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结合钢塑复合共挤工艺特点,建立了复合共挤出流动的数学模型。采用有限元分析软件Ansys对钢塑复合中空异型材共挤流道内熔体的三维等温非牛顿流动进行了数值模拟;讨论了内部芯材以不同速率移动时,流道内熔体压力、速度和粘度的分布特点及变化规律,并与普通异型材挤出进行了对比。结果表明:随着芯材移动速率的提高,流道内压降减小;在熔体与芯材接触结合区域,压力和速度梯度明显增加,粘度减小,易出现不稳定流动;流道内熔体有较高的轴向速率,径向速率对称分布,其流动特征为典型的收敛流动;由于芯材在牵动,熔体最大流速出现在口模成型段,即挤出熔体与芯材的会合处。 相似文献
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塑料熔体是具有记忆性的非线性黏弹性流体,为了准确分析板材挤出模具中熔体的流动,采用了积分型本构方程描述熔体的流变行为,同时给出熔体在狭缝流道中的控制方程。根据控制方程的特殊性,提出了把有限元半解析法应用于求解黏弹性流体流动问题这一思想,从而建立了有限单元体法,同时给出求解非线性有限元方程组的迭代方法,并采用以上方法对熔体在狭缝流道中的流动进行求解分析,将结果与三维有限元解法的结果相比较,证明结果是精确的,表明采用上述方法模拟熔体在狭缝中的流动是简便可行的。 相似文献
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基于复合共挤成型原理,建立了高密度聚乙烯(PE–HD)/玻璃纤维(GF)复合共挤有限元模型,采用有限元软件Polyfl ow对流道内熔体的三维等温非牛顿流动行为进行了数值模拟,给出了GF以不同速度移动时流道内熔体压力和速度的分布特点及变化规律。根据数值模拟结果确定了挤出工艺参数,研制了共挤模具,制备了PE–HD/GF复合带,并进行了力学性能测试。结果表明,随着GF移动速度的提高,流道内压力减小,熔体在复合成型段挤出速度明显增加;GF移动速度达到一定值时熔体挤出速度均匀,移动速度过大则导致熔体速度分布不均匀。研制的PE–HD/GF复合带拉伸强度保留率可达GF的82%。 相似文献
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鱼尾型片材机头内熔体流动的三维有限元模拟 总被引:1,自引:0,他引:1
利用ANSYS和MATLAB软件,对鱼尾型片材机头流道内熔体的速度、压力和剪切应力的分布进行三维有限元模拟和分析。通过对机头流道不同截面处熔体场量分布的模拟,探知了熔体在流道内的运动规律及特点,对口模设计具有一定的指导作用。 相似文献
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螺旋芯棒机头内熔体流动的分析及其数值模拟 总被引:2,自引:0,他引:2
本文对吹膜用螺旋芯棒机头内的熔体流动进行了非等温分析,建立了描述与温度相关的幂律熔体在机头内流动的数学模型,并给出了一套完整的数值分析和计算方法。为了度量熔体沿螺旋分流器园周各点的流动均匀性,我们提出了两个定量参数:(1)轴向纯漏流的分布均匀度 U;(2)螺旋流道未端的螺旋余流 Q_(3av)(x_(jo))。 相似文献
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Maxwellian fluid flow between asymmetric calenders was analyzed by the numerical solution to the simplified equations of motion
and energy equation. The solution techniques combined the power-law weighted upwind difference method for the energy equation
with the analytical solution of the momentum equations. The calculated results provided not only pressure and temperature
distributions of the flow field, but also the power consumption and the roll separating force of the calendering processes.
The decrease in the elastic shear modulus led to the reduction in the temperature profile as well as in the power requirement.
The asymmetry in the roll speeds generated higher temperature field throughout the whole flow region due to the higher viscous
heating, compared with the case of the symmetry in the roll speeds. 相似文献
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The extrusion head systems for both pipe and blow molding were analyzed theoretically and relationships derived between pressure drop and temperature rise for various materials at different flow rates and die restrictions. Because of the complexity of the geometry involved, the die was segmented into several sections axially and momentum and energy equations for these sections were solved with the help of IBM 360. The floating boundary conditions were used in order to take into account the nature of the flow phenomenon involved. To complement and support this theoretical work, rigid polyvinyl chloride (PVC) bottle compounds were used to obtain extrusion data on a 3½ inch extruder with several different die sizes. A good agreement was found between the predicted versus experimental data. Results showed that temperature rise in the die systems in significant and that neglecting it would result in a gross error in the calculated pressure drop. Based on this work, a simplified version of the theoretical equation was developed to serve as an engineering tool in estimating pressure drop and stock temperature for a given material where extreme accuracy is not essential. Results of the engineering equation which contains several empirical constants correlate well with the data and support the theoretical effort. 相似文献
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A fully-predictive steady-state computer model has been developed for a single-screw plasticating extruder. Included in the model are a model for solids flow in the feed hopper; a variation of the Darnell and Mol model for the solids conveying zone; a variation of Tadmor's melting model for the melting zone; an implicit finite difference solution of the mass, momentum, and energy conservation equations for the melt-conveying zone of the extruder and die; and a predictive correlation for the extrudate swell at the die exit. A temperature- and shear-rate-dependent viscosity equation is used to describe the melt-flow behavior in the model. The parameters in the viscosity equation are obtained by applying regression analysis to Instron capillary rheometer data. Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions, the following are predicted: flow rate of the polymer, pressure and temperature profiles along the extruder screw channel and in the die, and extrudate swell at the die exit. The predictions have been confirmed with experimental results from a 11/2 in. (38 mm) diameter, 24:1 L/D single-screw extruder with a 3/16 in. (4.76 mm) diameter cylindrical red die. High- and low-density polyethylene resins were used. 相似文献
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对已有的螺旋流道辊模型进行合理简化,运用流场仿真软件Fluent对流道辊的温度场进行了仿真分析,得到了流道辊的温度场,从而得到了流道辊内流体速率、流体温度场、辊筒表面温度场等。通过分析模拟仿真结果,得到了辊筒外表面温度不均匀的原因,并在此基础上,以提高辊筒外表面的温度分布均匀性为目标,对流道结构进行多次改进,找出一种最佳方案,明显改善了辊筒端部的温度分布均匀性,使辊面的有效利用长度延长了约50 mm。 相似文献
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D. Sharma T. A. McCarty J. A. Roux J. G. Vaughan 《Polymer Engineering and Science》1998,38(10):1611-1622
Fluid mechanics plays an important role in many manufacturing processes including the pultrusion of composite materials. The analysis of fluid mechanics problems generally involves determination of quantities such as pressure and velocity. During the pultrusion process, the short, tapered inlet region of the pultrusion die experiences a significant amount of fluid resin pressure rise. The quality of a pultruded product can be affected by the amount of pressure rise in the pultrusion die inlet. Void formation can be suppressed and good fiber “wet out” achieved by a sufficiently high pressure rise in the pultrusion die inlet region. In this study the change in fluid resin pressure rise as a function of die entrance geometry is investigated by developing a finite element model based on the assumptions of Darcy's law for flow in porous media. The momentum equations are combined with the continuity equation to save computational time and memory. A Galerkin weighted residual based finite element method is developed to solve the resulting equation. This model is capable of predicting the pressure rise in the tapered inlet region of the pultrusion die as well as the straight portion of the die. By varying the size of the preform plates the thickness of the fiber/resin matrix approaching the die inlet can be varied. The finite element model predicts the impact of changing the preform plate size on the fluid resin pressure rise in the pultrusion die. The effect of varying the wedge angle for a linearly tapered die inlet region is also studied using this model. The results in this work can be useful for designing a pultrusion die system. 相似文献
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简要阐述了径向流固定床反应器在化学工程中的重要性及研究该类流动问题的迫切性,回顾了文献中描述该反应器中流体流动的六类数学模型,提出了设计准则及均布措施,指出了存在的问题及解决的途径. 相似文献