This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and...This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.展开更多
We investigate the relationships between infrared excess(IRX = LIR/LUV) and Balmer decrement(Hα/Hβ) as indicators of dust attenuation for 609 H II regions at scales of ~50–200 pc in NGC 628, utilizing data from Ast...We investigate the relationships between infrared excess(IRX = LIR/LUV) and Balmer decrement(Hα/Hβ) as indicators of dust attenuation for 609 H II regions at scales of ~50–200 pc in NGC 628, utilizing data from AstroSat, the James Webb Space Telescope(JWST) and Multi Unit Spectroscopic Explorer. Our findings indicate that about three-fifths of the sample H II regions reside within the regime occupied by local star-forming galaxies(SFGs) along the dust attenuation correlation described by their corresponding color excess parameters E(B-V)IRX= 0.51 E(B-V)Hα/Hβ. Nearly 27% of the sample exhibits E(B-V)IRX> E(B-V)Hα/Hβ, while a small fraction(~13%) displays significantly lower E(B-V)IRXcompared to E(B-V)Hα/Hβ. These results suggest that the correlation between the two dust attenuation indicators no longer holds for spatially resolved H II regions. Furthermore, the ratio of E(B-V)IRXto E(B-V)Hα/Hβremains unaffected by various physical parameters of the H II regions, including star formation rate(SFR), SFR surface density, infrared luminosity(LIR),LIRsurface density, stellar mass, gas-phase metallicity, circularized radius, and the distance to the galactic center.We argue that the ratio is primarily influenced by the evolution of the surrounding interstellar medium of the starforming regions, transitioning from an early dense and thick phase to the late blown-away stage.展开更多
Aiming at the problem of deep surrounding rock instability induced by roadway excavation or mining disturbance,the true triaxial loading system was used to conduct graded cyclic maximum principal stress σ_(1) and int...Aiming at the problem of deep surrounding rock instability induced by roadway excavation or mining disturbance,the true triaxial loading system was used to conduct graded cyclic maximum principal stress σ_(1) and intermediate principal stress σ_(2) tests on sandstone to simulate the effect of mining stress in actual underground engineering.The influences of each principal stress cycle on the mechanical properties,acoustic emission(AE)characteristics,and fracture characteristics of sandstone were analyzed.The damage characteristics of sandstone under true triaxial cyclic loading were studied.Furthermore,the damage constitutive model of rock mass under true triaxial cyclic loading was established based on AE cumulative ringing count.The quantitative investigation was conducted on cumulative-damage changes in circulating sandstone,which elucidated the mechanism of damage deterioration in sandstone subjected to true triaxial cyclic loading.The results show that the influence of the graded cycleσ_(1) on limit maximum principal strain ɛ_(1max) and limit minimum principal strainɛ_(3max) was significantly greater than that of the limit intermediate principal strain ɛ_(2max).Graded cycleσ_(2) had a greater impact onɛ_(2max) and a smaller impact onɛ_(3max).The elasticity modulus of sandstone decreased exponentially with the increased cyclic load amplitude,while the Poisson ratio increased linearly.b of AE showed a trend of increasing,decreasing,slightly fluctuating,and finally decreasing during cyclingσ_(1).b showed a trend of slight fluctuation,large fluctuation,and finally increase during cyclingσ_(2).Sandstone specimens experienced mainly tensile failure,tensile-shear composite failure,and mainly shear failure with increased initialσ_(2) orσ_(3).This was determined by analyzing the rise angle-average frequency of the AE parameter,corresponding to the rock specimens from splitting failure to shear failure.Besides,the mechanical damage behavior of sandstone under true triaxial cyclic loading could be well described by the established constitutive model.At the same time,it was found that the sandstone damage variable decreased with increasedσ_(2) during cyclingσ_(1).The damage variable decreased first and then increased with increasedσ_(3) during cyclingσ_(2).展开更多
In this paper, a finite element model was developed for a turbine blade with thermal barrier coatings to investigate its failure behavior under cyclic thermal loading. Based on temperature and stress fields obtained f...In this paper, a finite element model was developed for a turbine blade with thermal barrier coatings to investigate its failure behavior under cyclic thermal loading. Based on temperature and stress fields obtained from finite element simulations, dangerous regions in ceramic coating were determined in terms of the maximum principal stress criterion. The results show that damage preferentially occurs in the chamfer and rabbet of a turbine blade with thermal barrier coatings and its thermal fatigue life decreases with the increase of thermal stress induced by high service temperature.展开更多
In this paper,an aluminum corrugated sandwich panel with triangular core under bending loads was investigated.Firstly,the equivalent material parameters of the triangular corrugated core layer,which could be considere...In this paper,an aluminum corrugated sandwich panel with triangular core under bending loads was investigated.Firstly,the equivalent material parameters of the triangular corrugated core layer,which could be considered as an orthotropic panel,were obtained by using Castigliano's theorem and equivalent homogeneous model.Secondly,contributions of the corrugated core layer and two face panels were both considered to compute the equivalent material parameters of the whole structure through the classical lamination theory,and these equivalent material parameters were compared with finite element analysis solutions.Then,based on the Mindlin orthotropic plate theory,this study obtain the closed-form solutions of the displacement for a corrugated sandwich panel under bending loads in specified boundary conditions,and parameters study and comparison by the finite element method were executed simultaneously.展开更多
The investigation on the oxidation behaviour of Si1-xGex alloys （x=0.05, 0.15, and 0.25） is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a...The investigation on the oxidation behaviour of Si1-xGex alloys （x=0.05, 0.15, and 0.25） is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a few Ge nanoparticles with diameters ranging from 5.5 nm to 10 nm are formed by the low-temperatu.re laser-assisted dry oxidation of Si1-xGex substrate. A new scanning method on the decline cross-section of the multiple-layer sample is adopted to measure the layer thickness and the composition. Some new peaks in photoluminescence （PL） spectra are discovered, which could be related to the nano-cap and the nano-particles of germanium. A suitable model and several new calculating formulae with the unrestricted Hartree-Fock-Roothaan （UHFR） method and quantum confinement analysis are proposed to interpret the PL spectra and the nano-structure mechanism in the oxide.展开更多
This paper presents the analysis of dynamic characteristics of horizontal axis wind turbine blade, where the mode coupling among axial extension, flap vibration （out-of-plane bend- ing）, lead/lag vibration （in-plan...This paper presents the analysis of dynamic characteristics of horizontal axis wind turbine blade, where the mode coupling among axial extension, flap vibration （out-of-plane bend- ing）, lead/lag vibration （in-plane bending） and torsion is emphasized. By using the Bernoulli-Euler beam to describe the slender blade which is mounted on rigid hub and subjected to unsteady aero- dynamic force, the governing equation and characteristic equation of the coupled vibration of the blade are obtained. Due to the combined influences of mode coupling, centrifugal effect, and the non-uniform distribution of mass and stiffness, the explicit solution of characteristic equation is impossible to obtain. An equivalent transformation based on Green＇s functions is taken for the characteristic equation, and then a system of integrodifferential equations is derived. The nu- merical difference methods are adopted to solve the integrodifferential equations to get natural frequencies and mode shapes. The influences of mode coupling, centrifugal effect, and rotational speed on natural frequencies and mode shapes are analyzed. Results show that： （1） the influence of bending-torsion coupling on natural frequency is tiny; （2） rotation has dramatic influence on bending frequency but little influence on torsion frequency; （3） the influence of bending-bending coupling on dynamic characteristics is notable at high rotational speed; （4） the effect of rotational speed on bending mode is tiny.展开更多
Ultrathin MoS2 nanosheets were prepared in high yield using a facile and effective hydrothermal intercalation and exfoliation route. The products were characterized in detail using X-ray diffraction, scanning electron...Ultrathin MoS2 nanosheets were prepared in high yield using a facile and effective hydrothermal intercalation and exfoliation route. The products were characterized in detail using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that the high yield of MoS2 nanosheets with good quality was successfully achieved and the dimensions of the immense nanosheets reached 1 μm-2/zm. As anode material for Li-ion batteries, the as-prepared MoS2 nanosheets electrodes exhibited a good initial capacity of 1190 mAh.g-l and excellent cyclic stability at constant current density of 50 mA.g-1. After 50 cycles, it still delivered reversibly sustained high capacities of 750 mAh.g-1.展开更多
The reverse analysis provides a convenient method to determine four elastic-plastic parameters through an indentation curve such as Young s modulus E, hardness H, yield strength σy and strain hardening exponent n. In...The reverse analysis provides a convenient method to determine four elastic-plastic parameters through an indentation curve such as Young s modulus E, hardness H, yield strength σy and strain hardening exponent n. In this paper, mathematical analysis on a reverse algorithm from Dao model （Dao et al., Acta Mater., 2001, 49, 3899） was carried out, which thought that only when 20 ≤E＊/σ0.033≤ 26 and 0.3n≤ 0.5, the reverse algorithm would yield two solutions of n by dimensionless function Π2. It is shown that, however, there are also two solutions of n when 20≤E＊/σ0.033≤ 26 and 0≤n0.1. A unique n can be obtained by dimensionless function Π3 instead of Π2 in these two ranges. E and H can be uniquely determined by a full indentation curve, and σy can be determined if n is unique. Furthermore, sensitivity analysis on obtaining n from dimensionless function Π3 or Π2 has been made.展开更多
In order to guide the explosive welding experiment of titanium-stainless steel,Three-dimensional numerical simulation of explosive welding,which select TA1 as flyer plate and 304 stainless steel as base plate,is carri...In order to guide the explosive welding experiment of titanium-stainless steel,Three-dimensional numerical simulation of explosive welding,which select TA1 as flyer plate and 304 stainless steel as base plate,is carried out by using the LS-DYNA software and SPH-FEM coupling algorithm in the present study.The explosive welding window is calculated and established.It is found that the numerical simulation results are in good agreement with the experimental results.The displacement,velocity and pressure-time curves of characteristic elements show that the quality of explosive welding composites is superior.It is proved that SPH-FEM coupling algorithm is effective for explosive welding of TA1/304 stainless steel and can effectively guide the selection of explosive welding parameters.展开更多
Ni nanocomposite films formed by Ni nanowires embedded in Ni matrix(Ni nanowire/Ni composite films)were fabricated by electrodeposition combined with supersonic stirring in a conventional Watts'bath containing Ni ...Ni nanocomposite films formed by Ni nanowires embedded in Ni matrix(Ni nanowire/Ni composite films)were fabricated by electrodeposition combined with supersonic stirring in a conventional Watts'bath containing Ni nanowires with diameter about 30 nm.The deposition temperature-dependent microstructure,crystal orientation,lattice constant and corrosion behavior of the Ni nanowire/Ni composite films were investigated by field emission scanning electron microscope,X-ray diffraction and potentiodynamic polarization tests,respectively.And the possible mechanism was discussed.It is found that to some extent,the deposition temperature has an impact on the microstructure,crystal orientation,lattice constant and corrosion property of the Ni nanowire/Ni composite films.The Ni nanowire/Ni composite films prepared at 50℃exhibit a novel inter-twisted-nanowire microstructure and have the best corrosion resistance.展开更多
Ag-modified TiO2 nanoflowers were prepared using a two-step process. The experimental process is green and free from contamination and can be synthesized directly at room temperature. Compared with pure TiO2, Ag-modif...Ag-modified TiO2 nanoflowers were prepared using a two-step process. The experimental process is green and free from contamination and can be synthesized directly at room temperature. Compared with pure TiO2, Ag-modified TiO2 enhances the absorption of visible light and effectively promotes the detachment of photoelectron pairs, Ag-TiO2 has a significantly enhanced visible light response activity to photodecomposition of methyl orange(MO). It is shown that the strong interaction between Ag nanoparticles and TiO2 enhances the photocatalytic activity of TiO2 nanoflowers. The self-made open-air reactor was used to test the photocatalytic performance of different samples. The results showed that Ag-modified TiO2 nanoflowers had excellent photodegradation ability. After repeated photodegradation of MO, Ag-modified TiO2 nanoflowers showed good stability.展开更多
Mg-doped ZnO radial spherical structures with nanorods grown on both sides of the spherical shell were successfully prepared via chemical vapor deposition （CVD） of Zn and Mg powders in the absence of a catalyst. The...Mg-doped ZnO radial spherical structures with nanorods grown on both sides of the spherical shell were successfully prepared via chemical vapor deposition （CVD） of Zn and Mg powders in the absence of a catalyst. The structures associated with different growth temperatures （700, 800, and 850°C） were monitored by scanning electron microscopy （SEM）, and the result shows that the length of the nanorods increase progressively with the growth temperature increasing. X-ray diffraction （XRD） shows that the as-obtained samples can be indexed to high crystallinity with wurtzite structure. The growth of the nanostructures mainly depends on the formation of sphere-like Mg-doped Zn droplets before adding oxygen. Photoluminescence （PL） spectra that show a 39 meV blue shift indicates that the band gap becomes large, because Mg substitutes Zn in the lattice.展开更多
We theoretically investigate the optical absorption coefficient(OAC)in asymmetrical Gaussian potential quantum dots subject to an applied electric field.Confined wave functions together with energies of electron energ...We theoretically investigate the optical absorption coefficient(OAC)in asymmetrical Gaussian potential quantum dots subject to an applied electric field.Confined wave functions together with energies of electron energies in an effective mass approximation framework are obtained.The OAC is expressed according to the iterative method and the compact-density-matrix approach.Based on our results,OAC is sensitively dependent on external electric field together with the incident optical intensity.Additionally,peak shifts into greater energy as the quantum dot radius decrease.Moreover,the parameters of Gaussian potential have a significant influence on the OAC.展开更多
A novel composite ultraviolet(UV)/blue photodetector is proposed in this paper.Lateral ring-shaped PN junction is used to separate photogenerated carriers and inject the non-equilibrium excess carriers to the bulk,cha...A novel composite ultraviolet(UV)/blue photodetector is proposed in this paper.Lateral ring-shaped PN junction is used to separate photogenerated carriers and inject the non-equilibrium excess carriers to the bulk,changing the bulk potential and shifting the threshold voltage of the metal-oxide-semiconductor field-effect transistor(MOSFET)as well as the drain current.Numerical simulation is carried out,and the simulation results show that the composite photodetector has the enhanced responsivity for UV/blue spectrum.It exhibits very high sensitivity to weak and especially ultra-weak light.A responsivity of 7000 A/W is obtained when the photodetector is illuminated under incident optical power of 0.01μW.As a result,this proposed combined photodetector has great potential for UV/blue and ultra-weak light applications.展开更多
The properties of exotic nuclei are the focus of the present research.Two-neutron halo structures of neutron-rich17,19B were experimentally confirmed.We studied the formation mechanism of halo phenomena in17,19B using...The properties of exotic nuclei are the focus of the present research.Two-neutron halo structures of neutron-rich17,19B were experimentally confirmed.We studied the formation mechanism of halo phenomena in17,19B using the complex momentum representation method applied to deformation and continuum coupling.By examining the evolution of the weakly bound and resonant levels near the Fermi surface,s–d orbital reversals and certain prolate deformations were observed.In addition,by analyzing the evolution of the occupation probabilities and density distributions occupied by valence neutrons,we found that the ground state of15B did not exhibit a halo and the ground states of17B and19B exhibited halos at 0.6≤β2≤0.7 and0.3≤β2≤0.7,respectively.The low-l components in the valence levels that are weakly bound or embedded in the continuous spectrum lead to halo formation.展开更多
To optimize the process parameters, it is necessary to exactly predict failure modes during deep drawing of coated metal sheets, where two main failure forms are fracture and wrinkling. In this paper, finite element s...To optimize the process parameters, it is necessary to exactly predict failure modes during deep drawing of coated metal sheets, where two main failure forms are fracture and wrinkling. In this paper, finite element simulations based on continuous damage mechanics were used to study the failure behavior during a cylindrical deep drawing of metal sheets with nickel coating. It is shown that taking the effect of blank holder force into account, these two failure modes can be predicted. The simulation results are well consistent with that obtained from experiments.展开更多
An inverse method for extracting the elastic-plastic properties of metallic thin films from instrumented sharp indentation has been proposed in terms of dimensional analysis and finite element modeling. A wide range o...An inverse method for extracting the elastic-plastic properties of metallic thin films from instrumented sharp indentation has been proposed in terms of dimensional analysis and finite element modeling. A wide range of materials with different elastic modulus, yield strength, and strain-hardening exponent were examined.Similar to the Nix-Gao model for the depth dependence of hardness H,the relationship between elastic modulus E and indentation depth h can be expressed as By combiningthese two formulas, we find that there is a relationship between yield stress and indentation depth h：where σyO is the yield strength associated with the strain-hardening exponent n, the true hardness Ho and the true elastic modulus Eo.is constant, whichis only related to n, and hH and hE are characteristic lengths for hardness and elastic modulus. The results obtained from inverse analysis show that the elastic-plastic properties of thin films can be uniquely extracted from the solution of this relationship when the indentation size effect has to be taken into account.展开更多
Transforming materials with evolving microstructures is one of the most important classes of smart materials that have many potential technological applications, and an unconventional phase field approach based on the...Transforming materials with evolving microstructures is one of the most important classes of smart materials that have many potential technological applications, and an unconventional phase field approach based on the characteristic functions of transforming variants has been developed to simulate the formation and evolution of their microstructures. This approach is advantageous in its explicit material symmetry and energy well structure, minimal number of ma- terial coefficients, and easiness in coupling multiple physical processes and order parameters, and has been applied successfully to study the microstructures and macroscopic prop- erties of shape memory alloys, ferroelectrics, ferromagnetic shape memory alloys, and multiferroic magnetoelectric crys- tals and films with increased complexity. In this topical re- view, the formulation of this unconventional phase field approach will be introduced in details, and its applications to various transforming materials will be discussed. Some ex- amples of specific microstructures will also be presented.展开更多
A novel carbon matrix/silicon nanowires(SiNWs) heterogeneous block was successfully produced by dispersing SiNWs into templated carbon matrix via a modified evaporation induced self-assembly method. The heterogeneous ...A novel carbon matrix/silicon nanowires(SiNWs) heterogeneous block was successfully produced by dispersing SiNWs into templated carbon matrix via a modified evaporation induced self-assembly method. The heterogeneous block was determined by X-ray diffraction, Raman spectra and scanning electron microscopy. As an anode material for lithium batteries, the block was investigated by cyclic voltammograms(CV), charge/discharge tests, galvanostatic cycling performance and A. C. impedance spectroscopy. We show that the SiNWs disperse into the framework, and are nicely wrapped by the carbon matrix. The heterogeneous block exhibits superior electrochemical reversibility with a high specific capacity of 529.3 mAh/g in comparison with bare SiNWs anode with merely about 52.6 mAh/g capacity retention. The block presents excellent cycle stability and capacity retention which can be attributed to the improvement of conductivity by the existence of carbon matrix and the enhancement of ability to relieve the large volume expansion of SiNWs during the lithium insertion/extraction cycle. The results indicate that the as-prepared carbon matrix/SiNWs heterogeneous block can be an attractive and potential anode material for lithium-ion battery applications.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11902002 and 51705002)the Sichuan Provincial Natural Science Foundation(Grant No.2022NSFSC0275)the University Outstanding Youth Researcher Support Program of the Education Department of Anhui Province,and the Teaching Project of the Education Department of Anhui Province(Grant No.2022xxsfkc023).
文摘This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.
基金supported by the National Key Research and Development Program of China (2023YFA1608100)the National Science Foundation of China (NSFC, Grant Nos.12233005, 12073078, 12173088, and 12303015)+3 种基金the China Manned Space Program with grants nos. CMS-CSST-2025-A20 and CMS-CSST-2025-A08the support from the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology(2024yjrc104)the National Science Foundation of Jiangsu Province (BK20231106)the science research grants from the China Manned Space Project
文摘We investigate the relationships between infrared excess(IRX = LIR/LUV) and Balmer decrement(Hα/Hβ) as indicators of dust attenuation for 609 H II regions at scales of ~50–200 pc in NGC 628, utilizing data from AstroSat, the James Webb Space Telescope(JWST) and Multi Unit Spectroscopic Explorer. Our findings indicate that about three-fifths of the sample H II regions reside within the regime occupied by local star-forming galaxies(SFGs) along the dust attenuation correlation described by their corresponding color excess parameters E(B-V)IRX= 0.51 E(B-V)Hα/Hβ. Nearly 27% of the sample exhibits E(B-V)IRX> E(B-V)Hα/Hβ, while a small fraction(~13%) displays significantly lower E(B-V)IRXcompared to E(B-V)Hα/Hβ. These results suggest that the correlation between the two dust attenuation indicators no longer holds for spatially resolved H II regions. Furthermore, the ratio of E(B-V)IRXto E(B-V)Hα/Hβremains unaffected by various physical parameters of the H II regions, including star formation rate(SFR), SFR surface density, infrared luminosity(LIR),LIRsurface density, stellar mass, gas-phase metallicity, circularized radius, and the distance to the galactic center.We argue that the ratio is primarily influenced by the evolution of the surrounding interstellar medium of the starforming regions, transitioning from an early dense and thick phase to the late blown-away stage.
基金Project(2022m07020007)supported by the Key Research and Development Projects of Anhui Province,ChinaProjects(52174102,52074006,51404011,51874002,51974009)supported by the National Natural Science Foundation of China+1 种基金Project(2024cx1017)supported by the Graduate Innovation Fund of Anhui University of Science and Technology,ChinaProject(2024AH040067)supported by the Natural Science Research Project of Anhui Educational Committee,China。
文摘Aiming at the problem of deep surrounding rock instability induced by roadway excavation or mining disturbance,the true triaxial loading system was used to conduct graded cyclic maximum principal stress σ_(1) and intermediate principal stress σ_(2) tests on sandstone to simulate the effect of mining stress in actual underground engineering.The influences of each principal stress cycle on the mechanical properties,acoustic emission(AE)characteristics,and fracture characteristics of sandstone were analyzed.The damage characteristics of sandstone under true triaxial cyclic loading were studied.Furthermore,the damage constitutive model of rock mass under true triaxial cyclic loading was established based on AE cumulative ringing count.The quantitative investigation was conducted on cumulative-damage changes in circulating sandstone,which elucidated the mechanism of damage deterioration in sandstone subjected to true triaxial cyclic loading.The results show that the influence of the graded cycleσ_(1) on limit maximum principal strain ɛ_(1max) and limit minimum principal strainɛ_(3max) was significantly greater than that of the limit intermediate principal strain ɛ_(2max).Graded cycleσ_(2) had a greater impact onɛ_(2max) and a smaller impact onɛ_(3max).The elasticity modulus of sandstone decreased exponentially with the increased cyclic load amplitude,while the Poisson ratio increased linearly.b of AE showed a trend of increasing,decreasing,slightly fluctuating,and finally decreasing during cyclingσ_(1).b showed a trend of slight fluctuation,large fluctuation,and finally increase during cyclingσ_(2).Sandstone specimens experienced mainly tensile failure,tensile-shear composite failure,and mainly shear failure with increased initialσ_(2) orσ_(3).This was determined by analyzing the rise angle-average frequency of the AE parameter,corresponding to the rock specimens from splitting failure to shear failure.Besides,the mechanical damage behavior of sandstone under true triaxial cyclic loading could be well described by the established constitutive model.At the same time,it was found that the sandstone damage variable decreased with increasedσ_(2) during cyclingσ_(1).The damage variable decreased first and then increased with increasedσ_(3) during cyclingσ_(2).
基金supported by the National Natural Science Foundation of China(Nos.11002122,51172192,11272275 and 11002121)the Natural Science Foundation of Hunan Province, China(No.11JJ4003)the Key Project of Scientific Research Conditions in Hunan Province,China(No.2012TT2040)
文摘In this paper, a finite element model was developed for a turbine blade with thermal barrier coatings to investigate its failure behavior under cyclic thermal loading. Based on temperature and stress fields obtained from finite element simulations, dangerous regions in ceramic coating were determined in terms of the maximum principal stress criterion. The results show that damage preferentially occurs in the chamfer and rabbet of a turbine blade with thermal barrier coatings and its thermal fatigue life decreases with the increase of thermal stress induced by high service temperature.
基金the National Natural Science Foundation of China(Grant 11572122)the Scientific Research Foundation of Huaihua University(Grant HHUY2017-02)+2 种基金111 Project(Grant B16015)Stake Key Laboratory of Mechanical Structural Strength and Vibration(Grant SV2017-KF-20)Joint Centre for Intelligent New Energy Vehicle.
文摘In this paper,an aluminum corrugated sandwich panel with triangular core under bending loads was investigated.Firstly,the equivalent material parameters of the triangular corrugated core layer,which could be considered as an orthotropic panel,were obtained by using Castigliano's theorem and equivalent homogeneous model.Secondly,contributions of the corrugated core layer and two face panels were both considered to compute the equivalent material parameters of the whole structure through the classical lamination theory,and these equivalent material parameters were compared with finite element analysis solutions.Then,based on the Mindlin orthotropic plate theory,this study obtain the closed-form solutions of the displacement for a corrugated sandwich panel under bending loads in specified boundary conditions,and parameters study and comparison by the finite element method were executed simultaneously.
基金Project supported by the Natural Science Foundation of Guizhou Province, China （Grant No 3067（2004））.
文摘The investigation on the oxidation behaviour of Si1-xGex alloys （x=0.05, 0.15, and 0.25） is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a few Ge nanoparticles with diameters ranging from 5.5 nm to 10 nm are formed by the low-temperatu.re laser-assisted dry oxidation of Si1-xGex substrate. A new scanning method on the decline cross-section of the multiple-layer sample is adopted to measure the layer thickness and the composition. Some new peaks in photoluminescence （PL） spectra are discovered, which could be related to the nano-cap and the nano-particles of germanium. A suitable model and several new calculating formulae with the unrestricted Hartree-Fock-Roothaan （UHFR） method and quantum confinement analysis are proposed to interpret the PL spectra and the nano-structure mechanism in the oxide.
基金supported by the National Natural Science Foundation of China(Nos.11372257 and 11601007)Sichuan Provincial Project for Young Research Group of Scientific and Technological Innovations(2013)+1 种基金the Anhui Provincial Natural Science Foundation(No.1708085QA17)Pre-research Project Funds of Anhui University of Science and Technology(No.2016yz007)
文摘This paper presents the analysis of dynamic characteristics of horizontal axis wind turbine blade, where the mode coupling among axial extension, flap vibration （out-of-plane bend- ing）, lead/lag vibration （in-plane bending） and torsion is emphasized. By using the Bernoulli-Euler beam to describe the slender blade which is mounted on rigid hub and subjected to unsteady aero- dynamic force, the governing equation and characteristic equation of the coupled vibration of the blade are obtained. Due to the combined influences of mode coupling, centrifugal effect, and the non-uniform distribution of mass and stiffness, the explicit solution of characteristic equation is impossible to obtain. An equivalent transformation based on Green＇s functions is taken for the characteristic equation, and then a system of integrodifferential equations is derived. The nu- merical difference methods are adopted to solve the integrodifferential equations to get natural frequencies and mode shapes. The influences of mode coupling, centrifugal effect, and rotational speed on natural frequencies and mode shapes are analyzed. Results show that： （1） the influence of bending-torsion coupling on natural frequency is tiny; （2） rotation has dramatic influence on bending frequency but little influence on torsion frequency; （3） the influence of bending-bending coupling on dynamic characteristics is notable at high rotational speed; （4） the effect of rotational speed on bending mode is tiny.
基金supported by the Grants from National Natural Science Foundation of China(No.51172191,51002129 and 11074211)the National Basic Research Program of China(2012CB921303)the Hunan Provincial Innovation Foundation for Graduate(No.CX2012B265)
文摘Ultrathin MoS2 nanosheets were prepared in high yield using a facile and effective hydrothermal intercalation and exfoliation route. The products were characterized in detail using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that the high yield of MoS2 nanosheets with good quality was successfully achieved and the dimensions of the immense nanosheets reached 1 μm-2/zm. As anode material for Li-ion batteries, the as-prepared MoS2 nanosheets electrodes exhibited a good initial capacity of 1190 mAh.g-l and excellent cyclic stability at constant current density of 50 mA.g-1. After 50 cycles, it still delivered reversibly sustained high capacities of 750 mAh.g-1.
基金supported by the National Natural Science Foundation of China (Nos. 11002121, 11002122,and 10828205)the Natural Science Foundation of Hu-nan Province for Innovation Group (No. 09JJ7004)+2 种基金the Key Special Program for Science and Technology of Hu-nan Province (No. 2009FJ1002)and the Natural Science Foundation of Xiangtan University (No. 09XZX04)One of the authors (C. Lu) is also grateful to the support from the Australian Research Council (No. DP0985450)
文摘The reverse analysis provides a convenient method to determine four elastic-plastic parameters through an indentation curve such as Young s modulus E, hardness H, yield strength σy and strain hardening exponent n. In this paper, mathematical analysis on a reverse algorithm from Dao model （Dao et al., Acta Mater., 2001, 49, 3899） was carried out, which thought that only when 20 ≤E＊/σ0.033≤ 26 and 0.3n≤ 0.5, the reverse algorithm would yield two solutions of n by dimensionless function Π2. It is shown that, however, there are also two solutions of n when 20≤E＊/σ0.033≤ 26 and 0≤n0.1. A unique n can be obtained by dimensionless function Π3 instead of Π2 in these two ranges. E and H can be uniquely determined by a full indentation curve, and σy can be determined if n is unique. Furthermore, sensitivity analysis on obtaining n from dimensionless function Π3 or Π2 has been made.
基金Project was supported by the National Natural Science Foundation of China(Grant No.11902003).
文摘In order to guide the explosive welding experiment of titanium-stainless steel,Three-dimensional numerical simulation of explosive welding,which select TA1 as flyer plate and 304 stainless steel as base plate,is carried out by using the LS-DYNA software and SPH-FEM coupling algorithm in the present study.The explosive welding window is calculated and established.It is found that the numerical simulation results are in good agreement with the experimental results.The displacement,velocity and pressure-time curves of characteristic elements show that the quality of explosive welding composites is superior.It is proved that SPH-FEM coupling algorithm is effective for explosive welding of TA1/304 stainless steel and can effectively guide the selection of explosive welding parameters.
基金Project(2008GK2001)supported by Natural Science Foundation of Hunan Province,ChinaProject(10772157)supported by the National Natural Science Foundation of ChinaProject(06C839)supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘Ni nanocomposite films formed by Ni nanowires embedded in Ni matrix(Ni nanowire/Ni composite films)were fabricated by electrodeposition combined with supersonic stirring in a conventional Watts'bath containing Ni nanowires with diameter about 30 nm.The deposition temperature-dependent microstructure,crystal orientation,lattice constant and corrosion behavior of the Ni nanowire/Ni composite films were investigated by field emission scanning electron microscope,X-ray diffraction and potentiodynamic polarization tests,respectively.And the possible mechanism was discussed.It is found that to some extent,the deposition temperature has an impact on the microstructure,crystal orientation,lattice constant and corrosion property of the Ni nanowire/Ni composite films.The Ni nanowire/Ni composite films prepared at 50℃exhibit a novel inter-twisted-nanowire microstructure and have the best corrosion resistance.
基金Fund by the National Natural Science Foundation of China(51502005,51602005,and 51702003)the Key Foundation for Young Talents in College of Anhui Province(gxyq ZD2016081)the Quality Engineering Project in Colleges and Universities of Anhui Province(2017sxzx15 and 2018zygc012)
文摘Ag-modified TiO2 nanoflowers were prepared using a two-step process. The experimental process is green and free from contamination and can be synthesized directly at room temperature. Compared with pure TiO2, Ag-modified TiO2 enhances the absorption of visible light and effectively promotes the detachment of photoelectron pairs, Ag-TiO2 has a significantly enhanced visible light response activity to photodecomposition of methyl orange(MO). It is shown that the strong interaction between Ag nanoparticles and TiO2 enhances the photocatalytic activity of TiO2 nanoflowers. The self-made open-air reactor was used to test the photocatalytic performance of different samples. The results showed that Ag-modified TiO2 nanoflowers had excellent photodegradation ability. After repeated photodegradation of MO, Ag-modified TiO2 nanoflowers showed good stability.
文摘Mg-doped ZnO radial spherical structures with nanorods grown on both sides of the spherical shell were successfully prepared via chemical vapor deposition （CVD） of Zn and Mg powders in the absence of a catalyst. The structures associated with different growth temperatures （700, 800, and 850°C） were monitored by scanning electron microscopy （SEM）, and the result shows that the length of the nanorods increase progressively with the growth temperature increasing. X-ray diffraction （XRD） shows that the as-obtained samples can be indexed to high crystallinity with wurtzite structure. The growth of the nanostructures mainly depends on the formation of sphere-like Mg-doped Zn droplets before adding oxygen. Photoluminescence （PL） spectra that show a 39 meV blue shift indicates that the band gap becomes large, because Mg substitutes Zn in the lattice.
基金the National Natural Science Foundation of China(Grant Nos.51702003,61775087,and 11674312)the Provincial Foundation for Excellent Top Talents of Colleges and Universities of Anhui Province of China(Grant No.gxgwfx2019016)+1 种基金the Anhui Provincial Natural Science Foundation,China(Grant Nos.1808085ME130 and 1508085QF140)University Outstanding Young Talents Support Program Fund(Grant No.gxyqZD2018039)。
文摘We theoretically investigate the optical absorption coefficient(OAC)in asymmetrical Gaussian potential quantum dots subject to an applied electric field.Confined wave functions together with energies of electron energies in an effective mass approximation framework are obtained.The OAC is expressed according to the iterative method and the compact-density-matrix approach.Based on our results,OAC is sensitively dependent on external electric field together with the incident optical intensity.Additionally,peak shifts into greater energy as the quantum dot radius decrease.Moreover,the parameters of Gaussian potential have a significant influence on the OAC.
基金supported by the National Natural Science Foundation of China(Nos.61233010 and 61274043)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-11-0975)
文摘A novel composite ultraviolet(UV)/blue photodetector is proposed in this paper.Lateral ring-shaped PN junction is used to separate photogenerated carriers and inject the non-equilibrium excess carriers to the bulk,changing the bulk potential and shifting the threshold voltage of the metal-oxide-semiconductor field-effect transistor(MOSFET)as well as the drain current.Numerical simulation is carried out,and the simulation results show that the composite photodetector has the enhanced responsivity for UV/blue spectrum.It exhibits very high sensitivity to weak and especially ultra-weak light.A responsivity of 7000 A/W is obtained when the photodetector is illuminated under incident optical power of 0.01μW.As a result,this proposed combined photodetector has great potential for UV/blue and ultra-weak light applications.
基金the National Natural Science Foundation of China(Nos.12205001,11935001,and 12204001)the Scientific Research program of Anhui University of Finance and Economics(Nos.ACKYC22080 and ACKYC220801).
文摘The properties of exotic nuclei are the focus of the present research.Two-neutron halo structures of neutron-rich17,19B were experimentally confirmed.We studied the formation mechanism of halo phenomena in17,19B using the complex momentum representation method applied to deformation and continuum coupling.By examining the evolution of the weakly bound and resonant levels near the Fermi surface,s–d orbital reversals and certain prolate deformations were observed.In addition,by analyzing the evolution of the occupation probabilities and density distributions occupied by valence neutrons,we found that the ground state of15B did not exhibit a halo and the ground states of17B and19B exhibited halos at 0.6≤β2≤0.7 and0.3≤β2≤0.7,respectively.The low-l components in the valence levels that are weakly bound or embedded in the continuous spectrum lead to halo formation.
基金supported by the National Natural Science Foundation of China(Nos.51172192 and 11102176)Hunan Provincial Natural Science Foundation of China(No.09JJ3003)+1 种基金the Natural Science Foundation of Hunan Province for Innovation Group,China(No.09JJ7004)the Key Special Program for Science and Technology of Hunan Province,China(No.2009FJ1002)
文摘To optimize the process parameters, it is necessary to exactly predict failure modes during deep drawing of coated metal sheets, where two main failure forms are fracture and wrinkling. In this paper, finite element simulations based on continuous damage mechanics were used to study the failure behavior during a cylindrical deep drawing of metal sheets with nickel coating. It is shown that taking the effect of blank holder force into account, these two failure modes can be predicted. The simulation results are well consistent with that obtained from experiments.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11102176,11002122,11172258,and 10828205)the Natural Science Foundation of Hunan Province for Innovation Group(Grant No. 09JJ7004)+1 种基金the Key Special Program for Science and Technology of Hunan Province (Grant No.2009FJ1002)the support from the Australian Research Council(Grant No. DP0985450)
文摘An inverse method for extracting the elastic-plastic properties of metallic thin films from instrumented sharp indentation has been proposed in terms of dimensional analysis and finite element modeling. A wide range of materials with different elastic modulus, yield strength, and strain-hardening exponent were examined.Similar to the Nix-Gao model for the depth dependence of hardness H,the relationship between elastic modulus E and indentation depth h can be expressed as By combiningthese two formulas, we find that there is a relationship between yield stress and indentation depth h：where σyO is the yield strength associated with the strain-hardening exponent n, the true hardness Ho and the true elastic modulus Eo.is constant, whichis only related to n, and hH and hE are characteristic lengths for hardness and elastic modulus. The results obtained from inverse analysis show that the elastic-plastic properties of thin films can be uniquely extracted from the solution of this relationship when the indentation size effect has to be taken into account.
基金supported by the NSF (DMR-1006194 and CMMI1100339)NSFC (10972189 and 11102175)NSC(100-2628-E-002-034-MY3)
文摘Transforming materials with evolving microstructures is one of the most important classes of smart materials that have many potential technological applications, and an unconventional phase field approach based on the characteristic functions of transforming variants has been developed to simulate the formation and evolution of their microstructures. This approach is advantageous in its explicit material symmetry and energy well structure, minimal number of ma- terial coefficients, and easiness in coupling multiple physical processes and order parameters, and has been applied successfully to study the microstructures and macroscopic prop- erties of shape memory alloys, ferroelectrics, ferromagnetic shape memory alloys, and multiferroic magnetoelectric crys- tals and films with increased complexity. In this topical re- view, the formulation of this unconventional phase field approach will be introduced in details, and its applications to various transforming materials will be discussed. Some ex- amples of specific microstructures will also be presented.
基金supported by the grants from the National Natural Science Foundation of China(Nos.51002129,51172191 and 11074211)the National Basic Research Program of China(2012CB921303)+2 种基金the Doctoral Program of Higher Education(No.200805300003)the Hunan Provincial InnovationFoundation for Graduate(No.CX2012B265)the Open Fund Based on Innovation Platform of Hunan Colleges and Universities(No.13K045)
文摘A novel carbon matrix/silicon nanowires(SiNWs) heterogeneous block was successfully produced by dispersing SiNWs into templated carbon matrix via a modified evaporation induced self-assembly method. The heterogeneous block was determined by X-ray diffraction, Raman spectra and scanning electron microscopy. As an anode material for lithium batteries, the block was investigated by cyclic voltammograms(CV), charge/discharge tests, galvanostatic cycling performance and A. C. impedance spectroscopy. We show that the SiNWs disperse into the framework, and are nicely wrapped by the carbon matrix. The heterogeneous block exhibits superior electrochemical reversibility with a high specific capacity of 529.3 mAh/g in comparison with bare SiNWs anode with merely about 52.6 mAh/g capacity retention. The block presents excellent cycle stability and capacity retention which can be attributed to the improvement of conductivity by the existence of carbon matrix and the enhancement of ability to relieve the large volume expansion of SiNWs during the lithium insertion/extraction cycle. The results indicate that the as-prepared carbon matrix/SiNWs heterogeneous block can be an attractive and potential anode material for lithium-ion battery applications.
