塑料挤出吹塑中型坯成型模拟采用的本构方程

型坯成型是塑料挤出吹塑中的一个重要阶段。对型坯成型阶段的数值模拟可分为两种方法：一种是将型坯机头内的聚合物熔体看作牛顿流体，另一种是将其看作粘弹性流体。在对粘弹性流体进行分析时，用到了微分型和积分型的本构方程，对此进行了较系统的介绍。     

挤出吹塑中型坯成型的神经网络模型的选取

型坯成型是挤出吹塑中的一个重要阶段,人工神经网络是一门新兴交叉科学.本文用几种不同的神经网络模型预测了挤出吹塑中型坯成型时的直径膨胀率,选取其中精度和效率均较高的模型,以用于下一步用神经网络来预测型坯成型时的壁厚膨胀率和最终制品的壁厚分布.     

注射吹塑成型设备及工艺

<正> 一、前言同挤出吹塑成型加工一样,注射吹塑成型也是生产中空塑料容器的一种两步成型方法。但它又完全不同于挤吹成型,生产过程中,由注射机将熔融物料在高压下注入注塑膜内形成特定的型坯,注塑模开模后型坯保留在芯棒体上,然后在一定温度下,通过机械传动将型坯置入吹塑模     

三大类吹塑成型

<正> 注射吹塑是一种双工位加工工艺,用以制得质量完全好的塑料容器。在第一工位,将塑料注入预成型模腔,制得型坯。塑料被注入成孔销周围和预成型模腔中,就形成容器的颈部和型坯的形状。型坯的     

挤出吹塑实验研究进展

对挤出吹塑过程的三个阶段：型坯成型、型坯吹胀以及制品冷却与固化阶段的实验方法和装置的研究现状进行了详细论述。     

塑料挤出吹塑的机理问题

采用不同的方法对挤出吹塑过程的型坯成型、型坯吹胀与制品冷却三阶段的机理问题进行了研究.采用人工神经网络方法预测了受模口温度和挤出流率影响的型坯成型阶段的膨胀.利用建立起来的神经网络模型预示的膨胀与实验结果很吻合,且可在一定范围内,预示不同工艺条件下型坯的直径膨胀和壁厚膨胀,为型坯的直径和壁厚的在线控制提供了理论依据.基于薄膜近似和neo-Hookean本构关系,建立了描述型坯自由吹胀的数学模型,并通过实验方法获得了型坯吹胀的瞬态图象.     

吨包装内胆挤出吹塑成型型坯吹胀的数值模拟

针对吨包装内胆挤出吹塑型坯吹胀阶段的成型工艺,采用Workbench-Polyflow分析软件实现型坯吹胀模拟。建立型坯及模具的几何模型和网格模型;利用Polyflow中的参数渐进方法建立型坯吹胀阶段中的模具闭合运动模型。获得型坯在吹胀过程中的型坯轮廓曲线分布以及吹胀完毕后的型坯壁厚分布;分析了模具运动速度和吹胀压力对型坯与模具的接触时间、吹胀时间及壁厚的影响。     

塑性和粉末成型在陶瓷工业中的应用

一、引言坯料的可塑性已广泛地应用于成熟的滚压成型工艺,以及塑性压坯成型或模压法工艺中。滚压成型是用来制造平盘餐具和简单的空心器物;塑性压坯成型是用来制造多种式样的盘碟和杯碗;粉末压坯成型是一种比较新的生产餐具的工艺,它是在相当高的压力下将经过喷雾干燥后的粉粒成坯。从粉粒的聚结和变形的意义上来讲,粉末压坯是一种塑性流动,而不是在传统塑性压坯中所发     

吹塑成型CAE技术研究与应用现状分析

吹塑成型是成型中空塑料制品的主要成型方法,其成型过程包括型坯成型、型坯吹胀和制品的冷却固化三个阶段。中空制品的吹型成型质量受各种工艺因素的影响,包括熔融温度、吹胀压力、拉仲速率、冷却时间、聚合物材料柱能等。吹塑成型数值模拟可预测制品的壁厚均匀性,残余应力和收缩状况等,指导吹塑成型模具的优化设计,并通过优化工艺参数获得最佳性能的吹塑制品。本文对吹塑成型CAE技术的发展状况进行了详细研究,并对其应用现状作了简单分析。     

中空吹塑成型过程数值分析技术的进展

论文对塑料中空吹塑成型过程数值分析的研究和发展状况进行了全面的阐述，针对成型过程的三个阶段：型坯形成，型坯吹胀以及冷却与固化阶段因内外研究者进行数值分析的具体谅才理论依据进行了较详细的论述，并指出毛坯熔融挤出，吹胀成型、冷却和固化是成型周期中紧密衔接的三个过程，目前对各个阶段分别进行研究的较多，而综合考虑气压、温度、冷却时间、高分子材料性能等因素对全过程进行数值模拟的较少见报道，因此还有许多研究工     

Melt‐spun hollow fibers: Modeling and experiments

Polypropylene hollow fibers were prepared via melt spinning at speeds of 1000–2500 m/min. The outside diameters of the fibers were measured on‐line with high‐speed photography. The fiber formation process was modeled with momentum, energy, and two continuity equations (one for the polymer, and one for the lumen fluid). The equations were solved numerically, and the results were compared to the on‐line diameter data. Both Newtonian and viscoelastic constitutive equations were considered.     

Processability and properties of novel glass-polymer melt blends

Dynamic mechanical analysis was used to study the viscoelastic properties of two novel highly filled phosphate glass-polymer melt blends to accelerate efforts to optimize their melt processing. The melt of one blend was thermally stable while that of the other blend was not, as evidenced by modulus growth over time of the latter. The frequency dependencies of storage and loss moduli for both blends at 400°C showed evidence of incomplete relaxation. Recrystallization, formation of some fibrillar structures within the polymer phase during flow, transesterification of the polymer phase, or interactions between the polymer and glass are thought to be responsible for the observed differences between the viscoelastic properties of the two blends.     

混炼机横截面PP熔体液滴分散过程的数值模拟研究

对Fluent进行二次开发,通过用户自定义函数,将黏弹性流体的动量方程和变形张量输运方程加载到Fluent中,从而实现了对聚合物黏弹性流体流动的模拟。采用VOF界面追踪方法,对聚合物熔体中的单个液滴在混炼机横截面流场作用下发生的变形、破碎行为和二次团聚过程进行了分析研究。探讨了液滴在混炼腔复杂流场中的分散过程和微观结构的形成机理,对揭示共混改性过程中分散相织态结构发展演变过程和机理具有指导意义。结果表明,PP液滴在混炼过程中经历了变形、破碎、聚并过程;PP液滴在C形区发生了不均匀变形行为,在相互作用窗混沌流场下发生了拉伸、挤压、交叉行为;PP液滴的破碎行为包括毛细不稳破碎、末端夹断以及在螺棱背风面的松弛破碎。     

数值模拟黏弹流体通过椭圆环模具的挤出胀大

The numerical simulation of extrudate swell is significant in extrusion processing.Precise prediction of extrudate swell is propitious to the control of melt flow and the quality of final products.A mathematical model of three-dimensional(3D)viscoelastic flow through elliptical ring die for polymer extrusion was investigated.The penalty function formulation of viscoelastic incompressible fluid was introduced to the finite element model to analyze 3D extrusion problem.The discrete elastic viscous split stress(DEVSS)and streamline-upwind PetrovGalerkin(SUPG)technology were used to obtain stable simulation results.Free surface was updated by updating the streamlines which needs less memory space.According to numerical simulation results,the effect of zero-shear viscosity and elongation parameter on extrudate swell was slight,but with the increase of volumetric flow rate and relax time the extrudate swell ratio increased markedly.Finally,the numerical simulation of extrudate swell flow for low-density polyethylene(LDPE)melts was investigated and the results agreed well with others’work.These conclusions provided quantitative basis for the forecasting extrudate swell ratio and the controlling of extrusion productivity shape.     

Instabilities and failure in elongational flow and melt spinning of fibers

A theoretical and experimental study of instability and failure behavior during melt spinning is presented. From an analysis of system dynamics, draw resonance is shown to be a continuous processing analogue of ductile failure. Using viscoelastic fluid mechanics and the White-Metzner constitutive model, it is shown that melts which exhibit ductile failure in elongational flow tend to show draw resonance in melt spinning. Deformation hardening melts exhibit cohesive fracture in elongational flow and melt-spinning processes.     

Effect of process conditions on birefringence development in injection-molded parts. I. Numerical analysis

Analysis of the injection-molding process based on Leonov viscoelastic fluid model has been employed to study the effects of process conditions on the residual stress and birefringence development in injection-molded parts during the entire molding process. An integrated formulation was derived and numerically implemented to solve the nonisothermal, compressible, and viscoelastic nature of polymer melt flow. Simulations under process conditions of different melt temperatures, mold temperatures, filling speeds, and packing pressures are performed to predict the birefringence variation in both gapwise and planar direction. It has been found that melt temperature and the associated frozen layer thickness are the dominant factors that determine the birefringence development within the molded part. For a higher mold temperature, melt temperature, and injection speed, the averaged birefringence along gapwise direction is lower. The birefringence also increases significantly with the increased packing pressure especially along gate area. The simulated results show good consistency with those measured experimentally. © 1995 John Wiley & Sons, Inc.     

Evaluation of typical rheological models fitting for polycarbonate squeeze flow

High viscous polycarbonate melt exhibits some special rheological characters different from generalized Newtonian fluid during squeezing. It is necessary to evaluate whether the typical rheological models are suitable for polycarbonate squeeze. To avoid the difficult of measuring the inner melt rheological behavior directly, this study presents a method of measuring the compressing force applied on the upper disc of the rheometer to reveal the melt rheology indirectly. The finite difference method (FDM) was employed to discretize the governing equations and constitutive equations established on cylinder coordinate system and to simulate the compressing force. The experiments were carried out under four temperatures and three compressing velocities to test the validations of Leonov, Phan‐Thien–Tanner (PTT), eXtended Pom‐Pom (XPP), and Cross Williams‐Landel‐Ferry (Cross‐WLF) models. The experimental results show the unique character of compressing force evolution as ‘steep—steady—steep—steady’ pattern. Comparison between experiments and simulations reveals that both viscoelastic and viscous models can predict the two steady regions correctly, but only viscoelastic models can simulate the steep increase and decrease of the compressing force. Among the evaluated viscoelastic models, XPP is the most suitable to describe polycarbonate melt compression flow. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42279.     

Numerical approach to modeling fiber motion during melt blowing

Melt blowing involves applying a jet of hot air to an extruding polymer melt and drawing the polymer stream into microfibers. This study deals with the dynamic modeling of the instabilities and related processes during melt blowing. A bead‐viscoelastic element model for fiber formation simulation in the melt blowing process was proposed. Mixed Euler‐Lagrange approach was adopted to derive the governing equations for modeling the fiber motion as it is being formed below a melt‐blowing die. The three‐dimensional paths of the fiber whipping in the melt blowing process were calculated. Predicted parameters include fiber diameter, fiber temperature, fiber stress, fiber velocity, and the amplitude of fiber whipping. The mathematical model provides a clear understanding on the mechanism of the formation of microfibers during melt blowing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Significance of deformation rate softening of memory in viscoelastic fluid mechanics and polymer processing

It is pointed out that in viscoelastic fluid constitutive equations, non-linear response to deformation rate and strain beyond the second order is usually interpreted in terms of the deformation rate or strain dependence of the memory function. These non-linearities act to decrease the extent of the memory. The dependence may be characterized by one or more dimensionless material parameters. A new dimensionless group based on the primary material parameters describing the intensity of the deformation rate dependence of the memory function is introduced and its significance is discussed. This is called the Yamamoto number. The solutions of viscoelastic fluid mechanics problems are considered to depend upon both the Weissenberg and Yamamoto numbers. Such problems include topics of interest in polymer melt processing such as uniaxial elouigatioiial flow, fiber spinning and vortex development in extrusion through a die entry.