管材机头流道的有限元参数化建模

在管材挤出机头流道设计中，利用具有友好图形用户界面的Visual C 语言，建立APDL代码文本，并从Visual C 直接调用ANSYS软件，建立管材机头流道的参数化几何模型，为流场的有限元分析奠定了基础。     

PVC–U管材挤出机头流道优化设计

为提高管材挤出机头的加工性能,加强机头流道的塑化作用,以挤出机头中直通式管材挤出机头作为研究对象,建立其挤出加工过程的数学模型,利用ANSYS Fluent软件对管材挤出机头流道的流动过程进行模拟研究,用CFD-post对模拟结果进行分析,并根据模拟结果对管材挤出机头流道的结构进行优化设计。模拟结果表明:优化后的管材挤出机头流道增加了熔体的流动速度,减少了熔体在机头流道内的停留时间,提高了流动性能;并降低了压缩段末端的压力降,提高了成型段上的压力降,增强了熔体的塑化性能,使制品变得更加紧密。     

基于正交试验与数值模拟的木塑异型材挤出机头流道设计方法

建立了一种基于正交试验与数值模拟的木塑异型材挤出机头流道的设计方法,其主要原理是在结合木塑复合材料流变数据的基础上,将异型材挤出机头流道的主要几何参数定义为正交试验的试验因素,利用正交试验设计方法对这些几何参数进行试验安排;使用Inventor软件三维参数化尺寸驱动系统实现流道模型的迅速建立;通过专业计算流体力学有限元分析软件Polyflow完成机头流道内熔体的模拟计算和仿真分析;选择适当的评价标准对模拟结果进行正交优化,最终获得机头流道的合理参数。依据这种方法,对立柱木塑异型材进行了机头流道的设计,最终得到其理想的设计结果。     

机头流道压缩段过渡形状对管材挤出成型的影响

在分析了塑料熔体经过机头流道的流动过程与流变学特性基础上，将机头流道压缩段的过渡形状设计为直线型和圆弧型。利用Ployfow软件对直线型和圆弧型过渡压缩段的机头流道进行数值模拟，分析不同压缩段过渡形状对流道压力场、速度场和剪切速率场的影响。结果表明，流道压缩段过渡形状设计为圆弧型后，增大了熔体在成型段内的压力降、流动速度几流道出口速度均匀性，提高了管材的密实度、壁厚均匀性和力学强度，减少了熔体在流道内的停留时间。改进后的流道成型段最大壁面剪切速率从99.6 s^-1降低至76.3 s^-1,远低于硬质聚氯乙烯(PVC-U)管材表面出现鲨鱼皮现象的临界剪切速率，流道出口壁面剪切速率均匀性与管材表面质量均得到显著提高。     

收敛流道内聚合物熔体流动的有限元模拟

利用Polyflow软件包,对收敛流道内聚合物熔体的三维流动进行了模拟,得出了压力、速度、剪切速率和延伸应变速率的分布.在此基础上,对熔体在收敛流道内的流动规律及特点进行了分析.这为流场参数的控制和机头结构的优化设计和改进提供了理论依据.     

PVC-U管材共用挤出机头设计与分析

为了生产不同直径的管材可以使用相同的挤出机头,减少机头的制造成本和生产周期,通过对硬质聚氯乙烯(PVC-U)材料的特性、机头的结构参数等进行分析的基础上,设计了一款压缩模座弧形过渡的PVC-U管材共用挤出机头.采用ANSYS FLUENT软件对机头流道进行了数值模拟,并利用CFD-POST对流场的压力、速度和壁面剪切应...     

基于响应面法的轮胎胎面挤出机机头流道结构参数优化

建立轮胎胎面挤出机机头流道几何模型,运用数值仿真方法对胶料在机头流道内的流场进行仿真分析;流道出口截面胶料流动速度方差为流动速度均匀性的评价指标,通过Plackett Burman(PB)试验方法从8个流道结构参数中筛选出3个关键结构参数(夹角A和B及出口宽度D);采用中心复合设计(CCD)方法对3个关键结构参数对胶料挤出质量的影响规律进行分析,并经响应面法分析获得优化结构参数。结果表明:机头流道的3个关键结构参数A,B和D是影响胶料挤出质量的关键因素;优化流道结构能显著改善挤出胶料流动速度均匀性,提高胶料挤出质量。     

螺旋式管材机头内熔体流动的计算机模拟

介绍了用于生产管材的螺旋机头及其主要设计方法和有限元建模方法,并用有限元软件POLYFLOW对机头内的熔体流动进行了三维模拟,分析了流道内的速度分布,压力分布和剪切速率分布,并指出了现有文献对螺旋机头的分析的某些不当之处。     

衣架机头三维数值模拟

利用美国FLUENT公司研究开发的Polyflow软件，以衣架型机头为基本的几何模型。对其流道内的聚合物熔体流动进行了数值模拟分析，建立控制方程，找出相关边界条件，以1组机头基本尺寸数据为例，计算得到了整个衣架机头流道内部的压力、速度分布图，最后通过分析幂律流体压力和速度分布图，对出口处料流的均匀性进行了讨论。     

螺杆分配机头内部压力场分布的CAE分析

用ANSYS有限元软件对生产宽幅橡胶板材的螺杆分配机头流道内部的压力场进行三维模拟与分析，选择Fluid 142三维六面体单元划分网格，建立螺杆分配机头内部流道的三维有限元模型，得到在一定工艺条件下机头流道内部的压力分布。分析了阻尼块几何形状对压力分布的影响，指出阻尼块可以增加流道内原来速度和压力较高部位的流动阻力，选择合适的阻尼块高度可以使胶料的压力值逐渐趋于横向均匀。     

Optimal cooling system design for the injection molding process

A computer-aided optimal design system was developed to improve the performance of a cooling system for injection molding. This was done by minimizing a weighted combination of the uniformity of the part temperature and the cooling time. The CONMIN algorithm was adopted to obtain the optimal design using the special boundary integral formulation and a corresponding design sensitivity analysis formulation. Design variables related to the processing conditions (i.e., inlet coolant temperature and volumetric flow rate of each cooling channel) and mold cooling system design (radius and location of each cooling channel) were considered. Three different optimization strategies are suggested, and three sample problems were solved to demonstrate the efficiency and the usefulness of this optimization procedure.     

Free Vibration Analysis of an Adhesively Bonded Functionally Graded Tubular Single Lap Joint

In this study, the three-dimensional free vibration analysis of an adhesively bonded functionally graded tubular single lap joint was carried out using the finite element method. The functionally graded tubes of the adhesive joint are composed of ceramic (Al₂O₃) and metal (Ni) phases varying through the tube thickness. The adhesive material properties, such as modulus of elasticity, Poisson's ratio, and density were found to have negligible effect on the first ten natural frequencies and mode shapes of the adhesive joint. The optimal design parameters of the adhesive joint, such as overlap length, inner radius of the inner tube, outer and inner tube thicknesses, and the through-the-thickness material composition variation were searched using both the artificial neural networks (ANNs) and the genetic algorithms (GAs). For this purpose, the natural frequencies and modal strain energy values were calculated for an adhesive joint with random geometrical properties and material compositions through the tube thicknesses, and were used for training the proposed artificial neural network models. The outer tube thickness, the inner tube-inner radius, and the compositional gradient exponent had considerable effect on the natural frequencies, mode shapes, and modal strain energies of the functionally graded tubular single lap joint, whereas the overlap length and the inner tube thickness had a minor effect. The GAs integrated with ANNs was employed to determine optimal design parameters satisfying both maximum natural frequency and minimum modal strain energy conditions for each natural mode of the tubular adhesive joint.     

Casson流体层流反应器中连串反应的产品分布

引　言目前化工流体力学涉及的范围已由传统的牛顿流体发展到非牛顿流体 .常见的非牛顿流体包括幂律流体、Bingham流体和Casson流体 .有许多高聚物反应物系和生化反应物系属于非牛顿流体 .特别是某些生化反应系统 ,所处理的物系常由各种天然物质组成 ,因而表现出典型的非牛顿流     

Optimal Design of the Adhesively-Bonded Tubular Single Lap Joint

In this paper, a method for the optimal design of the adhesively-bonded tubular single lap joint was proposed based on the failure model of the adhesively-bonded tubular single lap joint. The failure model incorporated the nonlinear mechanical behavior of the adhesive as well as the different failure modes in which the adhesive failure mode changed from bulk shear failure, via transient failure, to interfacial failure between the adhesive and the adherend, according to the magnitudes of the residual thermal stresses induced by fabrication.

The effects of the design parameters for the adhesively-bonded tubular single lap joint, such as the thicknesses of adhesive layer and adherends, the bonding length, and the scarfs of adherends, on the torque transmission capability and the efficiency of the adhesive joint were investigated.     

Optimal Design of the Adhesively-Bonded Tubular Single Lap Joint

In this paper, a method for the optimal design of the adhesively-bonded tubular single lap joint was proposed based on the failure model of the adhesively-bonded tubular single lap joint. The failure model incorporated the nonlinear mechanical behavior of the adhesive as well as the different failure modes in which the adhesive failure mode changed from bulk shear failure, via transient failure, to interfacial failure between the adhesive and the adherend, according to the magnitudes of the residual thermal stresses induced by fabrication.

The effects of the design parameters for the adhesively-bonded tubular single lap joint, such as the thicknesses of adhesive layer and adherends, the bonding length, and the scarfs of adherends, on the torque transmission capability and the efficiency of the adhesive joint were investigated.     

挤出机螺杆直槽式屏障混炼元件的优化设计

研究挤出机螺杆直槽式屏障混炼元件的优化设计问题。根据粘性流体流动基本方程。以单位产量能耗最小为优化目标,建立简化的挤出机螺杆直槽式屏障混炼元件优化设计的数学模型，并应用复合形法求解，确定剪切长度、剪切问隙、屏障长度和屏障槽数等主要几何参数。本研究优化结果均在文献所建议的最佳取值范围内。     

挤出机螺杆的计算机辅助优化设计

讨论了挤出机螺杆的计算机辅助优化设计问题。以单位产量能耗最小为优化目标，建立简化的挤出机螺杆优化设计的数学模型，应用复合形法求解。结果表明，螺杆的主要几何参数螺槽深度、螺纹顶宽度和螺纹升角均位于或接近文献中所建议的最佳取值范围。     

挤出机螺杆计量段的优化设计

讨论了挤出机螺杆计量段的优化设计问题。应用粘性流体动力学基本方程，分析了聚合物物料在螺槽中的流动。以单位产量能耗最小为优化目标，建立简化的挤出机计量段螺杆优化设计的数学模型，应用约束随机方向法求解。结果表明，螺槽深度、螺纹棱顶宽度、螺纹棱顶与机筒间隙和螺纹升角均位于或接近于献中所建议的最佳取值范围。     

Effect of the Flow Pattern on the Convective Heat Transfer Efficiency in Tubular Apparatuses

The heat-transfer coefficient in a divergent–convergent tubular apparatus is 1.4–1.7 times larger than that in a cylindrical apparatus, the specific output of the divergent–convergent tubular apparatus is 1.3–1.4 times higher than that of the cylindrical apparatus, and the residence time of a reaction mixture (or a heat-transfer medium) in the heat-transfer zone of the divergent–convergent tubular apparatus is 1.8 times shorter than that of the cylindrical apparatus. A relationship is revealed between the heat-transfer coefficient and the liquid flow pattern.     

Numerical investigation and experimental validation of the performance of a tubular packed bed reactor for hydrogenation of diene‐based polymers

A process which comprised a tubular reactor (that can be packed with different internal structures) has been modeled and theoretically analyzed for conducting the hydrogenation of nitrile butadiene rubber (NBR). The dynamics of the tubular reactor and the intrinsic hydrogenation kinetics are coupled, and detailed numerical simulations are performed under isothermal and isobaric conditions. The proposed model thus obtained involves coupled, nonlinear, partial differential equations (distributed parameter system). The effect of different reactor design parameters such as Peclet number, carbon–carbon double bond loading, mass transfer to reaction resistance, and solubility of hydrogen with respect to hydrogenation of the NBR has been investigated numerically. The conversions predicted using the proposed model for tubular packed bed reactor are compared with those possible in conventional plug flow reactor and continuous stirred tank reactor models. The optimal parameters and operating conditions for efficient production of hydrogenated NBR are suggested. Finally, the validity of the proposed model is confirmed by comparing the predicted and the experimental degree of hydrogenation obtained in a tubular reactor packed with Intalox saddles. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers