Numerical simulation of the filling stage in injection molding based on a 3D model

Most injection molded parts are three-dimensional, with complex geometrical configurations and thick/thin wall sections. The change of the thickness of parts has significant influence on flow during injection molding. This paper presents a 3D finite element model to deal with the three-dimensional flow, which can more accurately predict the filling process than a 2. 5D model. In this model, equal-order velocity-pressure interpolation method is successfully employed and the relation between velocity and pressure is obtained from the discretized momentum equation in order to derive the pressure equation. A 3D control volume scheme is employed to track the flow front. The validity of the model has been tested through the analysis of the flow in a cavity.     

Numerical Simulation of Phenolic Sheet Molding Compound in Compression Molding

1　IntroductionPhenolicsheetmoldingcompound (SMC)isanewindustrialproductwithahighperformancethathasbeenknownformanyyearsforitsexcellentfireresistanceandrelativelylowcost.Theseoutstandingpropertieshaveledittobeingwidelyusedinmanyindustrialdepartments ,suchasbuildingandtransportationdepartments ,etc .Es peciallyinrecentyears ,withtheeverdevelopingdemandoffireresistantmaterials ,thestudyandapplicationofthephenolicsheetmoldingcompoundhavereceivedmoreandmoreattentionintheworld .Thenumericalsimula…     

微构件的热注射近净成型控制

首先建立了微构件的热注射近净成型的数学模型,讨论了参数变量的控制。通过数据分析找到了参数的最佳控制范围,达到微构件的热注射近净成型过程中效率高、损失小的实验目标。     

撞击式冲击阀气冲造型过程的数值模拟

气冲紧实是一个复杂的动态过程，动态参数多，而冲击阀又增加了一个碰撞的过程，所以设计计算更加困难.实际建造试验装置要花费大量的人力、物力和时间，另外试验装置往往与实际系统有差距，带来一定的盲目性和局限性.为快速而经济地求得动态参数值，建立了数学模型，通过VC++语言，采用四阶龙格-库塔方法对气冲过程进行数值模拟，得到动态过程的模拟曲线，将模拟曲线与实验曲线进行对比，进一步验证模型的准确性及程序的正确性.     

基于正交试验法的注塑工艺多目标优化设计

结合正交试验法和注塑模拟分析软件Moldflow,对不同工艺条件下的塑件成型过程进行模拟分析,运用模糊数学中的综合评判法,对塑件成型后的体积收缩率、表面沉降指数和最大翘曲量三个目标值进行综合评判,确定综合目标值.通过对综合目标值的极差分析,确定模具温度、充填参数、保压参数、浇口位置、冷却形式等注塑工艺参数对综合目标值的影响程度的大小,并通过绘制因素水平影响趋势图,分析得出最优的注塑工艺参数组合方案,并对该工艺组合方案进行模拟验证.     

Fabrication of micro gear wheels by micropowder injection molding

The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 μm and with the center hole as small as 60 μm.     

气辅成型中气道形状和尺寸对气指缺陷的影响

研究了气体辅助注射成型制品中不同半径的半圆形气道、不同宽高比的矩形气道以及4种截面形状不同,但截面面积相同的气道对聚苯乙烯材质气辅制品的气指缺陷的影响。结果表明:对于半圆形气道,当量半径与板厚比在某一数值范围时,气指的程度最小;当矩形气道宽高比为某一确定值时,气指程度较为严重。对于4个不同截面形状的气道设计,带有肋板的气道设计比不带肋板的气道设计制品气指程度有所减轻。     

有限元数值模拟技术在汽车冲压件成形中的应用

板料冲压成形作为一种重要的塑性加工工艺,广泛应用于各种工业领域,在汽车制造业中显得尤为重要.介绍了板料冲压成形在汽车制造业中的重要地位以及国内外汽车冲压件成形的现状.综述了有限元数值模拟技术的发展状况、理论基础以及一些专用的有限元软件.板料在冲压成形过程中经常出现起皱、破裂及回弹等缺陷.通过对几种典型汽车冲压件的成形分析,证明了有限元数值模拟技术能够在成形过程中很好的预测成形缺陷.并指出数值模拟在冲压成形中正发挥着越来越重要的作用.     

缸内直接喷射LPG发动机混合气形成过程模拟

缸内直接喷射发动机具有良好的工作稳定性和负荷特性,可以在部分负荷下实现分层燃烧,大大提升了燃油经济性。其中,组织形成合适的缸内混合气分布是缸内直接喷射发动机稳定工作的关键。本文使用FIRE软件建立了液化石油气（LPG;Liquefied Petroleum Gas）的缸内直接喷射和混合气形成过程的数值模型,解析了液态IPG喷射以后缸内混合气的浓度场,以及IPG-空气在缸内的速度分布。     

缸内直接喷射LPG发动机混合气形成过程模拟

缸内直接喷射发动机具有良好的工作稳定性和负荷特性,可以在部分负荷下实现分层燃烧,大大提升了燃油经济性。其中,组织形成合适的缸内混合气分布是缸内直接喷射发动机稳定工作的关键。本文使用FIRE软件建立了液化石油气(LPG,Liquefied Petroleum Gas)的缸内直接喷射和混合气形成过程的数值模型,解析了液态LPG喷射以后缸内混合气的浓度场,以及LPG-空气在缸内的速度分布。     

液态LPG直喷发动机混合气形成的数值解析

首先数值解析了缸内电控直喷汽油机的混合气形成过程,并且与光学纹影实验结果比较,验证了解析方法的可行性。在此基础上,分别考察了电控LPG直喷发动机曲面活塞顶燃烧室和凹坑型活塞顶燃烧室在部分负荷工况下混合气的形成过程。结果表明:在部分负荷下、压缩行程后期喷射时,由于缸内滚流的作用,两种不同形状活塞顶的燃烧室在接近压缩终了时,缸内混合气都能呈明显分层构造,即在火花塞附近聚集了较浓的混合气,而离火花塞较远处则是较稀的混合气,整个燃烧室的空燃比达到40∶1。     

汽车保险杠树脂传递模塑工艺充模过程的数值模拟

首先建立了汽车保险杠树脂传递模塑充模过程的三维数学模型;然后利用有限元/控制体积法对该模型进行了数值模拟,并对树脂在模腔内的流动进行了表述;最后优化出该成型工艺的最佳工艺条件:前期注射压力设定在0.4 MPa以下,后期注射压力设定为0.6—0.8MPa,合理树脂黏度为0.15 Pa.s左右。采用该工艺条件可有效降低制件的气泡缺陷。     

Comparison of rheological analytic model with numerical simulation in powder injection molding filling process

Mathematical model of filling disk-shaped mold cavity in steady state was studied.And the mathematical model under vibration field was developed from the model in steady state.According to the model of filling disk-shaped mold cavity in steady state,the filling time,the distribution of velocity field and the pressure field were obtained.The analysis results from rheological analytic model were compared with the numerical simulation results using Moldflow software in the powder injection molding filling process.Through the comparison,it is found that it is unreasonable to neglect the influence of temperature when calculated the pressure changing with the time at the cavity gate,while it can be neglected in other situations such as calculating the distribution of the velocity fields.This provides a theoretical reference for the establishment of correct model both in steady state and under vibration force field in the future.     

Numerical Simulation of Multi-repaired Weld Residual Stress

In order to understand the change regulation of resichual stress during muhi-repaired uelding to provide theoretical guidance for correct repaired welding procedure and improvement of joint properties.and to simulate the magnitude and distribution of residual stress using the finite element method (FEM).A model of temperature field of weld repaired using FEM,which was simplified,was established.the weld stress consists of ther mal stress and orgaization stress.models of the thermal stress and organization stress were described ANSYS, a software of finite element,was applied to calculate the stress,BHW35 steel was taken as an example,the simulated and experimental results for the 1 st ,3rd and 5th weldrepaired were analyzed,the simulated results are in good agreement with experimental results it can be concluded that the residual stress,in the weld center changes little,and the high residual stress exists in HAZ and in the same place the more repaired weld.the higher residual tress and the area of residual stress becomes wider.     

The Simulation and Optimization of Aspheric Plastic Lens Injection Molding

For the purpose of reducing the volumetric shrinkage and volumetric shrinkage variation, the process in injection molding of aspheric plastic lens was simulated, and several process parameters which include holding pressure, melt temperature, mold temperature, fill time, holding pressure time and cooling time were optimized by using an orthogonal experimental design method. Finally, the optinuan process parameters and the influence degree of process parameters on the average volumetric shrinkage and the volumetric shrinkage variation are obtained.     

注射成形中聚合物熔体黏度的在线测量装置

设计并制造在线测量注射成形过程中聚合物熔体黏度变化的装置. 在测量装置中,非等温高剪切流变模具的型腔结构设计成厚度为1 mm或2 mm的狭缝,底部不封口,维持熔体的持续流动;在流动中心线上沿流动方向布置一组压力传感器实时检测聚合物熔体在模具型腔中的压力变化情况,并使用模温机控制模具温度. 使用PXIe采集系统采集、显示、记录实验数据. 实验通过压力传感器测量得到不同位置熔体压力,根据修正的牛顿黏性定律计算熔体黏度,并与Cross-WLF模型的理论值进行对比. 实验结果表明：所设计的模具安全可靠,可获得低密度聚乙烯(LDPE)熔体在注射成形过程中熔体压力的变化情况,从而可以计算出材料在成形过程中的表观黏度演化情况. 实验测量结果与理论值在剪切速率大于500 s^?1的高剪切速度范围内较吻合,误差均在18%以内,最小为4%. 该装置能满足真实成形条件下聚合物熔体信息的在线检测要求.     

FM全新卡车内饰顶棚把手气辅注射成型的模拟分析

利用Moldflow软件对FM全新卡车内饰顶棚把手的传统注射成型工艺和气体辅助注射成型工艺进行了分析．研究了熔体温度、注射时间、浇口位置对传统注射成型和气辅注射成型过程的影响以及熔体的预注射量、气体注射压力对气辅注射成型填充过程的影响。结果表明：采用气体辅助注射成型工艺熔体适宜的注入量为94％，可以节省原材料6％，熔体的注射压力降低了52．8％，锁模力下降了66．6％。     

水火弯板数值模拟中的水冷换热边界条件研究

在水火弯板过程数值模拟中,对流换热边界条件尤其是水冷对流换热边界条件对数值模拟的结果影响很大,其水冷对流换热系数的求解一直是水火弯板数值模拟中的一大难题.这里采用流动沸腾换热理论对水火弯板数值模拟中的水冷对流换热边界条件进行了研究,通过求得过冷水流动泡态沸腾起始点(ONB)和过冷水流动泡态沸腾临界点(CHF)的壁面过热度,比较水火弯板过程中钢板表面各处的温度和这2个壁面温度以确定冷却水的状态,根据冷却水的状态分别求其对应的过冷水单相流动对流换热系数和过冷水流动泡态沸腾换热系数.采用沸腾曲线对流换热边界条件和流动沸腾换热边界条件的数值模拟结果进行比较,结果表明流动沸腾换热边界条件的数值模拟结果精度明显提高,具有较高的研究价值.     

Numerical Simulation of Mold Filling in Resin Transfer Molding Using Isoparametric Method

The mold filling of RTM was simulated based on the control volume finite element method ( CV/FEM). The formulation using isoparametric transformation was discussed in detail and a computational code based on isoparametric technique was developed. The simulation results were compared with experimental data.Different isoparametric elements, quadrilateral and triangular, were compared in the simulation. It demonstrates that the use of bilinear quadrilaterol isoparametrie elements in simulating the process can produce a higher precision and cost a less time than the use of triangular ones.