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 PO...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.展开更多
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 addi...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.展开更多
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 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.展开更多
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 ...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.展开更多
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 bioc...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.展开更多
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 pharm...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.展开更多
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 e...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.展开更多
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 prope...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.展开更多
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 di...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.展开更多
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...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.展开更多
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...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.展开更多
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 m...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.展开更多
An AZ91–0.9Ca–0.6Y–0.5MM(AZXWMM91100) alloy, which has higher corrosion resistance, ignition resistance, and extrudability than a commercial AZ91 alloy, has been developed recently. In this study, the AZXWMM91100 a...An AZ91–0.9Ca–0.6Y–0.5MM(AZXWMM91100) alloy, which has higher corrosion resistance, ignition resistance, and extrudability than a commercial AZ91 alloy, has been developed recently. In this study, the AZXWMM91100 alloy is extruded at various temperatures(300–400 ℃) and ram speeds(1–14.5 mm/s), and the cracking behaviors, microstructure, and tensile properties of the extruded materials are systematically analyzed. On the basis of the pressure limit and surface and internal cracking limit, the extrusion limit diagram providing a safe extrusion processing zone is established. All of the materials extruded at temperatures and speeds within the safe extrusion processing zone have high surface quality and moderate tensile ductility with an elongation higher than 10%. Moreover, they have a fully recrystallized grain structure and contain undissolved particle stringers arranged parallel to the extrusion direction. The grain size of the extruded material does not show any relationship with the Zener–Hollomon parameter(Z). However, the yield strength(YS) of the extruded material is inversely proportional to the logarithm of the Z value, and their relationship is expressed as YS =-31.2·log(Z) + 536. These findings may broaden the understanding of the AZXWMM91100 alloy with excellent chemical and physical properties and provide valuable information for the development of high-performance extruded Mg products using this alloy.展开更多
In recent years, there has been an increase in demand of gluten free products that are suitable for people with celiac disease. The present study was carried out to produce gluten free flat bread and biscuits with goo...In recent years, there has been an increase in demand of gluten free products that are suitable for people with celiac disease. The present study was carried out to produce gluten free flat bread and biscuits with good quality. The ingredients under this study were cassava flour, rice flour, extruded soy protein (ESP) and pumpkin powder. Four levels of ESP were used for production of flat bread and biscuits: 2.5%, 5%, 7.5% and 10% for flat bread and 5%, 10%, 15% and 20% levels for biscuits. Results of flat bread samples showed that protein, fat, ash and fiber contents increased in all samples as increasing the level of ESP. Flat bread at level 10% ESP had the highest value of β-carotene. Alkaline water retention capacity (AWRC) at zero time and 24 h of flat bread storage had high values for levels 2.5% and 5% ESP. Water holding capacity (WHC) increased insignificantly by increasing the level of ESP. Color measurements revealed that the lightness decreased and the redness increased with increasing the level of ESP. Sensory evaluation of flat bread revealed that 2.5% followed by 5% ESP level had high score of overall acceptability. Physical properties of biscuits indicated that as the level of ESP increased the diameter, thickness, volume and specific volume decreased. Biscuits sample with 20% ESP had the highest values of protein, fat, ash and fiber but the lowest in total carbohydrates. Also β-carotene and vitamin A content increased in biscuit samples. Caloric values of biscuits in all treated samples were lower than control. Lightness decreased while redness increased with increasing the level of ESP. Data of texture profile analysis (TPA) showed that hardness and adhesiveness (g) increased as ESP level increased. Sensory evaluation of biscuits showed that addition of ESP at 20% level decreased significantly texture score from 9.51 to 6.61 (P < 0.05) but insignificantly affected the other sensory scores.展开更多
In the current study poly(lactic acid)PLA composites with a 3 wt%and 5 wt%of nanofibrillated cellulose(NFC)were produced by 3D-printing method.An enzymatic pretreatment coupled with mechanical fibrillation in a twin s...In the current study poly(lactic acid)PLA composites with a 3 wt%and 5 wt%of nanofibrillated cellulose(NFC)were produced by 3D-printing method.An enzymatic pretreatment coupled with mechanical fibrillation in a twin screw extruder was used to produce high consistency NFC.Scanning electron microscopy(SEM)equipped with Fibermetric software,FASEP fiber length distribution analysis,Furrier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),tensile tests,impact tests and differential scanning calorimetry were used to characterize NFC and PLA/NFC composites.The results of the fiber length and width measurements together with the results of the SEM analysis showed that enzymatic hydrolysis coupled with a twin screw extrusion could effectively reduce the diameter and length of cellulose fibers.The produced NFC consisted of microand nanosized fibers entangled in a characteristic 3D-network.Based on the FT-IR analysis,no new bonds were formed during the enzymatic hydrolysis or fibrillation process.The TGA analysis confirmed that produced NFC can be used in hightemperature extrusion processing without NFC degradation.During the PLA/NFC composites preparation the NFC agglomerates were formed,which negatively influenced PLA/NFC composites impact properties.The slightly improved tensile strength and elastic modulus were reported for all composites when compared to the neat PLA.The elongation at break was not affected by the NFC addition.No significant differences in thermal stability were detectable among composites nor in comparation with the neat PLA.However,the crystallinity degree of the composite containing 5 wt%NFC was increased in respect to the neat PLA.展开更多
In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging proc...In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging process,the paper designs a hardware-in-loop simulation of twin-screw extruder experiment system which is closer to scene,low cost and high safety.The system through the establishment of twin-screw extruder’s mathematical model on computer to simulate the realistic system and there is hardware practicality in the computer simulation loop.The hardware based on C8051F020 can operate in the simulation loop in real time.In computer software design, we desigh man-machine interface that is intuitive and easy to operate,can reflect twin-screw extruder main operation information vividly.Finally,twin-screw extruder’s 3 heater temperature mathematical model and PID incremental control algorithm are presented.展开更多
Phase transformation and microstructural change of an extruded eutectoid Zn-Al alloy Zn76Al22Cu2 (wt pct) were investigated during creep testing by using SEM and X-ray diffraction techniques. Creep induced decompositi...Phase transformation and microstructural change of an extruded eutectoid Zn-Al alloy Zn76Al22Cu2 (wt pct) were investigated during creep testing by using SEM and X-ray diffraction techniques. Creep induced decomposition of a metastable η'T phase and a four phase transformation, α+ ε →T' +η, occurred during the creep testing. Also a microstructural change was observed from a lamellar structure into a spheroidized structure in the rupture part of the extruded alloy. It provided evidence of creep induced phase transformations which occurred in ageing process. The mechanism of creep rupture of the extruded Zn-Al alloy was also discussed.展开更多
文摘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.
基金supported by the Materials and Components Technology Development Program(No.20024843)funded by the Ministry of Trade,Industry&Energy(MOTIE,South Korea)by the National Research Council of Science&Technology(NST)grant(No.CRC23011-000)funded by the Korea government(MSIT).
文摘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.
文摘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.
基金Financial support from the projects by the NSFC(51771166)the Hebei Natural Science Foundation(E2019203452,E2021203011)+4 种基金the central government guiding local science and technology development(216Z1001G)the talent project of human resources and social security department of Hebei province(A202002002)the key project of department of education of Hebei province(ZD2021107)Graduate Innovation Program of Hebei province(CXZZBS2020053)The work was supported by the State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology(P2020-013).
文摘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.
基金from The Hitachi Global Foundation Asia Innovation Award 2020.Also,the authors thank the facilities,scientific and technical support from Advanced Characterization Laboratories Serpong and Cibinong,National Research and Innovation Institute through E-Layanan Sains,Badan Riset dan Inovasi Nasional(BRIN).
文摘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.
文摘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.
基金the National Basic Research Program of China(No.2013CB632205).
文摘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.
基金The authors would like to acknowledge the financial support from the National Key Basic Research Program(973 Program),Project(2013CB632205).
文摘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.
基金This work was supported by National Natural Science Foundation of China(Nos.51401172 and 51601003)National University Student Innovation Experimental Project(No.201710613005)Sichuan Science and Technology Program(No.2019YJ0238).
文摘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.
基金the National Natural Science Foundation(Grant nos.5177117&51671152 and 51874225)the Key Research and Development Program of Shanxi Province(Grant nos.2020KWZ-007 and 2018ZDXMGY-149)the Youth Innovation Team of Shanxi Universities and the Natural Science Foundation of Jilin Province(Grant no.20180414016GH).
文摘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.
文摘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.
基金Supported by the Industrial Foundation(20091041038)
文摘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.
基金supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science, ICT and Future Planning (MSIP, South Korea) (No. 2019R1A2C1085272)by the R&D Center for Valuable Recycling (Global-Top R&BD Program) of the Ministry of Environment of Korea (No. 2016002220003)。
文摘An AZ91–0.9Ca–0.6Y–0.5MM(AZXWMM91100) alloy, which has higher corrosion resistance, ignition resistance, and extrudability than a commercial AZ91 alloy, has been developed recently. In this study, the AZXWMM91100 alloy is extruded at various temperatures(300–400 ℃) and ram speeds(1–14.5 mm/s), and the cracking behaviors, microstructure, and tensile properties of the extruded materials are systematically analyzed. On the basis of the pressure limit and surface and internal cracking limit, the extrusion limit diagram providing a safe extrusion processing zone is established. All of the materials extruded at temperatures and speeds within the safe extrusion processing zone have high surface quality and moderate tensile ductility with an elongation higher than 10%. Moreover, they have a fully recrystallized grain structure and contain undissolved particle stringers arranged parallel to the extrusion direction. The grain size of the extruded material does not show any relationship with the Zener–Hollomon parameter(Z). However, the yield strength(YS) of the extruded material is inversely proportional to the logarithm of the Z value, and their relationship is expressed as YS =-31.2·log(Z) + 536. These findings may broaden the understanding of the AZXWMM91100 alloy with excellent chemical and physical properties and provide valuable information for the development of high-performance extruded Mg products using this alloy.
文摘In recent years, there has been an increase in demand of gluten free products that are suitable for people with celiac disease. The present study was carried out to produce gluten free flat bread and biscuits with good quality. The ingredients under this study were cassava flour, rice flour, extruded soy protein (ESP) and pumpkin powder. Four levels of ESP were used for production of flat bread and biscuits: 2.5%, 5%, 7.5% and 10% for flat bread and 5%, 10%, 15% and 20% levels for biscuits. Results of flat bread samples showed that protein, fat, ash and fiber contents increased in all samples as increasing the level of ESP. Flat bread at level 10% ESP had the highest value of β-carotene. Alkaline water retention capacity (AWRC) at zero time and 24 h of flat bread storage had high values for levels 2.5% and 5% ESP. Water holding capacity (WHC) increased insignificantly by increasing the level of ESP. Color measurements revealed that the lightness decreased and the redness increased with increasing the level of ESP. Sensory evaluation of flat bread revealed that 2.5% followed by 5% ESP level had high score of overall acceptability. Physical properties of biscuits indicated that as the level of ESP increased the diameter, thickness, volume and specific volume decreased. Biscuits sample with 20% ESP had the highest values of protein, fat, ash and fiber but the lowest in total carbohydrates. Also β-carotene and vitamin A content increased in biscuit samples. Caloric values of biscuits in all treated samples were lower than control. Lightness decreased while redness increased with increasing the level of ESP. Data of texture profile analysis (TPA) showed that hardness and adhesiveness (g) increased as ESP level increased. Sensory evaluation of biscuits showed that addition of ESP at 20% level decreased significantly texture score from 9.51 to 6.61 (P < 0.05) but insignificantly affected the other sensory scores.
文摘In the current study poly(lactic acid)PLA composites with a 3 wt%and 5 wt%of nanofibrillated cellulose(NFC)were produced by 3D-printing method.An enzymatic pretreatment coupled with mechanical fibrillation in a twin screw extruder was used to produce high consistency NFC.Scanning electron microscopy(SEM)equipped with Fibermetric software,FASEP fiber length distribution analysis,Furrier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),tensile tests,impact tests and differential scanning calorimetry were used to characterize NFC and PLA/NFC composites.The results of the fiber length and width measurements together with the results of the SEM analysis showed that enzymatic hydrolysis coupled with a twin screw extrusion could effectively reduce the diameter and length of cellulose fibers.The produced NFC consisted of microand nanosized fibers entangled in a characteristic 3D-network.Based on the FT-IR analysis,no new bonds were formed during the enzymatic hydrolysis or fibrillation process.The TGA analysis confirmed that produced NFC can be used in hightemperature extrusion processing without NFC degradation.During the PLA/NFC composites preparation the NFC agglomerates were formed,which negatively influenced PLA/NFC composites impact properties.The slightly improved tensile strength and elastic modulus were reported for all composites when compared to the neat PLA.The elongation at break was not affected by the NFC addition.No significant differences in thermal stability were detectable among composites nor in comparation with the neat PLA.However,the crystallinity degree of the composite containing 5 wt%NFC was increased in respect to the neat PLA.
文摘In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging process,the paper designs a hardware-in-loop simulation of twin-screw extruder experiment system which is closer to scene,low cost and high safety.The system through the establishment of twin-screw extruder’s mathematical model on computer to simulate the realistic system and there is hardware practicality in the computer simulation loop.The hardware based on C8051F020 can operate in the simulation loop in real time.In computer software design, we desigh man-machine interface that is intuitive and easy to operate,can reflect twin-screw extruder main operation information vividly.Finally,twin-screw extruder’s 3 heater temperature mathematical model and PID incremental control algorithm are presented.
文摘Phase transformation and microstructural change of an extruded eutectoid Zn-Al alloy Zn76Al22Cu2 (wt pct) were investigated during creep testing by using SEM and X-ray diffraction techniques. Creep induced decomposition of a metastable η'T phase and a four phase transformation, α+ ε →T' +η, occurred during the creep testing. Also a microstructural change was observed from a lamellar structure into a spheroidized structure in the rupture part of the extruded alloy. It provided evidence of creep induced phase transformations which occurred in ageing process. The mechanism of creep rupture of the extruded Zn-Al alloy was also discussed.