Numerical Simulation of Viscoelastic Extrudate Swell Through Elliptical Ring Die

The numerical simulation of extrudate swell is significant in extrusion processing.Precise prediction of extrudate swell is propitious to the control of melt flow and the quality of final products.A mathematical model of three-dimensional（3D）viscoelastic flow through elliptical ring die for polymer extrusion was investigated.The penalty function formulation of viscoelastic incompressible fluid was introduced to the finite element model to analyze 3D extrusion problem.The discrete elastic viscous split stress（DEVSS）and streamline-upwind PetrovGalerkin（SUPG）technology were used to obtain stable simulation results.Free surface was updated by updating the streamlines which needs less memory space.According to numerical simulation results,the effect of zero-shear viscosity and elongation parameter on extrudate swell was slight,but with the increase of volumetric flow rate and relax time the extrudate swell ratio increased markedly.Finally,the numerical simulation of extrudate swell flow for low-density polyethylene（LDPE）melts was investigated and the results agreed well with others’work.These conclusions provided quantitative basis for the forecasting extrudate swell ratio and the controlling of extrusion productivity shape.

Simulation of phased array S-scan acoustic field in FSW joint of aluminum alloy extrudate with complex shape

The shape of aluminum alloy extrudate used in high-speed train is complex, structural noises from the surfaces of the extrudate will be received when using ultrasonic phased array to detect the flaws in FSW. To solve this problem, ultrasonic phased array acoustic field model and propagation simulation of acoustic waves were introduced to simulate the acoustic pressure distribution and the propagation of the acoustic waves. With the methods above, the detection parameters can be optimized and as a result, the experimental process can be simplified and the detection efficiency can be improved. Meanwhile, the echoes in the S-scan images can be predicted, which can help analyze the detection results and judge the defects.

Thermal and textural properties of extruded rice affect its cooking performances and the texture of the steamed extruded rice

Extruded rice has increasingly gained popularity in the market due to its convenience and acceptable texture.The objective of this study was to understand how the physicochemical,thermal,and textural properties of the extruded rice affected its cooking properties and texture of the cooked one.It was found that air trapped in the grains during extrusion reduced the transparency of extruded rice.More air trapped in the grains reduced the true density of the extruded rice,which in turn decreased the hardness of extruded rice.A looser internal structure of extruded rice grain,as indicated by the lower true density,resulted in a faster hydration and shorter optimum cooking time.Extruded rices showed two thermal-transition peaks,with peak 1 from 93.3℃ to 112.8℃ and peak 2 from 107.5℃ to 132.5℃.The increased hardness of extruded rice led to increases in its thermaltransition temperatures,longer optimum steaming time,and decreases in its water absorption and cooking loss,which resulted in an increase in the hardness and a reduction in the adhesiveness of the steamed one.This study provides insights into the key factors determining the eating quality of extruded rice,which is beneficial for food scientists in developing premium extruded rice.

Numerical Simulations of Polymer Melt Conveying in Co-Rotating Twin Screw Extruder

The 3 D non isothermal flow of non Newtonian viscous polymer melt in a co rotating twin screw extruder is modeled. The distributions of the velocity, temperature, pressure and the viscous dissipation in the flow domain are presented by using a fluid dynamics analysis package (Polyflow). The numerical results show that the temperatures are high in the intermeshing region and on the screw surface, the maximum pressure and the minimum pressure occur in the intermeshing region, and the flow rate is almost proportional to the screw speed.

响应面法优化香榧仁挤压-复形工艺

以香榧仁为原料,以复形率、整粒率以及二者的综合评分为评价指标,通过单因素试验和响应面试验优化挤压-复形香榧仁的制备工艺。结果表明:最佳挤压-复形工艺为香榧仁水分含量15%、挤压压力3MPa、挤压时间50s、复形时间5min。在此条件下,香榧仁复形率和整粒率分别为91.41%±2.39%、83.01%±1.86%,综合评分为88.05±1.17。微观结构分析结果显示,挤压-复形后的香榧仁组织结构更为疏松多孔。与炒制香榧仁相比,挤压-复形再烤制的成品去衣率更高、口感更为酥脆。

双螺杆捏合方式制备的三基发射药的流变性研究

为掌握三基发射药连续化捏合工艺中药料的流变特性,提高工艺模型的准确性,按照三基发射药代料配方制备了预混药料,使用双螺杆挤出机对预混药料进行捏合,并通过专用双料筒毛细管流变仪测试捏合后药料的流变特性。分别改变双螺杆挤出机的螺杆转速和捏合温度、药料的固含量和溶剂比,分析以上变量对三基发射药流变学参数的影响规律。结果表明:双螺杆捏合后,药料的本构方程与Carreau-Yasuda本构模型拟合程度较高;一定范围内,螺杆转速或捏合温度的提高会使捏合后的药料的剪切黏度降低;同时,螺杆转速的提高会使药料的停留时间减少,而过短的停留时间会导致捏合后的药料的黏度上升;固含量的增加或溶剂比的减小会使捏合后的药料的剪切黏度增大,而黏度增大会使药料的停留时间增长,一定程度上使药料受到更充分的捏合作用。

带有反向螺纹的同轴变速单螺杆三维流场分析

为了改善单螺杆挤出机混炼性能,设计了一种装配内嵌式摆线齿轮减速器和反向螺纹元件的新型螺杆。使用Solid works软件建模,利用ANSYS和CFX软件分析新型同轴变速单螺杆挤出机的流道内三维流场变化,根据流道内的压力、速度矢量、截面速度等变化,探究物料在其流道内的剪切和混合情况。结果表明:在外部情况相同时,新型螺杆建压能力弱于传统螺杆,即新型螺杆的挤出效率较低;新型螺杆因为装配内嵌式摆线齿轮减速器使其混炼区域的速度降为传统螺杆的1/6,引起物料对流,加快压力场变化,使其速度流线更加混乱;新型螺杆因为装配有反向螺纹元件,使其混炼区域出现反向建压能力,在此作用下物料出现反向速度,出现回流现象。综上,摆线齿轮减速器和反向螺纹元件均延长了物料在流道内的停留时间,增加了物料的挤压剪切次数,从而增强了挤出机的混合分布能力和挤压剪切效果。

双螺杆挤出机齿轮箱效率计算

为提高齿轮箱的传动效率,降低功率损耗,提出了一种齿轮箱传动效率的仿真计算方法。基于KISSsys建立齿轮箱系统的传动模型,计算齿轮、轴承、轴封等损耗,并应用于双螺杆挤出机齿轮箱的传动效率分析,通过加载试验得到齿轮箱的效率数值,并与理论仿真计算的结果进行对比,结果表明仿真计算与试验结果的最大偏差为0.28%,提出的仿真计算方法能够很好的预测双螺杆挤出机齿轮箱的效率;并分析齿轮的压力角和润滑油类型对传动效率的影响,KISSsys分析结果显示齿轮压力角从20°增大到25°,齿轮的负载损耗降低了22.26%,传动效率提高了0.24%;使用聚乙二醇类合成润滑油,齿轮负载损耗平均降低了28.83%,轴承损耗平均降低了19.68%,传动效率平均提高了0.59%。

单螺杆挤出机连续挤出制备的超活化胶粉及其改性沥青的性能研究

采用单螺杆挤出机对废旧轮胎胶粉进行连续活化挤出以制备超活化胶粉,对超活化胶粉及其硫化胶性能进行研究,探讨超活化胶粉在沥青改性中的应用。结果表明:废旧轮胎胶粉活化时,芳烃油用量为8份制得的超活化胶粉的交联密度最小,其硫化胶的拉伸强度和拉断伸长率最大,活化效果较好;超活化胶粉的傅里叶变换红外光谱的1645 cm^(-1)处的吸收峰较废旧轮胎胶粉增强,超活化胶粉与沥青的相容性好,超活化胶粉掺量(质量分数)为47%的改性沥青未产生离析分层现象。

减速器推力轴承定位偏差影响轴系径向跳动异常分析

双螺杆挤出机是一种常用的塑料加工设备,在双螺杆挤出机减速器的生产制造过程中,出现了输出轴径向误差检测异常现象。输出轴转动两周,百分表指针检测数值从零点回到零点。本文从推力轴承结构方面对其进行分析,详细介绍了出现此种情况的原因及解决此问题的方案。

Methane aromatization in the absence of oxygen over extruded and molded MoO_3/ZSM-5 catalysts:Influences of binder and molding method

The influences of binder and molding method on the catalytic performance of methane aromatization in the absence of O2 over MoO3/ZSM-5 catalysts were investigated.SEM,NH3-TPD,FT-IR of adsorbed pyridine,N2 adsorption-desorption,cyclohexane adsorption and XPS were employed to characterize the physical and chemical properties of the catalysts.It was found that SiO2 was a suitable binder for the catalyst due to its appropriate weak acidity.The laminar catalyst comprising of an inert spherical core and a MoO3/ZSM-5 laminar shell with 0.1 0.2 mm in thickness showed a better catalytic performance than the extruded catalyst.The improved activity of the laminar catalyst could be attributed to the easy carbonization of Mo species and the quick removal of reaction products from the catalyst surface.

建筑节能材料在室内装饰工程中的应用研究

随着人们环境保护意识的提升和节能减排政策的推动,建筑节能材料在室内装饰工程中的应用日益广泛。文章研究了常见建筑节能材料的类型、特性以及在室内装饰工程中的具体应用方法,包括聚苯乙烯泡沫板、挤塑聚苯乙烯泡沫板、矿物棉、聚氨酯泡沫和膨胀珍珠岩等常见材料在实际工程中的安装流程和技术要点,同时分析了这些材料对环境的影响和经济效益,以供参考。

Simulation of Polymer Melt Flow Fields in Intermeshing Co-Rotating Three-Screw Extruders

Three-dimension isothermal flows of polymer melt in the kneading blocks of triangularly-arranged and parallelly-arranged intermeshing co-rotating three-screw extruders are simulated using the finite element package POLYFLOW. Based on the velocity fields calculated, the particle trajectories in both machines are visualized using particle tracking technique. The numerical results indicate that the flow patterns in three-screw extruders are similar to those in twin-screw extruders. The triangularly-arranged three-screw extruder has the largest pumping capacity and also the highest extrusion stability in terms of flowrate fluctuation with screw rotation. The instantaneous mixing and cumulative residence time distribution （RTD） characteristics are also analyzed and compared with traditional intermeshing co-rotating twin-screw extruders. It is shown that the start section of the cumulative RTD curve for the triangularly-arranged machine has a small shoulder, which is attributed to the faster flow in the central region of this type of extruder.

Effects of single and multi-stage solid solution treatments on microstructure and properties of as-extruded AA7055 helical profile

The effects of single-stage solution treatment(SST),enhanced solution treatment(EST),high-temperature pre-precipitation(HTPP)and multi-stage solution treatment(MST)on the microstructure,mechanical properties and corrosion resistance of the as-extruded 7055 aluminium alloy(AA7055)helical profile were investigated using differential scanning calorimetry(DSC),optical microscopy(OM),scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD)and transmission electron microscopy(TEM).It was observed that EST and MST could promote the dissolution of the second-phase particles compared with the traditional SST,and the intergranular phases were distinctly discontinuously distributed after HTPP and MST.There was obvious difference in the main texture type and texture strength for the alloy after different solid solution treatments.HTPP could improve the corrosion resistance of the alloy by regulating the intergranular phases,but the mechanical properties were severely weakened.While the good corrosion resistance of the alloy could be obtained by MST without obvious strength loss.As a result,the MST is an ideal solid solution treatment scheme for AA7055.

Low cycle fatigue behavior of the extruded AZ80 magnesium alloy under different strain amplitudes and strain rates

Low cycle fatigue behavior of extruded AZ80 magnesium alloy was investigated under uniaxial tension-compression at different strain amplitudes and strain rates.The results show that the extruded AZ80 magnesium alloy exhibits cyclic hardening at strain amplitudes ranging from 0.4%to 1.0%,the asymmetry of hysteresis loops becomes increasingly obvious when the strain amplitude increases.Higher strain rates correspond to higher stress amplitudes,high mean stresses and short fatigue life.{10–12}extension twins play a role in the cyclic deformation under higher strain amplitudes(0.8%,1.0%).The relationship between total strain energy density and fatigue life can be described by the modified Morrow model.The effect of strain rate on the fatigue life can also be predicted by the model.

Texture evaluation in warm deformation of an extruded Mg-6Al-3Zn alloy

To assess the effect of strain and strain rate on texture evolution of an extruded Mg–6Al–3Zn alloy,compression tests were carried out.Samples were prepared in the extrusion direction(ED)and normal direction(ND).The compression tests were performed at 250℃ and with different strain rates of 0.01 sec−1 and 1 sec−1 and different strains.Microstructural observation and texture investigation show that at early stages of deformation,extension twins lead to the development of strong basal texture intensity along rolling direction(RD)in ED samples and contraction twins result in texture evolution along transverse direction(TD)in ND samples.Also,microstructural investigation at high strains reveals that dynamic recrystallization occurs in both samples and consequently the basal texture intensity has been decreased.

A comparison study of Ce/La and Ca microalloying on the bio-corrosion behaviors of extruded Mg-Zn alloys

The influences of Ca and Ce/La microalloying on the microstructure evolution and bio-corrosion resistances of extruded Mg-Zn alloys have been systematically investigated in the current study.Compared with single Ca or Ce/La addition,the Ca-Ce/La cooperative microalloying results in an outstanding grain refinement,because the fine secondary phase particles effectively hinder the recrystallized grain growth.The coarse Ca2Mg6Zn3 phases promote the formation of Ca3(PO4)2 or hydroxyapatite particles during the immersion process and accelerate the dissolution of the corrosion product film,which destroys its integrity and results in the deterioration of anti-corrosive performance.The Ce/La elements can be dispersed within the conventional Mg7Zn3 phases,which reduce the internal galvanic corrosion between Mg matrix and the secondary phases,leading to an obvious improvement of corrosion resistance.Therefore,the Ca-Ce/La cooperative microalloying achieves a homogenous fine-grained microstructure and improves the protective ability of surface film,which will pave a new avenue for the design of biomedical Mg alloys in the coming future.

Numerical study on mixing performance of screw elements in intermeshing counter-rotating and co-rotating twin-screw extrudes

The flow process of unplasticized polyvinyl chloride （U PVC） through the mixing zone of intermeshing counter rotating and co rotating twin screw extruders （TSEs） were numerically simula ted by the finite element method. Three dimensional isothermal flow field of U-PVC in two kinds of TSE was calculated. The mixing performance of the screw elements of the extruders was statistically analyzed by particle tracking method. The dispersive mixing performance was characterized by the mixing index, the logarithm of stretching, and the segregation scale. The distributive mixing per forulance was characterized by the resident time distribution. The results indicate that the counter rotating TSE can build higher pressure and generate higher axial velocity and shear rate, whereas the co rotating TSE has better performance in dispersive and distributive mixing.

Effect of Replacing Fish Meal with Extruded Soybean Meal on Growth, Feed Utilization and Apparent Nutrient Digestibility of Juvenile White Shrimp(Litopenaeus vannamei)

Extruded soybean meal （ESBM） was evaluated as a protein source for partial replacement of fish meal （FM） in diets of juvenile Litopenaeus vannarnei. In the control diet （Diet 1）, FM protein was replaced with increasing dietary levels of ESBM （4.28%, 8.40%, 12.62%, 16.82%, and 25.26%） at 10%, 20%, 30%, 40%, and 60% levels （Diets 2 to 6, respectively）. An eight-week feeding trial was conducted on 720 juvenile shrimp （0.67 g ± 0.01 g mean initial Weight）, and nutrient digestibility of the six diets was determined. ESBM could replace 20% of FM without causing a significant reduction in growth of shrimp, but other dietary treatments strongly affected whole body composition. Crude protein content of the whole body fed Diet 6 was significantly lower than that fed Diet 2 （P〈0.05）, while crude lipid content of the whole body fed Diet 5 or 6 was significantly higher than that fed Diet 2 （P〈0,05）. Protein digestibilities of Diets 5 and 6 were significantly lower than that of Diet 1 （P〈0.05）. Digestibility of lipids ranged from 96.97% in Diet 6 to 98.34% in Diet 3, whereas dry matter digestibility decreased with increasing replacement level. This study indicates that 20% FM replacement with ESBM in the basic diet containing 40% protein and 30% FM is optimal for juvenile L. vannamei.

Effects of Y content and temperature on the damping capacity of extruded Mg-Y sheets

The damping behavior of extruded Mg-xY(x=0.5,1.0,3.0 wt.%)sheets were investigated in detail concerning the effects of Y addition and temperature,and the relationship between damping capacity and yield strength was discussed.At room temperature(RT),with Y content increasing from 0.5%to 3.0%,the damping capacity(Q-1)significantly decreased from 0.037 to 0.015.For all the studied sheets,the relationship between strain amplitude and Q-1 fitted well with the Granato and Liicke(G-L)dislocation damping model.With temperature increased,the G-L plots deviated from linearity indicating that the dislocation damping was not the only dominate mechanism,and the grain boundary sliding(GBS)could contribute to damping capacity.Consequently,the Q-1 increased remarkably above the critical temperature,and the critical temperature increased significantly from 50℃ to 290℃ with increasing Y contents from 0 to 3.0wt.%.This result implied that the segregation of Y solutes at grain boundary could depress the GBS,which was consistent with the recent finding of segregation tendency for rare-earth solutes.The extruded Mg-IY sheet exhibited slightly higher yield strength(Rp0.2)and Q-1 comparing with high-damping Mg-0.6Zr at RT.At an elevated temperature of 325℃,the Mg-IY sheet had similar Q-1 but over 3 times larger Rp0.2 than that of the pure Mg.The present study indicated that the extruded Mg-Y based alloys exhibited promising potential for developing high-performance damping alloys,especially for the elevated-temperature application.