Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventi...Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventional bending,laser-assisted energy field bending and CEF-assisted bending experiments on TC4 titanium alloy,the effects of bending force,laser-assisted energy field and CEF on the springback angle and fillet radius of TC4 titanium alloy specimens in V-shape bending were analyzed.The impact of the CEF-assisted bending process on the microstructure of TC4 titanium alloy was also investigated.The results show that CEF-assisted bending process has the advantages of high energy density,simple operation process and small influence area of the microstructure performances.It is effective in reducing the springback and fillet radius of bending specimens.Thus,CEF-assisted bending effectively improves the formability and surface quality of titanium alloy specimens.展开更多
High-power laser melting deposition stands as a viable solution for the high-quality and efficient manufacturing of large-sized titani-um alloy components.This article explores how laser influences the quality of depo...High-power laser melting deposition stands as a viable solution for the high-quality and efficient manufacturing of large-sized titani-um alloy components.This article explores how laser influences the quality of deposited layers when operating within a laser power range of 3-8 kW,and a H-shaped TC4 component with half-meter high was successfully fabricated by the laser melting deposition technology with a power of 5 kW,exhibiting a well-formed surface.In addition,the microstructure and properties of deposited TC4 components were examined.The as-deposited component is mainly composed of coarse columnar crystals.However,the distribu-tion and size of grains are particularly uneven with a range of 1-5 mm in length.The deposited TC4 is made up of lots of basketweave structure and a bit Widmanstatten structures at the grain boundaries.What’s more,lath-shapedαphase and a small amount ofβphase can be found in the grain.There is no significant disparity in grain size along the height direction;however,the heat accumula-tion resulting from deposition leads to a reduced length-to-width ratio ofα-laths in the bottom region.The tensile performance of samples from the top area marginally surpasses that of the bottom,and the tensile performance in the vertical direction is marginally better than that in the horizontal direction.According to the prevailing GB/T 38915-2020 and HB 5432-89 standards,the tensile properties of the fabricated components,sampled from various regions and directions,exceed those of forgings.The direction of sampling has weak influence on impact energy;however,fatigue crack propagation experiments indicate that cracks are more pre-valent and propagate at a slightly faster rate in horizontally-oriented specimens,a phenomenon attributed to the combined effects of grain morphology and microstructure.展开更多
This study introduces electromagnetic dynamic self-piercing riveting(ED-SPR),an innovative technique that integrates electromagnetic riveting principles with static self-piercing riveting(S-SPR)for highperformance str...This study introduces electromagnetic dynamic self-piercing riveting(ED-SPR),an innovative technique that integrates electromagnetic riveting principles with static self-piercing riveting(S-SPR)for highperformance structural joints.A dedicated methodology and experimental apparatus for ED-SPR were systematically designed and validated.Quantitative comparative analyses between ED-SPR and S-SPR were conducted on three critical material combinations:CFRP/Al,low-strength steel HC340 LA/Al,and high-strength steel DP590/Al.Key findings demonstrate that the electromagnetic-driven process reduces installation resistance by 60%and achieves a 30%larger interlock distance at the joint base compared to S-SPR.These quantitative advantages directly contribute to an approximately 30%increase in load-bearing capacity and superior damage tolerance in ED-SPR joints,as evidenced by tensile-shear testing of single-lap joints.Furthermore,distinct failure modes were observed:ED-SPR joints exhibited top plate pull-out failure in CFRP/Al and DP590/Al configurations,contrasting with the predominant rivet pull-out failure in S-SPR counterparts.Surface morphology and damage evolution were characterized via scanning electron microscopy(SEM)on post-assembly and tensile-failed specimens.The study establishes a foundation for optimizing electromagnetic-driven riveting parameters to mitigate CFRP delamination and further enhance joint reliability in vehicle body and aircraft fuselage structures.展开更多
2A12 aluminum alloy powders were hot-isostatic-pressed （HIPed） at representative temperatures for investi- gating the variation in microstructure, tensile property and fracture mode of the powder compact. It was fou...2A12 aluminum alloy powders were hot-isostatic-pressed （HIPed） at representative temperatures for investi- gating the variation in microstructure, tensile property and fracture mode of the powder compact. It was found that the microstructure of raw powders changed from a dendrite structure to an equiaxed structure from room temperature to 600 ℃. The liquid phase produced by the eutectic reaction in the powder was gradually increased and finally formed a liquid pathway that ran through the entire powder from 490 to 600℃. Prior particle boundaries were observed in the powder compacts HIPed at 490 and 520℃. The liquid phase in the powder compacts was squeezed into the powder boundaries and the triple points of powder when HIPed at 580℃. However, the liquid phase located at the triple points of the powder was forced out and moved toward a small powder particle by HIP pressure under an HIPing temperature of 600℃, which led to a decrease in the mechanical properties and relative density. Better comprehensive properties were obtained at HIPing temperatures of 490 and 580℃. The low ductility exhibited by the P/M aluminum alloy HIPed at different temperatures was believed to arise from a combination of the existence of oxide film on the powder particle surface and the distribution characteristics of the liquid phase. Finally, three typical types of de-cohesion were classified.展开更多
Nickel-based Superalloy Honeycomb(NBSH) is widely used in aerospace field due to the high temperature resistance, high specific strength and light weight. However, the NBSH is extremely prone to form burrs during proc...Nickel-based Superalloy Honeycomb(NBSH) is widely used in aerospace field due to the high temperature resistance, high specific strength and light weight. However, the NBSH is extremely prone to form burrs during processing. The unreasonable burr morphology causes insufficient welding strength or false welding between NBSH and skin, resulting in premature failure of the parts. Hence, the burr formation mechanism and morphological transformation critical conditions in grinding NBSH were investigated based on finite element method(FEM) and experiments. Furthermore, the orthogonal experiments were carried out to investigate the effects of grinding parameters on burr and obtain the suitable parameter intervals to restrain the flash burr formation. The results indicate that due to the absence of supporting material, the extruded material of edge transforms into the Fourth Deformation Zone(FDZ). The FDZ rotates a certain angle due to the extrusion of abrasive particle, which leads to the fact that the FDZ cannot be removed and remains on the honeycomb wall, thus forming micro burr. If the material removal per unit time is large, the chip is not removed from FDZ. The parts that should have been chips are bonded with micro burr to form a flash burr. To restrain the flash burr formation, the suitable intervals of grinding depth,grinding speed and feed speed are 5–15 μm, 60–70 m/min and 500–1000 mm/min, respectively.展开更多
The mechanical and wear behavior of copper-tungsten disulfide（Cu/WS_2） composites fabricated by spark plasma sintering（SPS） and hot pressing（HP） was investigated, comparatively. Results indicated that the additi...The mechanical and wear behavior of copper-tungsten disulfide（Cu/WS_2） composites fabricated by spark plasma sintering（SPS） and hot pressing（HP） was investigated, comparatively. Results indicated that the addition of lubricant WS_2 substantially reduced wear rate of the Cu matrix composites fabricated by SPS,and the optimum content of WS_2 is 20 wt% with regard to the wear behavior. However, it affected a little to the wear rate while dramatically decreased the friction coefficient of the composite fabricated by HP.This difference in friction behavior of the self-lubricating composites fabricated by the two techniques was closely related to their different mechanical properties. Severe interfacial reaction occurred during spark plasma sintering, leading to brittle phase formation at interface.展开更多
The response surface methodology is used to study the effect of stirring parameters on the mechanical properties of magnesium matrix composites(MMCs).The composites are manufactured using different stirring speeds(500...The response surface methodology is used to study the effect of stirring parameters on the mechanical properties of magnesium matrix composites(MMCs).The composites are manufactured using different stirring speeds(500,600,and 700 r/min),stirring time(10,20,and 30 min),and weight fractions(0,2.5%,5%,and10%)of silicon carbide particles.The experimental results show that 700 r/min and 20 min are the best conditions for obtaining the best mechanical properties.Based on the desirability function methodology,the optimum parameter values for the best mechanical characteristics of produced composites are reached at 696.102 r/min,19.889 min,and9.961%(in weight).展开更多
A series of non-covalently functionalized molybdenum disulfide-silica(f-MoS_(2)-SiO_(2))nanocomposites was prepared by an in-situ assembled method and used to fabricate the oriented molybdenum disulfide-SiO_(2)/Hydrog...A series of non-covalently functionalized molybdenum disulfide-silica(f-MoS_(2)-SiO_(2))nanocomposites was prepared by an in-situ assembled method and used to fabricate the oriented molybdenum disulfide-SiO_(2)/Hydrogenated Nitrile Butadiene Rubber(f-MoS2-SiO_(2)/HNBR)composites.The characterization results show the synergistic dispersion between the functionalized molybdenum disulfide(f-MoS2)nanosheets and SiO_(2)nanoparticles.The addition of f-MoS2 nanosheets can improve the dispersion of fillers in the rubber matrix and weaken the filler network.The non-covalently functionalization improves the interface interaction between f-MoS_(2)nanosheets and the rubber matrix.Furthermore,the tensile strength of f-MoS2-SiO_(2)/HNBR is 65.9%higher than that of SiO_(2)/HNBR by adding 1.0wt%of f-MoS_(2).At the same time,the dielectric constant of f-MoS2-SiO_(2)/HNBR is increased by 23.7%compared to SiO_(2)/HNBR due to the micro-capacitor structure of parallel f-MoS2 nanosheets in the rubber matrix.Our work provides new ideas for the development of high-performance elastomer materials.展开更多
In response to the complex composition,scattered data storage,and differences in management levels of manufacturing resources in the production site of complex products,the research and application of digital technolo...In response to the complex composition,scattered data storage,and differences in management levels of manufacturing resources in the production site of complex products,the research and application of digital technology for perception and control of manufacturing resources in the production site of complex products are of great significance for accelerating the digital transformation and upgrading of complex product manufacturing enterprises.Firstly,focusing on the problems of single element of local management,high cost of heterogeneous integration of multiple data sources,and the difficulty in cleaning up the global status of manufacturing resources in the production site of complex products,basic requirements and core requirements of enterprises for global management and control of manufacturing resources in the production site are deeply analyzed.Secondly,the indicators and data sources of different manufacturing resources that managers at different levels are concerned about are analyzed,providing guidance for refined management.Thirdly,a reference architecture of the manufacturing resource management and control platform for the production site of complex products is proposed,supporting access,integration,and global unified management of manufacturing resource information through the access strategy,data,basic component,and APP layers.Finally,the feasibility,effectiveness,and practicality of the architecture are verified through practical cases,aiming to provide a reference for the manufacturing resource management of complex product manufacturing enterprises.展开更多
The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical m...The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical method based on computational fluid mechanics(CFD).The transient aerodynamic behaviors when opening door under various flight altitudes and the corresponding structure deformation evolution in the unsteady flow fields are analyzed respectively and presented.The rules of aircraft attitude parameters′impacting to the responses of structure and the bay-door′s opening process are obtained by comparing with the analysis results.These rules can be applied to the structure design of bay-door and route specification of missile when disengaged and launched from within store.展开更多
During the automated placement process of dry fibers,the positioning and fixation of dry fiber gauze belts are achieved by spraying setting agents.The amount of the setting agent is difficult to control when it is spr...During the automated placement process of dry fibers,the positioning and fixation of dry fiber gauze belts are achieved by spraying setting agents.The amount of the setting agent is difficult to control when it is sprayed manually.Furthermore,it can also affect the permeability of the preform,resin injection and the quality of the vacuum assisted resin infusion(VARI)molding,resulting in a decrease in the mechanical properties of composite materials.This study utilizes dry fiber automated placement equipment and an automated spraying system to manufacture preform structures,followed by VARI process to prepare composite samples with varying setting agent contents.Subsequently,mechanical characterization including interlaminar shear,bending and tensile testing is conducted to investigate the influence of setting agent content on both the manufacturing process and the mechanical properties of composite products.The results show that the interlaminar shear strength,bending strength and tensile strength of the sample gradually decrease with the increase of the content of the setting agent.The optimal setting agent content for automated laying of dry fiber is determined to be 4%-6%,balancing the preformed body’s layup quality and its impact on mechanical properties.Compared with agent-free samples,this range results in reductions of 3% in interlaminar shear strength,9% in bending strength,11% in bending modulus,and 13%-16% in tensile strength.展开更多
Based on the analysis of factors affecting transient temperature field of aircraft fuel tank and coupled heat transfer mechanism, a mathematical model of transient coupled heat transfer, including the dynamic- chan...Based on the analysis of factors affecting transient temperature field of aircraft fuel tank and coupled heat transfer mechanism, a mathematical model of transient coupled heat transfer, including the dynamic- change of fuel quality, the internal heat transfer, the external aerodynamic convection and the radiation heat transfer, is established. Taking the aerodynamic convection and radiation heat transfer outside the tank as the third kinds of thermal boundary conditions for the thermal analysis of the fuel tank, calculation of internal and external coupling heat of fuel tank is decoupled. Ther^nal network method combined with hierarchical dynamic- grid is used to deal with the fuel consumption, and carry on the heat transfer analysis of the fuel tank. The numerical method for the transient temperature field of aircraft fuel tank is established. Through the simulation calculation, the transient temperature distribution of the fuel tank under different flight conditions is obtained, and the influence of the fuel mass and the external thermal environment on the temperature field is analyzed.展开更多
A dual-band and high-isolation shared-aperture antenna for unmanned aerial vehicle(UAV)platforms has been proposed.This shared-aperture antenna consists of a rectangular monopole antenna and a 4-element multiple input...A dual-band and high-isolation shared-aperture antenna for unmanned aerial vehicle(UAV)platforms has been proposed.This shared-aperture antenna consists of a rectangular monopole antenna and a 4-element multiple input multiple output(MIMO)antenna.In order to increase the isolation,several double split ring metamaterial(MTM)structures are introduced between antenna elements.The antenna radiator and the MTM structure are located on the front and back of the same dielectric substrate,respectively,and are perpendicular to a circular metal plate.The overall size of the antenna substrate is 124 mm×38 mm×1.016 mm.Moreover,the antenna prototype is constructed and measured,and the simulated and measured results are in good agreement.The measured results show that the-10 dB bandwidth of the monopole antenna is 1.92 GHz to 2.75 GHz,and the common-6.0 dB bandwidth of the MIMO antenna element is 4.75 GHz to 4.91 GHz,covering 2.2 GHz to 2.4 GHz in the S-band and 4.8 GHz to 4.9 GHz in the 5G band,respectively.In the 5G band,the isolation between any element of the MIMO antenna and the S-band monopole antenna is not less than 21 dB,and the isolation between the MIMO antenna elements is better than 23 dB,indicating t-hat the isolation between the antenna elements is high.The proposed antenna is suitable for the application on UAV airborne platforms.展开更多
Tracking interferometer based on bi-rotary milling head is a novel scheme to conduct volumetric accuracy measurement of a five-axis machine tool.The laser beam direction of the interferometer can be regulated to follo...Tracking interferometer based on bi-rotary milling head is a novel scheme to conduct volumetric accuracy measurement of a five-axis machine tool.The laser beam direction of the interferometer can be regulated to follow the retroreflector by moving the bi-rotary head.This is a low-cost implementation of multilateration measurement,and its measurement accuracy is mainly affected by the error motion of the rotary axes.This paper proposes an improved multilateration principle to identify the positionindependent geometric errors of rotary axis and laser beam,and minimize their impact on the measurement uncertainty.A closed-loop tracking interferometer system installed on the spindle is developed to perform the measurement with high tracking accuracy.The device can be installed on an ordinary five-axis machine tool without modifying the machine tool structure.The proposed scheme is conducive to improving the accuracy and practical application of the tracking interferometer based on birotary milling head.Experiments with the corresponding closed-loop tracking interferometer and uncertainty analysis are conducted to verify the performance of the proposed measurement scheme.展开更多
Traditional machine learning relies on a centralized data pipeline for model training in various applications;however,data are inherently fragmented.Such a decentralized nature of databases presents the serious challe...Traditional machine learning relies on a centralized data pipeline for model training in various applications;however,data are inherently fragmented.Such a decentralized nature of databases presents the serious challenge for collaboration:sending all decentralized datasets to a central server raises serious privacy concerns.Although there has been a joint effort in tackling such a critical issue by proposing privacy-preserving machine learning frameworks,such as federated learning,most state-of-the-art frameworks are built still in a centralized way,in which a central client is needed for collecting and distributing model information(instead of data itself)from every other client,leading to high communication burden and high vulnerability when there exists a failure at or an attack on the central client.Here we propose a principled decentralized federated learning algorithm(DeceFL),which does not require a central client and relies only on local information transmission between clients and their neighbors,representing a fully decentralized learning framework.It has been further proven that every client reaches the global minimum with zero performance gap and achieves the same convergence rate O(1=T)(where T is the number of iterations in gradient descent)as centralized federated learning when the loss function is smooth and strongly convex.Finally,the proposed algorithm has been applied to a number of applications to illustrate its effectiveness for both convex and nonconvex loss functions,time-invariant and time-varying topologies,as well as IID and Non-IID of datasets,demonstrating its applicability to a wide range of real-world medical and industrial applications.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.52075347,51575364)the Natural Science Foundation of Liaoning Provincial(No.2022-MS-295)。
文摘Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventional bending,laser-assisted energy field bending and CEF-assisted bending experiments on TC4 titanium alloy,the effects of bending force,laser-assisted energy field and CEF on the springback angle and fillet radius of TC4 titanium alloy specimens in V-shape bending were analyzed.The impact of the CEF-assisted bending process on the microstructure of TC4 titanium alloy was also investigated.The results show that CEF-assisted bending process has the advantages of high energy density,simple operation process and small influence area of the microstructure performances.It is effective in reducing the springback and fillet radius of bending specimens.Thus,CEF-assisted bending effectively improves the formability and surface quality of titanium alloy specimens.
基金supported by National Key Research and Development Program Project(2022YFB4602300)National Natural Science Foundation Sponsored Project(52205419)Major Science and Technology Projects in Sichuan Province(2023ZDZX0003).
文摘High-power laser melting deposition stands as a viable solution for the high-quality and efficient manufacturing of large-sized titani-um alloy components.This article explores how laser influences the quality of deposited layers when operating within a laser power range of 3-8 kW,and a H-shaped TC4 component with half-meter high was successfully fabricated by the laser melting deposition technology with a power of 5 kW,exhibiting a well-formed surface.In addition,the microstructure and properties of deposited TC4 components were examined.The as-deposited component is mainly composed of coarse columnar crystals.However,the distribu-tion and size of grains are particularly uneven with a range of 1-5 mm in length.The deposited TC4 is made up of lots of basketweave structure and a bit Widmanstatten structures at the grain boundaries.What’s more,lath-shapedαphase and a small amount ofβphase can be found in the grain.There is no significant disparity in grain size along the height direction;however,the heat accumula-tion resulting from deposition leads to a reduced length-to-width ratio ofα-laths in the bottom region.The tensile performance of samples from the top area marginally surpasses that of the bottom,and the tensile performance in the vertical direction is marginally better than that in the horizontal direction.According to the prevailing GB/T 38915-2020 and HB 5432-89 standards,the tensile properties of the fabricated components,sampled from various regions and directions,exceed those of forgings.The direction of sampling has weak influence on impact energy;however,fatigue crack propagation experiments indicate that cracks are more pre-valent and propagate at a slightly faster rate in horizontally-oriented specimens,a phenomenon attributed to the combined effects of grain morphology and microstructure.
基金sponsored by National Natural Science Foundation of China(Nos.52305146 and 52275165)Natural Science Foundation of Chongqing,China(No.cstb2022nscqmsx1290)+1 种基金the financial support from the Major Special Project for Technological Innovation and Application Development of Chongqing(No.CSTB2024TIAD-STX0015)the Key Laboratory Project of Shaanxi Province(No.2025SYS-SYSZD-064)。
文摘This study introduces electromagnetic dynamic self-piercing riveting(ED-SPR),an innovative technique that integrates electromagnetic riveting principles with static self-piercing riveting(S-SPR)for highperformance structural joints.A dedicated methodology and experimental apparatus for ED-SPR were systematically designed and validated.Quantitative comparative analyses between ED-SPR and S-SPR were conducted on three critical material combinations:CFRP/Al,low-strength steel HC340 LA/Al,and high-strength steel DP590/Al.Key findings demonstrate that the electromagnetic-driven process reduces installation resistance by 60%and achieves a 30%larger interlock distance at the joint base compared to S-SPR.These quantitative advantages directly contribute to an approximately 30%increase in load-bearing capacity and superior damage tolerance in ED-SPR joints,as evidenced by tensile-shear testing of single-lap joints.Furthermore,distinct failure modes were observed:ED-SPR joints exhibited top plate pull-out failure in CFRP/Al and DP590/Al configurations,contrasting with the predominant rivet pull-out failure in S-SPR counterparts.Surface morphology and damage evolution were characterized via scanning electron microscopy(SEM)on post-assembly and tensile-failed specimens.The study establishes a foundation for optimizing electromagnetic-driven riveting parameters to mitigate CFRP delamination and further enhance joint reliability in vehicle body and aircraft fuselage structures.
文摘2A12 aluminum alloy powders were hot-isostatic-pressed （HIPed） at representative temperatures for investi- gating the variation in microstructure, tensile property and fracture mode of the powder compact. It was found that the microstructure of raw powders changed from a dendrite structure to an equiaxed structure from room temperature to 600 ℃. The liquid phase produced by the eutectic reaction in the powder was gradually increased and finally formed a liquid pathway that ran through the entire powder from 490 to 600℃. Prior particle boundaries were observed in the powder compacts HIPed at 490 and 520℃. The liquid phase in the powder compacts was squeezed into the powder boundaries and the triple points of powder when HIPed at 580℃. However, the liquid phase located at the triple points of the powder was forced out and moved toward a small powder particle by HIP pressure under an HIPing temperature of 600℃, which led to a decrease in the mechanical properties and relative density. Better comprehensive properties were obtained at HIPing temperatures of 490 and 580℃. The low ductility exhibited by the P/M aluminum alloy HIPed at different temperatures was believed to arise from a combination of the existence of oxide film on the powder particle surface and the distribution characteristics of the liquid phase. Finally, three typical types of de-cohesion were classified.
基金supported by the Fund of Shanghai Academy of Spaceflight Technology(No.USCAST2020-3)National Key Research and Development Program of China(No.2020YFB2010603)National Natural Science Foundation of China(No.51875355).
文摘Nickel-based Superalloy Honeycomb(NBSH) is widely used in aerospace field due to the high temperature resistance, high specific strength and light weight. However, the NBSH is extremely prone to form burrs during processing. The unreasonable burr morphology causes insufficient welding strength or false welding between NBSH and skin, resulting in premature failure of the parts. Hence, the burr formation mechanism and morphological transformation critical conditions in grinding NBSH were investigated based on finite element method(FEM) and experiments. Furthermore, the orthogonal experiments were carried out to investigate the effects of grinding parameters on burr and obtain the suitable parameter intervals to restrain the flash burr formation. The results indicate that due to the absence of supporting material, the extruded material of edge transforms into the Fourth Deformation Zone(FDZ). The FDZ rotates a certain angle due to the extrusion of abrasive particle, which leads to the fact that the FDZ cannot be removed and remains on the honeycomb wall, thus forming micro burr. If the material removal per unit time is large, the chip is not removed from FDZ. The parts that should have been chips are bonded with micro burr to form a flash burr. To restrain the flash burr formation, the suitable intervals of grinding depth,grinding speed and feed speed are 5–15 μm, 60–70 m/min and 500–1000 mm/min, respectively.
基金supported by the National Natural Science Foundation of China (No. 51471177)the Youth Innovation PromotionAssociation CAS (No. 2016178)the Fundamental Research Funds for the Central Universities (No. N160205001)
文摘The mechanical and wear behavior of copper-tungsten disulfide（Cu/WS_2） composites fabricated by spark plasma sintering（SPS） and hot pressing（HP） was investigated, comparatively. Results indicated that the addition of lubricant WS_2 substantially reduced wear rate of the Cu matrix composites fabricated by SPS,and the optimum content of WS_2 is 20 wt% with regard to the wear behavior. However, it affected a little to the wear rate while dramatically decreased the friction coefficient of the composite fabricated by HP.This difference in friction behavior of the self-lubricating composites fabricated by the two techniques was closely related to their different mechanical properties. Severe interfacial reaction occurred during spark plasma sintering, leading to brittle phase formation at interface.
基金supported by the Fundamental Research Funds for the Central Universities(Nos.NS2015055,NP2020413)the Administration of the Ministries and Commissions of the Central Government(No.011951G19061)+1 种基金the National Natural Science Foundation of China(No.51105202)the State Administration of P.R.China and the Ministry of Education of P.R.China(No.B16024)
文摘The response surface methodology is used to study the effect of stirring parameters on the mechanical properties of magnesium matrix composites(MMCs).The composites are manufactured using different stirring speeds(500,600,and 700 r/min),stirring time(10,20,and 30 min),and weight fractions(0,2.5%,5%,and10%)of silicon carbide particles.The experimental results show that 700 r/min and 20 min are the best conditions for obtaining the best mechanical properties.Based on the desirability function methodology,the optimum parameter values for the best mechanical characteristics of produced composites are reached at 696.102 r/min,19.889 min,and9.961%(in weight).
基金supported by the National Basic Research Program of China(No.2015CB654703)。
文摘A series of non-covalently functionalized molybdenum disulfide-silica(f-MoS_(2)-SiO_(2))nanocomposites was prepared by an in-situ assembled method and used to fabricate the oriented molybdenum disulfide-SiO_(2)/Hydrogenated Nitrile Butadiene Rubber(f-MoS2-SiO_(2)/HNBR)composites.The characterization results show the synergistic dispersion between the functionalized molybdenum disulfide(f-MoS2)nanosheets and SiO_(2)nanoparticles.The addition of f-MoS2 nanosheets can improve the dispersion of fillers in the rubber matrix and weaken the filler network.The non-covalently functionalization improves the interface interaction between f-MoS_(2)nanosheets and the rubber matrix.Furthermore,the tensile strength of f-MoS2-SiO_(2)/HNBR is 65.9%higher than that of SiO_(2)/HNBR by adding 1.0wt%of f-MoS_(2).At the same time,the dielectric constant of f-MoS2-SiO_(2)/HNBR is increased by 23.7%compared to SiO_(2)/HNBR due to the micro-capacitor structure of parallel f-MoS2 nanosheets in the rubber matrix.Our work provides new ideas for the development of high-performance elastomer materials.
文摘In response to the complex composition,scattered data storage,and differences in management levels of manufacturing resources in the production site of complex products,the research and application of digital technology for perception and control of manufacturing resources in the production site of complex products are of great significance for accelerating the digital transformation and upgrading of complex product manufacturing enterprises.Firstly,focusing on the problems of single element of local management,high cost of heterogeneous integration of multiple data sources,and the difficulty in cleaning up the global status of manufacturing resources in the production site of complex products,basic requirements and core requirements of enterprises for global management and control of manufacturing resources in the production site are deeply analyzed.Secondly,the indicators and data sources of different manufacturing resources that managers at different levels are concerned about are analyzed,providing guidance for refined management.Thirdly,a reference architecture of the manufacturing resource management and control platform for the production site of complex products is proposed,supporting access,integration,and global unified management of manufacturing resource information through the access strategy,data,basic component,and APP layers.Finally,the feasibility,effectiveness,and practicality of the architecture are verified through practical cases,aiming to provide a reference for the manufacturing resource management of complex product manufacturing enterprises.
文摘The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical method based on computational fluid mechanics(CFD).The transient aerodynamic behaviors when opening door under various flight altitudes and the corresponding structure deformation evolution in the unsteady flow fields are analyzed respectively and presented.The rules of aircraft attitude parameters′impacting to the responses of structure and the bay-door′s opening process are obtained by comparing with the analysis results.These rules can be applied to the structure design of bay-door and route specification of missile when disengaged and launched from within store.
基金supported by Jiangsu Provincial Key Research and Development Program(No.BE2023014-4).
文摘During the automated placement process of dry fibers,the positioning and fixation of dry fiber gauze belts are achieved by spraying setting agents.The amount of the setting agent is difficult to control when it is sprayed manually.Furthermore,it can also affect the permeability of the preform,resin injection and the quality of the vacuum assisted resin infusion(VARI)molding,resulting in a decrease in the mechanical properties of composite materials.This study utilizes dry fiber automated placement equipment and an automated spraying system to manufacture preform structures,followed by VARI process to prepare composite samples with varying setting agent contents.Subsequently,mechanical characterization including interlaminar shear,bending and tensile testing is conducted to investigate the influence of setting agent content on both the manufacturing process and the mechanical properties of composite products.The results show that the interlaminar shear strength,bending strength and tensile strength of the sample gradually decrease with the increase of the content of the setting agent.The optimal setting agent content for automated laying of dry fiber is determined to be 4%-6%,balancing the preformed body’s layup quality and its impact on mechanical properties.Compared with agent-free samples,this range results in reductions of 3% in interlaminar shear strength,9% in bending strength,11% in bending modulus,and 13%-16% in tensile strength.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51676055 and 51536001)
文摘Based on the analysis of factors affecting transient temperature field of aircraft fuel tank and coupled heat transfer mechanism, a mathematical model of transient coupled heat transfer, including the dynamic- change of fuel quality, the internal heat transfer, the external aerodynamic convection and the radiation heat transfer, is established. Taking the aerodynamic convection and radiation heat transfer outside the tank as the third kinds of thermal boundary conditions for the thermal analysis of the fuel tank, calculation of internal and external coupling heat of fuel tank is decoupled. Ther^nal network method combined with hierarchical dynamic- grid is used to deal with the fuel consumption, and carry on the heat transfer analysis of the fuel tank. The numerical method for the transient temperature field of aircraft fuel tank is established. Through the simulation calculation, the transient temperature distribution of the fuel tank under different flight conditions is obtained, and the influence of the fuel mass and the external thermal environment on the temperature field is analyzed.
基金supported by the National Natural Science Foundation of China under Grants No.61801406 and No.U23A20651in part by the Research Fund of Sichuan Provincial under Grants No.2024NSFSC0478 and No.2022YFG0259+1 种基金in part by the Research Fund of Key R&D Projects in Sichuan Province under Grant No.2022-ZY00-00009-GXin part by the Mianyang Central Guiding Local Science and Technology Development Fund Project under Grants No.2023ZYDF002 and No.2023ZYDF092.
文摘A dual-band and high-isolation shared-aperture antenna for unmanned aerial vehicle(UAV)platforms has been proposed.This shared-aperture antenna consists of a rectangular monopole antenna and a 4-element multiple input multiple output(MIMO)antenna.In order to increase the isolation,several double split ring metamaterial(MTM)structures are introduced between antenna elements.The antenna radiator and the MTM structure are located on the front and back of the same dielectric substrate,respectively,and are perpendicular to a circular metal plate.The overall size of the antenna substrate is 124 mm×38 mm×1.016 mm.Moreover,the antenna prototype is constructed and measured,and the simulated and measured results are in good agreement.The measured results show that the-10 dB bandwidth of the monopole antenna is 1.92 GHz to 2.75 GHz,and the common-6.0 dB bandwidth of the MIMO antenna element is 4.75 GHz to 4.91 GHz,covering 2.2 GHz to 2.4 GHz in the S-band and 4.8 GHz to 4.9 GHz in the 5G band,respectively.In the 5G band,the isolation between any element of the MIMO antenna and the S-band monopole antenna is not less than 21 dB,and the isolation between the MIMO antenna elements is better than 23 dB,indicating t-hat the isolation between the antenna elements is high.The proposed antenna is suitable for the application on UAV airborne platforms.
基金supported by the National Natural Science Foundation of China(Grant No.51875357)the State Key Program of National Natural Science Foundation of China(Grant No.U21B2081)the National Defense Science and Technology Excellence Youth Foundation(Grant No.2020-JCJQ-ZQ-079)。
文摘Tracking interferometer based on bi-rotary milling head is a novel scheme to conduct volumetric accuracy measurement of a five-axis machine tool.The laser beam direction of the interferometer can be regulated to follow the retroreflector by moving the bi-rotary head.This is a low-cost implementation of multilateration measurement,and its measurement accuracy is mainly affected by the error motion of the rotary axes.This paper proposes an improved multilateration principle to identify the positionindependent geometric errors of rotary axis and laser beam,and minimize their impact on the measurement uncertainty.A closed-loop tracking interferometer system installed on the spindle is developed to perform the measurement with high tracking accuracy.The device can be installed on an ordinary five-axis machine tool without modifying the machine tool structure.The proposed scheme is conducive to improving the accuracy and practical application of the tracking interferometer based on birotary milling head.Experiments with the corresponding closed-loop tracking interferometer and uncertainty analysis are conducted to verify the performance of the proposed measurement scheme.
基金supported by the National Natural Science Foundation of China(Grant Nos.92167201,52188102,62133003,61991403,61991404,and 61991400)Jiangsu Industrial Technology Research Institute(JITRI).
文摘Traditional machine learning relies on a centralized data pipeline for model training in various applications;however,data are inherently fragmented.Such a decentralized nature of databases presents the serious challenge for collaboration:sending all decentralized datasets to a central server raises serious privacy concerns.Although there has been a joint effort in tackling such a critical issue by proposing privacy-preserving machine learning frameworks,such as federated learning,most state-of-the-art frameworks are built still in a centralized way,in which a central client is needed for collecting and distributing model information(instead of data itself)from every other client,leading to high communication burden and high vulnerability when there exists a failure at or an attack on the central client.Here we propose a principled decentralized federated learning algorithm(DeceFL),which does not require a central client and relies only on local information transmission between clients and their neighbors,representing a fully decentralized learning framework.It has been further proven that every client reaches the global minimum with zero performance gap and achieves the same convergence rate O(1=T)(where T is the number of iterations in gradient descent)as centralized federated learning when the loss function is smooth and strongly convex.Finally,the proposed algorithm has been applied to a number of applications to illustrate its effectiveness for both convex and nonconvex loss functions,time-invariant and time-varying topologies,as well as IID and Non-IID of datasets,demonstrating its applicability to a wide range of real-world medical and industrial applications.
