深水水平井砾石充填数值模拟研究

深水油气田开发成本高，为获得更大的泄漏面积和更高的产量，长水平井越来越成为石油公司的优先选择。由于深水油气田特殊的沉积环境，砾石充填成为一种常用的防砂方式。梳理了水平井砾石充填机理及深水水平井充填的作业风险，建立了水平井砾石充填不同阶段模型。以南海某水平井为例，进行了数值模拟分析，分析了不同影响因素对α波砂丘比、α波充填长度的影响变化规律以及充填过程中充填压力的变化，同时分析计算了轻质砾石和常规砾石的充填效果。计算模拟结果为现场及后续砾石充填的实施提供技术支持。     

PA66/GF汽车进气歧管工艺模拟及优化

运用相关理论和塑料充型凝固有限元模拟软件Moldflow对玻璃纤维增强尼龙66进气歧管的熔模型芯法成型工艺进行充填流动过程数值模拟,在分析、比较了多组工艺参数方案(即不同的注射温度、模具温度和充填时间)的数值模拟结果后,得到了优化的成型工艺参数,即注射温度为290℃、充填时间为3.9s、模具温度为80℃。     

胶结充填在二步回采中的应用研究

结合某金矿二步回采,胶结充填工艺,采用有限差分数值软件FLAC3D模拟非线性大变形问题,建立数值模型,模拟矿体的回采和充填过程,为安全开采提供了依据,论证了胶结充填的可行性,保证安全生产。     

顺序共注射成型充填过程的数值模拟

基于Hele Shaw流动模型,推导出顺序共注射成型充填过程的数值模型;并引入厚度分数,采用控制体积法来实现运动界面的追踪。数值模拟结果与moldflow的模拟结果相吻合,并且能够正确反映芯皮层熔体黏度比对注射压力和界面形貌的影响。     

细观尺度下充填体损伤演化元胞自动机模型研究

为模拟单轴压缩条件下充填体损伤破坏过程,直观反映其细观结构的演化规律,建立了细观尺度下充填体损伤演化的元胞自动机模型。借助SEM图像推演充填体破坏阈值的分布,并采用阈值反比加权法确定摩尔邻居吸收能量的比率,在此基础上利用元胞自动机模型对试样进行单轴压缩模拟试验。模拟结果表明,充填体的损伤是集随机性和确定性于一身的行为,加载初期试样的损伤呈现出整体无序性,随着加载步数的推移,试样损伤演化逐步向局部有序化发展,峰值应力后试样损伤再次呈现整体无序性。充填体的应力、损伤值的演化曲线与实际试验结果基本吻合,二者仅在数值上略有差异,模型精度较高,可为充填体损伤演化过程的模拟提供一种新的思路。     

多场耦合条件下充填料浆管道输送数值模拟研究

为探究温度场对料浆管道输送过程的影响,揭示料浆大倍线输送规律,进行了流变场和温度场耦合条件下充填料浆输送过程的数值模拟。首先通过塌落度试验对充填料浆的流变特征进行了简要分析,确定高质量分数充填料浆的流变模型,在此基础上建立了高质量分数全尾砂管道输送的数值模型。利用COMSOL软件的多物理场耦合功能对温度场及流变场进行耦合,基于此对高质量分数料浆的管道输送过程进行模拟,分析温度场对充填倍线的影响,最后以冀东某铁矿为例,对模型进行了检验。研究结果表明,在温度场的作用下,料浆管道输送倍线显著增加,且其增长幅度与料浆质量分数呈正相关。在考虑温度场的条件下,模拟结果与其实际情况一致,证明模拟结果可靠,可为料浆大倍线输送的设计提供理论依据。     

点柱式充填采矿方法在缓倾斜中厚矿体中的应用研究

针对瓮福磷矿磨坊矿段缓倾斜中厚矿体开采后所产生较大沉降的问题,提出采用点柱式充填开采的方法,并对其进行数值模拟验证。通过对充填与未充填两种情况的数值模拟结果可以发现,点柱式充填开采方法能有效控制上覆岩层沉降,同时也合理地处理了采空区,保证了生产的安全。     

充填时间及材料性质对注射压力的影响

本文介绍用数值模拟方法模拟注塑成型过程充填时间及材料性质对注射压力的影响，并以实实详细讨论了各因素对注射压力影响的原因，给出出充填时间的估算公式。     

气辅共注成型工艺中气道截面影响的CAE研究

基于气辅共注成型充填过程控制方程和7参数Cross—WLF黏度模型，采用数值模拟的方法研究了气辅共注成型工艺中气道截面的大小对熔体流动、气体穿透与压力分布的影响。采用改进的控制体积／有限元／有限差分法实现对充填过程中多重运动界面的追踪以及压力、温度等场量分布的预测，编写了相应的模拟程序。对气道等效直径分别为5mm、8mm和12mm的矩形板的气辅共注成型充填过程进行了数值模拟。通过对模拟结果的比较发现：随着气道等效直径的增大，气道中的熔体与薄壁区的熔体流速差越来越大，熔体流动的“跑道”效应越来越突出；“薄壁穿透”缺陷由明显到缓解直至基本消除；压力损失越小，压力分布也变得更为均匀。因而在制件设计时，气道截面尺寸宜稍大而不宜过小。     

Haake混合器中双组分聚合物熔体共混过程的数值模拟研究

采用有限元分析软件POLYFLOW对发生在Haake密闭式混合器中的双组分聚合物熔体共混过程进行了二维等温数值模拟，并进行了实验验证。首先采用仅和流场有关的黏度模型对共混过程进行了数值模拟，模拟结果与实验结果符合较好。进而又考虑了共混体系中组分含量对共混体系黏度的影响，对原来的黏度模型进行了修正，修正后的数值模拟结果和实验结果更接近。通过利用数值模拟的方法进一步获悉了双组分聚合物体系对流混合的规律。     

Polymer flow length simulation during injection mold filling

The maximum flow length of a polymer for a given set of processing conditions is important in injection molding to avoid incomplete mold filling. Experimental analysis, using various processing conditions, can generate the actual influence of processing conditions on the maximum flow length. However, the experimental determination of the flow length for all known industrial polymers would be time consuming and expensive. A non-Newtonian, nonisothermal model of mold filling was developed to evaluate the flow length without requiring large amounts of computation time. The model implements the use of both a temperature and shear rate–dependent viscosity as well as viscous heating. This paper presents the model and its numerical implementation, followed by simulation results. The model is compared with other simulation programs and experimental results using both an amorphous Styron 484-27 polystyrene and a semicrystalline 640I polyethylene in a spiral mold geometry. Good agreement between the three is observed.     

An unsteady multifluid flow model: Application to sandwich injection molding process

The sandwich molding process consists of injecting sequentially a skin and core polymers. The thermomechanical model describing the flow of the two polymers into the mold cavity is based on the lubrication approximations. A transport equation characterizes the displacement of the interface between the two fluids. An experimental study has been performed in order to test the influence of processing parameters (viscosities, flow rates, etc.) on the interface location. Numerical simulations are in agreement with measurements.     

Measurement of stress birefringence patterns in molten polymers flowing through geometrically complex channels

Measurements were taken of stress birefringence patterns in molten polymers flowing through geometrically complex channels. Six different flow channels were constructed for experiment, some representing the flow geometries of spinnerettes encountered in fiber spinning, and others representing mold cavities encountered in injection molding. All the flow channels had two glass windows, which permitted one to take photographs of the flow birefringence patterns of molten polymers with the aid of a polariscope. Quantitative information on the stress distributions in a flow channel was obtained, with the aid of the stress-optical laws, from the pictures taken of both isochromatic and isoclinic fringe patterns. The significance of flow birefringence measurement is discussed from the standpoint of die design for extrusion operation and mold design for injection molding operation.     

Effect of processing conditions on shrinkage in injection molding

A systematic study on the effect of processing conditions on mold shrinkage was undertaken for seven common thermoplastic polymers. It turned out that the holding pressure was always the key parameter. The effect of the melt temperature is slightly less important. Injection velocity and mold temperature do not show a general trend for all polymers. It was shown that at least for amorphous polymers a simple thermoelastic model could describe all experimental results. For semi-crystalline materials the model overpredicts shrinkage.     

Flow of polymers with pressure-dependent viscosity in injection molding dies

Considerable effort has been expended recently by a number of researchers to develop methods of simulating the flow of polymers in injection molding dies. The computer models developed by these researchers provide the mold designer with useful quantitative information concerning the predicted effect of design parameters on mold, filling characteristics. This paper will describe some recent work which is aimed at increasing the usefulness of these models by more accurately describing the flow behavior of those polymers, such as polycarbonate resins, which exhibit a strong effect of pressure on viscosity.     

板坯连铸电磁制动下结晶器内金属流场的研究

以水银为实验工质,通过物理模拟实验研究电磁制动下,板坯结晶器内钢水流动规律. 实验通过超声多普勒测速仪获取不同电磁制动方式[单条型电磁制动(EMBr-Ruler)和流动控制结晶器(FC Mold)]、水口浸入深度和结晶器宽度下的液流特征. 结果表明,在EMBr-Ruler或FC Mold II电磁制动下,结晶器窄壁处形成"液流通道",不利于结晶器内快速形成向下的活塞流. 水口出口距下区磁场越近或被磁场所覆盖,则通道效应减弱; 结晶器宽度增大,亦可降低该通道内液流的冲击效果. FC Mold II下,液面流速和湍流度比EMBr-Ruler时低[液面水平流速最大值分别为0.155 (Case 1)和0.134 m/s (Case 2)],且加大水口浸入深度,可降低液流撞击结晶器窄壁的水平流速[其最大值0.071 (Case 2)和0.068 m/s (Case 3)]. 结晶器宽度的变化不改变水口浸入深度对结晶器流场的影响规律.     

Rheology studies of foam flow during injection mold filling

This work studies the flow behavior of a developing two‐phase gas‐polymer suspension during injection into the instrumented mold cavity of an injection molding machine. In the experiments, blowing agent type and concentration were varied along with processing conditions, to generate controlled cell structures in two different polymers, low density polyethylene and thermoplastic polyolefin. Experimental results indicate that the rheological properties of two phase gas‐polymer suspensions were sensitive to shear rate, blowing agent concentration, melt temperature, and mold temperature. The viscosity of all gas‐polymer suspensions revealed a reduction compared with neat polymer melt in the presence of gas bubbles, because of the reduced volume fraction of polymer matrix. A two‐phase rheological model has been used for fitting with our experimental results for estimating the shear viscosity of two‐phase flow in the mold cavity of the injection molding machine. POLYM. ENG. SCI., 47:522–529, 2007. © 2007 Society of Plastics Engineers.     

Some aspects of orientation in injection molded objects

The birefringences of injection molded plates and the birefringence during steady, isothermal shear flow were compared for some amorphous polymers. The materials studied were a polystyrene, a “toughened” polystyrene and an acrylonitrile-butadiene-styrene copolymer. The birefringence of the plates, notably the maximum value for the average over the thickness was found to be related to the shear stress at the cavity wall that had occurred during the mold filling process. This relationship was independent of temperature. To a good approximation, it was also the same as the relationship between the flow birefringence and the shear stress at the wall in isothermal channel flow. It thus appears that the anisotropy of injection molded objects is dominated by the shear stresses during the mold filling process regardless of the temperature and of the macroscopic rate of deformation.     

Stress birefringence patterns in molten polymers during the mold-filling and cooling process

An experimental study has been carried out to better understand the phenomenon of stress buildup during the mold-filling process in the injection molding operation. For the study, a rectangular mold with two glass windows was constructed, so that stress birefringence patterns of molten polymers flowing into the mold could be photographed with the aid of a polariscope. As a feeding system, a 1-in. extruder was used attached to the mold with a 2-ft length of stainless steel tubing having a relief valve. In this way, the injection pressure (and injection velocity) was carefully controlled to ensure that the glass windows would not be damaged. The development of stress birefringence patterns during the mold-filling process was recorded on a movie film. It was observed that, in isothermal operation, when flow stopped after the mold was filled, stresses relaxed immediately because of the very slow cooling of the mold by ambient air. However, it was observed that, as cooling proceeded, stresses were gradually built up again in the mold. It was possible, therefore, to determine the residual stress in the mold, which originates from the cooling process alone.