Casting-cold extrusion technology was presented to fabricate alttminum/copper clad composite, and copper tubes with different sketch sections were designed. The technology of aluminum/copper clad composite fabricated ...Casting-cold extrusion technology was presented to fabricate alttminum/copper clad composite, and copper tubes with different sketch sections were designed. The technology of aluminum/copper clad composite fabricated by casting-cold extrusion was simulated by DEFORM software using tubes with four arc grooves. The stress and strain in different deformation zones were analyzed. The groove size reduces gradually and the groove shape drives to triangle during the extrusion procedure. The maximum values of equivalent effective stress and radial stress appear in groove zones, and the maximum equivalent effective strain firstly is obtained also in groove zones. The grain size in groove zones is less than that in other zones. The experimental results are consistent with simulation results, which prove that the copper tubes with sketch section are favorable to the metallurgy bond of boundary interface between aluminum and copper.展开更多
The edge stress problem in composite laminates under uniform axial extension is analyzed. The displacement distribution in three directions along the thickness are derived respectively by use of the sectional warping ...The edge stress problem in composite laminates under uniform axial extension is analyzed. The displacement distribution in three directions along the thickness are derived respectively by use of the sectional warping corrective theory, and the hierarchical displacement functions are adopted in the width direction. Finally, based on the principle of virtual work, a special finite element model for boundary layer effects is obtained. Accuracy and convergence of the solution are studied, and the present resu...展开更多
The cross-sectional analysis on hydroxyapatite （HA） coating and HA+TiO2 composite coating was conducted by using electron probe microanalyser （EPMA）. The results reveal that annealing at 650 ℃ leads to the cracki...The cross-sectional analysis on hydroxyapatite （HA） coating and HA+TiO2 composite coating was conducted by using electron probe microanalyser （EPMA）. The results reveal that annealing at 650 ℃ leads to the cracking within the HA coating or along the coating/substrate interface. The ribbon-like regions in HA coating are verified to contain less PO4-4 groups resulted from the high temperature melting of HA particles in plasma flame. From the viewpoint of microstructural observation, it can be concluded that the addition of TiO2 into HA coating can effectively strengthen and toughen the whole coating system with a shift of the well-bonded interface from the THA （top HA） coating/HTBC （HA+TiO2 bond coat） interface in the as-sprayed THBC （top HA-HTBC） coating to the HTBC/Ti substrate interface in the heat treated THBC coating. The THA coating bonds well to Ti substrate perhaps via its TiO2 hobnobbing with the Ti oxides formed on the Ti substrate.展开更多
with the constant popularity of the precast assembly gasification, the application of the composite section beam which can change into different sections is wilder. This passage, based on the hypothesis that the inter...with the constant popularity of the precast assembly gasification, the application of the composite section beam which can change into different sections is wilder. This passage, based on the hypothesis that the interface is smooth, simplify the double composite section beam and deduce the anchorage-bolt-shear and composite-section-beam-bending-capacity formulas when there is a slip on the interface in elastic stage. Moreover, it contains some prospect and summarizes of the later research.展开更多
The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. F...The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. Firstly, the high-aspect-ratio wing is modeled as a composite thin-walled closed section Euler beam whose displacement and rotation both could be of finite value, and the nonlinear dynamic equations is build up on it with all the effects of geometric nonlinearity, aerodynamic nonlinearity and anisotropy of material being considered. Then vibration equations are deduced through perturbing the dynamic equations at wing＇s equilibrium position, and coupled with unsteady stall aerodynamic model and ONERA model, to obtain the nonlinear stall flutter analysis equations of wing. Finally, the flutter stabilities with various wind speeds are determined by the harmonic balance method. With several exampies, the validity of the stall flutter model is proved, and the significant effects of geometric nonlinearity on the stall flutter various characters as wall as the effects of ply angle on the stall flutter speed and frequency also are discussed.展开更多
This work deals with the evolution of carbon isotope composition in the Luoyixi （罗依溪） Section, a candidate of the Global Standard Stratotype-section and Point （GSSP）, defining the base of the as-yet-undefined s...This work deals with the evolution of carbon isotope composition in the Luoyixi （罗依溪） Section, a candidate of the Global Standard Stratotype-section and Point （GSSP）, defining the base of the as-yet-undefined seventh stage of Cambrian System at the first appearance of the cosmopolitan agnostoid Lejopyge iaevigata. This level is favored in a vote of International Subcommission on Cambrian Stratigraphy （ISCS） as the biohorizon for defining the base of a global stage. Two hundred and sixty-four samples for carbon and oxygen isotope analysis have been collected from the carbonate successions at an interval of 0.25 to 0.5 m in this section. Results of the carbon isotope data exhibit a remarkable disciplinarian trend. The pattern of the carbon isotope evolution is gently undulant with a relatively long period during the underlying Drumian Stage, and then the values of δ13C fluctuate sharply with a short period in provisional seventh stage. The onset of sharp fluctuation in the δ13C values begins at the proposed GSSP level, defining the base of the global seventh stage, where δ13C values change from a gentle trend to a sharp trend. Distinct covariant-relationships among δ13C,δ18O, and sea level fluctuations suggest that a warming change in paleoclimate took place during the early global seventh stage, which led to a positive shift in δ13C values.展开更多
Fiber-reinforced polymer composite materials have become materials of choice for manufacturing application due to their high specific stiffness, strength and fatigue life, low density and thermal expansion coefficient...Fiber-reinforced polymer composite materials have become materials of choice for manufacturing application due to their high specific stiffness, strength and fatigue life, low density and thermal expansion coefficient. However, there are some types of defects such as porosity that form during the manufacturing processes of composites and alter their mechanical behavior and material properties. In his study, hand lay-up was conducted to fabricate samples of carbon fiber-reinforced polymer composites with three different vacuum levels in order to vary porosity content. Nondestructive evaluation, destructive techniques and mechanical testing were conducted. Nondestructive evaluation results showed the trend in percentages of porosity through-thickness. Serial sectioning images revealed significant details about the composite’s internal structure such as the volume, morphology and distribution of porosity. Mechanical testing results showed that porosity led to a decrease in both Mode I static interlaminar fracture toughness and Mode I cyclic strain energy release rate fatigue life. The fractographic micrographs showed that porosity content increased as the vacuum decreased, and it drew a relationship between fracture mechanisms and mechanical properties of the composite under different modes of loading as a result of the porosity effects. Finally, in order to accurately quantify porosity percentages included in the samples of different vacuum levels, a comparison was made between the parameters and percentages resulted from the nondestructive evaluation and mechanical testing and the features resulted from fractography and serial sectioning.展开更多
Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of t...Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.展开更多
In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a me...In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a metasurface and plasma.A metasurface with three absorption peaks is designed by means of an equivalent circuit based on an electromagnetic resonance type metamaterial absorber.The reflection and absorption of the composite structure are numerically and experimentally verified.The finite integration method was used to simulate a composite structure of finite size to obtain the RCS.The experimental measurements of electromagnetic wave reflection were conducted by a vector network analyzer(Keysight N5234A)and horn antennas,etc.The research showed that the absorption capacity of this composite structure was substantially improved compared to either the plasma or the metasurface,and it is more convenient for application due to its low plasma thickness requirement and easy fabrication.展开更多
There are two classes of continuities, parametric continuities and geometric continuities, which are used to illuminate the smoothness of a composite surface in surface construction and reconstruction in computer grap...There are two classes of continuities, parametric continuities and geometric continuities, which are used to illuminate the smoothness of a composite surface in surface construction and reconstruction in computer graphics (CG) and computer aided design (CAD). A parametric continuity is more stiff than its corresponding geometric continuity of the same order. This paper uncovers the geometric properties of parametric and geometric continuities less than and equal to second order and presents the proofs for the corresponding propositions. These propositions can be applied to the existent or promising schemes of surface construction or reconstruction, which can provide a convincing theory for researchers to establish their schemes in surface construction. Three examples are used in this paper to show the applications of these propositions.展开更多
In order to study the web-crippling behavior of aluminum hollow sectionsubjected to concentrated load, sixteen aluminum hollow tubes with different loadingconditions, bearing length and web slenderness ratios were tes...In order to study the web-crippling behavior of aluminum hollow sectionsubjected to concentrated load, sixteen aluminum hollow tubes with different loadingconditions, bearing length and web slenderness ratios were tested. This paper alsodiscussed a method to improve the web crippling strength of the aluminum hollowsections by infilling the mortar as composite section, and four aluminum compositesections were tested. The literature has reported lots of web crippling tests, but there isfew reports on web crippling behavior of aluminum composite sections. Interior-Ground(IG) and End-Ground (EG) loading conditions were adopted, with the specimens placedon the ground to simulate the load of floor joists. Specimens were also placed on abearing plate with end (ETF) or interior (ITF) bearing load. The influence of supportingconditions, loading positions, bearing length and web slenderness ratios on web cripplingultimate bearing capacity and ductility of aluminum hollow sections was studied. Theenhancements of infilling mortar were also evaluated. The results obtained from theexperiments show that infilling the mortar in aluminum hollow tubes is an effectivemethod for enhancing the ultimate capacity of the web, especially for specimens underInterior-Ground (IG) condition. Based on the results of parameter research, this paperproposes a series of design formulas for well predicting web crippling ultimate capacityof aluminum hollow and composite tubes under four different loading and boundaryconditions.展开更多
Formulations of double differential cross sections of light composite particleconsidering (1,m) and (2,m) pickup type reactions simultaneously for semi-classicalmulti-step compound and direct processes are presented.T...Formulations of double differential cross sections of light composite particleconsidering (1,m) and (2,m) pickup type reactions simultaneously for semi-classicalmulti-step compound and direct processes are presented.The calculated results of crosssections,spectra,and double differential cross sections indicate that generally the con-tributions of the (2,m) pickup type reactions are about 15%-25% when the incident en-ergies are below 50 MeV but can become dominant when the incident energies areabove 50 MeV in some region of the outgoing energies and angles.The forward tenden-cy of the calculated angular distributions by (2,m) configuration is weaker than those by(1,m) configuration.For the reactions of outgoing composite particle with higher inci-dent energy,the multi-step direct process must be considered.展开更多
横跨色尔腾山山前断裂布设一条长10.77 km的浅层地震勘探测线L1,结果发现,色尔腾山山前断裂在剖面上清晰可见,其主断裂在上部存在分叉,由断层F_(P1.1)和F_(P1)组成,均为正断层,视倾向南;结合地质地貌调查认为,F_(P1.1)断层的最新活动时...横跨色尔腾山山前断裂布设一条长10.77 km的浅层地震勘探测线L1,结果发现,色尔腾山山前断裂在剖面上清晰可见,其主断裂在上部存在分叉,由断层F_(P1.1)和F_(P1)组成,均为正断层,视倾向南;结合地质地貌调查认为,F_(P1.1)断层的最新活动时代为全新世。针对色尔腾山山前断裂的F_(P1)断层开展钻孔联合地质剖面探测,划分出Fa、Fb两个断层,结合光释光测年结果发现,断层Fa和Fb为全新世断层,其最新活动时代晚于2.5±0.6 ka BP。色尔腾山山前断裂在近地表呈叉状结构,是该断裂在晚第四纪具有多次活动的反映。展开更多
文摘Casting-cold extrusion technology was presented to fabricate alttminum/copper clad composite, and copper tubes with different sketch sections were designed. The technology of aluminum/copper clad composite fabricated by casting-cold extrusion was simulated by DEFORM software using tubes with four arc grooves. The stress and strain in different deformation zones were analyzed. The groove size reduces gradually and the groove shape drives to triangle during the extrusion procedure. The maximum values of equivalent effective stress and radial stress appear in groove zones, and the maximum equivalent effective strain firstly is obtained also in groove zones. The grain size in groove zones is less than that in other zones. The experimental results are consistent with simulation results, which prove that the copper tubes with sketch section are favorable to the metallurgy bond of boundary interface between aluminum and copper.
基金Key Program of National Natural Science Foundation of China (1993 2 0 3 0 )
文摘The edge stress problem in composite laminates under uniform axial extension is analyzed. The displacement distribution in three directions along the thickness are derived respectively by use of the sectional warping corrective theory, and the hierarchical displacement functions are adopted in the width direction. Finally, based on the principle of virtual work, a special finite element model for boundary layer effects is obtained. Accuracy and convergence of the solution are studied, and the present resu...
文摘The cross-sectional analysis on hydroxyapatite （HA） coating and HA+TiO2 composite coating was conducted by using electron probe microanalyser （EPMA）. The results reveal that annealing at 650 ℃ leads to the cracking within the HA coating or along the coating/substrate interface. The ribbon-like regions in HA coating are verified to contain less PO4-4 groups resulted from the high temperature melting of HA particles in plasma flame. From the viewpoint of microstructural observation, it can be concluded that the addition of TiO2 into HA coating can effectively strengthen and toughen the whole coating system with a shift of the well-bonded interface from the THA （top HA） coating/HTBC （HA+TiO2 bond coat） interface in the as-sprayed THBC （top HA-HTBC） coating to the HTBC/Ti substrate interface in the heat treated THBC coating. The THA coating bonds well to Ti substrate perhaps via its TiO2 hobnobbing with the Ti oxides formed on the Ti substrate.
文摘with the constant popularity of the precast assembly gasification, the application of the composite section beam which can change into different sections is wilder. This passage, based on the hypothesis that the interface is smooth, simplify the double composite section beam and deduce the anchorage-bolt-shear and composite-section-beam-bending-capacity formulas when there is a slip on the interface in elastic stage. Moreover, it contains some prospect and summarizes of the later research.
文摘The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. Firstly, the high-aspect-ratio wing is modeled as a composite thin-walled closed section Euler beam whose displacement and rotation both could be of finite value, and the nonlinear dynamic equations is build up on it with all the effects of geometric nonlinearity, aerodynamic nonlinearity and anisotropy of material being considered. Then vibration equations are deduced through perturbing the dynamic equations at wing＇s equilibrium position, and coupled with unsteady stall aerodynamic model and ONERA model, to obtain the nonlinear stall flutter analysis equations of wing. Finally, the flutter stabilities with various wind speeds are determined by the harmonic balance method. With several exampies, the validity of the stall flutter model is proved, and the significant effects of geometric nonlinearity on the stall flutter various characters as wall as the effects of ply angle on the stall flutter speed and frequency also are discussed.
基金the National Natural Science Foundation of China (Nos. 40672023, 40332018)Chinese Academy of Sciences (KZCX2-YW-122) and the Major Basic Research Project of MST (2006CB806400).
文摘This work deals with the evolution of carbon isotope composition in the Luoyixi （罗依溪） Section, a candidate of the Global Standard Stratotype-section and Point （GSSP）, defining the base of the as-yet-undefined seventh stage of Cambrian System at the first appearance of the cosmopolitan agnostoid Lejopyge iaevigata. This level is favored in a vote of International Subcommission on Cambrian Stratigraphy （ISCS） as the biohorizon for defining the base of a global stage. Two hundred and sixty-four samples for carbon and oxygen isotope analysis have been collected from the carbonate successions at an interval of 0.25 to 0.5 m in this section. Results of the carbon isotope data exhibit a remarkable disciplinarian trend. The pattern of the carbon isotope evolution is gently undulant with a relatively long period during the underlying Drumian Stage, and then the values of δ13C fluctuate sharply with a short period in provisional seventh stage. The onset of sharp fluctuation in the δ13C values begins at the proposed GSSP level, defining the base of the global seventh stage, where δ13C values change from a gentle trend to a sharp trend. Distinct covariant-relationships among δ13C,δ18O, and sea level fluctuations suggest that a warming change in paleoclimate took place during the early global seventh stage, which led to a positive shift in δ13C values.
文摘Fiber-reinforced polymer composite materials have become materials of choice for manufacturing application due to their high specific stiffness, strength and fatigue life, low density and thermal expansion coefficient. However, there are some types of defects such as porosity that form during the manufacturing processes of composites and alter their mechanical behavior and material properties. In his study, hand lay-up was conducted to fabricate samples of carbon fiber-reinforced polymer composites with three different vacuum levels in order to vary porosity content. Nondestructive evaluation, destructive techniques and mechanical testing were conducted. Nondestructive evaluation results showed the trend in percentages of porosity through-thickness. Serial sectioning images revealed significant details about the composite’s internal structure such as the volume, morphology and distribution of porosity. Mechanical testing results showed that porosity led to a decrease in both Mode I static interlaminar fracture toughness and Mode I cyclic strain energy release rate fatigue life. The fractographic micrographs showed that porosity content increased as the vacuum decreased, and it drew a relationship between fracture mechanisms and mechanical properties of the composite under different modes of loading as a result of the porosity effects. Finally, in order to accurately quantify porosity percentages included in the samples of different vacuum levels, a comparison was made between the parameters and percentages resulted from the nondestructive evaluation and mechanical testing and the features resulted from fractography and serial sectioning.
文摘Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.
基金financially supported by National Natural Science Foundation of China(No.12175050)the Foundation of National Key Laboratory of Electromagnetic Environment of China(No.202101003)。
文摘In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a metasurface and plasma.A metasurface with three absorption peaks is designed by means of an equivalent circuit based on an electromagnetic resonance type metamaterial absorber.The reflection and absorption of the composite structure are numerically and experimentally verified.The finite integration method was used to simulate a composite structure of finite size to obtain the RCS.The experimental measurements of electromagnetic wave reflection were conducted by a vector network analyzer(Keysight N5234A)and horn antennas,etc.The research showed that the absorption capacity of this composite structure was substantially improved compared to either the plasma or the metasurface,and it is more convenient for application due to its low plasma thickness requirement and easy fabrication.
文摘There are two classes of continuities, parametric continuities and geometric continuities, which are used to illuminate the smoothness of a composite surface in surface construction and reconstruction in computer graphics (CG) and computer aided design (CAD). A parametric continuity is more stiff than its corresponding geometric continuity of the same order. This paper uncovers the geometric properties of parametric and geometric continuities less than and equal to second order and presents the proofs for the corresponding propositions. These propositions can be applied to the existent or promising schemes of surface construction or reconstruction, which can provide a convincing theory for researchers to establish their schemes in surface construction. Three examples are used in this paper to show the applications of these propositions.
基金has been supported by the National NaturalScience Foundation of China (Nos. 51478047 and 51778066)the Natural ScienceFoundation of Hubei Province (No. 2018CFB730)Foundation project of College ofengineering and technology, Yangtze University (No. 2017KY06)。
文摘In order to study the web-crippling behavior of aluminum hollow sectionsubjected to concentrated load, sixteen aluminum hollow tubes with different loadingconditions, bearing length and web slenderness ratios were tested. This paper alsodiscussed a method to improve the web crippling strength of the aluminum hollowsections by infilling the mortar as composite section, and four aluminum compositesections were tested. The literature has reported lots of web crippling tests, but there isfew reports on web crippling behavior of aluminum composite sections. Interior-Ground(IG) and End-Ground (EG) loading conditions were adopted, with the specimens placedon the ground to simulate the load of floor joists. Specimens were also placed on abearing plate with end (ETF) or interior (ITF) bearing load. The influence of supportingconditions, loading positions, bearing length and web slenderness ratios on web cripplingultimate bearing capacity and ductility of aluminum hollow sections was studied. Theenhancements of infilling mortar were also evaluated. The results obtained from theexperiments show that infilling the mortar in aluminum hollow tubes is an effectivemethod for enhancing the ultimate capacity of the web, especially for specimens underInterior-Ground (IG) condition. Based on the results of parameter research, this paperproposes a series of design formulas for well predicting web crippling ultimate capacityof aluminum hollow and composite tubes under four different loading and boundaryconditions.
文摘Formulations of double differential cross sections of light composite particleconsidering (1,m) and (2,m) pickup type reactions simultaneously for semi-classicalmulti-step compound and direct processes are presented.The calculated results of crosssections,spectra,and double differential cross sections indicate that generally the con-tributions of the (2,m) pickup type reactions are about 15%-25% when the incident en-ergies are below 50 MeV but can become dominant when the incident energies areabove 50 MeV in some region of the outgoing energies and angles.The forward tenden-cy of the calculated angular distributions by (2,m) configuration is weaker than those by(1,m) configuration.For the reactions of outgoing composite particle with higher inci-dent energy,the multi-step direct process must be considered.
文摘横跨色尔腾山山前断裂布设一条长10.77 km的浅层地震勘探测线L1,结果发现,色尔腾山山前断裂在剖面上清晰可见,其主断裂在上部存在分叉,由断层F_(P1.1)和F_(P1)组成,均为正断层,视倾向南;结合地质地貌调查认为,F_(P1.1)断层的最新活动时代为全新世。针对色尔腾山山前断裂的F_(P1)断层开展钻孔联合地质剖面探测,划分出Fa、Fb两个断层,结合光释光测年结果发现,断层Fa和Fb为全新世断层,其最新活动时代晚于2.5±0.6 ka BP。色尔腾山山前断裂在近地表呈叉状结构,是该断裂在晚第四纪具有多次活动的反映。
