Conventional cross rolling is influenced by the force couple effect of symmetrical rollers,resulting in the c-axis of the plate grains being oriented perpendicular to the rolling surface.This orientation contributes t...Conventional cross rolling is influenced by the force couple effect of symmetrical rollers,resulting in the c-axis of the plate grains being oriented perpendicular to the rolling surface.This orientation contributes to a high degree of work hardening and mechanical anisotropy,thereby complicating subsequent processing.In this study,the hard plate cross rolling(HP-CR)process is put forward for the first time,and the microstructure evolution and mechanical properties of rolled AZ31 Magnesium plate were analyzed.The results indicate that,in comparison to traditional cross rolling(CR),the average grain size of the HP-CR is refined to 5.33µm.Additionally,the average yield strength and elongation of the sheet are enhanced by 15.2%and 35.2%,respectively,while the average tensile strength is 283 MPa,and the r value decreases by 39.8%.These changes are attributed to the combined effects of grain refinement,microstructural homogenization,and basal texture weakening.On the one hand,the substantial energy stored in the original lattice distortion serves as a driving force for the dynamic recrystallization process,facilitating the elimination of the deformed grain structure.This process increases the proportion of recrystallized grains from 5%to 82%,reduces the degree of work hardening,and correspondingly decreases the density of geometrically necessary dislocations(ρ^(GND))by 70.8%,accompanied by the formation of high-angle grain boundaries(HAGB).On the other hand,dynamic recrystallization promotes grain rearrangement,resulting in an increased number of grains oriented in the transverse direction(TD),which diminishes the texture strength of the basal plane.Concurrently,the activation of non-basal slip systems reduces the resistance to dislocation sliding in various directions,significantly reduces the degree of mechanical anisotropy and enhancing the plastic deformation capacity of the plate.This research provides valuable scientific insights and technical foundations for the large-scale manufacturing of high-performance AZ31 magnesium alloy sheets.展开更多
Negative Poisson’s ratio materials and structures exhibit lateral expansion under tensile loading,demonstrating significant mechanical advantages over conventional materials.This study systematically investigated thr...Negative Poisson’s ratio materials and structures exhibit lateral expansion under tensile loading,demonstrating significant mechanical advantages over conventional materials.This study systematically investigated three typical two-dimensional negative Poisson’s ratio metamaterial structures(Concave honeycomb,Anti-chiral,and Anti-chiral concave honeycomb hybrid structures)through both experimental tests and numerical analysis.The test specimens were fabricated using selective laser melting(SLM)additive manufacturing technology,and the experimental test was conducted with the use of a DIC strain measurement system.The numerical studies were performed considering both static tensile loading and dynamic impact loading with different strain rates.The deformation behaviors,failure process,negative Poisson’s ratio effects,and energy absorption capacity of the three different metamaterial structures are systematically investigated,and the associated mechanical mechanisms are thoroughly revealed.Results and findings of this work could provide valuable guidance for the engineering design and application of negative Poisson’s ratio metamaterials and structures.展开更多
This study produced wide(900-1200 mm)AZ31 alloy sheets with varying thicknesses via continuous casting direct rolling(7 mm,6 mm)combined with stepwise warm rolling(4.5 mm,2 mm),examining the effects of this process on...This study produced wide(900-1200 mm)AZ31 alloy sheets with varying thicknesses via continuous casting direct rolling(7 mm,6 mm)combined with stepwise warm rolling(4.5 mm,2 mm),examining the effects of this process on microstructure,corrosion durability,mechanical properties,and discharge properties.Results showed that the reduced thickness significantly refined the grain size from 131.20µm to 7.90µm with the basal texture intensity reached 52%.Synergistic grain refinement,dislocation,and texture strengthening improved the yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)of the 2 mm-thick sheet by 59.11%,39.75%,and 83.52%,respectively,compared to those of the 7 mm-thick sheet.Corrosion durability was also improved,with a corrosion rate of 2.19 mm·y^(-1)for the 2 mm sheet,which was 41%lower than that of the 7 mm sheet(3.72 mm·y^(-1)),due to the formation of a dense Al(OH)3 and layered double hydroxide corrosion film with mitigated micro-galvanic corrosion.As an Mg-air battery anode,the 2 mm sheet performed the best at 10 mA/cm^(2),achieving an anode efficiency of 61.18%,specific energy of 1660.50 mWh·g^(-1),easy discharge product detachment,and reduced self-corrosion.In summary,this study demonstrates a cost-effective and industrially viable approach that combines continuous casting direct rolling with stepwise warm rolling to produce ultra-wide AZ31 sheets with simultaneously improved overall properties,offering a novel strategy to expand the opportunity for commercial Mg alloys in both structural and functional applications.展开更多
The flow of a tetra-hybrid Casson nanofluid(Al_(2)O_(3)-CuO-TiO_(2)-Ag/H_(2)O)over a nonlinear stretching sheet is investigated.The Buongiorno model is used to account for thermophoresis and Brownian motion,while ther...The flow of a tetra-hybrid Casson nanofluid(Al_(2)O_(3)-CuO-TiO_(2)-Ag/H_(2)O)over a nonlinear stretching sheet is investigated.The Buongiorno model is used to account for thermophoresis and Brownian motion,while thermal radiation is incorporated to examine its influence on the thermal boundary layer.The governing partial differential equations(PDEs)are reduced to a system of nonlinear ordinary differential equations(ODEs)with fully non-dimensional similarity transformations involving all independent variables.To solve the obtained highly nonlinear system of differential equations,a novel Clique polynomial collocation method is applied.The analysis focuses on the effects of the Casson parameter,power index,radiation parameter,thermophoresis parameter,Brownian motion parameter,and Lewis number.The key findings show that thermal radiation intensifies the thermal boundary layer,the Casson parameter reduces the velocity,and the Lewis number suppresses the concentration with direct relevance to polymer processing,coating flows,electronic cooling,and biomedical applications.展开更多
Road traffic flow forecasting provides critical information for the operational management of road mobility challenges, and models are used to generate the forecast. This paper uses a random process to present a novel...Road traffic flow forecasting provides critical information for the operational management of road mobility challenges, and models are used to generate the forecast. This paper uses a random process to present a novel traffic modelling framework for aggregate traffic on urban roads. The main idea is that road traffic flow is random, even for the recurrent flow, such as rush hour traffic, which is predisposed to congestion. Therefore, the structure of the aggregate traffic flow model for urban roads should correlate well with the essential variables of the observed random dynamics of the traffic flow phenomena. The novelty of this paper is the developed framework, based on the Poisson process, the kinematics of urban road traffic flow, and the intermediate modelling approach, which were combined to formulate the model. Empirical data from an urban road in Ghana was used to explore the model’s fidelity. The results show that the distribution from the model correlates well with that of the empirical traffic, providing a strong validation of the new framework and instilling confidence in its potential for significantly improved forecasts and, hence, a more hopeful outlook for real-world traffic management.展开更多
In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded s...In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets.At the same time,the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets.In this work,the bulging process of the tailor-welded overlapping sheets was taken as the research object.Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification.The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality.When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength,the deformation of the tailor-welded sheets are more uniform,the offset of the weld seam is minimal,the limit bulging height is maximal,and the forming quality is optimal.展开更多
The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood.In this article,we present an electron current layer detected at the edge of the magnetotail plasma sh...The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood.In this article,we present an electron current layer detected at the edge of the magnetotail plasma sheet.The ions were demagnetized inside the electron current layer,but the electrons were still frozen in with the magnetic field line.Thus,this decoupling of ions and electrons gave rise to a strong Hall electric field,which could be the reason for the formation of the embedded thin current layer.The magnetized electrons,the absence of the nongyrotropic electron distribution,and negligible energy dissipation in the layer indicate that magnetic reconnection had not been triggered within the embedded thin current layer.The highly asymmetric plasma on the two sides of the current layer and low magnetic shear across it could suppress magnetic reconnection.The observations indicate that the embedded electric current layer,probably generated by the Hall electric field,even down to electron scale,is not a sufficient condition for magnetic reconnection.展开更多
The influence of geometric configuration on the friction characteristics during incremental sheet forming of AA5052 was analyzed by integrating surface morphology and its characteristic parameters,along with plastic s...The influence of geometric configuration on the friction characteristics during incremental sheet forming of AA5052 was analyzed by integrating surface morphology and its characteristic parameters,along with plastic strain,contact pressure,and area.The interface promotes lubrication and support when wall angles were≤40°,a 0.5 mm-thin sheet was used,and a 10 mm-large tool radius was employed.This mainly results in micro-plowing and plastic extrusion flow,leading to lower friction coefficient.However,when wall angles exceed 40°,significant plastic strain roughening occurs,leading to inadequate lubrication on the newly formed surface.Increased sheet thickness and decreased tool radius elevate contact pressure.These actions trigger micro-cutting and adhesion,potentially leading to localized scuffing and dimple tears,and higher friction coefficient.The friction mechanisms remain unaffected by the part’s plane curve features.As the forming process progresses,abrasive wear intensifies,and surface morphology evolves unfavorably for lubrication and friction reduction.展开更多
This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the pre...This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.展开更多
基金supported by the Natural Science Foundation of Heilongjiang Province(No.JQ2022E004).
文摘Conventional cross rolling is influenced by the force couple effect of symmetrical rollers,resulting in the c-axis of the plate grains being oriented perpendicular to the rolling surface.This orientation contributes to a high degree of work hardening and mechanical anisotropy,thereby complicating subsequent processing.In this study,the hard plate cross rolling(HP-CR)process is put forward for the first time,and the microstructure evolution and mechanical properties of rolled AZ31 Magnesium plate were analyzed.The results indicate that,in comparison to traditional cross rolling(CR),the average grain size of the HP-CR is refined to 5.33µm.Additionally,the average yield strength and elongation of the sheet are enhanced by 15.2%and 35.2%,respectively,while the average tensile strength is 283 MPa,and the r value decreases by 39.8%.These changes are attributed to the combined effects of grain refinement,microstructural homogenization,and basal texture weakening.On the one hand,the substantial energy stored in the original lattice distortion serves as a driving force for the dynamic recrystallization process,facilitating the elimination of the deformed grain structure.This process increases the proportion of recrystallized grains from 5%to 82%,reduces the degree of work hardening,and correspondingly decreases the density of geometrically necessary dislocations(ρ^(GND))by 70.8%,accompanied by the formation of high-angle grain boundaries(HAGB).On the other hand,dynamic recrystallization promotes grain rearrangement,resulting in an increased number of grains oriented in the transverse direction(TD),which diminishes the texture strength of the basal plane.Concurrently,the activation of non-basal slip systems reduces the resistance to dislocation sliding in various directions,significantly reduces the degree of mechanical anisotropy and enhancing the plastic deformation capacity of the plate.This research provides valuable scientific insights and technical foundations for the large-scale manufacturing of high-performance AZ31 magnesium alloy sheets.
基金supported by the National Natural Science Foundation of China(No.12472136)Innovation Fund of Marine Defense Technology Innovation Center(No.25GFC-JJ16-3608).
文摘Negative Poisson’s ratio materials and structures exhibit lateral expansion under tensile loading,demonstrating significant mechanical advantages over conventional materials.This study systematically investigated three typical two-dimensional negative Poisson’s ratio metamaterial structures(Concave honeycomb,Anti-chiral,and Anti-chiral concave honeycomb hybrid structures)through both experimental tests and numerical analysis.The test specimens were fabricated using selective laser melting(SLM)additive manufacturing technology,and the experimental test was conducted with the use of a DIC strain measurement system.The numerical studies were performed considering both static tensile loading and dynamic impact loading with different strain rates.The deformation behaviors,failure process,negative Poisson’s ratio effects,and energy absorption capacity of the three different metamaterial structures are systematically investigated,and the associated mechanical mechanisms are thoroughly revealed.Results and findings of this work could provide valuable guidance for the engineering design and application of negative Poisson’s ratio metamaterials and structures.
基金funded by the National Natural Science Foundation of China(No.52204407,No.22208220,No.52304408,No.52304398)the Zhejiang Provincial Natural Science Foundation of China(No.LQN25E010012)the Key Industrial Technology Research and Basic public welfare program projects in Shaoxing city(2023B41003,2023A11004 and 2023A11005).
文摘This study produced wide(900-1200 mm)AZ31 alloy sheets with varying thicknesses via continuous casting direct rolling(7 mm,6 mm)combined with stepwise warm rolling(4.5 mm,2 mm),examining the effects of this process on microstructure,corrosion durability,mechanical properties,and discharge properties.Results showed that the reduced thickness significantly refined the grain size from 131.20µm to 7.90µm with the basal texture intensity reached 52%.Synergistic grain refinement,dislocation,and texture strengthening improved the yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)of the 2 mm-thick sheet by 59.11%,39.75%,and 83.52%,respectively,compared to those of the 7 mm-thick sheet.Corrosion durability was also improved,with a corrosion rate of 2.19 mm·y^(-1)for the 2 mm sheet,which was 41%lower than that of the 7 mm sheet(3.72 mm·y^(-1)),due to the formation of a dense Al(OH)3 and layered double hydroxide corrosion film with mitigated micro-galvanic corrosion.As an Mg-air battery anode,the 2 mm sheet performed the best at 10 mA/cm^(2),achieving an anode efficiency of 61.18%,specific energy of 1660.50 mWh·g^(-1),easy discharge product detachment,and reduced self-corrosion.In summary,this study demonstrates a cost-effective and industrially viable approach that combines continuous casting direct rolling with stepwise warm rolling to produce ultra-wide AZ31 sheets with simultaneously improved overall properties,offering a novel strategy to expand the opportunity for commercial Mg alloys in both structural and functional applications.
基金the UGC,New Delhi,India for financial assistance via the UGC-Junior Research Fellowship(CSIR-UGC NET JULY 2024)(Student ID:241610090610)。
文摘The flow of a tetra-hybrid Casson nanofluid(Al_(2)O_(3)-CuO-TiO_(2)-Ag/H_(2)O)over a nonlinear stretching sheet is investigated.The Buongiorno model is used to account for thermophoresis and Brownian motion,while thermal radiation is incorporated to examine its influence on the thermal boundary layer.The governing partial differential equations(PDEs)are reduced to a system of nonlinear ordinary differential equations(ODEs)with fully non-dimensional similarity transformations involving all independent variables.To solve the obtained highly nonlinear system of differential equations,a novel Clique polynomial collocation method is applied.The analysis focuses on the effects of the Casson parameter,power index,radiation parameter,thermophoresis parameter,Brownian motion parameter,and Lewis number.The key findings show that thermal radiation intensifies the thermal boundary layer,the Casson parameter reduces the velocity,and the Lewis number suppresses the concentration with direct relevance to polymer processing,coating flows,electronic cooling,and biomedical applications.
文摘Road traffic flow forecasting provides critical information for the operational management of road mobility challenges, and models are used to generate the forecast. This paper uses a random process to present a novel traffic modelling framework for aggregate traffic on urban roads. The main idea is that road traffic flow is random, even for the recurrent flow, such as rush hour traffic, which is predisposed to congestion. Therefore, the structure of the aggregate traffic flow model for urban roads should correlate well with the essential variables of the observed random dynamics of the traffic flow phenomena. The novelty of this paper is the developed framework, based on the Poisson process, the kinematics of urban road traffic flow, and the intermediate modelling approach, which were combined to formulate the model. Empirical data from an urban road in Ghana was used to explore the model’s fidelity. The results show that the distribution from the model correlates well with that of the empirical traffic, providing a strong validation of the new framework and instilling confidence in its potential for significantly improved forecasts and, hence, a more hopeful outlook for real-world traffic management.
基金Funded by the National Natural Science Foundation of China(Nos.52075347,51575364)and the Natural Science Foundation of Liaoning Provincial(No.2022-MS-295)。
文摘In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets.At the same time,the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets.In this work,the bulging process of the tailor-welded overlapping sheets was taken as the research object.Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification.The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality.When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength,the deformation of the tailor-welded sheets are more uniform,the offset of the weld seam is minimal,the limit bulging height is maximal,and the forming quality is optimal.
基金the National Natural Science Founda-tion of China(NSFC,Grant No.42174181)and the Key Research Program of Frontier Sciences,CAS(Grant No.QYZDJ-SSW-DQC010).
文摘The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood.In this article,we present an electron current layer detected at the edge of the magnetotail plasma sheet.The ions were demagnetized inside the electron current layer,but the electrons were still frozen in with the magnetic field line.Thus,this decoupling of ions and electrons gave rise to a strong Hall electric field,which could be the reason for the formation of the embedded thin current layer.The magnetized electrons,the absence of the nongyrotropic electron distribution,and negligible energy dissipation in the layer indicate that magnetic reconnection had not been triggered within the embedded thin current layer.The highly asymmetric plasma on the two sides of the current layer and low magnetic shear across it could suppress magnetic reconnection.The observations indicate that the embedded electric current layer,probably generated by the Hall electric field,even down to electron scale,is not a sufficient condition for magnetic reconnection.
基金the support of the Key Research and Development Program of Shaanxi Province,China(No.2021GXLH-Z-049)。
文摘The influence of geometric configuration on the friction characteristics during incremental sheet forming of AA5052 was analyzed by integrating surface morphology and its characteristic parameters,along with plastic strain,contact pressure,and area.The interface promotes lubrication and support when wall angles were≤40°,a 0.5 mm-thin sheet was used,and a 10 mm-large tool radius was employed.This mainly results in micro-plowing and plastic extrusion flow,leading to lower friction coefficient.However,when wall angles exceed 40°,significant plastic strain roughening occurs,leading to inadequate lubrication on the newly formed surface.Increased sheet thickness and decreased tool radius elevate contact pressure.These actions trigger micro-cutting and adhesion,potentially leading to localized scuffing and dimple tears,and higher friction coefficient.The friction mechanisms remain unaffected by the part’s plane curve features.As the forming process progresses,abrasive wear intensifies,and surface morphology evolves unfavorably for lubrication and friction reduction.
基金Project(4013311)supported by the National Science Foundation of Iran(INSF)。
文摘This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.
