Investigating the ignition response of nitrate ester plasticized polyether(NEPE) propellant under dynamic extrusion loading is of great significant at least for two cases. Firstly, it helps to understand the mechanism...Investigating the ignition response of nitrate ester plasticized polyether(NEPE) propellant under dynamic extrusion loading is of great significant at least for two cases. Firstly, it helps to understand the mechanism and conditions of unwanted ignition inside charged propellant under accident stimulus.Secondly, evaluates the risk of a shell crevice in a solid rocket motor(SRM) under a falling or overturning scene. In the present study, an innovative visual crevice extrusion experiment is designed using a dropweight apparatus. The dynamic responses of NEPE propellant during extrusion loading, including compaction and compression, rapid shear flow into the crevice, stress concentration, and ignition reaction, have been firstly observed using a high-performance high-speed camera. The ignition reaction is observed in the triangular region of the NEPE propellant sample above the crevice when the drop weight velocity was 1.90 m/s. Based on the user material subroutine interface UMAT provided by finite element software LS-DYNA, a viscoelastic-plastic model and dual ignition criterion related to plastic shear dissipation are developed and applied to the local ignition response analysis under crevice extrusion conditions. The stress concentration occurs in the crevice location of the propellant sample, the shear stress is relatively large, the effective plastic work is relatively large, and the ignition reaction is easy to occur. When the sample thickness decreases from 5 mm to 2.5 mm, the shear stress increases from 22.3 MPa to 28.6 MPa, the critical value of effective plastic work required for ignition is shortened from 1280 μs to 730 μs, and the triangular area is easily triggering an ignition reaction. The propellant sample with a small thickness is more likely to stress concentration, resulting in large shear stress and effective work, triggering an ignition reaction.展开更多
Carbon nanotubes(CNTs)with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon aerogels.However,there remains a major challenge for achieving the on-demand shapi...Carbon nanotubes(CNTs)with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon aerogels.However,there remains a major challenge for achieving the on-demand shaping of carbon aerogels with tailored micro-nano structural textures and geometric features.Herein,a facile extrusion 3D printing strategy has been proposed for fabricating CNT-assembled carbon(CNT/C)aerogel nanocomposites through the extrusion printing of pseudoplastic carbomer-based inks,in which the stable dispersion of CNT nanofibers has been achieved relying on the high viscosity of carbomer microgels.After extrusion printing,the chemical solidification through polymerizing RF sols enables 3D-printed aerogel nanocomposites to display high shape fidelity in macroscopic geometries.Benefiting from the micro-nano scale assembly of CNT nanofiber networks and carbon nanoparticle networks in composite phases,3D-printed CNT/C aerogels exhibit enhanced mechanical strength(fracture strength,0.79 MPa)and typical porous structure characteristics,including low density(0.220 g cm^(-3)),high surface area(298.4 m^(2)g^(-1)),and concentrated pore diameter distribution(~32.8nm).More importantly,CNT nanofibers provide an efficient electron transport pathway,imparting 3D-printed CNT/C aerogel composites with a high electrical conductivity of 1.49 S cm^(-1).Our work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.展开更多
In order to study the laws of the extrusion pressure changing with the extrusion parameters in the process of hydrostatic extrusion for the tungsten alloys, the large deformation elasto plastic theory and the sof...In order to study the laws of the extrusion pressure changing with the extrusion parameters in the process of hydrostatic extrusion for the tungsten alloys, the large deformation elasto plastic theory and the software of ANSYS 5 5 are used to carry out the numerical simulation research. The laws of the extrusion pressure changing with the extrusion parameters, such as the die angle, extrusion ratio, and friction coefficient, are obtained. The simulation results are in good agreement with the experimental ones, and the simulated results are believable.展开更多
Wall slip boundary condition is first introduced into twin-screw extrusion with the Navier slip law. Three-dimensional isothermal flow in the twin-screw extruder is simulated by using the finite element package POLYFL...Wall slip boundary condition is first introduced into twin-screw extrusion with the Navier slip law. Three-dimensional isothermal flow in the twin-screw extruder is simulated by using the finite element package POLYFLOW. Profiles of velocity contours in the screw channel and shear rate distributions in the intermeshing region are presented for different slip coefficients. Curves of axial pressure difference, average shear rate and dispersive mixing index vs. the slip coefficient are plotted and discussed. Comparisons are also made between the wall slip conditions and the non-slip condition. The simulation results indicate that, as the level of wall slip decreases, the axial pressure difference rises, the shear effect is intensified and the axial mixing is also enhanced. All these flow characteristics seem to level off with the increase of the slip coefficient. However, because of the inherent limitation of the Navier slip law, use of an overestimated slip coefficient would predict an over-sticky state between the screw surface and the polymer melt.展开更多
β-Conglycinin,the main component of 7S globulin in soybean protein,is also a key soybean antigen protein that causes allergic reactions.Extrusion technologies have received considerable attention as amethod for modif...β-Conglycinin,the main component of 7S globulin in soybean protein,is also a key soybean antigen protein that causes allergic reactions.Extrusion technologies have received considerable attention as amethod for modifying soybean protein allergens.This study investigated the changes inβ-conglycinin structure and antigenicity upon extrusion.Isoelectric precipitation,ammoniumsulfate precipitation,and sepharose CL-6B gel filtration were used to isolate and purifyβ-conglycinin from soybean powder,and single-factor and orthogonal tests were used to study the effects of water content,extrusion temperature,screw rotation speed,and feeding speed on the antigenicity ofβ-conglycinin after extrusion.Fourier transforminfrared spectrometry(FTIR)was then employed to analyze the structure ofβ-conglycinin after extrusion under the optimal conditions determined by the orthogonal test.The results showed that extrusion significantly reduced the antigenicity ofβ-conglycinin(P<0.05),and the degree of influence of the factors studied may be ordered as extrusion temperature>feeding speed>screw rotation speed>water content.The optimal parameters were temperature at 130°C,screwrotation speed at 140 r/min,and feeding speed at 35 g/min.Under these conditions,the contents ofα-helix,β-pleated sheet,andβ-turn structures inβ-conglycinin were significantly reduced(P<0.05),while the contents of random coils were significantly increased(P<0.05).The peak absorption intensity of amides I,II,and III also decreased.Taken together,the findings suggest that extrusion could be an effective method for reducing the antigenicity ofβ-conglycinin.展开更多
304L H-shaped stainless steel is used as the support frame of the passive residual heat removal heat exchanger(PRHR HX) in a nuclear fission reactor. The extrusion process is adopted to manufacture the 304L H-shaped s...304L H-shaped stainless steel is used as the support frame of the passive residual heat removal heat exchanger(PRHR HX) in a nuclear fission reactor. The extrusion process is adopted to manufacture the 304L H-shaped stainless steel. Finite element method simulation is herein used to analyze metal flow characteristics, optimize the extrusion die, and predict the extrusion force at different temperatures and speeds. A Φ400-mm container and Φ388-mm forging billet are selected, and the 304L H-shaped stainless steel is successfully manufactured using a Germany SMS 60 MN horizontal extruder. The mechanical properties and microstructure of the manufactured 304L H-shaped stainless steel meet the requirements of the PRHR HX, and the surfaces of the product pass the dye penetration test. The H-shaped stainless steels are used in Haiyang nuclear power plant in Shandong Province.展开更多
Swell and sag drawdown significantly influence the high density polyethylene parison. Nu- merical simulations of the flow field of a HDPE melt were performed using the finite element method for the die of plastic pipe...Swell and sag drawdown significantly influence the high density polyethylene parison. Nu- merical simulations of the flow field of a HDPE melt were performed using the finite element method for the die of plastic pipe extrusion and parison formation. The constitutive equation of Carreau law was used to describe the polymer melt in the flow domain. The distributions of the velocity, shear rate, viscosity, pressure, thickness and radius are presented with Polyflow. The effect of flow rate and temperature on extrusion swell and parison sag was investigated. The results show that the thickness of the parison increases with increasing flow rate. The thickness and radius of the parison are more sensitive to changes in flow rates than to changes in temperatures.展开更多
A more universal and flexible method of constructing the streamlined die surfaces is presented. The streamlined die surfaces are interpolated by the arbitrarily cross sectional shapes of the die entrance and exit. Th...A more universal and flexible method of constructing the streamlined die surfaces is presented. The streamlined die surfaces are interpolated by the arbitrarily cross sectional shapes of the die entrance and exit. The boundaries of the die entrance and exit are represented by Ferguson curves with tension parameters. By adjusting the tension parameter, the cross sectional shapes of the die entrance and exit with line segments can be accurately constructed. The upper bound method is used to analyze the procedure of extrusion, the pseudo independent parameters in kinematically admissible velocity and die surface are computed by minimizing the extrusion load, so the optimum die surface is obtained. The effects of frictional condition, die length, area reduction and product shaped complexity are discussed in relation to the extrusion load.展开更多
Based on the observation and analysis of cores and thin sections,and combined with cathodoluminescence,laser Raman,fluid inclusions,and in-situ LA-ICP-MS U-Pb dating,the genetic mechanism and petroleum geological sign...Based on the observation and analysis of cores and thin sections,and combined with cathodoluminescence,laser Raman,fluid inclusions,and in-situ LA-ICP-MS U-Pb dating,the genetic mechanism and petroleum geological significance of calcite veins in shales of the Cretaceous Qingshankou Formation in the Songliao Basin were investigated.Macroscopically,the calcite veins are bedding parallel,and show lenticular,S-shaped,cone-in-cone and pinnate structures.Microscopically,they can be divided into syntaxial blocky or columnar calcite veins and antitaxial fibrous calcite veins.The aqueous fluid inclusions in blocky calcite veins have a homogenization temperature of 132.5–145.1℃,the in-situ U-Pb dating age of blocky calcite veins is(69.9±5.2)Ma,suggesting that the middle maturity period of source rocks and the conventional oil formation period in the Qingshankou Formation are the sedimentary period of Mingshui Formation in Late Cretaceous.The aqueous fluid inclusions in fibrous calcite veins with the homogenization temperature of 141.2–157.4℃,yields the U-Pb age of(44.7±6.9)Ma,indicating that the middle-high maturity period of source rocks and the Gulong shale oil formation period in the Qingshankou Formation are the sedimentary period of Paleocene Yi'an Formaiton.The syntaxial blocky or columnar calcite veins were formed sensitively to the diagenetic evolution and hydrocarbon generation,mainly in three stages(fracture opening,vein-forming fluid filling,and vein growth).Tectonic extrusion activities and fluid overpressure are induction factors for the formation of fractures,and vein-forming fluid flows mainly as diffusion in a short distance.These veins generally follow a competitive growth mode.The antitaxial fibrous calcite veins were formed under the driving of the force of crystallization in a non-competitive growth environment.It is considered that the calcite veins in organic-rich shale of the Qingshankou Formation in the study area has important implications for local tectonic activities,fluid overpressure,hydrocarbon generation and expulsion,and diagenesis-hydrocarbon accumulation dating of the Songliao Basin.展开更多
In this study, we investigated the performance improvement caused by the addition of copper(Cu)nanoparticles to high-density polyethylene(HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0...In this study, we investigated the performance improvement caused by the addition of copper(Cu)nanoparticles to high-density polyethylene(HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 wt% were synthesized through the material extrusion(MEX)3D printing technique. The synthesized nanocomposite filaments were utilized for the manufacturing of specimens suitable for the experimental procedure that followed. Hence, we were able to systematically investigate their tensile, flexural, impact, and microhardness properties through various mechanical tests that were conducted according to the corresponding standards. Broadband Dielectric Spectroscopy was used to investigate the electrical/dielectric properties of the composites. Moreover, by employing means of Raman spectroscopy and thermogravimetric analysis(TGA) we were also able to further investigate their vibrational, structural, and thermal properties. Concomitantly, means of scanning electron microscopy(SEM), as well as atomic force microscopy(AFM), were used for the examination of the morphological and structural characteristics of the synthesized specimens, while energy-dispersive Xray spectroscopy(EDS) was also performed in order to receive a more detailed picture on the structural characteristics of the various synthesized composites. The corresponding nanomaterials were also assessed for their antibacterial properties regarding Staphylococcus aureus(S. aureus) and Escherichia coli(E. coli) with the assistance of a method named screening agar well diffusion. The results showed that the mechanical properties of HDPE benefited from the utilization of Cu as a filler, as they showed a notable improvement. The specimen of HDPE/Cu 4.0 wt% was the one that presented the highest levels of reinforcement in four out of the seven tested mechanical properties(for example, it exhibited a 36.7%improvement in the flexural strength, compared to the pure matrix). At the same time, the nanocomposites were efficient against the S. aureus bacterium and less efficient against the E. coli bacterium.The use of such multi-functional, robust nanocomposites in MEX 3D printing is positively impacting applications in various fields, most notably in the defense and security sectors. The latter becomes increasingly important if one takes into account that most firearms encompass various polymeric parts that require robustness and improved mechanical properties, while at the same time keeping the risk of spreading various infectious microorganisms at a bare minimum.展开更多
Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt- spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6A10.2B0.9 （wt%） is used as starting materi...Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt- spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6A10.2B0.9 （wt%） is used as starting material. The effects of process variables, such as deformation temperature （Td）, strain rate （ε） and height reduction （△h%）, on the magnetic properties of the rings are investigated. A scanning electron microscope （SEM） equipped with an energy spectrum device is used to study the metallograph and microfracture of the extruded rings. The Br and （BH）max reach the optimum values at Td =800℃,ε= 0.01 mm/s, and △h% = 70%. It is found by SEM observations that the particle boundaries, which seemingly correspond to the interfaces of the starting melt-spun powders, emerge after the corrosion of metallography specimens. This is helpful for studying the effects of powder-powder interface on the local deformation and deformation homogeneity in the rings. For different spatial positions of the extruded rings, there are characteristic metallographies and microfractures. The upper end of the rings has the least deformation and worst texture, and therefore the worst magnetic properties. The magnetic properties in the radial direction increase slightly along the axis from the bottom to the middle, then steeply decrease at the upper end of the ring. The deformation and the formation-of-texturing processes are discussed. The deformation and the texturing formation of melt-spun Nd-Fe-B alloys probably involve grain boundary sliding and grain rotation, the solution-precipitation process and preferential growth of Nd2Fel4B nanograins along the easy growth a-axis.展开更多
Foxtail millet, originated from China and now cultivated worldwide, is a kind of high dietary fiber whole grain food, and has a high level of vitamins and proteins. Furthermore, foxtail millet has many positive effect...Foxtail millet, originated from China and now cultivated worldwide, is a kind of high dietary fiber whole grain food, and has a high level of vitamins and proteins. Furthermore, foxtail millet has many positive effects on the adjuvant treatment of diabetes, cancer, and cardiovascular diseases because of the abundance in polyphenols. Nonetheless, foxtail millet has poor processing characteristics due to the absence of gluten, restricting the development of foxtail millet products. Studies have demonstrated that heat-moisture treatment, extrusion, superfine grinding, and microbial fermentation are promising methods to improve the processing qualities of foxtail millet. Heat-moisture treatment is helpful to increase the content of resistant starch but has less influence on other components, further reduce the GI value of foxtail millet. The extrusion has positive effects on improving the solubility of foxtail millet starch and increasing the contents of polyunsaturated fatty acid, linoleic and linolenic acids, and adverse effects on reducing the solubility of foxtail millet proteins and causing losses of nutrients due to Maillard reaction. Superfine grinding can reduce the particle size of foxtail millet to obtain a better mouthfeel of foxtail millet products. The superfine foxtail millet flour has better solubility, higher freeze-thaw stability, and lower gelatinization temperature. Microbial fermentation contributes positively to reducing the molecular weight and retrogradation value of foxtail millet starch, degrading rapidly digested starch, and improving the digestibility of foxtail millet protein. This paper briefly introduced the effects of different processing methods on foxtail millet nutrients, aiming to provide references for increasing the variety and improving the quality of foxtail millet products.展开更多
With the aid of hydrogenation/dehydrogenation, nanorod whiskers of transition metal Mn can grow spontaneously from Zrl_xTi^MnCr Laves phase alloys at room temperature. The finding introduces a distinguishingly differe...With the aid of hydrogenation/dehydrogenation, nanorod whiskers of transition metal Mn can grow spontaneously from Zrl_xTi^MnCr Laves phase alloys at room temperature. The finding introduces a distinguishingly different element into metal whisker family, and provides a potential technique for fabrication of one-dimensional metal nanostructures. Moreover, it is found that the segregated Mn in whiskers forms a novel hexagonal structure, which partially fulfills the long predicted allotropic form and adds more complexity to the structures of Mn.展开更多
Multigrain noodles were made by corn and wheat flour as the main ingredients and with small ratios of oat flour, soybean flour and millet flour through extrusion process. Simplex centroid design was used to analyze ge...Multigrain noodles were made by corn and wheat flour as the main ingredients and with small ratios of oat flour, soybean flour and millet flour through extrusion process. Simplex centroid design was used to analyze gelatinization characteristics of the mixed flour, rheological characteristics of the doughs, cooking qualities and sensory qualities of noodles. A proper formula for multigrain noodles obtained as outcome: 45% corn flour, 40% wheat flour, 4% oat flour, 11% millet flour. Compared to the wheat noodles, the multigrain noodles had higher content in fat, dietary fiber and total resistant starch, but it did content less proteins than wheat noodles.展开更多
Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)proc...Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)procedure.This can be very important in defense-related applications,where optimum performance needs to be guaranteed.The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters,namely,infill percentage,layer height,deposition angle,travel speed,nozzle,and bed temperature.The quality indicators were the root mean square(Rq)and average(Ra)roughness,porosity,and the actual to nominal dimensional deviation.The examination was performed with optical profilometry,optical microscopy,and micro-computed tomography scanning.The Taguchi design of experiments was applied,with twenty-five runs,five levels for each control parameter,on five replicas.Two additional confirmation runs were conducted,to ensure reliability.Prediction equations were constructed to express the quality indicators in terms of the control parameters.Three modeling approaches were applied to the experimental data,to compare their efficiency,i.e.,Linear Regression Model(LRM),Reduced Quadratic Regression Model,and Quadratic Regression Model(QRM).QRM was the most accurate one,still the differences were not high even considering the simpler LRM model.展开更多
This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printin...This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printing(3DP)by improving its mechanical properties while simultaneously adding antibacterial properties.The latter can find extremely important and versatile properties that are applicable in defense and security domains.PP/Ag nanocomposites were prepared using a novel method based on a reaction occurring while mixing appropriate quantities of the starting polymers and additives,namely polyvinylpyrrolidone(PVP)as the matrix material and silver nitrate(AgNO_(3))as the filler.This process produced three-dimensional(3D)printed filaments,which were then used to create specimens for a series of standardized tests.It was found that the mechanical properties of the nanocomposites were enhanced in relation to pristine PP,especially for the PP matrix with various loadings of AgNO_(3)and PVP,such as 5.0 wt%and 2.5 wt%,respectively.The voids,inclusions,and actual-to-nominal dimensions also showed improved results.The 3DP specimens exhibited a more effective biocidal performance against Staphylococcus aureus than Escherichia coli,which developed an inhibition zone only in the case of PP with filler loading percentages of AgNO_(3)and PVP at 10.0 wt%and 5.0 wt%,respectively Compounds possessing such properties can be beneficial for various applications requiring increased mechanical properties and biocidal capabilities,such as in the Defence or medical industries.展开更多
基金National Natural Science Foundation of China(U22B20131)State Key Laboratory of Explosion Science and Technology(QNKT23-10)for supporting this project.
文摘Investigating the ignition response of nitrate ester plasticized polyether(NEPE) propellant under dynamic extrusion loading is of great significant at least for two cases. Firstly, it helps to understand the mechanism and conditions of unwanted ignition inside charged propellant under accident stimulus.Secondly, evaluates the risk of a shell crevice in a solid rocket motor(SRM) under a falling or overturning scene. In the present study, an innovative visual crevice extrusion experiment is designed using a dropweight apparatus. The dynamic responses of NEPE propellant during extrusion loading, including compaction and compression, rapid shear flow into the crevice, stress concentration, and ignition reaction, have been firstly observed using a high-performance high-speed camera. The ignition reaction is observed in the triangular region of the NEPE propellant sample above the crevice when the drop weight velocity was 1.90 m/s. Based on the user material subroutine interface UMAT provided by finite element software LS-DYNA, a viscoelastic-plastic model and dual ignition criterion related to plastic shear dissipation are developed and applied to the local ignition response analysis under crevice extrusion conditions. The stress concentration occurs in the crevice location of the propellant sample, the shear stress is relatively large, the effective plastic work is relatively large, and the ignition reaction is easy to occur. When the sample thickness decreases from 5 mm to 2.5 mm, the shear stress increases from 22.3 MPa to 28.6 MPa, the critical value of effective plastic work required for ignition is shortened from 1280 μs to 730 μs, and the triangular area is easily triggering an ignition reaction. The propellant sample with a small thickness is more likely to stress concentration, resulting in large shear stress and effective work, triggering an ignition reaction.
基金supported by the Hunan Provincial Natural Science Foundation of China (Grant no.2023JJ30632)National Key R&D Program (Grant no.2022YFC2204403)Key R&D Program of Hunan Province (Grant no.2022GK2027)。
文摘Carbon nanotubes(CNTs)with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon aerogels.However,there remains a major challenge for achieving the on-demand shaping of carbon aerogels with tailored micro-nano structural textures and geometric features.Herein,a facile extrusion 3D printing strategy has been proposed for fabricating CNT-assembled carbon(CNT/C)aerogel nanocomposites through the extrusion printing of pseudoplastic carbomer-based inks,in which the stable dispersion of CNT nanofibers has been achieved relying on the high viscosity of carbomer microgels.After extrusion printing,the chemical solidification through polymerizing RF sols enables 3D-printed aerogel nanocomposites to display high shape fidelity in macroscopic geometries.Benefiting from the micro-nano scale assembly of CNT nanofiber networks and carbon nanoparticle networks in composite phases,3D-printed CNT/C aerogels exhibit enhanced mechanical strength(fracture strength,0.79 MPa)and typical porous structure characteristics,including low density(0.220 g cm^(-3)),high surface area(298.4 m^(2)g^(-1)),and concentrated pore diameter distribution(~32.8nm).More importantly,CNT nanofibers provide an efficient electron transport pathway,imparting 3D-printed CNT/C aerogel composites with a high electrical conductivity of 1.49 S cm^(-1).Our work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.
文摘In order to study the laws of the extrusion pressure changing with the extrusion parameters in the process of hydrostatic extrusion for the tungsten alloys, the large deformation elasto plastic theory and the software of ANSYS 5 5 are used to carry out the numerical simulation research. The laws of the extrusion pressure changing with the extrusion parameters, such as the die angle, extrusion ratio, and friction coefficient, are obtained. The simulation results are in good agreement with the experimental ones, and the simulated results are believable.
文摘Wall slip boundary condition is first introduced into twin-screw extrusion with the Navier slip law. Three-dimensional isothermal flow in the twin-screw extruder is simulated by using the finite element package POLYFLOW. Profiles of velocity contours in the screw channel and shear rate distributions in the intermeshing region are presented for different slip coefficients. Curves of axial pressure difference, average shear rate and dispersive mixing index vs. the slip coefficient are plotted and discussed. Comparisons are also made between the wall slip conditions and the non-slip condition. The simulation results indicate that, as the level of wall slip decreases, the axial pressure difference rises, the shear effect is intensified and the axial mixing is also enhanced. All these flow characteristics seem to level off with the increase of the slip coefficient. However, because of the inherent limitation of the Navier slip law, use of an overestimated slip coefficient would predict an over-sticky state between the screw surface and the polymer melt.
基金NSFC-Joint Research Fund of Henan (U1404323), Grain & Corn Engineering Technology Research CenterState Administration of Grain (GA2017004)Science and Technology Research Project of Henan (172102110205 and 182102310676) for providing funds
文摘β-Conglycinin,the main component of 7S globulin in soybean protein,is also a key soybean antigen protein that causes allergic reactions.Extrusion technologies have received considerable attention as amethod for modifying soybean protein allergens.This study investigated the changes inβ-conglycinin structure and antigenicity upon extrusion.Isoelectric precipitation,ammoniumsulfate precipitation,and sepharose CL-6B gel filtration were used to isolate and purifyβ-conglycinin from soybean powder,and single-factor and orthogonal tests were used to study the effects of water content,extrusion temperature,screw rotation speed,and feeding speed on the antigenicity ofβ-conglycinin after extrusion.Fourier transforminfrared spectrometry(FTIR)was then employed to analyze the structure ofβ-conglycinin after extrusion under the optimal conditions determined by the orthogonal test.The results showed that extrusion significantly reduced the antigenicity ofβ-conglycinin(P<0.05),and the degree of influence of the factors studied may be ordered as extrusion temperature>feeding speed>screw rotation speed>water content.The optimal parameters were temperature at 130°C,screwrotation speed at 140 r/min,and feeding speed at 35 g/min.Under these conditions,the contents ofα-helix,β-pleated sheet,andβ-turn structures inβ-conglycinin were significantly reduced(P<0.05),while the contents of random coils were significantly increased(P<0.05).The peak absorption intensity of amides I,II,and III also decreased.Taken together,the findings suggest that extrusion could be an effective method for reducing the antigenicity ofβ-conglycinin.
基金supported by the State Key Laboratory for Mechanical Behavior of Materials(No.20171909)
文摘304L H-shaped stainless steel is used as the support frame of the passive residual heat removal heat exchanger(PRHR HX) in a nuclear fission reactor. The extrusion process is adopted to manufacture the 304L H-shaped stainless steel. Finite element method simulation is herein used to analyze metal flow characteristics, optimize the extrusion die, and predict the extrusion force at different temperatures and speeds. A Φ400-mm container and Φ388-mm forging billet are selected, and the 304L H-shaped stainless steel is successfully manufactured using a Germany SMS 60 MN horizontal extruder. The mechanical properties and microstructure of the manufactured 304L H-shaped stainless steel meet the requirements of the PRHR HX, and the surfaces of the product pass the dye penetration test. The H-shaped stainless steels are used in Haiyang nuclear power plant in Shandong Province.
文摘Swell and sag drawdown significantly influence the high density polyethylene parison. Nu- merical simulations of the flow field of a HDPE melt were performed using the finite element method for the die of plastic pipe extrusion and parison formation. The constitutive equation of Carreau law was used to describe the polymer melt in the flow domain. The distributions of the velocity, shear rate, viscosity, pressure, thickness and radius are presented with Polyflow. The effect of flow rate and temperature on extrusion swell and parison sag was investigated. The results show that the thickness of the parison increases with increasing flow rate. The thickness and radius of the parison are more sensitive to changes in flow rates than to changes in temperatures.
文摘A more universal and flexible method of constructing the streamlined die surfaces is presented. The streamlined die surfaces are interpolated by the arbitrarily cross sectional shapes of the die entrance and exit. The boundaries of the die entrance and exit are represented by Ferguson curves with tension parameters. By adjusting the tension parameter, the cross sectional shapes of the die entrance and exit with line segments can be accurately constructed. The upper bound method is used to analyze the procedure of extrusion, the pseudo independent parameters in kinematically admissible velocity and die surface are computed by minimizing the extrusion load, so the optimum die surface is obtained. The effects of frictional condition, die length, area reduction and product shaped complexity are discussed in relation to the extrusion load.
基金Supported by the Natural Science Foundation of Hebei(D2024501002)Fundamental Research Funds for the Central Universities(N2423020)Major Science and Technology Projects of CNPC(2021ZZ10)。
文摘Based on the observation and analysis of cores and thin sections,and combined with cathodoluminescence,laser Raman,fluid inclusions,and in-situ LA-ICP-MS U-Pb dating,the genetic mechanism and petroleum geological significance of calcite veins in shales of the Cretaceous Qingshankou Formation in the Songliao Basin were investigated.Macroscopically,the calcite veins are bedding parallel,and show lenticular,S-shaped,cone-in-cone and pinnate structures.Microscopically,they can be divided into syntaxial blocky or columnar calcite veins and antitaxial fibrous calcite veins.The aqueous fluid inclusions in blocky calcite veins have a homogenization temperature of 132.5–145.1℃,the in-situ U-Pb dating age of blocky calcite veins is(69.9±5.2)Ma,suggesting that the middle maturity period of source rocks and the conventional oil formation period in the Qingshankou Formation are the sedimentary period of Mingshui Formation in Late Cretaceous.The aqueous fluid inclusions in fibrous calcite veins with the homogenization temperature of 141.2–157.4℃,yields the U-Pb age of(44.7±6.9)Ma,indicating that the middle-high maturity period of source rocks and the Gulong shale oil formation period in the Qingshankou Formation are the sedimentary period of Paleocene Yi'an Formaiton.The syntaxial blocky or columnar calcite veins were formed sensitively to the diagenetic evolution and hydrocarbon generation,mainly in three stages(fracture opening,vein-forming fluid filling,and vein growth).Tectonic extrusion activities and fluid overpressure are induction factors for the formation of fractures,and vein-forming fluid flows mainly as diffusion in a short distance.These veins generally follow a competitive growth mode.The antitaxial fibrous calcite veins were formed under the driving of the force of crystallization in a non-competitive growth environment.It is considered that the calcite veins in organic-rich shale of the Qingshankou Formation in the study area has important implications for local tectonic activities,fluid overpressure,hydrocarbon generation and expulsion,and diagenesis-hydrocarbon accumulation dating of the Songliao Basin.
文摘In this study, we investigated the performance improvement caused by the addition of copper(Cu)nanoparticles to high-density polyethylene(HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 wt% were synthesized through the material extrusion(MEX)3D printing technique. The synthesized nanocomposite filaments were utilized for the manufacturing of specimens suitable for the experimental procedure that followed. Hence, we were able to systematically investigate their tensile, flexural, impact, and microhardness properties through various mechanical tests that were conducted according to the corresponding standards. Broadband Dielectric Spectroscopy was used to investigate the electrical/dielectric properties of the composites. Moreover, by employing means of Raman spectroscopy and thermogravimetric analysis(TGA) we were also able to further investigate their vibrational, structural, and thermal properties. Concomitantly, means of scanning electron microscopy(SEM), as well as atomic force microscopy(AFM), were used for the examination of the morphological and structural characteristics of the synthesized specimens, while energy-dispersive Xray spectroscopy(EDS) was also performed in order to receive a more detailed picture on the structural characteristics of the various synthesized composites. The corresponding nanomaterials were also assessed for their antibacterial properties regarding Staphylococcus aureus(S. aureus) and Escherichia coli(E. coli) with the assistance of a method named screening agar well diffusion. The results showed that the mechanical properties of HDPE benefited from the utilization of Cu as a filler, as they showed a notable improvement. The specimen of HDPE/Cu 4.0 wt% was the one that presented the highest levels of reinforcement in four out of the seven tested mechanical properties(for example, it exhibited a 36.7%improvement in the flexural strength, compared to the pure matrix). At the same time, the nanocomposites were efficient against the S. aureus bacterium and less efficient against the E. coli bacterium.The use of such multi-functional, robust nanocomposites in MEX 3D printing is positively impacting applications in various fields, most notably in the defense and security sectors. The latter becomes increasingly important if one takes into account that most firearms encompass various polymeric parts that require robustness and improved mechanical properties, while at the same time keeping the risk of spreading various infectious microorganisms at a bare minimum.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50804011 and 50931001)
文摘Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt- spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6A10.2B0.9 （wt%） is used as starting material. The effects of process variables, such as deformation temperature （Td）, strain rate （ε） and height reduction （△h%）, on the magnetic properties of the rings are investigated. A scanning electron microscope （SEM） equipped with an energy spectrum device is used to study the metallograph and microfracture of the extruded rings. The Br and （BH）max reach the optimum values at Td =800℃,ε= 0.01 mm/s, and △h% = 70%. It is found by SEM observations that the particle boundaries, which seemingly correspond to the interfaces of the starting melt-spun powders, emerge after the corrosion of metallography specimens. This is helpful for studying the effects of powder-powder interface on the local deformation and deformation homogeneity in the rings. For different spatial positions of the extruded rings, there are characteristic metallographies and microfractures. The upper end of the rings has the least deformation and worst texture, and therefore the worst magnetic properties. The magnetic properties in the radial direction increase slightly along the axis from the bottom to the middle, then steeply decrease at the upper end of the ring. The deformation and the formation-of-texturing processes are discussed. The deformation and the texturing formation of melt-spun Nd-Fe-B alloys probably involve grain boundary sliding and grain rotation, the solution-precipitation process and preferential growth of Nd2Fel4B nanograins along the easy growth a-axis.
基金supported by the Key scientific and technological project of Henan Province(No.202102110143)State Scholarship Fund of China Scholarship Council(No.202008410106)。
文摘Foxtail millet, originated from China and now cultivated worldwide, is a kind of high dietary fiber whole grain food, and has a high level of vitamins and proteins. Furthermore, foxtail millet has many positive effects on the adjuvant treatment of diabetes, cancer, and cardiovascular diseases because of the abundance in polyphenols. Nonetheless, foxtail millet has poor processing characteristics due to the absence of gluten, restricting the development of foxtail millet products. Studies have demonstrated that heat-moisture treatment, extrusion, superfine grinding, and microbial fermentation are promising methods to improve the processing qualities of foxtail millet. Heat-moisture treatment is helpful to increase the content of resistant starch but has less influence on other components, further reduce the GI value of foxtail millet. The extrusion has positive effects on improving the solubility of foxtail millet starch and increasing the contents of polyunsaturated fatty acid, linoleic and linolenic acids, and adverse effects on reducing the solubility of foxtail millet proteins and causing losses of nutrients due to Maillard reaction. Superfine grinding can reduce the particle size of foxtail millet to obtain a better mouthfeel of foxtail millet products. The superfine foxtail millet flour has better solubility, higher freeze-thaw stability, and lower gelatinization temperature. Microbial fermentation contributes positively to reducing the molecular weight and retrogradation value of foxtail millet starch, degrading rapidly digested starch, and improving the digestibility of foxtail millet protein. This paper briefly introduced the effects of different processing methods on foxtail millet nutrients, aiming to provide references for increasing the variety and improving the quality of foxtail millet products.
基金Supported by the National Natural Science Foundation of China under Grant No 50371086. We thank Li Yu-Sheng, Zheng Shi-Jian and Yang Chun-Na for help in the TEM experiments.
文摘With the aid of hydrogenation/dehydrogenation, nanorod whiskers of transition metal Mn can grow spontaneously from Zrl_xTi^MnCr Laves phase alloys at room temperature. The finding introduces a distinguishingly different element into metal whisker family, and provides a potential technique for fabrication of one-dimensional metal nanostructures. Moreover, it is found that the segregated Mn in whiskers forms a novel hexagonal structure, which partially fulfills the long predicted allotropic form and adds more complexity to the structures of Mn.
基金Supported by National Natural Science Foundation of China(31401642)
文摘Multigrain noodles were made by corn and wheat flour as the main ingredients and with small ratios of oat flour, soybean flour and millet flour through extrusion process. Simplex centroid design was used to analyze gelatinization characteristics of the mixed flour, rheological characteristics of the doughs, cooking qualities and sensory qualities of noodles. A proper formula for multigrain noodles obtained as outcome: 45% corn flour, 40% wheat flour, 4% oat flour, 11% millet flour. Compared to the wheat noodles, the multigrain noodles had higher content in fat, dietary fiber and total resistant starch, but it did content less proteins than wheat noodles.
文摘Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)procedure.This can be very important in defense-related applications,where optimum performance needs to be guaranteed.The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters,namely,infill percentage,layer height,deposition angle,travel speed,nozzle,and bed temperature.The quality indicators were the root mean square(Rq)and average(Ra)roughness,porosity,and the actual to nominal dimensional deviation.The examination was performed with optical profilometry,optical microscopy,and micro-computed tomography scanning.The Taguchi design of experiments was applied,with twenty-five runs,five levels for each control parameter,on five replicas.Two additional confirmation runs were conducted,to ensure reliability.Prediction equations were constructed to express the quality indicators in terms of the control parameters.Three modeling approaches were applied to the experimental data,to compare their efficiency,i.e.,Linear Regression Model(LRM),Reduced Quadratic Regression Model,and Quadratic Regression Model(QRM).QRM was the most accurate one,still the differences were not high even considering the simpler LRM model.
文摘This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printing(3DP)by improving its mechanical properties while simultaneously adding antibacterial properties.The latter can find extremely important and versatile properties that are applicable in defense and security domains.PP/Ag nanocomposites were prepared using a novel method based on a reaction occurring while mixing appropriate quantities of the starting polymers and additives,namely polyvinylpyrrolidone(PVP)as the matrix material and silver nitrate(AgNO_(3))as the filler.This process produced three-dimensional(3D)printed filaments,which were then used to create specimens for a series of standardized tests.It was found that the mechanical properties of the nanocomposites were enhanced in relation to pristine PP,especially for the PP matrix with various loadings of AgNO_(3)and PVP,such as 5.0 wt%and 2.5 wt%,respectively.The voids,inclusions,and actual-to-nominal dimensions also showed improved results.The 3DP specimens exhibited a more effective biocidal performance against Staphylococcus aureus than Escherichia coli,which developed an inhibition zone only in the case of PP with filler loading percentages of AgNO_(3)and PVP at 10.0 wt%and 5.0 wt%,respectively Compounds possessing such properties can be beneficial for various applications requiring increased mechanical properties and biocidal capabilities,such as in the Defence or medical industries.
