Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled pre...Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.展开更多
This article, in order to improve the deformation homogeneity in aerospace forgings, proposes an approach that combines the fnite element method （FEM） and the response surface method （RSM） to optimize the preform ...This article, in order to improve the deformation homogeneity in aerospace forgings, proposes an approach that combines the fnite element method （FEM） and the response surface method （RSM） to optimize the preform shapes. New expressions that take into account the influences of equivalent effective strain distribution are developed to evaluate the homogeneity of deformation distribution in aerospace forgings. In order to reduce the number of design variables, the domain-division method is put forward to determine the optimal design variables. On the basis of FEM results, the RSM is used to establish an approximate model to depict the relationship between the responses （deformation homogeneity and die underfilling） and the design variables repre- sented by geometric parameters of the preform shape. With a typical aeroengine disk as an example, the proposed method is verified by achieving an optimal combination of design variables. By comparing the preform shape obtained with the proposed method to that with the existing one, it is evidenced that the former could achieve more homogeneous deformation in forging.展开更多
C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high...C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.展开更多
On the basis of the minimum energy principle and the minimum resistance law,this article proposes a new method,termed equipotential field method,to design the proper preform for producing isothermo forged P/M superall...On the basis of the minimum energy principle and the minimum resistance law,this article proposes a new method,termed equipotential field method,to design the proper preform for producing isothermo forged P/M superalloy disks. Using this new method,six variant preform contours are acquired with software ANSYS. The isothermal forging process of the P/M superalloy disk is simulated by using the industrial software MSC/Superform with thus obtained preforms so as to achieve the equivalent strain distribution in...展开更多
The multiple objective preform design optimization was put forward. The final forging＇s shape and deformation uniformity were considered in the multiple objective. The objective is to optimize the shape and the defor...The multiple objective preform design optimization was put forward. The final forging＇s shape and deformation uniformity were considered in the multiple objective. The objective is to optimize the shape and the deformation uniformity of the final forging at the same time so that a more high integrate quality of the final forging can be obtained. The total objective was assembled by the shape and uniformity objective using the weight adding method. The preform die shape is presented by cubic B-spline curves. The control points of B-spline curves are used as the design variables. The forms of the total objective function, shape and uniformity sub-objective function are given. The sensitivities of the total objective function and the sub-objective functions with respect to the design variables are developed. Using this method, the preform die shape of an H-shaped forging process is optimally designed. The optimization results are very satisfactory.展开更多
The lethality of a semi-preformed fragment warhead is closely related to the expand velocity and spatial distribution of the fragments from ruptured metal casing. The topic of how to improve the utilization of charge ...The lethality of a semi-preformed fragment warhead is closely related to the expand velocity and spatial distribution of the fragments from ruptured metal casing. The topic of how to improve the utilization of charge of have been drawing great attention from researchers and designer in this filed. In present paper,in order to investigate the influence of charge initiation manners on the scattering characteristics of semi-preformed fragment warhead, the numerical simulations and experimental test are conducted.Firstly, the influence of grid density on numerical results is investigated, and a proper numerical model with relatively high accuracy and effectiveness is determined. Then. numerical simulations of three kinds of different initiation position of a semi-preformed fragment warhead are carried out. An experimental test of the explosion of a semi-preformed fragment warhead is carried out. By comparing and analyzing the numerical results and experimental data, it is found that the initiation manners have great influence on scattering characteristics of semi-preformed fragment warhead. The researcher work of this paper would provide an effective alternative method to optimize the design of warhead.展开更多
Preformed albumin corona of albumin-nonselective nanoparticles(NPs)is widely exploited to inhibit the unavoidable protein adsorption upon intravenous administration.However,very few studies have concerned the preforme...Preformed albumin corona of albumin-nonselective nanoparticles(NPs)is widely exploited to inhibit the unavoidable protein adsorption upon intravenous administration.However,very few studies have concerned the preformed albumin corona of albumin-selective NPs.Herein,we report a novel type of albumin-selective NPs by decorating 6-maleimidocaproyl polyethylene glycol stearate(SA)onto PLGA NPs(SP NPs)surface,taking albuminnonselective PLGA NPs as control.PLGA NPs and SP NPs were prepared by emulsion-solvent evaporation method and the resultant NPs were in spherical shape with an average diameter around 180 nm.The corresponding albumin-coating PLGA NPs(PLGA@BSA NPs)and albumin-coating SP NPs(SP@BSA NPs)were formulated by incubating SP NPs or PLGA NPs with bovine serum albumin solution,respectively.The impact of albumin corona on particle characteristics,stability,photothermal effect,cytotoxicity,cell uptake,spheroid penetration and pharmacokinetics was investigated.In line with previous findings of preformed albumin coating,PLGA@BSA NPs exhibited higher stability,cytotoxicity,cell internalization and spheroid penetration performances in vitro,and longer blood circulation time in vivo than those of albumin-nonselective PLGA NPs,but albumin-selective SP NPs is capable of achieving a comparable in vitro and in vivo performances with both SP@BSA NPs and PLGA@BSA NPs.Our results demonstrate that SA decorated albumin-selective NPs pave a versatile avenue for optimizing nanoparticulate delivery without preformed albumin corona.展开更多
A finite element based sensitivity analysis method for preform die shape design in metal forging is developed. The optimization goal is to obtain more uniform deformation within the final forging by controlling the de...A finite element based sensitivity analysis method for preform die shape design in metal forging is developed. The optimization goal is to obtain more uniform deformation within the final forging by controlling the deformation uniformity. The objective function expressed by the effective strain is constructed. The sensitivity equations of the objective function, elemental volume, elemental effective strain rate and the elemental strain rate with respect to the design variables are constituted. The preform die shapes of an H-shaped forging process in axisymmetric deformation are designed using this method.展开更多
Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by th...Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by the pyrolysis of copper formate at 210℃ during the sinter bonding removed the native oxide and other oxides grown on bulk Cu finishes,enabling interface bonding.Moreover,Cu produced in situ by the reduction of Cu(II)accelerated the sinter bonding.Consequently,the bonding achieved at 300−350℃ under 5 MPa exhibited sufficient shear strength of 20.0−31.5 MPa after 180−300 min of sinter bonding.In addition,an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250℃,and a near-full-density bondline was achieved after 300 s.The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed sinter bonding.展开更多
The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with ti...The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with time as the Al alloys infiltrate into SiCp preforms at different temperatures.The results show that infiltration of SiCp preforms by Al melt is a thermal activation process and there is an incubation period before the infiltration becomes stable.With the increase of Mg content in the Al alloys from 0wt% to 8wt%,the infiltration will become much easier,the incubation period becomes shorter and the infiltration rate is faster,but these effects are not obvious when the Mg content is higher than 8wt%.As for Si addition to the Al alloys,it has no obvious effect on the incubation period,but the infiltration rate increases markedly with the increase of Si content from 0wt% to 12wt% and the rate has no obvious change when the content is bigger than 12wt%.The effect of Mg and Si on the incubation period is related to the infiltration mechanism of Al pressureless infiltration into SiCp preforms and their impact on the infiltration rate is a combined result from viscosity and surface tension of Al melt and SiC-Al wetting ability.展开更多
Production of A6063/SiC-B4C hybrid composite using vacuum assisted block mould investment casting was investigated. Firstly,SiC-B4C hybrid preforms were fabricated in cylindrical shape.The preferred mean particle size...Production of A6063/SiC-B4C hybrid composite using vacuum assisted block mould investment casting was investigated. Firstly,SiC-B4C hybrid preforms were fabricated in cylindrical shape.The preferred mean particle size of the SiC and B4C powders were 60μm and 55μm respectively.In early experiments,single powder ratio of 85%SiC and 15%B4C was selected to produce the tough preforms.Subsequently,the preforms were placed into the cylindrical shape gypsum bonded block investment moulds and A6063 alloy was infiltrated into the preforms using vacuum assisted（-10 5 Pa）casting machine.Porosity fraction of preforms was determined using Archimedes’test.The fabricated cast specimens were characterized using hardness tests,image analysis and SEM observations and EDX analysis.The result indicates that,by the vacuum assisted block mould investment casting technique,the infiltration of the preforms by molten metal was successfully realized.展开更多
The development of unconventional petroleum resources has gradually become an important succession for increasing oil production.However,the related engineers and researchers are paying more and more attention to the ...The development of unconventional petroleum resources has gradually become an important succession for increasing oil production.However,the related engineers and researchers are paying more and more attention to the application of temporary plugging agents(TPAs)for their efficient development.TPAs can expand the stimulated reservoir volume(SRV)and facilitate the flow of oil and gas to the bottom of the well.Particle-gels used as temporary plugging agents have the characteristics of the simple injection process,good deformation,high plugging strength,and complete self-degradation performance,which have been widely applied in recent years.In this paper,five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared.In addition,infrared spectroscopy analysis,differential calorimetry scanning(DSC)analysis,static particle gel swelling and degradation performance evaluation experiments,and dynamic temporary plugging performance experiments in cores were conducted at 34°C.Results show that as the molecular weight of the cross-linking agent(at 0.01 g)in the DPPG molecule decreased from 1,000 to 200 Da,the fewer cross-linking sites of DPPG,the looser the microscopic three-dimensional mesh structure formed.The swelling ratio increased from 7 to 33 times.However,the complete degradation time increased from 40 to 210 min.Moreover,the DSC results confirmed that the higher the molecular weight of the cross-linking agent,the worse is chemical stability and the more prone it to self-degradation.DPPG samples had good temporary plugging performance in reservoir cores.DPPGs prepared by the cross-linking agent with smaller molecular weight has a stronger swelling ratio,higher gel strength,and greater plugging strength in the core permeabilities.Moreover,the degraded DPPG is less damaging to the cores.However,their slower degradation rates take a slightly longer times to reach complete degradation.The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-type temporary plugging agents(TPA)with controllable degradation time in low-temperature reservoirs.It can help to expand the application range of existing DPPG reservoir conditions.展开更多
A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding（VARTM）. T...A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding（VARTM）. Two modified preforms were prepared under 0.1 and 0.6 MPa in an autoclave and then were used to fabricate the laminates via VARTM. Permeability and thickness distribution of the laminates were obtained by using a special device. Moreover, the tensile and compressive strengths of the obtained laminates were studied and compared with the unmodified ones. Results show that the tackified laminates present a maximum and minimum thickness under 0.1 and 0.6 MPa, respectively. The thicknesses and in-plane permeability of the tackified laminates, with better thickness uniformity, are significantly decreased compared with that of the unmodified cases, while the tensile and compressive strengths of the tackified laminates are improved obviously. Results show that the mechanical property of the tackified laminates prepared by hotpressing at 0.1 MPa is better than that processed at 0.6 MPa.展开更多
A particle preform was designed and prepared by conglomerating and cold-pressed process, which was condensed by chemical vapor infiltration （CVI） process to fabricate silicon nitride particles reinforced silicon nit...A particle preform was designed and prepared by conglomerating and cold-pressed process, which was condensed by chemical vapor infiltration （CVI） process to fabricate silicon nitride particles reinforced silicon nitride composites. The conglomerations are of almost sphericity after conglomerated. There are large pores among the conglomerations and small pores within themselves in the preform according to the design and the test of pore size distribution. The pore size of the preform is characterized by a double-peak distribution. The pore size distribution is influenced by conglomeration size. Large pores among the conglomerations still exist after infiltrated Si3N4 matrix. The conglomerations, however, are very compact. The CVI Si3N4 looks like cauliflowershaped structure. 2008 University of Science and Technology Beijing. All rights reserved.展开更多
An efficient hyper-elastic model that can reflect the primary mechanical behaviors of Carbon-Kevlar hybrid woven reinforcement was developed and implemented with VUMAT constitutive code for preforming simulation.The m...An efficient hyper-elastic model that can reflect the primary mechanical behaviors of Carbon-Kevlar hybrid woven reinforcement was developed and implemented with VUMAT constitutive code for preforming simulation.The model parameters were accurately determined through the uniaxial and bias-extension tests.To calibrate the simulation code,preforming experiments of hybrid woven reinforcement over the hemisphere mold and tetrahedron mold were respectively conducted to validate the proposed hyper-elastic model.The comparison between the simulations and experiments shows that the model can not only accurately capture shear angle distribution and geometry shape after deformation,but also accurately predict the force–displacement curve and potential fiber tensile failure during the preforming process.This result indicates that the proposed model can be used to predict the preforming behavior of Carbon-Kevlar hybrid woven reinforcement,and simulate its manufacturing process of complicated geometry.展开更多
The paper discusses the difference in the formulation concepts of alumina - spinel （spinel containing ） and alumina - magnesia （ spin, el forming） castables and the influence on their physical properties. The indi...The paper discusses the difference in the formulation concepts of alumina - spinel （spinel containing ） and alumina - magnesia （ spin, el forming） castables and the influence on their physical properties. The individual property profile is discussed with respect to the requirements of refactory lining materials for the different zones of a steel ladle.展开更多
Analysis on the deposition behavior of spray on deposition surface was made and an optimization method for the movement parameters （u, ω） of substrate was obtained. Simultaneously, a mathematical model of growth of...Analysis on the deposition behavior of spray on deposition surface was made and an optimization method for the movement parameters （u, ω） of substrate was obtained. Simultaneously, a mathematical model of growth of tubular preform, specifically aimed at the kind of atomizer that is fixed and with a tilt angle was established. By in- tegrating the optimization method and the mathematical model, the growth process and shape of preform were simu- lated. The results show that the tilt angle of atomizer plays an important role on the dimensions and shapes of tubular preforms and it can provide a guidance for the development of spray forming equipment.展开更多
This present paper investigates the friction and wear properties of friction material developed by ‘Hot Powder Preform Forging’ technique. The conventional technique to manufacture Metallo-ceramic brake pads was suc...This present paper investigates the friction and wear properties of friction material developed by ‘Hot Powder Preform Forging’ technique. The conventional technique to manufacture Metallo-ceramic brake pads was successfully and economically tried to replace the above process. Compacting and sintering technology suffers from certain major limitations such as inadequate joining of friction element with backing plate, poor density levels achieved in friction element owing to limited application of pressure during compacting, poor thermal conductivity due to high levels of porosity in the product, poor strength due to segregation of the impurities along prior particle boundaries (PPB’s) and, wide variations in final characteristics due to large number of variables involved. In contrast to these limitations, the present technique can offer brake pads of much simpler chemistry but with improved performance on account of simultaneous application of pressure and temperature and with better control of variables. Fade and recovery studies were carried out on a Krauss machine tester following the Economic Commission for Europe Regulation for replacement brake linings (ECE R-90). μfade, μrecovery, μperformance, % age fade , % age recovery & temperature rise lie within the range for friction materials used for low duty applications. The mechanical properties of these materials were characterized using ASTM standards.展开更多
Improved Resin Transfer Molding (RTM) technology and equipment were established.Void content and morphology of the 3-D braided preform/phenolic composite were investigated using different RTM processes.The results sho...Improved Resin Transfer Molding (RTM) technology and equipment were established.Void content and morphology of the 3-D braided preform/phenolic composite were investigated using different RTM processes.The results showed that void content of the vacuum and compression co-assisted RTM process was the lowest.Void morphologies of the specimen cross-section were analyzed with metallographic microscope.In traditional RTM process,the crack of cross-section was in evidence.In vacuum assisted RTM process,the void shape was divided into three categories:irregular crack,triangle,rotundity and ellipse.The most voids distributed in resin rich areas and were observed as large void based on equivalent diameter.In compression assisted RTM,vacuum and compression co-assisted RTM process,the polygonal voids mostly existed inter tows.Void size was mainly intermediate and small based equivalent diameter separately.展开更多
A new geometric model of Multiaxial Warp-Knitted (MWK) performs, which is based on the experimental observations and analysis of basic stitch, is developed to relate the geometric parameters and process variables. The...A new geometric model of Multiaxial Warp-Knitted (MWK) performs, which is based on the experimental observations and analysis of basic stitch, is developed to relate the geometric parameters and process variables. The fiber volume fraction and fibre orientation of MWK reinforced composites are described in terms of structural and processing parameters in the model. And this model provides a basis for the prediction of mechanical behavior of the MWK reinforced composites.展开更多
基金Supported by Jiangsu Provincial Frontier Leading Technology Basic Research Project(Grant No.BK20212007)Aero-Engine and Gas Turbine Basic Science Center(Grant No.P2022-B-IV-014-001)+1 种基金China Postdoctoral Program Fund(Grant No.1005/YBA23044)China Postdoctoral Assistance Fund(Grant No.1005/YBA23031)。
文摘Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.
文摘This article, in order to improve the deformation homogeneity in aerospace forgings, proposes an approach that combines the fnite element method （FEM） and the response surface method （RSM） to optimize the preform shapes. New expressions that take into account the influences of equivalent effective strain distribution are developed to evaluate the homogeneity of deformation distribution in aerospace forgings. In order to reduce the number of design variables, the domain-division method is put forward to determine the optimal design variables. On the basis of FEM results, the RSM is used to establish an approximate model to depict the relationship between the responses （deformation homogeneity and die underfilling） and the design variables repre- sented by geometric parameters of the preform shape. With a typical aeroengine disk as an example, the proposed method is verified by achieving an optimal combination of design variables. By comparing the preform shape obtained with the proposed method to that with the existing one, it is evidenced that the former could achieve more homogeneous deformation in forging.
基金Project (50802115) supported by the National Natural Science Foundation of ChinaProject (2011CB605801) supported by the National Basic Research Program of China
文摘C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.
基金Aeronautical Science Foundation of China (03H53048)
文摘On the basis of the minimum energy principle and the minimum resistance law,this article proposes a new method,termed equipotential field method,to design the proper preform for producing isothermo forged P/M superalloy disks. Using this new method,six variant preform contours are acquired with software ANSYS. The isothermal forging process of the P/M superalloy disk is simulated by using the industrial software MSC/Superform with thus obtained preforms so as to achieve the equivalent strain distribution in...
文摘The multiple objective preform design optimization was put forward. The final forging＇s shape and deformation uniformity were considered in the multiple objective. The objective is to optimize the shape and the deformation uniformity of the final forging at the same time so that a more high integrate quality of the final forging can be obtained. The total objective was assembled by the shape and uniformity objective using the weight adding method. The preform die shape is presented by cubic B-spline curves. The control points of B-spline curves are used as the design variables. The forms of the total objective function, shape and uniformity sub-objective function are given. The sensitivities of the total objective function and the sub-objective functions with respect to the design variables are developed. Using this method, the preform die shape of an H-shaped forging process is optimally designed. The optimization results are very satisfactory.
基金supported by the Joint Foundation project for Young Scientists of Ministry of Education(6141A02033108)National Natural Science Foundation of China(11502180)
文摘The lethality of a semi-preformed fragment warhead is closely related to the expand velocity and spatial distribution of the fragments from ruptured metal casing. The topic of how to improve the utilization of charge of have been drawing great attention from researchers and designer in this filed. In present paper,in order to investigate the influence of charge initiation manners on the scattering characteristics of semi-preformed fragment warhead, the numerical simulations and experimental test are conducted.Firstly, the influence of grid density on numerical results is investigated, and a proper numerical model with relatively high accuracy and effectiveness is determined. Then. numerical simulations of three kinds of different initiation position of a semi-preformed fragment warhead are carried out. An experimental test of the explosion of a semi-preformed fragment warhead is carried out. By comparing and analyzing the numerical results and experimental data, it is found that the initiation manners have great influence on scattering characteristics of semi-preformed fragment warhead. The researcher work of this paper would provide an effective alternative method to optimize the design of warhead.
基金financially supported by the National Basic Research Program of China(973 Program,No.2015CB932100)National Natural Science Foundation of China(No.81703451,81573371,81473164)。
文摘Preformed albumin corona of albumin-nonselective nanoparticles(NPs)is widely exploited to inhibit the unavoidable protein adsorption upon intravenous administration.However,very few studies have concerned the preformed albumin corona of albumin-selective NPs.Herein,we report a novel type of albumin-selective NPs by decorating 6-maleimidocaproyl polyethylene glycol stearate(SA)onto PLGA NPs(SP NPs)surface,taking albuminnonselective PLGA NPs as control.PLGA NPs and SP NPs were prepared by emulsion-solvent evaporation method and the resultant NPs were in spherical shape with an average diameter around 180 nm.The corresponding albumin-coating PLGA NPs(PLGA@BSA NPs)and albumin-coating SP NPs(SP@BSA NPs)were formulated by incubating SP NPs or PLGA NPs with bovine serum albumin solution,respectively.The impact of albumin corona on particle characteristics,stability,photothermal effect,cytotoxicity,cell uptake,spheroid penetration and pharmacokinetics was investigated.In line with previous findings of preformed albumin coating,PLGA@BSA NPs exhibited higher stability,cytotoxicity,cell internalization and spheroid penetration performances in vitro,and longer blood circulation time in vivo than those of albumin-nonselective PLGA NPs,but albumin-selective SP NPs is capable of achieving a comparable in vitro and in vivo performances with both SP@BSA NPs and PLGA@BSA NPs.Our results demonstrate that SA decorated albumin-selective NPs pave a versatile avenue for optimizing nanoparticulate delivery without preformed albumin corona.
基金This research work was supported by Science Fund of the Post Doctor of China ([2000]23).
文摘A finite element based sensitivity analysis method for preform die shape design in metal forging is developed. The optimization goal is to obtain more uniform deformation within the final forging by controlling the deformation uniformity. The objective function expressed by the effective strain is constructed. The sensitivity equations of the objective function, elemental volume, elemental effective strain rate and the elemental strain rate with respect to the design variables are constituted. The preform die shapes of an H-shaped forging process in axisymmetric deformation are designed using this method.
基金supported by the Materials&Components Technology Development Program(10080187)funded by the Ministry of Trade,Industry&Energy(MI,Korea)。
文摘Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by the pyrolysis of copper formate at 210℃ during the sinter bonding removed the native oxide and other oxides grown on bulk Cu finishes,enabling interface bonding.Moreover,Cu produced in situ by the reduction of Cu(II)accelerated the sinter bonding.Consequently,the bonding achieved at 300−350℃ under 5 MPa exhibited sufficient shear strength of 20.0−31.5 MPa after 180−300 min of sinter bonding.In addition,an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250℃,and a near-full-density bondline was achieved after 300 s.The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed sinter bonding.
基金supported by the National Natural Science Foundation of China (No.51004010)the Research Fund for the Doctoral Program of Higher Education of China (No.20090006120022)
文摘The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with time as the Al alloys infiltrate into SiCp preforms at different temperatures.The results show that infiltration of SiCp preforms by Al melt is a thermal activation process and there is an incubation period before the infiltration becomes stable.With the increase of Mg content in the Al alloys from 0wt% to 8wt%,the infiltration will become much easier,the incubation period becomes shorter and the infiltration rate is faster,but these effects are not obvious when the Mg content is higher than 8wt%.As for Si addition to the Al alloys,it has no obvious effect on the incubation period,but the infiltration rate increases markedly with the increase of Si content from 0wt% to 12wt% and the rate has no obvious change when the content is bigger than 12wt%.The effect of Mg and Si on the incubation period is related to the infiltration mechanism of Al pressureless infiltration into SiCp preforms and their impact on the infiltration rate is a combined result from viscosity and surface tension of Al melt and SiC-Al wetting ability.
基金Yildiz Technical University and Balkan Center for Advanced Casting Technologies (BCACT) for their financial support
文摘Production of A6063/SiC-B4C hybrid composite using vacuum assisted block mould investment casting was investigated. Firstly,SiC-B4C hybrid preforms were fabricated in cylindrical shape.The preferred mean particle size of the SiC and B4C powders were 60μm and 55μm respectively.In early experiments,single powder ratio of 85%SiC and 15%B4C was selected to produce the tough preforms.Subsequently,the preforms were placed into the cylindrical shape gypsum bonded block investment moulds and A6063 alloy was infiltrated into the preforms using vacuum assisted（-10 5 Pa）casting machine.Porosity fraction of preforms was determined using Archimedes’test.The fabricated cast specimens were characterized using hardness tests,image analysis and SEM observations and EDX analysis.The result indicates that,by the vacuum assisted block mould investment casting technique,the infiltration of the preforms by molten metal was successfully realized.
基金supported by the Research Foundation of China University of Petroleum-Beijing at Karamay (No. YJ2018B02002 and XQZX20200010)the Natural Science Foundation of Xinjiang Uygur Autonomous Region (No. 2021D01E23 and 2019D01B57)+3 种基金the University Scientific Research Project of Xinjiang Uygur Autonomous Region (No. XJEDU2019Y067)the Xinjiang Uygur Autonomous Region Innovation Environment Construction Project (No. 2019Q025)the Sichuan Province Regional Innovation Cooperation Project (No. 2020YFQ0036)the CNPC Strategic Cooperation Science and Technology Project (ZLZX2020-01-04-04)
文摘The development of unconventional petroleum resources has gradually become an important succession for increasing oil production.However,the related engineers and researchers are paying more and more attention to the application of temporary plugging agents(TPAs)for their efficient development.TPAs can expand the stimulated reservoir volume(SRV)and facilitate the flow of oil and gas to the bottom of the well.Particle-gels used as temporary plugging agents have the characteristics of the simple injection process,good deformation,high plugging strength,and complete self-degradation performance,which have been widely applied in recent years.In this paper,five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared.In addition,infrared spectroscopy analysis,differential calorimetry scanning(DSC)analysis,static particle gel swelling and degradation performance evaluation experiments,and dynamic temporary plugging performance experiments in cores were conducted at 34°C.Results show that as the molecular weight of the cross-linking agent(at 0.01 g)in the DPPG molecule decreased from 1,000 to 200 Da,the fewer cross-linking sites of DPPG,the looser the microscopic three-dimensional mesh structure formed.The swelling ratio increased from 7 to 33 times.However,the complete degradation time increased from 40 to 210 min.Moreover,the DSC results confirmed that the higher the molecular weight of the cross-linking agent,the worse is chemical stability and the more prone it to self-degradation.DPPG samples had good temporary plugging performance in reservoir cores.DPPGs prepared by the cross-linking agent with smaller molecular weight has a stronger swelling ratio,higher gel strength,and greater plugging strength in the core permeabilities.Moreover,the degraded DPPG is less damaging to the cores.However,their slower degradation rates take a slightly longer times to reach complete degradation.The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-type temporary plugging agents(TPA)with controllable degradation time in low-temperature reservoirs.It can help to expand the application range of existing DPPG reservoir conditions.
基金Funded by the National Engineering and Research Center for Commercial Aircraft Manufacturing(No.SAMC 13-JS-15-034)
文摘A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding（VARTM）. Two modified preforms were prepared under 0.1 and 0.6 MPa in an autoclave and then were used to fabricate the laminates via VARTM. Permeability and thickness distribution of the laminates were obtained by using a special device. Moreover, the tensile and compressive strengths of the obtained laminates were studied and compared with the unmodified ones. Results show that the tackified laminates present a maximum and minimum thickness under 0.1 and 0.6 MPa, respectively. The thicknesses and in-plane permeability of the tackified laminates, with better thickness uniformity, are significantly decreased compared with that of the unmodified cases, while the tensile and compressive strengths of the tackified laminates are improved obviously. Results show that the mechanical property of the tackified laminates prepared by hotpressing at 0.1 MPa is better than that processed at 0.6 MPa.
基金the National Natural Science Foundation of China(No.50672076 and 50642039)the Key Foundation of National Natural Science in China(No.90405015)+1 种基金the National Young Elitist Foundation in China(No.50425208)the Doctorate Foundation of Northwestern Polytechnical University(No.CX200505).
文摘A particle preform was designed and prepared by conglomerating and cold-pressed process, which was condensed by chemical vapor infiltration （CVI） process to fabricate silicon nitride particles reinforced silicon nitride composites. The conglomerations are of almost sphericity after conglomerated. There are large pores among the conglomerations and small pores within themselves in the preform according to the design and the test of pore size distribution. The pore size of the preform is characterized by a double-peak distribution. The pore size distribution is influenced by conglomeration size. Large pores among the conglomerations still exist after infiltrated Si3N4 matrix. The conglomerations, however, are very compact. The CVI Si3N4 looks like cauliflowershaped structure. 2008 University of Science and Technology Beijing. All rights reserved.
基金support from the Young Fund of Natural Science Foundation of Shaanxi Province,China(Nos.2020JQ-701 and 2020JQ-121)the Open Fund of State Key Laboratory of Applied Optics,China(No.SKLAO2020001A09).
文摘An efficient hyper-elastic model that can reflect the primary mechanical behaviors of Carbon-Kevlar hybrid woven reinforcement was developed and implemented with VUMAT constitutive code for preforming simulation.The model parameters were accurately determined through the uniaxial and bias-extension tests.To calibrate the simulation code,preforming experiments of hybrid woven reinforcement over the hemisphere mold and tetrahedron mold were respectively conducted to validate the proposed hyper-elastic model.The comparison between the simulations and experiments shows that the model can not only accurately capture shear angle distribution and geometry shape after deformation,but also accurately predict the force–displacement curve and potential fiber tensile failure during the preforming process.This result indicates that the proposed model can be used to predict the preforming behavior of Carbon-Kevlar hybrid woven reinforcement,and simulate its manufacturing process of complicated geometry.
文摘The paper discusses the difference in the formulation concepts of alumina - spinel （spinel containing ） and alumina - magnesia （ spin, el forming） castables and the influence on their physical properties. The individual property profile is discussed with respect to the requirements of refactory lining materials for the different zones of a steel ladle.
基金Sponsored by National Natural Science Foundation of China (50474082)
文摘Analysis on the deposition behavior of spray on deposition surface was made and an optimization method for the movement parameters （u, ω） of substrate was obtained. Simultaneously, a mathematical model of growth of tubular preform, specifically aimed at the kind of atomizer that is fixed and with a tilt angle was established. By in- tegrating the optimization method and the mathematical model, the growth process and shape of preform were simu- lated. The results show that the tilt angle of atomizer plays an important role on the dimensions and shapes of tubular preforms and it can provide a guidance for the development of spray forming equipment.
文摘This present paper investigates the friction and wear properties of friction material developed by ‘Hot Powder Preform Forging’ technique. The conventional technique to manufacture Metallo-ceramic brake pads was successfully and economically tried to replace the above process. Compacting and sintering technology suffers from certain major limitations such as inadequate joining of friction element with backing plate, poor density levels achieved in friction element owing to limited application of pressure during compacting, poor thermal conductivity due to high levels of porosity in the product, poor strength due to segregation of the impurities along prior particle boundaries (PPB’s) and, wide variations in final characteristics due to large number of variables involved. In contrast to these limitations, the present technique can offer brake pads of much simpler chemistry but with improved performance on account of simultaneous application of pressure and temperature and with better control of variables. Fade and recovery studies were carried out on a Krauss machine tester following the Economic Commission for Europe Regulation for replacement brake linings (ECE R-90). μfade, μrecovery, μperformance, % age fade , % age recovery & temperature rise lie within the range for friction materials used for low duty applications. The mechanical properties of these materials were characterized using ASTM standards.
基金Tianjin Natural Science Foundation of China(No.06YFJ MJC03100,08JCZDJC24500)
文摘Improved Resin Transfer Molding (RTM) technology and equipment were established.Void content and morphology of the 3-D braided preform/phenolic composite were investigated using different RTM processes.The results showed that void content of the vacuum and compression co-assisted RTM process was the lowest.Void morphologies of the specimen cross-section were analyzed with metallographic microscope.In traditional RTM process,the crack of cross-section was in evidence.In vacuum assisted RTM process,the void shape was divided into three categories:irregular crack,triangle,rotundity and ellipse.The most voids distributed in resin rich areas and were observed as large void based on equivalent diameter.In compression assisted RTM,vacuum and compression co-assisted RTM process,the polygonal voids mostly existed inter tows.Void size was mainly intermediate and small based equivalent diameter separately.
文摘A new geometric model of Multiaxial Warp-Knitted (MWK) performs, which is based on the experimental observations and analysis of basic stitch, is developed to relate the geometric parameters and process variables. The fiber volume fraction and fibre orientation of MWK reinforced composites are described in terms of structural and processing parameters in the model. And this model provides a basis for the prediction of mechanical behavior of the MWK reinforced composites.
