COOLING AND SOLIDIFICATION IN THE PRESENCE OF RECIPROCATING NON-NEWTONIAN SHEAR FLOW: THE LIVE FEED INJECTION MOULDING PROCESS

The cooling and solidification of a non-Newtonian material in the presence of reciprocating flow is analysed. Finite difference solutions are obtained for a transient I-space-dimensional model of a shear thinning material with temperature dependent properties, contained between plane parallel surfaces to which it looses heat by conduction in the presence of periodically reversing flow. This situation is relevant to live feed injection moulding - an advanced technology for thermoplastics processing - in which alternating direction shear is imposed on melt in the mould cavity during the holding and packing stages. Interest centres on the effects of flow on cooling and solidification and the development of frozen-in strains, which have important implications for the control of material alignment and mechanical properties of mouldings. The governing dimensionless parameters are identified and their influence investigated in a series of numerical simulations, where the parameters range over the following values: Pearson number 0.5–5.0; Brinkman number 0.001–1.0; Stefan number 0.1 – 1.0; Power Law Index 0.2–1.0; dimensionless flow reversal time 0.01–1.0. Two operating modes are considered: (1) fixed applied pressure gradient, with a falling flow rate; (2) flow rate initially fixed, followed by a falling flow rate period at a fixed limiting pressure gradient. In mode 1 operation viscous heating does not significantly influence cooling rates, but in mode 2, for high Brinkman numbers, a dynamic equilibrium temperature field can be attained. Complex profiles of frozen-in material strain through the thickness of the moulding are predicted. In mode 1 operation the magnitude of the principle stretch rises to a peak close to the mould walls, and falls in a series of oscillations to unity (zero deformation) on the centre plane. High values of the Pearson number or low values of the Power Law Index damp these oscillations. In mode 2 operation sharply alternating regions of high and low strain are obtained indicating a structure with alternating layers of high and low material orientation.     

尼龙11的注射成型与挤出成型技术

介绍尼龙１１的注射成型和挤出成型工艺,并讨论了生产中易出现的问题及其解决办法。     

CAE技术在塑料注塑中的应用和发展

介绍了计算机辅助工程 (ComputerAidedEngineering ,简称CAE)技术在塑料注塑和注塑模具设计中的发展 ,以及国内外的应用现状及趋势。     

注射成型制品缺陷及其对策研究

研究了注射成型参数的效应,利用传热、传动、传质的原理,分析了制品缺陷及其产生的原因,以及消除质量缺陷的三种方法。     

PP注射成型中的压力及熔体流动过程

讨论了聚丙烯在注射成型中充模、增密、保压、冷却各个阶段的压力变化情况和熔体流动过程，以及二者对制品成功质量的影响。认为在聚丙烯注射成型过程中，要保证制品成型质量，不应以升温的办法来降低熔体的粘度，而应以提高注塑压力和剪切速率为主。     

BLASIUS AND SAKIADIS FLOW WITH UNIFORM BLOWING OR SUCTION IN NON-NEWTONIAN POWER-LAW FLUIDS

The Blasius and Sakiadis flows of a non-Newtonian power-law fluid are considered. The plate is porous and fluid can be either injected or sucked through it. The boundary layer equations are transformed into a nondimensional form and are solved with a finite difference method. For the case of uniform suction, new results have been found, although this problem has been investigated in the past. Among them are analytical solutions for dilatant fluids of the Blasius flow and analytical solutions of the Sakiadis flow for all values of the power-law index. For the case of uniform injection, the characteristics of the flow until a separation state are investigated and discussed.     

充模过程Fountain区的流动分析

提出了一种研究和分析注塑充模过程中Fountain(喷泉)区流动的方法,得到充模过程的流线图、速度分布和压力分布的图形,从而使得充模过程数值化,对确定工艺条件和提高产品的产量和质量都有实际意义。     

我国首台数码光盘精密注塑机的研制

研制了我国首台数码光盘精密注塑机,针对数码光盘生产对精密注塑机的高速、超精密、高洁净度的要求,提出了精密注塑机必须满足的技术指标要求,在对精密注塑机结构分析的基础上,加强了研制过程的质量控制,解决了一系列技术难题;并阐述了数码光盘精密注塑机研制成功的意义。     

注塑用聚氯乙烯干混粉料流变性能的研究

用国产注塑机直接采用聚氯乙烯(PVC)干混粉料注塑硬质聚氯乙烯(RPVC)管件是一个新课题。本文着重介绍在美国哈克(HAAKE)EU-5型转矩流变仪上筛选配方,对PVC干混粉料在加强稳定化、阻止热分解、改善加工性能和实现内外润滑的平衡等方面,进行初步探讨;同时结合生产实践,阐述了干混粉料的制备,机筒模具温度、塑化注塑压力等工艺全过程的控制条件,以及注塑管件在出现缺陷时的解决办法。     

炭-石墨制品冷模压及模具设计

对炭—石墨制品冷模压工艺和模具设计进行了简要介绍，并对炭—石墨制品冷模压的成型原理、压制过程、压制时的注意事项、压机的选择、成型、模具的结构、设计计算方法及模具的材料选择进行了探讨。     

变频器在注塑机调速系统中的节能分析及应用

运用变频器对注塑机进行节能改造设计,采用比例流量、比例压力信号动态控制变频器的输出频率,从而控制油泵电机的转速,实现变压节能。设计了变频器外部接口电路,进行了变频器参数设定和机电联调。经改造的注塑机系统的精度和稳定性极大提高,操作方便,节能效果明显,产生了显著的经济效益和社会效益。     

注塑级PVC／ABS合金的性能及其加工

阐述了注塑用聚氯乙烯/丙烯腈-丁二烯-苯乙烯共聚物(PVC/ABS)合金的制备工艺以及合金组成与冲击强度和屈服应力的关系,分析了影响注塑工艺条件的因素,并对体系的热稳定性和流变特性及其影响因素也作了简要的论述。     

EFFECT OF COOLING RATES ON SEGREGATION AND DENSITY VARIATION IN THE MUSHY ZONE DURING SOLIDIFICATION OF SUPERALLOY INCONEL 718

The microstructure and segregation of experimental samples of the superalloy Inconel 718 solidified at different cooling rates have been investigated by SEM and EDAX. The equilibrium phase fraction diagrams of Inconel 718 and the segregated liquid composition were calculated by Thermo-Calc. The experimental and calculated results were in good agreement with those of an Inconel 718 ingot, and they indicated that, at a cooling rate less than 3°C/min, heavy Nb and Mo segregation resulted in Laves phase formation directly from the liquid. The density of the liquid surrounding the Laves phase decreased and the region between the two Laves precipitates (inter-precipitate) often had the lowest density. A density difference (or micro inter-precipitate density inversion) existed between the inter-precipitate liquid and the original liquid at the same or higher temperatures where there were no liquid-precipitated Laves.     

FLOW OF A NON-NEWTONIAN FLUID WITH HEAT TRANSFER ABOVE A ROTATING DISK CONSIDERING THE ION SLIP

The steady flow and heat transfer of a conducting non-Newtonian fluid due to the rotation of an infinite nonconducting disk in the presence of an axial uniform steady magnetic field are studied considering the ion slip. The governing nonlinear equations are solved numerically using finite differences, and the solution shows that the ion slip and the non-Newtonian fluid characteristics give some interesting results.     

FLOW OF A NON-NEWTONIAN FLUID WITH HEAT TRANSFER ABOVE A ROTATING DISK CONSIDERING THE ION SLIP

The steady flow and heat transfer of a conducting non-Newtonian fluid due to the rotation of an infinite nonconducting disk in the presence of an axial uniform steady magnetic field are studied considering the ion slip. The governing nonlinear equations are solved numerically using finite differences, and the solution shows that the ion slip and the non-Newtonian fluid characteristics give some interesting results.     

SiCW／Si3N4复相陶瓷注射成型的流变特性与动态过程

对以热塑性树脂和石蜡为主要结合剂，ＳｉＣ晶须含量为０￣２０％（ｖｏｌ）的ＳｉＣＷ／Ｓｉ３Ｎ４复相陶瓷混合物料注射熔体的流变特性进行了研究。实验发现：该体系的流变模型为非牛顿假塑性体，具有剪切变稀特征；其本构方程满足幂律函数：τ＝ｋγ＾ｎ；并在较高剪切速率下（在实际陶瓷注射成型范围内１００￣１０００ｓ＾－１），ＳｉＣ晶须的引入对注射熔体表观粘度影响较小。本文同时对体积比为１５：８５的ＳｉＣＷ／Ｓｉ３     

陶瓷粉末注射成型计算机模拟研究与应用

本文介绍了计算机模拟软件在陶瓷粉末注射成型工艺中的应用现状,举例说明了C-Mold软件在陶瓷粉末注射成形工艺模拟薄体半球的填充,并与实验的实际情况做比较,以探讨陶瓷材料在充填过程中的现象。     

多型腔注塑模的流动平衡计算与分析

给出一种基于流动模拟的多型腔注塑模流动平衡计算方法,在流道和型腔布置确定后,根据流动模拟的结果,通过迭代调整流道和浇口尺寸,自动实现非平衡布置多型腔注塑模的流动平衡。利用数值模拟试验研究了注射时间、料温和模温等成型条件变化对流动平衡的影响,结果表明,注射时间的变化对流动平衡有显著影响。     

A SIMPLE MODEL FOR PREDICTING THE VOID FRACTION OF GAS/NON-NEWTONIAN FLUID INTERMITTENT FLOWS IN UPWARD INCLINED PIPES

In this work, a simple correlation, which incorporates the mixture velocity, drift velocity, and the correction factor of Farooqi and Richardson, was proposed to predict the void fraction of gas/non-Newtonian intermittent flow in upward inclined pipes. The correlation was based on 352 data points covering a wide range of flow rates for different CMC solutions at diverse angles. A good agreement was obtained between the predicted and experimental results. These results substantiated the general validity of the model presented for gas/non-Newtonian two-phase intermittent flows.     

THE ROLE OF NATURAL CONVECTION DURING MELTING AND SOLIDIFICATION OF PCM IN A VERTICAL CYLINDER

Measurements of heat transfer during melting and solidfkation of n-eicosane and rt-hexadecane were performed in vertical cylinders with two different lengths and diameters. Radial temperature distibutions were measured with lime at different heights in all the tests. To evaluate the rate of heat charged and discharged from the cylinder at different heights, the data were recorded and processed directly usinj; on-line computer. A theoretical model was developed based on solving the one-dimensional unsteady heat conduction equation in both phases. Convection in the liquid was included using an effective thermal conductivity; a lumped parameter that includes also the effect of the two-dimensional heat transfer during melting. The model, which may be used for the prediction of both melting and solidfkation experiments, takes into account the effect of initial subcooling or superheating and includes the heat capacity of the cylinder containing the PCM. The agreement of the model was good not only with the experimental results of this work, but also with the published work of the others.