共查询到17条相似文献,搜索用时 187 毫秒
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在单螺杆挤出机中,通过螺杆的轴向振动将振动力场引入聚合物固体输送过程,提出振动力场强化固体输送过程的新概念.以螺槽中运动的物料为对象建立了振动力场强化固体输送过程的数学模型,并获得了物料沿螺槽方向输送的压力(密度)、速度的近似解析解.传统固体输送过程就是当螺杆轴向振动的振幅为零时的特例,此时的压力降与Darnell and Mol 理论一致,但不同的是物料速度及密度沿螺槽方向是变化的,从而修正了Darnell and Mol 固体输送理论.螺杆的轴向振动提高了固体输送平均压力,缩短了固体输送的长度,增加了固体输送角.透明料筒全程可视化实验挤出机证明了螺杆轴向振动确实缩短了物料固体压实输送所需的螺槽长度. 相似文献
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研究了聚合物电磁动态注射成型过程中熔体在轴向振动力场作用下在圆柱形流道中的流动情况。从理论上分析了动态熔体流动过程,为研究聚合物熔体的动态充模过程提供流道系统压力降。得出在施加了轴向振动的情况下,熔体的压力梯度有明显的降低,并且随着振动强度的增强,降低的幅度加大。 相似文献
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振动力场下聚合物熔体流变行为的响应与分析——I.毛细管压力降和熔体表观粘度 总被引:1,自引:0,他引:1
在自行设计的恒速型毛细管动态流变装置上,对聚合物熔体进行动态挤出实验。借助已建立的振动力场下聚合物熔体流变行为的表征公式,分别计算振动力场下聚合物熔体在毛细管壁处的剪切应力、剪切速率和表观粘度。与稳态挤出时相比,引入振动力场后,发现毛细管压力降、表观粘度均显著降低,且随着振动频率和振幅的改变呈非线性变化趋势,作者对此进行了深入分析。 相似文献
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振动技术在塑料成型加工中的应用 总被引:4,自引:0,他引:4
介绍了在塑料成型加工中施加振动力场的动态加工方法,阐述了振动力场在挤出和注射成型中的作用.运用高分子链及链段运动理论,分析说明振动力场的作用可使聚合物熔体的粘弹性减小,表现在实际加工中压力降低、流率增加、能耗减小和制品质量提高. 相似文献
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采用Tanner方法修正的非线性MaxweⅡ本构方程,对振动力场作用下的聚合物熔体在平行异向双螺杆挤出机螺槽内的行为与响应进行了近似解析研究。分析了不同幂律指数的聚合物熔体在螺槽内的速度分布及其对振动力场的响应。随着幂律指数减小,C型室中上部混合变差,但振动力场使速度场随时间周期性变化,促进了流体界面再取向,进而提高混合效果。 相似文献
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在壁面滑移条件下建立了超高分子量聚乙烯(UHMWPE)单螺杆挤出过程有限元模型,模拟了不同滑移系数对挤出成型过程的影响。由Navier线性滑移定律建立了螺杆壁面熔体所受剪切应力与熔体滑移速度之间的关系,基于Polyflow软件,采用不同滑移系数对单螺杆计量段内UHMWPE熔体的三维等温流动开展了有限元模拟,获得了熔体的速度、压力的分布规律。结果表明:滑移系数增大,沿着螺槽方向的速度和垂直于螺槽方向的速度明显增大,螺杆的均化质量和挤出产量明显提高;但熔体在螺槽间的压力降增大,易导致挤出过程不稳定。 相似文献
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借助于三维数值模拟思想,对双波螺杆混炼段构建物理简化模型,并应用聚合物流动分析软件POLYFLOW及粒子示踪法对比研究该混炼段在稳态与动态条件下的混炼性能。结果表明,双波螺杆螺槽的特殊结构导致熔体粒子各流场参数波动周期性变化;引入振动场可使熔体粒子受到的压力和作用力降低,并可使流场获得稳定的黏度;存在最佳振动强度,使得波状螺槽内熔体粒子受到剪切作用达到最大值及粒子受力实现稳定降低。 相似文献
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Quan Wang 《Polymer-Plastics Technology and Engineering》2013,52(11):1055-1061
In the reciprocating extrusion, the vibration force field (VFF) is applied to the entire plasticating process by the axial vibration of screw and the novel concept on the polymer dynamic plasticating process being strengthened has been brought forward in the paper. The mathematical model is established that describes the plasticating process under the VFF and the approximative analytical solutions of the velocity distribution, pressure gradient in the screw channel and the plasticating capability are obtained. The theoretical results show that the axial vibration of screw can accelerate the blend capability of polymer and make melt temperature more uniform. With increase of the vibration intensity, the effect of blend and plasticating is enhanced further. The average pressure gradient drops down the channel under the VFF because of lower virtual viscosity of polymer melt and smaller flow resistance in the channel. The comparison between the theoretical analysis and the experimental results shows the plasticating capability of melt is improved with increase of vibration intensity. 相似文献
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In the single‐screw extruder, the vibration force field is applied to the solids conveying process by the axial vibration of the screw and the novel concept on the solids conveying process being strengthened with the vibration force field has been brought forward in this study. We establish the mathematical model that describes the solids conveying process with the vibration force field and obtain the approximative analytical solutions of the pressure and velocity of the solids conveying in the down‐channel. In the new theory, if the screw has no axial vibration the solids conveying pressure is the same as that of the Darnell and Mol theory, but the density and velocity of solids conveying along the screw channel is variable, which has modified the Darnell and Mol theory in which the density and velocity of the solids conveying along the screw channel was considered invariable. The results reveal that the axial vibration of the screw can increase the average pressure of solids conveying, decrease the channel length of the solids conveying section and increase the solids conveying angle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2998–3007, 2006 相似文献
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Influence of the melt viscosity and operating conditions on the degree of filling,pressure, temperature,and residence time in a co‐kneader 下载免费PDF全文
Benjamin Monchatre Claude Raveyre Christian Carrot 《Polymer Engineering and Science》2018,58(2):133-141
The effect of the melt viscosity and operating conditions on processing parameters in a co‐kneader with a discharge die was experimentally investigated. Filling ratio, pressure, temperature, and residence time distribution were measured. Experiments were performed with polypropylene resins. The viscosity of the melt was varied either by changing the regulation temperature of the kneader or the molecular weight of the polymer. The filling pattern in the co‐kneader shows the conveying capability of the various elements without any effect of the melt viscosity. Experimental residence time distributions remain the same at a given feed rate and screw speed, regardless of the viscosity of the material. The global degree of filling in a zone combining conveying elements, kneading elements, and restriction ring was found to be nearly constant in the conditions of this study and therefore a simple relation exists between the mean residence time and the feed rate. Beside expected variations of the die pressure and melt temperature when the viscosity, screw speed or feed rates change, a model based on heat equation and experimental data demonstrate the high capability of the co‐kneader for heat exchange and for the control of self‐heating during mixing. POLYM. ENG. SCI., 58:133–141, 2018. © 2017 Society of Plastics Engineers 相似文献
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The transport theory for the solids conveying zone in a single‐screw extruder was applied to calculate the pressure distributions along the screw channel for several bisphenol A polycarbonate resins based on the screw revolution speed and the flow rate. The pressure distributions and the flow rates of the resins were related to the structural and rheological properties. When polymers have the same chemical structure and number‐average molecular weight and the same mechanical properties, the polymer having a broader molecular weight distribution showed a lower glass transition temperature. For the polymer with broader MWD a relatively low pressure was developed along the screw channel, and an increased flow rate was observed. A relatively short melting length was also observed for this polymer and, accordingly, it was concluded that the polymer with a broader MWD has a better processability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2921–2929, 2002 相似文献
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Jinping Qu Yanhong Feng Hezhi He Gang Jin Xianwu Cao 《Polymer Engineering and Science》2006,46(2):198-204
An analytic model has been developed to analyze the residence time distribution of melt in the screw channel of the melt conveying section in a novel extruder of which the screw can vibrate axially. A comparison of the residence time distribution of melt in screw channel with and without vibration shows that the residence time of melt increases with the apply of vibration and the larger the vibration frequency and amplitude are, the longer time it will take the melt to travel through the melt conveying section, which is in favor of the improvement of the effect of melt mixing. POLYM. ENG. SCI. 46:198–204, 2006. © 2005 Society of Plastics Engineers 相似文献
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在自行设计的恒速型毛细管动态流变装置上,对聚合物熔体进行动态挤出实验。实时采集毛细管的挤出胀大值,借助已建立的振动力场下聚合物熔体弹性行为的表征公式,计算振动力场下聚合物熔体在毛细管壁处的第一法向应力差。通过对比分析有无振动场下以及不同振动强度下聚合物熔体的流变性能,找到聚合物熔体弹性行为对振动力场的响应规律。 相似文献