共查询到19条相似文献,搜索用时 93 毫秒
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挤出吹塑的型坯成型研究中的本构方程 总被引:1,自引:0,他引:1
型坯成型是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,用到了微分型的和积分型的本构方程。 相似文献
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挤出吹塑中型坯成型的神经网络模型的选取 总被引:3,自引:0,他引:3
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. 相似文献
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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 相似文献
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介绍了模拟技术在吹塑型坯成型中的研究和发展状况,针对型坯成型过程,对国内外学者进行数值分析的方法和理论依据进行了论述,着重论述了神经网络方法。并指出型坯成型是吹塑过程的核心,是一个受聚合物材料性能、熔融温度、成型加工条件等因素综合影响的过程。 相似文献
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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。 相似文献
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<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 相似文献
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挤出吹塑中型坯成型的有限元模拟——型坯尺寸预测 总被引:1,自引:0,他引:1
建立了塑料挤出吹塑中平直型机头内非牛顿粘弹性熔体的流动模型,并利用POLYFLOW有限元软件进行求解,预测了不同型坯长度和不同流量时的型坯尺寸分布。 相似文献
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Many technical processes involve viscoelastic flows, which makes the subject interesting for CFD. Despite the complex fluid rheology and related numerical problems in solving the constitutive equations, recent stabilization approaches allow for a robust simulation of viscoelastic flows in the technical relevant range at high degrees of fluid elasticity. A recent general‐purpose numerical stabilization framework, based on the finite‐volume method of OpenFOAM is presented and its capability for the robust simulation of viscoelastic single‐, as well as two‐phase flows is shown. 相似文献
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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. 相似文献
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为了形成对粘弹性聚合物溶液在微观孔隙中流动行为的完整的数学描述,便于从理论上研究粘弹性流体的微观驱油效率,本文针对残余油的微观存在形式,使用了凹槽流道模型。并结合非线性上随体Maxwell本构方程,动量方程、连续性方程以及两种流道的边界条件,建立了完整的数学模型。采用有限体积法求解了由UCM本构方程、动量方程、连续性方程和流道的边界条件构成的非线性耦合方程组。为了解决流场计算中的一个关键问题,即不合理的压力场的检测,同时为了保证计算的准确度及对压力的物理特性模拟,本文对整个计算域采用交错网格,并且采用乘方格式对动量方程进行离散,从而得出控制方程组的离散方程式。本文选择交替方向隐式迭代法,并补以块修正技术以促进收敛,最后得到了粘弹性流体在收缩流道内流动时的速度场、流函数场。 相似文献
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黏弹性表面活性剂溶液悬浮颗粒流广泛存在于自然界和工业生产中,黏弹性表面活性剂溶液的非线性流变性质及应力松弛效应对其中颗粒沉降有着显著影响。采用FENE-P和Giesekus黏弹性本构模型对表面活性剂溶液中颗粒沉降特性进行研究,发现两种本构模型不仅表现出剪切稀化,而且出现拉伸硬化。颗粒在沉降初期的不稳定性主要是由溶液自身的弹性效应引起,弹性效应越强,颗粒沉降速度不稳定性越强,而剪切稀化效应会减弱颗粒沉降速度的不稳定。颗粒沉降过程中在其尾部形成一个“负尾迹”,随着剪切稀化和拉伸硬化效应增强,负尾迹区增大,弹性效应增加,负尾迹增强,负尾迹区流体内部反向速度分布导致的表面活性剂溶液中微观胶束的拉伸断裂和重构可能是引起颗粒沉降速度持续波动的原因。 相似文献
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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. 相似文献
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A theoretical model is developed for modelling the non-spherical bubble formation at an orifice submerged in non-Newtonian fluids under constant flowrate conditions. The equations of motion are, respectively, the radial expansion and vertical ascension of the bubble interface. They are combined with the thermodynamic equations for the gas in the bubble and the chamber below the orifice as well as the fluid rheological equation. In particular, the influence of in-line interactions between bubbles due to the fluid memory effects of the viscoelastic characteristics is taken into account for the first time. The present model is able to compute the instantaneous growing shape of the bubble during its formation and determine the final size of detachment as well as the frequency of bubble formation. The values predicted by this model compare satisfactorily with the experimental results obtained under different operating conditions. 相似文献