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
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
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
The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after proces...The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraaffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin-screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0. 23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.展开更多
In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model...In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions relative residual thickness of billet (T/R0),frictional factor (m) or relative land length of ram and chamber are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).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
An extensive technical review of studies on food extrusion processes which involves forcing mixed food ingredients through a die to produce food snacks has been carried out in this paper. This technical review include...An extensive technical review of studies on food extrusion processes which involves forcing mixed food ingredients through a die to produce food snacks has been carried out in this paper. This technical review includes some historical development, food extruder types, extrusion principles and applications, flow simulation and heat transfer modeling in extruders, process parameters and product quality, extruder die and extrudate expansion among others. The research and application of extrusion in food industry was mainly based on the adaptation of plastic extrusion technology which has been in existence for over hundred years. Studies show that twin-screw extruder are more efficient than single-screw extruders because of better mixing and better handling of different combinations of food ingredients. A thorough knowledge of the flow and heat behavior inside an extruder provide an insight into the mechanism of mixing and facilitates estimation of RTD, flow rate, pressure drop, heat transfer mechanism and power consumption. Until recently, very little work has been published on the mechanism of material flow and energy transfer in intermeshing co-rotating extruder mainly due to the complexity of the geometry and the flow behavior. A more recent approach to research in modeling of food extrusion is the 2D or 3D flow modeling using finite element computer package. This research area is gaining recognition in modeling different sections of food extruder. This work also points out some of the achievements and shortcomings of the reviewed works and where necessary, possible solutions are suggested. Areas needing further research have been highlighted. This study will reveal that understanding and application of extrusion technology in developing countries of Asia and Africa are still far from being satisfactory and this work would serve as a good reference material for researchers and operators in food extrusion technology.展开更多
A new continuum theory of the constitutive equation of co-rotational derivative type was developed by the author for anisotropic viscoelastic fluid-liquid crystalline (LC) polymers (S.F. Han, 2008, 2010) . This paper ...A new continuum theory of the constitutive equation of co-rotational derivative type was developed by the author for anisotropic viscoelastic fluid-liquid crystalline (LC) polymers (S.F. Han, 2008, 2010) . This paper is a continuation of the recent publication [1] to study extrusion-extensional flow of the fluid. A new concept of simple anisotropic fluid is introduced. On the basis of anisotropic simple fluid, stress behavior is described by velocity gradient tensor F and spin tensor W instead of the velocity gradient tensor D in the classic Leslie?Ericksen continuum theory. A special form of the constitutive equation of the co-rotational type is established for the fluid. Using the special form of the constitutive equation in components a computational analytical theory of the extrusion-extensional flow is developed for the LC polymer liquids - anisotropic viscoelastic fluid. Application of the constitutive theory to the flow is successful in predicting bifurcation of elongational viscosity and contraction of extrudate for LC polymer liquids–anisotropic viscoelastic fluid. The contraction of extrudate of LC polymer liquids may be associated with the stored elastic energy conversion into that necessary for bifurcation of elongational viscosity in extrusion extensional flow of the fluid.展开更多
The numerical simulation of extrudate swell is significant in extrusion processing.Precise prediction of extrudate swell is propitious to the control of melt flow and the quality of final products.A mathematical model...The numerical simulation of extrudate swell is significant in extrusion processing.Precise prediction of extrudate swell is propitious to the control of melt flow and the quality of final products.A mathematical model of three-dimensional(3D)viscoelastic flow through elliptical ring die for polymer extrusion was investigated.The penalty function formulation of viscoelastic incompressible fluid was introduced to the finite element model to analyze 3D extrusion problem.The discrete elastic viscous split stress(DEVSS)and streamline-upwind PetrovGalerkin(SUPG)technology were used to obtain stable simulation results.Free surface was updated by updating the streamlines which needs less memory space.According to numerical simulation results,the effect of zero-shear viscosity and elongation parameter on extrudate swell was slight,but with the increase of volumetric flow rate and relax time the extrudate swell ratio increased markedly.Finally,the numerical simulation of extrudate swell flow for low-density polyethylene(LDPE)melts was investigated and the results agreed well with others’work.These conclusions provided quantitative basis for the forecasting extrudate swell ratio and the controlling of extrusion productivity shape.展开更多
One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a sp...One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a special conical twin-screw extruder,resulting in stronger feeding ability,more stable extrusion pressure,and better quality of products. The integrated mathematical model of mixing-extruding process was also established by theoretical derivation and optimization according to the experimental results.Then its accuracy was verified by the influences of the pressure of floating weight and the cooling water temperature of extruder on the mixing-extruding integrated process. The results showed that the changes of both parameters could give rise to the fluctuation of the temperature and apparent viscosity of polyblends, thus further influencing the screw rotation speed.展开更多
Hydroforming of magnesium and aluminum alloy tube at elevated temperature is becoming a very promising method to manufacture light-weight hollow components.Uniaxial tensile test and hydrobulging test were used to inve...Hydroforming of magnesium and aluminum alloy tube at elevated temperature is becoming a very promising method to manufacture light-weight hollow components.Uniaxial tensile test and hydrobulging test were used to investigate the formability of AZ31B magnesium tube at different temperatures.The tube was manufactured by porthole die extrusion.Results show that as temperature increase,the tension formability along the extrusion direction measured by tensile test increases significantly,whereas the maximum hydrobulging ratio measured by hydrobulging test does not change accordingly.This anisotropy character of the tube,i.e.,different properties in axial direction and hoop direction,is mainly dependant on the extrusion process.In addition,there exists several weld lines along the extrusion direction.These weld lines will become the weakest positions when formed at elevated temperature,and will consequently decrease the formability of the tube during hydroforming process.展开更多
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.
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The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraaffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin-screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0. 23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.
文摘In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions relative residual thickness of billet (T/R0),frictional factor (m) or relative land length of ram and chamber are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).
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An extensive technical review of studies on food extrusion processes which involves forcing mixed food ingredients through a die to produce food snacks has been carried out in this paper. This technical review includes some historical development, food extruder types, extrusion principles and applications, flow simulation and heat transfer modeling in extruders, process parameters and product quality, extruder die and extrudate expansion among others. The research and application of extrusion in food industry was mainly based on the adaptation of plastic extrusion technology which has been in existence for over hundred years. Studies show that twin-screw extruder are more efficient than single-screw extruders because of better mixing and better handling of different combinations of food ingredients. A thorough knowledge of the flow and heat behavior inside an extruder provide an insight into the mechanism of mixing and facilitates estimation of RTD, flow rate, pressure drop, heat transfer mechanism and power consumption. Until recently, very little work has been published on the mechanism of material flow and energy transfer in intermeshing co-rotating extruder mainly due to the complexity of the geometry and the flow behavior. A more recent approach to research in modeling of food extrusion is the 2D or 3D flow modeling using finite element computer package. This research area is gaining recognition in modeling different sections of food extruder. This work also points out some of the achievements and shortcomings of the reviewed works and where necessary, possible solutions are suggested. Areas needing further research have been highlighted. This study will reveal that understanding and application of extrusion technology in developing countries of Asia and Africa are still far from being satisfactory and this work would serve as a good reference material for researchers and operators in food extrusion technology.
文摘A new continuum theory of the constitutive equation of co-rotational derivative type was developed by the author for anisotropic viscoelastic fluid-liquid crystalline (LC) polymers (S.F. Han, 2008, 2010) . This paper is a continuation of the recent publication [1] to study extrusion-extensional flow of the fluid. A new concept of simple anisotropic fluid is introduced. On the basis of anisotropic simple fluid, stress behavior is described by velocity gradient tensor F and spin tensor W instead of the velocity gradient tensor D in the classic Leslie?Ericksen continuum theory. A special form of the constitutive equation of the co-rotational type is established for the fluid. Using the special form of the constitutive equation in components a computational analytical theory of the extrusion-extensional flow is developed for the LC polymer liquids - anisotropic viscoelastic fluid. Application of the constitutive theory to the flow is successful in predicting bifurcation of elongational viscosity and contraction of extrudate for LC polymer liquids–anisotropic viscoelastic fluid. The contraction of extrudate of LC polymer liquids may be associated with the stored elastic energy conversion into that necessary for bifurcation of elongational viscosity in extrusion extensional flow of the fluid.
基金Supported by the National Science Foundation for Distinguished Young Scholars of China(50425517) the Shandong Province Natural Science Foundation(Y2007F59)
文摘The numerical simulation of extrudate swell is significant in extrusion processing.Precise prediction of extrudate swell is propitious to the control of melt flow and the quality of final products.A mathematical model of three-dimensional(3D)viscoelastic flow through elliptical ring die for polymer extrusion was investigated.The penalty function formulation of viscoelastic incompressible fluid was introduced to the finite element model to analyze 3D extrusion problem.The discrete elastic viscous split stress(DEVSS)and streamline-upwind PetrovGalerkin(SUPG)technology were used to obtain stable simulation results.Free surface was updated by updating the streamlines which needs less memory space.According to numerical simulation results,the effect of zero-shear viscosity and elongation parameter on extrudate swell was slight,but with the increase of volumetric flow rate and relax time the extrudate swell ratio increased markedly.Finally,the numerical simulation of extrudate swell flow for low-density polyethylene(LDPE)melts was investigated and the results agreed well with others’work.These conclusions provided quantitative basis for the forecasting extrudate swell ratio and the controlling of extrusion productivity shape.
基金National Natural Science Foundation of China(No.51345006)Specialized Research Fund for the Doctoral Program of Higher Education,China(No.20123719120004)
文摘One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a special conical twin-screw extruder,resulting in stronger feeding ability,more stable extrusion pressure,and better quality of products. The integrated mathematical model of mixing-extruding process was also established by theoretical derivation and optimization according to the experimental results.Then its accuracy was verified by the influences of the pressure of floating weight and the cooling water temperature of extruder on the mixing-extruding integrated process. The results showed that the changes of both parameters could give rise to the fluctuation of the temperature and apparent viscosity of polyblends, thus further influencing the screw rotation speed.
基金This work is financially supported by the National Natural Science Fund for Distinguished Young Scholars(No50525516)the Specialized Research Fund for the Doctoral Program of Higher Edu-cation (No20050213041)
文摘Hydroforming of magnesium and aluminum alloy tube at elevated temperature is becoming a very promising method to manufacture light-weight hollow components.Uniaxial tensile test and hydrobulging test were used to investigate the formability of AZ31B magnesium tube at different temperatures.The tube was manufactured by porthole die extrusion.Results show that as temperature increase,the tension formability along the extrusion direction measured by tensile test increases significantly,whereas the maximum hydrobulging ratio measured by hydrobulging test does not change accordingly.This anisotropy character of the tube,i.e.,different properties in axial direction and hoop direction,is mainly dependant on the extrusion process.In addition,there exists several weld lines along the extrusion direction.These weld lines will become the weakest positions when formed at elevated temperature,and will consequently decrease the formability of the tube during hydroforming process.