筋的口模流道设计

本文结合数百套塑料异型材挤出模具设计经验,简述了在不同挤出速度下,塑料异型材挤出模具中的支撑型内筋、板材型内筋、突出物加强筋、十字花型内筋的模头流道结构和供料方式的设计和选择。     

塑料挤出模头设计简析

挤出模是异型材挤出生产中的关键设备之一。挤出模主要由挤出模头和定型模组成，异型材挤出模头的主要功能就是将挤出机挤出的熔融塑料流束改变成截面近似于所需异型材截面的料坯。因此，在成型机组中，挤出机的挤出模头是非常重要的，它决定了型材的形状和型材制品质量的好坏，是挤出模设计中重点考虑问题之一。     

塑料异型材挤出口模设计的数值模拟概述

从挤出口模设计原则出发,综述了数值模拟技术在塑料异型材口模流道的曲面构型,入口角和压缩比、降低或消除挤出胀大和挤出口模成型段的设计、熔体流动平衡和压力降的研究进展,以及口模设计的发展趋势.     

隔热条异型材挤出模具设计

通过对隔热条异型材截面形状及原材料挤出成型性能的分析,设计了异型材挤出口模形状、流线形流道及挤出模具结构。经实践证明,该模具口模形状及尺寸设计正确,流线形流道设计合理,能生产出满足尺寸精度要求的隔热条异型材。     

片膜挤出机头结构设计探讨

基于物料在片膜机头中均质流动的原则，考虑了物料分配和压力稳定作用，对片膜机头的流道结构、歧管类型、阻流调节机构及溢缝现象进行了探讨。     

Experimental studies on extrudate swell behavior of PS and LLDPE melts in single and dual capillary dies

Extrudate swell behavior of polystyrene (PS) and linear low‐density polyethylene (LLDPE) melts was investigated using a constant shear rate capillary rheometer. Two capillary dies with different design configurations were used, one being a single flow channel and the other being a dual flow channel. A number of extrudate swell related parameters were examined, and used to explain the discrepancies in the extrudate swell results obtained from the single and dual flow channel dies, the parameters including output rate and output rate ratio, power law index, wall shear rate, wall shear stress, melt residence time, pressure drop induced temperature rise, flow channel position relative to the barrel centerline, and the flow patterns. It was found in this work that the power law index (n value) was the main parameter to determine the output rate ratio and the extrudate swell between the large and small holes for the dual flow channel die: the greater the n value the lower the output rate ratio and thus decreased extrudate swell ratio. The differences in the extrudate swell ratio and flow properties for PS and LLDPE melts resulted from the output rate ratio and the molecular chain structure, respectively. The extrudate swell was observed to increase with wall shear rate. The discrepancies in the extrudate swell results from single and dual dies for a given shear rate were caused by differences in the flow patterns in the barrel and die, and the change in the melt velocities flowing from the barrel and in the die to the die exit. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1713–1722, 2003     

A new design procedure for profile extrusion dies

A new design procedure for complex profile extrusion dies is presented. This method applies to multiple channel dies, i.e. dies provided with melt flow independent channels in the land. The approach is based on the resolution of the flow inverse problem, which consists of finding the channel topology (channel land lengths, approach angles in the transition region), which gives a balanced flow at the die orifice from the knowledge of the die contour. The methodology uses a blend of the network approach and the cross-section method. The procedure is used to design an industrial die that has been tested in a manufacturing environment, showing the performance of the proposed approach.     

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

This study was devoted to the effect of extensional flow during film extrusion on the formation of the β‐crystalline phase and on the piezoelectric properties of the extruded poly(vinylidine fluoride) (PVDF) films after cold drawing. The PVDF films were extruded at different draw ratios with two different dies, a conventional slit die and a two‐channel die, of which the latter was capable of applying high extensional flow to the PVDF melt. The PVDF films prepared with the two‐channel die were drawn at different temperatures, strain rates, and strains. The optimum stretching conditions for the achievement of the maximum β‐phase content were determined as follows: temperature = 90°C, strain = 500%, and strain rate = 0.083 s^?1. The samples prepared from the dies were then drawn under optimum stretching conditions, and their β‐phase content and piezoelectric strain coefficient (d₃₃) values were compared at equal draw ratios. Measured by the Fourier transform infrared technique, a maximum of 82% β‐phase content was obtained for the samples prepared with the two‐channel die, which was 7% higher than that of the samples prepared by the slit die. The d₃₃ value of the two‐channel die was 35 pC/N, which was also 5 pC/N higher than that of the samples prepared with the slit die. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

挤塑过程熔体流动的数值模拟

通过对挤出过程不可压缩粘弹性熔体流动的数值模拟、求出速度场、温度场、压力场以及膨胀比,有利于确定挤塑过程的工艺条件和口模尺寸。     

芯棒式机头流道形状参数优化

以流道间隙处熔体体积均匀变化为条件，对芯棒式机头的流道形状曲线参数进行分析优化，并且对几种机头导出了一套数学模型     

衣架式机头口模设计公式的修正探讨

基于表征值方法和熔体等压线平行于模唇这一流动模型,对衣架式机头口模进行了流动分析,并发现了文献[1]提出的口模设计公式中的一个缺陷,即计算的扇形狭缝区域与歧管发生了分离,针对该缺陷给出了修正公式。     

A finite piece method for simulating polymer melt flows in extrusion sheet dies

A finite piece method is proposed to simulate three‐dimensional slit flows in extrusion sheet dies in this paper. The simulations concern incompressible fluids obeying different constitutive equations: generalized Newtonian (Carreau‐Yasuda law), and viscoelastic Phan‐Thien Tanner (PTT) models. Numerical simulations are carried out for the isothermal and nonisothermal flows of polymer melt through sheet dies. The Picard iteration method is utilized to solve nonlinear equations. The results of the finite piece method are compared with the three‐dimensional (3D) finite element method (FEM) simulation and experiments. At the die exit, the relative error of the volumetric flow between the finite piece method and the 3D FEM is below 1.2%. The discrepancy of the pressure distributions does not exceed 6%. The Maximum error of the uniformity index between the simulations and experiments is about 2.3%. It shows that the solution accuracy of the finite piece method is excellent, and a substantial amount of computing time and memory requirement can be saved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012