The stress and strain fields in self-organized growth coherent quantum dots （QD） structures are investigated in detail by two-dimension and three-dimension finite element analyses for lensed-shaped QDs. The nonobjec...The stress and strain fields in self-organized growth coherent quantum dots （QD） structures are investigated in detail by two-dimension and three-dimension finite element analyses for lensed-shaped QDs. The nonobjective isolate quantum dot system is used. The calculated results can he directly used to evaluate the conductive band and valence band confinement potential and strain introduced by the effective mass of the charge carriers in strain QD.展开更多
Diamond,as an ultra-wide bandgap semiconductor,has become a promising candidate for next-generation microelec-tronics and optoelectronics due to its numerous advantages over conventional semiconductors,including ultra...Diamond,as an ultra-wide bandgap semiconductor,has become a promising candidate for next-generation microelec-tronics and optoelectronics due to its numerous advantages over conventional semiconductors,including ultrahigh carrier mo-bility and thermal conductivity,low thermal expansion coefficient,and ultra-high breakdown voltage,etc.Despite these ex-traordinary properties,diamond also faces various challenges before being practically used in the semiconductor industry.This review begins with a brief summary of previous efforts to model and construct diamond-based high-voltage switching diodes,high-power/high-frequency field-effect transistors,MEMS/NEMS,and devices operating at high temperatures.Following that,we will discuss recent developments to address scalable diamond device applications,emphasizing the synthesis of large-area,high-quality CVD diamond films and difficulties in diamond doping.Lastly,we show potential solutions to modulate diamond’s electronic properties by the“elastic strain engineering”strategy,which sheds light on the future development of diamond-based electronics,photonics and quantum systems.展开更多
The effect of the elastic strain energy on the core-shell structures was studied in an Al-0.06Sc-0.02Er （at.%） alloy. A theoretical model for the calculation of the elastic strain energy caused by core-shell precipi...The effect of the elastic strain energy on the core-shell structures was studied in an Al-0.06Sc-0.02Er （at.%） alloy. A theoretical model for the calculation of the elastic strain energy caused by core-shell precipitates, which is applicable to materials with weak elastic anisotropy, was adopted. It was demonstrated that the partitioning of Er to the precipitate core did not reduce the elastic strain energy as expected in the previous study. The resistance due to the elastic strain energy to form an Al3（Sc0.36Ero.64）-Al3（Sc0.8Er0.2） core-shell precipitate was quite small, and could be easily overcome by the decrease of the total interracial energy, which was consistent with the previous experimental results. On the other hand, the resistance due to the elastic strain energy to form an Al3Er-Al3Sc core-shell precipitate was much larger than that to form an Al3（Sc0.36Er0.64）-Al3（Sc0.8Er0.2） core-shell precipitate, thus the partitioning of all the Er atoms to the core was strongly hindered by the elastic strain energy and was not observed in the experiment of the previous study.展开更多
To systematically assess the rockburst proneness considering specimen shape,multiple groups of laboratory tests were performed on 5 rock materials in cylindrical and cuboid shapes.The linear energy storage(LES)law of ...To systematically assess the rockburst proneness considering specimen shape,multiple groups of laboratory tests were performed on 5 rock materials in cylindrical and cuboid shapes.The linear energy storage(LES)law of both cylindrical and cuboid rock specimens under uniaxial compressive load was confirmed,and the energy storage coefficient was found to be unrelated to specimen shape.On the basis of LES law,two rockburst proneness indexes,namely the strain energy storage index(W_(et))and the potential energy of elastic strain(PES),were modified.Subsequently,the W_(et),PES,peak-strength strain energy storage index(W_(et))p,and peak-strength potential energy of elastic strain(PESp)were used to assess the rockburst proneness of the cylindrical and cuboid specimens.In addition,the fragment ejection course of specimens under test was recorded by a high-speed camera.Then,the rockburst proneness judgments obtained from the 4 indexes were compared with the qualitative data during rock destruction.The results show that,under similar stress conditions,specimen shape has an ignorable effect on the rockburst proneness as a whole.The judgment accuracy of the two modified indexes,especially that of the PESp,is favorably improved to evaluate the rockburst proneness of both cylindrical and cuboid specimens.However,misjudgment ofW_(et)^(p)and PESp may still occur in the assessment of rockburst proneness as these two indexes only consider the energy state before rock peak strength and the W_(et)^(p)is formulated in a ratio form.展开更多
An explicit form of the elastic strain-energy function for direction-dependent large elastic strain behaviors of soft fiber-reinforced composites is first presented based upon a decoupled approach for simulating compl...An explicit form of the elastic strain-energy function for direction-dependent large elastic strain behaviors of soft fiber-reinforced composites is first presented based upon a decoupled approach for simulating complex nonlinear coupling effects.From this form,the exact closed-form solutions are then obtained for the uniaxial tension responses in the fiber and cross-fiber directions.With such exact solutions,the issue of simultaneously simulating strongly coupling nonlinear responses in the fiber and cross-fiber directions may be reduced to the issue of separately treating each decoupled uniaxial stress-strain response,thus bypassing usual complexities and uncertainties involved in identifying a large number of strongly coupled adjustable parameters.The numerical examples given are in good agreement with the experimental data for large strain responses.展开更多
The deformation behaviors of W nanowires embedded in a TiNi matrix were investigated by means of in-situ synchrotron high energy X-ray diffraction(HEXRD) and in-situ transmission electron microscopy(TEM) analysis duri...The deformation behaviors of W nanowires embedded in a TiNi matrix were investigated by means of in-situ synchrotron high energy X-ray diffraction(HEXRD) and in-situ transmission electron microscopy(TEM) analysis during tensile deformation.The HEXRD measurement indicated that the W nanowires exhibited an average lattice strain of about 1.50 %,whereas the TEM examination revealed a local elastic strain of about 4.59 % in areas adjacent to the TiNi matrix where stress-induced martensitic transfo rmation occurred.This strain corresponds to a stress of ~15 GPa for the W nanowires.In addition,in areas adjacent to the TiNi matrix where plastic deformation and cracking were generated,the W nanowire showed significant ductile necking with ~80 % reduction in cross-section area.The ductile necking of W nanowire is attributed to the lack of protection from the stress-induced martensitic transformation of the TiNi matrix.展开更多
Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TM...Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TMOs)are regarded as potential substitutes for PGMs because of their stability in oxidizing environments and excellent catalytic performance.In this study,comprehensive investigation into the influence of elastic strains on the adsorption energies of carbon(C),hydrogen(H)and oxygen(O)on TMOs was conducted.Based on density functional theory(DFT)calculations,these effects in both tetragonal structures(PtO_(2),PdO_(2))and hexagonal structures(ZnO,CdO),along with their respective transition metals were systematically explored.It was identified that the optimal adsorption sites on metal oxides pinpointed the top of oxygen or the top of metal atom,while face-centered cubic(FCC)and hexagonal close-packed(HCP)holes were preferred for the transition metals.Furthermore,under the influence of elastic strains,the results demonstrated significant disparities in the adsorption energies of H and O between oxides and transition metals.Despite these differences,the effect of elastic strains on the adsorption energies of C,H and O on TMOs mirrored those on transition metals:adsorption energies increased under compressive strains,indicating weaker adsorption,and decreased under tension strains,indicating stronger adsorption.This behavior was rationalized based on the d-band model for adsorption atop a metallic atom or the p-band model for adsorption atop an oxygen atom.Consequently,elastic strains present a promising avenue for tailoring the catalytic properties of TMOs.展开更多
A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for a...A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.展开更多
To understand and develop new nanostructure materials with specific mechanical properties, a good knowledge of the elastic strain response is mandatory. Here we investigate the linear elasticity response in the modifi...To understand and develop new nanostructure materials with specific mechanical properties, a good knowledge of the elastic strain response is mandatory. Here we investigate the linear elasticity response in the modified phase-field-crystal（MPFC） model. The results show that two different propagation modes control the elastic interaction length and time, which determine whether the density waves can propagate or not. By quantitatively calculating the strain field, we find that the strain distribution is indeed extremely uniform in case of elasticity. Further, we present a detailed theoretical analysis for the orientation dependence and temperature dependence of shear modulus. The simulation results show that the shear modulus reveals strong anisotropy and the one-mode analysis provides a good guideline for determining elastic shear constants until the system temperature falls below a certain value.展开更多
This paper presents the analytical solutions for the responses of tunnels excavated in rock masses exhibiting strain-softening behavior. Since previous analyses give little consideration to the effect of the intermedi...This paper presents the analytical solutions for the responses of tunnels excavated in rock masses exhibiting strain-softening behavior. Since previous analyses give little consideration to the effect of the intermediate principal stress on the strain-softening rock behavior, the unified strength theory was introduced to analyze the tunnel response. Four cases of different definitions of the elastic strain in the softening and residual regions, used in the existing solutions, were considered. The tunnel displacements,stresses, radii of the softening and residual zones and critical stresses were deduced. The proposed solutions were verified by comparing with numerical simulations, model tests and existing solutions. Furthermore, the solutions of the four cases were compared with each other to investigate the influence of the elastic strain expressions on the tunnel responses. The results showed that the intermediate principal stress coefficient b has a significant effect on the tunnel displacements, stress fields, and plastic radii. Parametric studies were performed to analyze the influences of the softening and residual dilatancy coefficients,softening modulus and residual strength on the tunnel responses. The parametric analysis indicated that the existing models should be carefully evaluated in the analysis of tunnels constructed through average-quality rocks;the proposed solutions outperformed the existing models in solving the mentioned problem.展开更多
In this work,the static and dynamic response of a piezoelectric semiconductor cantilever under the transverse end force with consideration of flexoelectricity and strain gradient elasticity is systematically investiga...In this work,the static and dynamic response of a piezoelectric semiconductor cantilever under the transverse end force with consideration of flexoelectricity and strain gradient elasticity is systematically investigated.The one-dimensional governing equations and the corresponding boundary conditions are derived based on Hamilton’s principle.After that,combining with the linearized equations for the conservation of charge,the effects of characteristic length and flexoelectric coefficient on the working performance of a ZnO nanowire are demonstrated as a numerical case,including the static mechanical and electric fields,natural frequencies,and the frequency–response characteristics at resonances.The results indicate that the flexoelectric effect has a great influence on the electric properties of the nanowire,while the strain gradient effect directly contributes to its mechanical properties.To some extent,the increase in characteristic length is equivalent to the stiffness strengthening.The qualitative results and quantitative data are beneficial for revealing the underlying physical mechanism and provide guidance for the design of piezoelectric semiconductor devices.展开更多
The demand for titanium alloys simultaneously having high elastic admissible strain and large recovery strain for bio-implant applications is increasing.Ni-free Ti-based shape memory alloys are promising candidates fo...The demand for titanium alloys simultaneously having high elastic admissible strain and large recovery strain for bio-implant applications is increasing.Ni-free Ti-based shape memory alloys are promising candidates for obtaining the required multifunctional properties.In this study,a wide content range of(0-15)wt%of low-cost,toxicity-free,and high-biocompatible Sn element was added to the Ti-8Mo(wt%)alloy to study its effect on the superelastic recovery and mechanical properties of biomedical Ti-Mo-Sn alloys.By tailoring Sn content,desired multifunctional properties of high elastic admissible strain and room temperature superelasticity were achieved in the studied Ti-Mo-Sn alloys.It was found that the increase in Sn content stabilized theβphase and a singleβphase was obtained at room temperature in Ti-8Mo-(13,15)Sn alloys.The addition of Sn modified the lattice parameters of theα″martensite andβphase and affected the lattice deformation stain ofβ→α″.The lattice deformation strain along the[011]βdirection was found to be decreased by-0.26%/wt%Sn.The room temperature superelasticity with a recovery strain of 3.1%and an elastic admissible strain of 1%was obtained in the Ti-8Mo-13Sn alloy.As Sn content increased to 15 wt%,a high elastic admissible strain of 1.56%and a recovery strain of 2.0%were obtained.These Ti-Mo-Sn alloys with excellent multifunctional properties are promising candidates for bio-implant applications.展开更多
A micro scale nonlinear beam model based on strain gradient elasticity is developed. Governing equations of motion and boundary conditions are obtained in a variational framework. As an example, the nonlinear vibratio...A micro scale nonlinear beam model based on strain gradient elasticity is developed. Governing equations of motion and boundary conditions are obtained in a variational framework. As an example, the nonlinear vibration of microbeams is analyzed. In a beam having a thickness to length parameter ratio close to unity, the strain gradient effect on increasing the natural frequency is predominant. By increasing the beam thickness, this effect decreases and geometric nonlinearity plays the main role on increasing the natural frequency. For some specific ratios, both geometric nonlinearity and size effects have a significant role on increasing the natural frequency.展开更多
This study evaluated the myocardial strain and aortic elasticity in patients with bicuspid aortic valve（BAV） and then investigated the relation between them. Thirty-nine patients（30 males; mean age 44±19 years...This study evaluated the myocardial strain and aortic elasticity in patients with bicuspid aortic valve（BAV） and then investigated the relation between them. Thirty-nine patients（30 males; mean age 44±19 years; range 6 to 75 years） with BAV were recruited as BAV group, and 29 age- and sex-matched healthy controls（21 males; mean age 42±11 years; range 20 to 71 years） served as control group. Aortic strain, distensibility and stiffness index were derived using M-mode echocardiography. Left ventricular global myocardial strain was acquired with speckle-tracking echocardiography. Correlation between aortic elasticity and myocardial strain was also analyzed. The results showed that aortic stiffness was higher（17.5±14.0 vs. 5.3±2.7, P〈0.001）, and aortic strain（4.9±4.7 vs. 11.0±4.1, P〈0.001） and distensibility（1.8±2.1 vs. 3.7±1.6, P〈0.001） were lower significantly in BAV group than in control group. Global circumferential strain（–19.1±4.2 vs. –22.5±3.7, P〈0.001）, radial stain（29.8±14.9 vs. 38.0±8.8, P〈0.001） and longitudinal stain（–18.4±3.4 vs. –20.8±3.5, P〈0.001） were significantly lower in BAV group than in control group. There was weak association between aortic elasticity and myocardial strain. These findings indicated BAV patients manifest reduced myocardial strain which had weak relationship with aortic elastic lesion.展开更多
C^1 natural element method （C^1 NEM） is applied to strain gradient linear elasticity, and size effects on mi crostructures are analyzed. The shape functions in C^1 NEM are built upon the natural neighbor interpolati...C^1 natural element method （C^1 NEM） is applied to strain gradient linear elasticity, and size effects on mi crostructures are analyzed. The shape functions in C^1 NEM are built upon the natural neighbor interpolation （NNI）, with interpolation realized to nodal function and nodal gradient values, so that the essential boundary conditions （EBCs） can be imposed directly in a Galerkin scheme for partial differential equations （PDEs）. In the present paper, C^1 NEM for strain gradient linear elasticity is constructed, and sev- eral typical examples which have analytical solutions are presented to illustrate the effectiveness of the constructed method. In its application to microstructures, the size effects of bending stiffness and stress concentration factor （SCF） are studied for microspeciem and microgripper, respectively. It is observed that the size effects become rather strong when the width of spring for microgripper, the radius of circular perforation and the long axis of elliptical perforation for microspeciem come close to the material characteristic length scales. For the U-shaped notch, the size effects decline obviously with increasing notch radius, and decline mildly with increasing length of notch.展开更多
Mechanical metamaterials are architectured cellular materials with unusual properties.Herein we report another type of metal mechanical metamaterials-their elastic admissible strain(EAS)is on the order of 0.1,compared...Mechanical metamaterials are architectured cellular materials with unusual properties.Herein we report another type of metal mechanical metamaterials-their elastic admissible strain(EAS)is on the order of 0.1,compared to about 0.01 for common metallic materials.Four conditions are required for a metal mechanical metamaterial to achieve this super EAS:(i)bending-dominated deformation;(ii)low density;(iii)an appropriate lattice topology,and(iv)an intrinsically high EAS for the lattice strut constituent material.The findings of this work extend perspectives on metal mechanical metamaterials.展开更多
A new size-dependent axially functionally graded(AFG) micro-beam model is established with the application of a reformulated strain gradient elasticity theory(RSGET). The new micro-beam model incorporates the strain g...A new size-dependent axially functionally graded(AFG) micro-beam model is established with the application of a reformulated strain gradient elasticity theory(RSGET). The new micro-beam model incorporates the strain gradient, velocity gradient,and couple stress effects, and accounts for the material variation along the axial direction of the two-component functionally graded beam. The governing equations and complete boundary conditions of the AFG beam are derived based on Hamilton's principle. The correctness of the current model is verified by comparing the static behavior results of the current model and the finite element model(FEM) at the micro-scale. The influence of material inhomogeneity and size effect on the static and dynamic responses of the AFG beam is studied. The numerical results show that the static and vibration responses predicted by the newly developed model are different from those based on the classical model at the micro-scale. The new model can be applied not only in the optimization of micro acoustic wave devices but also in the design of AFG micro-sensors and micro-actuators.展开更多
The coherent elastic strain-induced morphological transformation of a binarycubic model alloy was simulated with different strain energy parameters. The microscopic diffusionequation was combined with the theory of mi...The coherent elastic strain-induced morphological transformation of a binarycubic model alloy was simulated with different strain energy parameters. The microscopic diffusionequation was combined with the theory of microscopic elasticity. The results show that when thestrain energy is neglected, the randomly distributed equiaxed particles are obtained with isotropiccharacteristic. It is coarsening that follows the Ostwald ripening mechanism: smaller particlesdwindle and larger particles grow; when the elastic strain is considered, plate precipitates tend toalign along the elastically soft directions <01> with anisotropic characteristic. The particlesgrow in the soft directions and coarsen further; particles dwindle in out of the soft directions.While the coarsening of the particles localized in the same row or column follows the rule: smallerparticles shrink and larger ones grow.展开更多
To investigate the early-age behaviors of concrete under a restrained condition, a set of apparatus was developed. In this way, the tensile creep and other early-age properties can be investigated in depth. By measuri...To investigate the early-age behaviors of concrete under a restrained condition, a set of apparatus was developed. In this way, the tensile creep and other early-age properties can be investigated in depth. By measuring the modulus of elasticity of concrete, synchronous shrinkage of concrete and steel rings and free shrinkage of concrete, the deformations of concrete ring can be quantified respectively. The experimental results show the tensile stress in concrete is time-dependent, and the stress at cracking is much lower than the tensile strength at that age; the tensile creep plays an important role in relaxing the tensile stress and postponing the cracking of concrete.展开更多
This study presents the size-dependent nonlinear thermal postbuckling characteristics of a porous functionally graded material(PFGM) microplate with a central cutout with various shapes using isogeometric numerical te...This study presents the size-dependent nonlinear thermal postbuckling characteristics of a porous functionally graded material(PFGM) microplate with a central cutout with various shapes using isogeometric numerical technique incorporating nonuniform rational B-splines. To construct the proposed non-classical plate model, the nonlocal strain gradient continuum elasticity is adopted on the basis of a hybrid quasithree-dimensional(3D) plate theory under through-thickness deformation conditions by only four variables. By taking a refined power-law function into account in conjunction with the Touloukian scheme, the temperature-porosity-dependent material properties are extracted. With the aid of the assembled isogeometric-based finite element formulations,nonlocal strain gradient thermal postbuckling curves are acquired for various boundary conditions as well as geometrical and material parameters. It is portrayed that for both size dependency types, by going deeper in the thermal postbuckling domain, gaps among equilibrium curves associated with various small scale parameter values get lower, which indicates that the pronounce of size effects reduces by going deeper in the thermal postbuckling regime. Moreover, we observe that the central cutout effect on the temperature rise associated with the thermal postbuckling behavior in the presence of the effect of strain gradient size and absence of nonlocality is stronger compared with the case including nonlocality in absence of the strain gradient small scale effect.展开更多
文摘The stress and strain fields in self-organized growth coherent quantum dots （QD） structures are investigated in detail by two-dimension and three-dimension finite element analyses for lensed-shaped QDs. The nonobjective isolate quantum dot system is used. The calculated results can he directly used to evaluate the conductive band and valence band confinement potential and strain introduced by the effective mass of the charge carriers in strain QD.
基金the support from the Research Grants Council of the Hong Kong Special Administrative Region,China(Grant RFS2021-1S05)the National Natural Science Foundation of China(Grant 11922215)+1 种基金the funding from the National Natural Science Foundation of China(Grant 11902200)the Science and Technology Commission of Shanghai Municipality(Grant19YF1433600)。
文摘Diamond,as an ultra-wide bandgap semiconductor,has become a promising candidate for next-generation microelec-tronics and optoelectronics due to its numerous advantages over conventional semiconductors,including ultrahigh carrier mo-bility and thermal conductivity,low thermal expansion coefficient,and ultra-high breakdown voltage,etc.Despite these ex-traordinary properties,diamond also faces various challenges before being practically used in the semiconductor industry.This review begins with a brief summary of previous efforts to model and construct diamond-based high-voltage switching diodes,high-power/high-frequency field-effect transistors,MEMS/NEMS,and devices operating at high temperatures.Following that,we will discuss recent developments to address scalable diamond device applications,emphasizing the synthesis of large-area,high-quality CVD diamond films and difficulties in diamond doping.Lastly,we show potential solutions to modulate diamond’s electronic properties by the“elastic strain engineering”strategy,which sheds light on the future development of diamond-based electronics,photonics and quantum systems.
基金Project supported by National Natural Science Foundation of China (50731002, 51271027)
文摘The effect of the elastic strain energy on the core-shell structures was studied in an Al-0.06Sc-0.02Er （at.%） alloy. A theoretical model for the calculation of the elastic strain energy caused by core-shell precipitates, which is applicable to materials with weak elastic anisotropy, was adopted. It was demonstrated that the partitioning of Er to the precipitate core did not reduce the elastic strain energy as expected in the previous study. The resistance due to the elastic strain energy to form an Al3（Sc0.36Ero.64）-Al3（Sc0.8Er0.2） core-shell precipitate was quite small, and could be easily overcome by the decrease of the total interracial energy, which was consistent with the previous experimental results. On the other hand, the resistance due to the elastic strain energy to form an Al3Er-Al3Sc core-shell precipitate was much larger than that to form an Al3（Sc0.36Er0.64）-Al3（Sc0.8Er0.2） core-shell precipitate, thus the partitioning of all the Er atoms to the core was strongly hindered by the elastic strain energy and was not observed in the experiment of the previous study.
基金National Natural Science Foundation of China,Grant/Award Number:41877272Fundamental Research Funds for the Central Universities,Grant/Award Number:2242022k30054。
文摘To systematically assess the rockburst proneness considering specimen shape,multiple groups of laboratory tests were performed on 5 rock materials in cylindrical and cuboid shapes.The linear energy storage(LES)law of both cylindrical and cuboid rock specimens under uniaxial compressive load was confirmed,and the energy storage coefficient was found to be unrelated to specimen shape.On the basis of LES law,two rockburst proneness indexes,namely the strain energy storage index(W_(et))and the potential energy of elastic strain(PES),were modified.Subsequently,the W_(et),PES,peak-strength strain energy storage index(W_(et))p,and peak-strength potential energy of elastic strain(PESp)were used to assess the rockburst proneness of the cylindrical and cuboid specimens.In addition,the fragment ejection course of specimens under test was recorded by a high-speed camera.Then,the rockburst proneness judgments obtained from the 4 indexes were compared with the qualitative data during rock destruction.The results show that,under similar stress conditions,specimen shape has an ignorable effect on the rockburst proneness as a whole.The judgment accuracy of the two modified indexes,especially that of the PESp,is favorably improved to evaluate the rockburst proneness of both cylindrical and cuboid specimens.However,misjudgment ofW_(et)^(p)and PESp may still occur in the assessment of rockburst proneness as these two indexes only consider the energy state before rock peak strength and the W_(et)^(p)is formulated in a ratio form.
基金Project supported by the National Natural Science Foundation of China(Nos.12172151 and12172149)the Research Project of Introducing High-level Foreign Experts from the Ministry of Sicence and Technology of China(No.G20221990122)the Start-up Fund from Jinan University(Guangzhou)of China(No.88019062)。
文摘An explicit form of the elastic strain-energy function for direction-dependent large elastic strain behaviors of soft fiber-reinforced composites is first presented based upon a decoupled approach for simulating complex nonlinear coupling effects.From this form,the exact closed-form solutions are then obtained for the uniaxial tension responses in the fiber and cross-fiber directions.With such exact solutions,the issue of simultaneously simulating strongly coupling nonlinear responses in the fiber and cross-fiber directions may be reduced to the issue of separately treating each decoupled uniaxial stress-strain response,thus bypassing usual complexities and uncertainties involved in identifying a large number of strongly coupled adjustable parameters.The numerical examples given are in good agreement with the experimental data for large strain responses.
基金supported financially by the National Natural Science Foundation of China(Nos.51571212,51731010,51831006 and 51971243)the Australian Research Council(Nos.DP180101955 and DP180101744)。
文摘The deformation behaviors of W nanowires embedded in a TiNi matrix were investigated by means of in-situ synchrotron high energy X-ray diffraction(HEXRD) and in-situ transmission electron microscopy(TEM) analysis during tensile deformation.The HEXRD measurement indicated that the W nanowires exhibited an average lattice strain of about 1.50 %,whereas the TEM examination revealed a local elastic strain of about 4.59 % in areas adjacent to the TiNi matrix where stress-induced martensitic transfo rmation occurred.This strain corresponds to a stress of ~15 GPa for the W nanowires.In addition,in areas adjacent to the TiNi matrix where plastic deformation and cracking were generated,the W nanowire showed significant ductile necking with ~80 % reduction in cross-section area.The ductile necking of W nanowire is attributed to the lack of protection from the stress-induced martensitic transformation of the TiNi matrix.
基金Science and Technology Commission of Shanghai Municipality(21ZR1472900,22ZR1471600)。
文摘Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TMOs)are regarded as potential substitutes for PGMs because of their stability in oxidizing environments and excellent catalytic performance.In this study,comprehensive investigation into the influence of elastic strains on the adsorption energies of carbon(C),hydrogen(H)and oxygen(O)on TMOs was conducted.Based on density functional theory(DFT)calculations,these effects in both tetragonal structures(PtO_(2),PdO_(2))and hexagonal structures(ZnO,CdO),along with their respective transition metals were systematically explored.It was identified that the optimal adsorption sites on metal oxides pinpointed the top of oxygen or the top of metal atom,while face-centered cubic(FCC)and hexagonal close-packed(HCP)holes were preferred for the transition metals.Furthermore,under the influence of elastic strains,the results demonstrated significant disparities in the adsorption energies of H and O between oxides and transition metals.Despite these differences,the effect of elastic strains on the adsorption energies of C,H and O on TMOs mirrored those on transition metals:adsorption energies increased under compressive strains,indicating weaker adsorption,and decreased under tension strains,indicating stronger adsorption.This behavior was rationalized based on the d-band model for adsorption atop a metallic atom or the p-band model for adsorption atop an oxygen atom.Consequently,elastic strains present a promising avenue for tailoring the catalytic properties of TMOs.
基金This work was financially supported by the "973" National Basic Research Program of China (No. 2003CB314901)the National "863" High Technology Project of China (No. 2003AA311070)the Open Project of State Key Laboratory on Integrated Opto-electronics.
文摘A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.
基金Project supported by the National Natural Science foundation of China(Grant Nos.51571165 and 51371151)Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase),Chinathe Fundamental Research Funds for the Central Universities,China(Grant No.3102015BJ(II)ZS001)
文摘To understand and develop new nanostructure materials with specific mechanical properties, a good knowledge of the elastic strain response is mandatory. Here we investigate the linear elasticity response in the modified phase-field-crystal（MPFC） model. The results show that two different propagation modes control the elastic interaction length and time, which determine whether the density waves can propagate or not. By quantitatively calculating the strain field, we find that the strain distribution is indeed extremely uniform in case of elasticity. Further, we present a detailed theoretical analysis for the orientation dependence and temperature dependence of shear modulus. The simulation results show that the shear modulus reveals strong anisotropy and the one-mode analysis provides a good guideline for determining elastic shear constants until the system temperature falls below a certain value.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 2021RC202)the National Natural Science Foundation of China (Grant No. 51738002)
文摘This paper presents the analytical solutions for the responses of tunnels excavated in rock masses exhibiting strain-softening behavior. Since previous analyses give little consideration to the effect of the intermediate principal stress on the strain-softening rock behavior, the unified strength theory was introduced to analyze the tunnel response. Four cases of different definitions of the elastic strain in the softening and residual regions, used in the existing solutions, were considered. The tunnel displacements,stresses, radii of the softening and residual zones and critical stresses were deduced. The proposed solutions were verified by comparing with numerical simulations, model tests and existing solutions. Furthermore, the solutions of the four cases were compared with each other to investigate the influence of the elastic strain expressions on the tunnel responses. The results showed that the intermediate principal stress coefficient b has a significant effect on the tunnel displacements, stress fields, and plastic radii. Parametric studies were performed to analyze the influences of the softening and residual dilatancy coefficients,softening modulus and residual strength on the tunnel responses. The parametric analysis indicated that the existing models should be carefully evaluated in the analysis of tunnels constructed through average-quality rocks;the proposed solutions outperformed the existing models in solving the mentioned problem.
基金supported by the National Natural Science Foundation of China(12061131013 and 11972276)the State Key Laboratory of Mechanics and Control of Mechanical Structures at NUAA(No.MCMS-E-0520K02)+1 种基金the Fundamental Research Funds for the Central Universities(NE2020002 and NS2019007)the start-up fund supported by NUAA,and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘In this work,the static and dynamic response of a piezoelectric semiconductor cantilever under the transverse end force with consideration of flexoelectricity and strain gradient elasticity is systematically investigated.The one-dimensional governing equations and the corresponding boundary conditions are derived based on Hamilton’s principle.After that,combining with the linearized equations for the conservation of charge,the effects of characteristic length and flexoelectric coefficient on the working performance of a ZnO nanowire are demonstrated as a numerical case,including the static mechanical and electric fields,natural frequencies,and the frequency–response characteristics at resonances.The results indicate that the flexoelectric effect has a great influence on the electric properties of the nanowire,while the strain gradient effect directly contributes to its mechanical properties.To some extent,the increase in characteristic length is equivalent to the stiffness strengthening.The qualitative results and quantitative data are beneficial for revealing the underlying physical mechanism and provide guidance for the design of piezoelectric semiconductor devices.
基金the Korean Ministry of Trade,Industry and Energy(Grant No.200116572).
文摘The demand for titanium alloys simultaneously having high elastic admissible strain and large recovery strain for bio-implant applications is increasing.Ni-free Ti-based shape memory alloys are promising candidates for obtaining the required multifunctional properties.In this study,a wide content range of(0-15)wt%of low-cost,toxicity-free,and high-biocompatible Sn element was added to the Ti-8Mo(wt%)alloy to study its effect on the superelastic recovery and mechanical properties of biomedical Ti-Mo-Sn alloys.By tailoring Sn content,desired multifunctional properties of high elastic admissible strain and room temperature superelasticity were achieved in the studied Ti-Mo-Sn alloys.It was found that the increase in Sn content stabilized theβphase and a singleβphase was obtained at room temperature in Ti-8Mo-(13,15)Sn alloys.The addition of Sn modified the lattice parameters of theα″martensite andβphase and affected the lattice deformation stain ofβ→α″.The lattice deformation strain along the[011]βdirection was found to be decreased by-0.26%/wt%Sn.The room temperature superelasticity with a recovery strain of 3.1%and an elastic admissible strain of 1%was obtained in the Ti-8Mo-13Sn alloy.As Sn content increased to 15 wt%,a high elastic admissible strain of 1.56%and a recovery strain of 2.0%were obtained.These Ti-Mo-Sn alloys with excellent multifunctional properties are promising candidates for bio-implant applications.
文摘A micro scale nonlinear beam model based on strain gradient elasticity is developed. Governing equations of motion and boundary conditions are obtained in a variational framework. As an example, the nonlinear vibration of microbeams is analyzed. In a beam having a thickness to length parameter ratio close to unity, the strain gradient effect on increasing the natural frequency is predominant. By increasing the beam thickness, this effect decreases and geometric nonlinearity plays the main role on increasing the natural frequency. For some specific ratios, both geometric nonlinearity and size effects have a significant role on increasing the natural frequency.
基金supported by the National Natural Science Foundation of China(No.81571695)
文摘This study evaluated the myocardial strain and aortic elasticity in patients with bicuspid aortic valve（BAV） and then investigated the relation between them. Thirty-nine patients（30 males; mean age 44±19 years; range 6 to 75 years） with BAV were recruited as BAV group, and 29 age- and sex-matched healthy controls（21 males; mean age 42±11 years; range 20 to 71 years） served as control group. Aortic strain, distensibility and stiffness index were derived using M-mode echocardiography. Left ventricular global myocardial strain was acquired with speckle-tracking echocardiography. Correlation between aortic elasticity and myocardial strain was also analyzed. The results showed that aortic stiffness was higher（17.5±14.0 vs. 5.3±2.7, P〈0.001）, and aortic strain（4.9±4.7 vs. 11.0±4.1, P〈0.001） and distensibility（1.8±2.1 vs. 3.7±1.6, P〈0.001） were lower significantly in BAV group than in control group. Global circumferential strain（–19.1±4.2 vs. –22.5±3.7, P〈0.001）, radial stain（29.8±14.9 vs. 38.0±8.8, P〈0.001） and longitudinal stain（–18.4±3.4 vs. –20.8±3.5, P〈0.001） were significantly lower in BAV group than in control group. There was weak association between aortic elasticity and myocardial strain. These findings indicated BAV patients manifest reduced myocardial strain which had weak relationship with aortic elastic lesion.
基金supported by the SDUST Spring Bud (2009AZZ021)Taian Science and Technology Development (20112001)
文摘C^1 natural element method （C^1 NEM） is applied to strain gradient linear elasticity, and size effects on mi crostructures are analyzed. The shape functions in C^1 NEM are built upon the natural neighbor interpolation （NNI）, with interpolation realized to nodal function and nodal gradient values, so that the essential boundary conditions （EBCs） can be imposed directly in a Galerkin scheme for partial differential equations （PDEs）. In the present paper, C^1 NEM for strain gradient linear elasticity is constructed, and sev- eral typical examples which have analytical solutions are presented to illustrate the effectiveness of the constructed method. In its application to microstructures, the size effects of bending stiffness and stress concentration factor （SCF） are studied for microspeciem and microgripper, respectively. It is observed that the size effects become rather strong when the width of spring for microgripper, the radius of circular perforation and the long axis of elliptical perforation for microspeciem come close to the material characteristic length scales. For the U-shaped notch, the size effects decline obviously with increasing notch radius, and decline mildly with increasing length of notch.
基金the China Scholarship Council(CSC)for a CSC scholarship(No.201706230108)Funding from the National Natural Science Foundation of China(No.51971145)and the Australian Research Council(Nos.DP200102666 and No.DE230101344)is acknowledged.
文摘Mechanical metamaterials are architectured cellular materials with unusual properties.Herein we report another type of metal mechanical metamaterials-their elastic admissible strain(EAS)is on the order of 0.1,compared to about 0.01 for common metallic materials.Four conditions are required for a metal mechanical metamaterial to achieve this super EAS:(i)bending-dominated deformation;(ii)low density;(iii)an appropriate lattice topology,and(iv)an intrinsically high EAS for the lattice strut constituent material.The findings of this work extend perspectives on metal mechanical metamaterials.
基金Project supported by the National Natural Science Foundation of China (No. 12002086)the Fundamental Research Funds for the Central Universities of China (No. 2242022R40040)。
文摘A new size-dependent axially functionally graded(AFG) micro-beam model is established with the application of a reformulated strain gradient elasticity theory(RSGET). The new micro-beam model incorporates the strain gradient, velocity gradient,and couple stress effects, and accounts for the material variation along the axial direction of the two-component functionally graded beam. The governing equations and complete boundary conditions of the AFG beam are derived based on Hamilton's principle. The correctness of the current model is verified by comparing the static behavior results of the current model and the finite element model(FEM) at the micro-scale. The influence of material inhomogeneity and size effect on the static and dynamic responses of the AFG beam is studied. The numerical results show that the static and vibration responses predicted by the newly developed model are different from those based on the classical model at the micro-scale. The new model can be applied not only in the optimization of micro acoustic wave devices but also in the design of AFG micro-sensors and micro-actuators.
基金National Natural Science Foundation of China (No.50071046).
文摘The coherent elastic strain-induced morphological transformation of a binarycubic model alloy was simulated with different strain energy parameters. The microscopic diffusionequation was combined with the theory of microscopic elasticity. The results show that when thestrain energy is neglected, the randomly distributed equiaxed particles are obtained with isotropiccharacteristic. It is coarsening that follows the Ostwald ripening mechanism: smaller particlesdwindle and larger particles grow; when the elastic strain is considered, plate precipitates tend toalign along the elastically soft directions <01> with anisotropic characteristic. The particlesgrow in the soft directions and coarsen further; particles dwindle in out of the soft directions.While the coarsening of the particles localized in the same row or column follows the rule: smallerparticles shrink and larger ones grow.
基金the National Natural Science Foundation of China (50678054)
文摘To investigate the early-age behaviors of concrete under a restrained condition, a set of apparatus was developed. In this way, the tensile creep and other early-age properties can be investigated in depth. By measuring the modulus of elasticity of concrete, synchronous shrinkage of concrete and steel rings and free shrinkage of concrete, the deformations of concrete ring can be quantified respectively. The experimental results show the tensile stress in concrete is time-dependent, and the stress at cracking is much lower than the tensile strength at that age; the tensile creep plays an important role in relaxing the tensile stress and postponing the cracking of concrete.
基金Project supported by the Natural Science Foundation of Jiangxi Science and Technology Department(No. 20202BAB204027)。
文摘This study presents the size-dependent nonlinear thermal postbuckling characteristics of a porous functionally graded material(PFGM) microplate with a central cutout with various shapes using isogeometric numerical technique incorporating nonuniform rational B-splines. To construct the proposed non-classical plate model, the nonlocal strain gradient continuum elasticity is adopted on the basis of a hybrid quasithree-dimensional(3D) plate theory under through-thickness deformation conditions by only four variables. By taking a refined power-law function into account in conjunction with the Touloukian scheme, the temperature-porosity-dependent material properties are extracted. With the aid of the assembled isogeometric-based finite element formulations,nonlocal strain gradient thermal postbuckling curves are acquired for various boundary conditions as well as geometrical and material parameters. It is portrayed that for both size dependency types, by going deeper in the thermal postbuckling domain, gaps among equilibrium curves associated with various small scale parameter values get lower, which indicates that the pronounce of size effects reduces by going deeper in the thermal postbuckling regime. Moreover, we observe that the central cutout effect on the temperature rise associated with the thermal postbuckling behavior in the presence of the effect of strain gradient size and absence of nonlocality is stronger compared with the case including nonlocality in absence of the strain gradient small scale effect.
