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.

Chemical and mechanical properties of stainless, environment-friendly, and nonflammable Mg alloys (SEN alloys): A review

This review article provides overall understanding of stainless,environment-friendly,and nonflammable Mg alloys(SEN alloys)recently developed at the Korea Institute of Materials Science.SEN alloys are produced by adding small amounts of Ca and Y(each<1 wt%)into commercial Mg–Al based alloys,resulting in exceptional ignition and corrosion resistances and impressive mechanical properties.Their main advantages of SEN alloys are as follows.(1)A dense multi-oxide layer of SEN alloys comprising MgO,CaO,and Y_(2)O_(3) impedes the outward dispersion of Mg vapor and the inward penetration of O_(2) during oxidation,thereby enhancing the oxidation and ignition resistances.(2)The presence of Ca-and Y-based second-phase particles in SEN alloys can enhance their corrosion resistance because Ca-containing particles prevent the spread of corrosion,and the replacement of Al-containing particles with less noble ones containing Y(e.g.,Al–Mn–Y or Al–Y particles)retards corrosion.(3)The addition of minor amounts of Ca and Y renders excellent mechanical properties due to improved strengthening effects.These enhanced properties are attributed to more pronounced dynamic recrystallization and grain refining behaviors caused by the second-phase particles during extrusion.(4)Despite the presence of various types of second-phase particles,the fatigue properties of SEN9 alloys are similar to those of commercial AZ91 alloys.(5)Simultaneous introduction of Ca and Y suppresses the formation of Mg17Al12 discontinuous precipitates during aging,leading to the enhanced elongation of aged SEN alloys.(6)Adding mischmetal into the SEN9 alloy leads to a six-fold enhancement in extrudability.Consequently,the studies conducted on SEN alloys demonstrate their excellent ignition and corrosion resistances and mechanical properties,which broaden the industrial applications of Mg alloys by addressing their inherent weaknesses.

A desktop customised 3D printer with dual extruders to produce electronic circuitry

3D printing has opened new horizons for the manufacturing industry in general, and 3D printers have become the tools for technological advancements. There is a huge divide between the pricing of industrial and desktop 3D printers with the former being on the expensive side capable of producing excellent quality products and latter being on the low-cost side with moderate quality results. However, there is a larger room for improvements and enhancements for the desktop systems as compared to the industrial ones. In this paper, a desktop 3D printer called Prusa Mendel i2 has been modified and integrated with an additional extruder so that the system can work with dual extruders and produce bespoke electronic circuits. The communication between the two extruders has been established by making use of the In-Chip Serial Program- ming port on the Arduino Uno controlling the printer. The biggest challenge is to control the flow of electric paint （to be dispensed by the new extruder） and CFD （Computa- tional Fluid Dynamics） analysis has been carried out to ascertain the optimal conditions for proper dispensing. The final product is a customised electronic circuit with the base of plastic （from the 3D printer＇s extruder） and electronic paint （from the additional extruder） properly dispensed to create a live circuit on a plastic platform. This low-cost enhancement to a desktop 3D printer can provide a new prospect to produce multiple material parts where the additional extruder can be filled with any material that can be properly dispensed from its nozzle.

The roles of stress state and pre-straining on Swift effect for an extruded AZ31 Mg alloy

The Swift effect of Mg alloy is sensitive to initial texture.However,dislocation slip is the main deformation mechanism during torsion of Mg alloy.The underlying relation of Swift effect and dislocation slip is still not clarified.The effect of stress state and pre-straining on Swift effect was studied experimentally during free-end torsion for an extruded AZ31 alloy.The free-end torsion was performed with axial tension and compression stress which is lower than yield stress.It is found that the transition of axial deformation from contraction to elongation occurs when the axial stress changes from negative to positive.The pre-dislocations introduced by pre-tension promote axial shortening during torsion.While the pre-twins introduced by pre-compression are inhibition of axial shortening.The change of axial deformation is attributed to competition between twinning and prismatic slip.The axial shortening of extruded Mg alloy is generated by tensile twinning leading to c-axis strain.In contrast,the axial elongation can be generated by the activation of prismatic slip.The magnitude of axial strain generated by twinning is larger than that by prismatic slip.Moreover,the occurrence of detwinning results in axial elongation at low shear strain.

Preparation and Characterization of Thermoplastic Starch from Sugar Palm (Arenga pinnata) by Extrusion Method

Sugar palm(Arenga pinnata)starch is considered an important renewable,biodegradable,and eco-friendly polymer,which is derived from agricultural by-products and residues,with great potential for the development of biocomposite materials.This research was aimed at investigating the development of TPS biocomposites from A.pinnata palm starch using an extrusion process.Palm starch,glycerol,and stearic acid were extruded in a twin-screw extruder.Scanning electron microscopy(SEM)analysis of TPS showed that the starch granules were damaged and gelatinized in the extrusion process.The density of TPS was 1.3695 g/mL,lower than that of palm starch,and the addition of stearic acid resulted in increased TPS density.X-ray diffraction(XRD)results showed that palm starch had a C-type pattern crystalline structure.The tensile strength,elongation at break,and modulus of elasticity of TPS were 7.19 MPa,33.95%,and 0.56 GPa,respectively.The addition of stearic acid reduced the tensile strength,elongation at break and modulus of elasticity of TPS.The rheological properties,i.e.,melt flow rate(MFR)and viscosity of TPS,were 7.13 g/10 min and 2482.19 Pa.s,respectively.The presence of stearic acid in TPS resulted in increased MFR and decreased viscosity values.The peak gelatinization temperature of A.pinnata palm starch was 70°C,while Tg of TPS was 65°C.The addition of stearic acid reduced the Tg of TPS.The thermogravimetric analysis(TGA)analysis showed that the addition of glycerol and stearic acid decreased the thermal stability,but extended the temperature range of thermal degradation.TPS derived from A.pinnata palm starch by extrusion method has the potential to be applied in industrial practice as a promising raw material for manufacturing bio-based packaging as a sustainable and green alternative to petroleum-based plastics.

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.

Hot melt extrusion:An industrially feasible approach for casting orodispersible film

Over the recent few decades,many groups of formulation scientists are concentrating on rapid release dosage forms in oral cavity.Among all fast release dosage forms,orodispersible films are successful to attract pharmaceutical industry due to ease of formulation and extension patent life.Films are popular in patients too because of quick onset and user friendliness of dosage form.From the beginning,solvent casting has been selected as method of choice for manufacturing of orodispersible films.Solvent casting has been proved as a benchmark technology because of ease in product development,process optimization,process validation and technology transfer to production scale despite of some drawbacks like more number of unit operations involved and consumption of large quantity of solvents with controlled limits of organic volatile impurities in final formulation.The application of hot-melt extrusion(HME)in the pharmaceutical industry is consecutively increasing due to its proven innumerable advantages like solvent free continuous process with fewer unit operations and better content uniformity.Very few development activities has been initiated in the field of hot melt extruded orodispersible films so far.This extensive review covers detailed discussion of heavy duty industrial extruders,selection of downstream equipments,selection of excipients,common problems found in formulations and their remedies.Successive part of review addresses identification of critical quality attributes,quality target profile of product,criticality in selection of process parameters and material for substantial simulation in laboratory scale and production for successful technology transfer.

Engineering Review Food Extrusion Technology and Its Applications

An extensive technical review of studies on food extrusion processes which involves forcing mixed food ingredients through a die to produce food snacks has been carried out in this paper. This technical review includes some historical development, food extruder types, extrusion principles and applications, flow simulation and heat transfer modeling in extruders, process parameters and product quality, extruder die and extrudate expansion among others. The research and application of extrusion in food industry was mainly based on the adaptation of plastic extrusion technology which has been in existence for over hundred years. Studies show that twin-screw extruder are more efficient than single-screw extruders because of better mixing and better handling of different combinations of food ingredients. A thorough knowledge of the flow and heat behavior inside an extruder provide an insight into the mechanism of mixing and facilitates estimation of RTD, flow rate, pressure drop, heat transfer mechanism and power consumption. Until recently, very little work has been published on the mechanism of material flow and energy transfer in intermeshing co-rotating extruder mainly due to the complexity of the geometry and the flow behavior. A more recent approach to research in modeling of food extrusion is the 2D or 3D flow modeling using finite element computer package. This research area is gaining recognition in modeling different sections of food extruder. This work also points out some of the achievements and shortcomings of the reviewed works and where necessary, possible solutions are suggested. Areas needing further research have been highlighted. This study will reveal that understanding and application of extrusion technology in developing countries of Asia and Africa are still far from being satisfactory and this work would serve as a good reference material for researchers and operators in food extrusion technology.

在VISUAL LISP环境下圆柱状螺旋弹簧建模的实现

在AUTOCAD的实际应用中,使用常用工具圆柱状螺旋弹簧的建模很难实现,甚至根本无法完成.为了解决这个问题,本文通过编制VISUAL LISP程序来实现.这样,在AUTOCAD环境下该程序不仅可以完成圆柱状螺旋线自动绘图,简化建模的过程,也可以完成使用常用工具建模所不能实现的模型.

Study of glue extrusion after endoscopic N-butyl-2-cyanoacrylate injection on gastric variceal bleeding

AIM:To investigate glue extrusion after endoscopic N-butyl-2-cyanoacrylate injection on gastric variceal bleeding and to evaluate the long-term efficacy and safety of this therapy.METHODS:A total of 148 cirrhotic patients in our hospital with esophagogastric variceal bleeding(EGVB) were included in this study.N-butyl-2-cyanoacrylate was mixed with lipiodol in a 1:1 ratio and injected as a bolus of 1-3 mL according to variceal size.Patients underwent endoscopic follow-up the next week,fourth week,second month,fourth month,and seventh month after injection and then every 6 mo to determine the cast shape.An abdominal X-ray fi lm and ultrasound or computed tomographic scan were also carried out in order to evaluate the time of variceal disappearance and complete extrusion of the cast.The average follow-up time was 13.1 mo.RESULTS:The instantaneous hemostatic rate was 96.2%.Early re-bleeding after injection in 9 cases(6.2%) was estimated from rejection of adhesive.Late re-bleeding occurred in 12 patients(8.1%) at 2-18 mo.The glue cast was extruded into the lumen within one month in 86.1% of patients and eliminated within one year.Light erosion was seen at the injection position and mucosa edema in the second week.The glue casts were extruded in 18 patients(12.1%) after one week and in 64 patients(42.8%) after two weeks.All kinds of glue clumping shapes and colors on endoscopic examination were observed in 127 patients(86.1%) within one month,including punctiform,globular,pillar and variform.Forty one patients(27.9%) had glue extrusion after 3 mo and 28 patients(28.9%) after six months.The extrusion time was not related to the injection volume of histoacryl.Obliteration was seen in 70.2%(104 cases) endoscopically.The main complication was re-bleeding resulting from extrusion.The prognosis of the patients depended on the severity of the underlying liver disease.CONCLUSION:Endoscopic injection of cyanoacrylate is highly effective for gastric varices bleeding.The glue clump shape is correlated with anatomic structure of vessels.The time of extrusion was not related to dosage of the glue.

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.

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.

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.

Dynamic compressive property and failure behavior of extruded Mg-Gd-Y alloy under high temperatures and high strain rates

For the purpose of investigating the dynamic deformational behavior and failure mechanisms of magnesium under high strain rates,the Split Hopkinson Pressure Bar(SHPB)was used for investigating dynamic mechanical properties of extruded Mg-Gd-Y Magnesium alloy at ambient temperature(300 K),200℃(473 K)and 300℃(573 K)temperature.The samples after compression were analyzed by scanning electron microscope(SEM)and metallographic microscope.Dynamic mechanical properties,crack performance and plastic deformation mechanism of extruded Mg-Gd-Y Magnesium alloy along the extrusion direction(ED)were discussed.The results show that,extruded Mg-Gd-Y Magnesium alloy has the largest dynamic compressive strength which is 535 MPa at ambient temperature(300 K)and strain rate of 2826 s^(−1).When temperature increases,dynamic compressive strength decreases,while ductility increases.The dynamic compression fracture mechanism of extruded Mg-Gd-Y Magnesium alloy is multi-crack propagation and intergranular quasi-cleavage fracture at both ambient temperature and high temperature.The dynamic compressive deformation mechanism of extruded Mg-Gd-Y Magnesium alloy is a combination of twinning,slipping and dynamic recrystallization at both ambient temperature and high temperature.

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.

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.

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 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.

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.

Fabrication and Mechanical Properties of 2024 Aluminum Alloy Reinforced by FeNiCrCoAl_3 High Entropy Particles

This article mainly discussed bulk material lHvl^ared by powder metallurgy, and the commercial 2024 aluminum alloy powder and FeNiCrCoA13 high entropy alloy powder （both produced by argon gas atomization process） were ball-milled for different hours. The prepared powder was consolidated by hot extrusion method. The microstruetures of the milled powder and bulk alloy were examined by X - Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM） and Transmission Electron Microscopy （TEM）. The thermal stability was tested by differential scanning calorimetry （DSC）. Mechanical properties of the extruded alloy were examined by Vickers hardness tester and mechanical testing machine. The results show that after milling, the mixed particle sizes and microstructures of the alloy powder change obviously. The compressive strength of the extruded alloy has reached 580 MPa under certain conditions of milling time and composition.