This work investigates the indentation response of an elastic plate resting upon a thin,transversely isotropic elastic layer supported by a rigid substrate.Such a scenario is encountered across a range of length scale...This work investigates the indentation response of an elastic plate resting upon a thin,transversely isotropic elastic layer supported by a rigid substrate.Such a scenario is encountered across a range of length scales from piezoresistive tests on graphite nanoflakes to the bending of floating ice shelves atop seabed,where the elastic layer commonly exhibits certain anisotropy.We first develop an approximate model to describe the elastic response of a transversely isotropic layer by exploiting the slenderness of the layer.We show that this approximate model can be reduced to the classic compressible Winkler foundation model as the elastic constants of the layer are set isotropic.We then investigate the combined response of an elastic plate on the transversely isotropic elastic layer.Facilitated by the simplicity of our proposed approximate model,we can derive simple analytical solutions for the cases of small and large indenter radi.The analytical results agree well with numerical calculations obtained via finite element methods,as long as the system is sufficiently slender in a mechanical sense.These results offer quantitative insights into the mechanical behavior of numerous semiconductor materials characterized by transverse isotropy and employed with slender geometries in various practical applications where the thin layer works as conductive and functional layers.展开更多
Understanding the effects of point liquid loading on transversely isotropic poroelastic media is crucial for advancing geomechanics and biomechanics, where precise modeling of fluid-structure interactions is essential...Understanding the effects of point liquid loading on transversely isotropic poroelastic media is crucial for advancing geomechanics and biomechanics, where precise modeling of fluid-structure interactions is essential. This paper presents a comprehensive analysis of infinite transversely isotropic poroelasticity under a fluid source, based on Biot's theory, aiming to uncover new and previously unexplored insights in the literature. We begin our study by deriving a general solution for fluid-saturated, transversely isotropic poroelastic materials in terms of harmonic functions that satisfy sixth-order homogeneous partial differential equations, using potential theory and Almansi's theorem. Based on these general solutions and potential functions, we construct a Green's function for a point fluid source, introducing three new harmonic functions with undetermined constants. These constants are determined by enforcing continuity and equilibrium conditions. Substituting these into the general solution yields fundamental solutions for poroelasticity that provide crucial support for a wide range of project problems. Numerical results and comparisons with existing literature are provided to illustrate physical mechanisms through contour plots. Our observations reveal that all components tend to zero in the far field and become singular at the concentrated source. Additionally, the contours exhibit rapid changes near the point fluid source but display gradual variations at a distance from it. These findings highlight the intricate behavior of the system under point liquid loading, offering valuable insights for further research and practical applications.展开更多
The mechanical properties of bedding rock in cold regions are frequently affected by freeze-thaw(F-T)cycles and ani-sotropy.Research on the mechanical characteristics of rock damage under the combined action of F-T an...The mechanical properties of bedding rock in cold regions are frequently affected by freeze-thaw(F-T)cycles and ani-sotropy.Research on the mechanical characteristics of rock damage under the combined action of F-T and bedding angles is limited,and most traditional rock damage models cannot accurately capture these characteristics.We performed axial compression tests to ex-plore the strength characteristics of bedding slates at the bedding angles ofβ=0°,30°,45°,60°,and 90°under various F-T cycles.The experimental findings suggest that the elastic modulus and uniaxial compressive strength of the slate declined exponentially as the number of F-T cycles increased.Axial compressive strength was characterized by a U-shaped tendency with the bedding angle.This study proposes a damage model for the uniaxial compressive strength of transversely isotropic rock,which integrates the F-T effect,utilizing the enhanced anisotropic Hoek-Brown strength criterion and a statistical damage model.This model was validated using experimental data.This statistical damage model can precisely capture the dual attributes of rock mass strength reduction with F-T cy-cles and variations arising from the loading direction.展开更多
A solution for the lithospheric deformation of a uniform,elastically isotropic layer(EIL)of uniform thickness welded with a uniform,elastically orthotropic half-space(EOHS)due to a vertical tensile line fault(VTLF)wit...A solution for the lithospheric deformation of a uniform,elastically isotropic layer(EIL)of uniform thickness welded with a uniform,elastically orthotropic half-space(EOHS)due to a vertical tensile line fault(VTLF)with an opening in the horizontal direction located in the isotropic layer is derived in the integral form by employing Airy’s stress function approach for the plane strain case.The linear combination of exponential terms appearing in the denominator of the integral expressions of the deformation field of the EIL is expressed as a finite sum of exponential terms(FSET)by applying the method of least squares to analytically compute the deformation field.The displacement field is discussed in detail and computed numerically by considering the EOHS as olivine or barytes material or considering half-space to be isotropic.展开更多
Isotropic laser cooling(ILC)is widely recognized for its distinct advantages and demonstrates significant potential in quantum precision measurements and quantum sensing technologies.The morphology and density distrib...Isotropic laser cooling(ILC)is widely recognized for its distinct advantages and demonstrates significant potential in quantum precision measurements and quantum sensing technologies.The morphology and density distribution of the cold atomic cloud generated by ILC are strongly influenced by the distribution of cooling light and the structural geometry of the cavity,making precise characterization and optimization of cold atom distribution essential for practical applications.In this paper,we present an innovative flat diffuse cavity design with the dimensions approximating a quasi-two-dimensional configuration,which generates a sheet-like isotropic laser field inside the cavity through diffuse reflections.We thoroughly characterized the system’s performance under different optical parameter settings.A two-dimensional(2D)movable detection system was employed to detect the quasi-two-dimensional distribution of cold atoms.These results demonstrate the ability of ILC to produce diverse morphological and density distributions of cold atoms,which we anticipate will be suitable for quantum sensing.展开更多
Metallic lattice structures represent advanced architected materials delivering exceptional properties with promising lightweight potential.With the rapid advancement of additive manufacturing,these structures have ga...Metallic lattice structures represent advanced architected materials delivering exceptional properties with promising lightweight potential.With the rapid advancement of additive manufacturing,these structures have garnered increasing research interest.However,most metallic lattice structures generally exhibit anisotropic characteristics,which limits their application ranges.Additionally,a limited number of studies have successfully developed precise mechanical models,which have undergone experimental validation,for the purpose of describing the mechanical response exhibited by additively manufactured metallic lattice structures.In this study,Kelvin lattice structures with varying porosities were systematically designed and fabricated using laser powder bed fusion(LPBF)technology.By integrating finite element simulations with experimental characterization,an enhanced mechanical model was developed through a modification of the Gibson-Ashby model,providing an accurate quantitative description of the relationship between porosity and mechanical properties.The results show that the revised mechanical model can accurately describe the relationship between the geometric parameters and properties of metallic lattice structures.Specifically,the designed Kelvin lattice structures exhibit a smooth stress-strain curve with an obvious yield platform,demonstrating isotropic mechanical properties in all the three spatial directions.This enhances their suitability for complex loading conditions.Meanwhile,the microstructure and manufacturing accuracy of the Kelvin lattice structures were observed and analyzed by micro computed tomography.The results show that the fabricated metallic lattice structures achieved precise dimensional control and optimal densification.This study presents the complete process involved in modeling the Kelvin structure,including its conceptualization,manufacturing,implementation,and ultimately,disposal.展开更多
As an emerging microscopic detection tool,quantum microscopes based on the principle of quantum precision measurement have attracted widespread attention in recent years.Compared with the imaging of classical light,qu...As an emerging microscopic detection tool,quantum microscopes based on the principle of quantum precision measurement have attracted widespread attention in recent years.Compared with the imaging of classical light,quantum-enhanced imaging can achieve ultra-high resolution,ultra-sensitive detection,and anti-interference imaging.Here,we introduce a quantum-enhanced scanning microscope under illumination of an entangled NOON state in polarization.For the phase imager with NOON states,we propose a simple four-basis projection method to replace the four-step phase-shifting method.We have achieved the phase imaging of micrometer-sized birefringent samples and biological cell specimens,with sensitivity close to the Heisenberg limit.The visibility of transmittance-based imaging shows a great enhancement for NOON states.Besides,we also demonstrate that the scanning imaging with NOON states enables the spatial resolution enhancement of√N compared with classical measurement.Our imaging method may provide some reference for the practical application of quantum imaging and is expected to promote the development of microscopic detection.展开更多
Natural soil generally exhibits significant transverse isotropy(TI)due to weathering and sedimentation,meaning that horizontal moduli differ from their vertical counterpart.The TI mechanical model is more appropriate ...Natural soil generally exhibits significant transverse isotropy(TI)due to weathering and sedimentation,meaning that horizontal moduli differ from their vertical counterpart.The TI mechanical model is more appropriate for actual situations.Although soil exhibits material nonlinearity under earthquake excitation,existing research on the TI medium is limited to soil linearity and neglects the nonlinear response of TI sites.A 2D equivalent linear model for a layered TI half-space subjected to seismic waves is derived in the transformed wave number domain using the exact dynamic stiffness matrix of the TI medium.This study introduces a method for determining the effective shear strain of TI sites under oblique wave incidence,and further describes a systematic study on the effects of TI parameters and soil nonlinearity on site responses.Numerical results indicate that seismic responses of the TI medium significantly differ from those of isotropic sites and that the responses are highly dependent on TI parameters,particularly in nonlinear cases,while also being sensitive to incident angle and excitation intensity.Moreover,the differences in peak acceleration and waveform for various TI materials may also be amplified due to the strong nonlinearity.The study provides valuable insights for improving the accuracy of seismic response analysis in engineering applications.展开更多
We present an assumed enhanced strain finite element framework for the simulation of tensile fracturing processes in transversely isotropic rocks.Fractures along the weak bedding planes and through the anisotropic roc...We present an assumed enhanced strain finite element framework for the simulation of tensile fracturing processes in transversely isotropic rocks.Fractures along the weak bedding planes and through the anisotropic rock matrix are treated with distinct enrichment,and a recently proposed dualmechanism tensile failure criterion for transversely isotropic rocks is adopted to determine crack initiation for the two failure modes.The cohesive crack model is adopted to characterize the response of embedded cracks.As for the numerical implementation of the proposed framework,both algorithms for the update of local history variables at Gauss points and of the global finite element system are derived.Four boundary-value problem simulations are carried out with the proposed framework,including uniaxial tension tests of Argillite,pre-notched square loaded in tension,three-point bending tests on Longmaxi shale,and simulations of tensile cracks induced by a strip load around a tunnel in transversely isotropic rocks.Simulation results reveal that the proposed framework can properly capture the tensile strength anisotropy and the anisotropic evolution of tensile cracks in transversely isotropic rocks.展开更多
In this paper,we develop an advanced computational framework for the topology optimization of orthotropic materials using meshless methods.The approximation function is established based on the improved moving least s...In this paper,we develop an advanced computational framework for the topology optimization of orthotropic materials using meshless methods.The approximation function is established based on the improved moving least squares(IMLS)method,which enhances the efficiency and stability of the numerical solution.The numerical solution formulas are derived using the improved element-free Galerkin(IEFG)method.We introduce the solid isotropic microstructures with penalization(SIMP)model to formulate a mathematical model for topology opti-mization,which effectively penalizes intermediate densities.The optimization problem is defined with the numerical solution formula and volume fraction as constraints.The objective function,which is the minimum value of flexibility,is optimized iteratively using the optimization criterion method to update the design variables efficiently and converge to an optimal solution.Sensitivity analysis is performed using the adjoint method,which provides accurate and efficient gradient information for the optimization algorithm.We validate the proposed framework through a series of numerical examples,including clamped beam,cantilever beam,and simply supported beam made of orthotropic materials.The convergence of the objective function is demonstrated by increasing the number of iterations.Additionally,the stability of the iterative process is analyzed by examining the fluctuation law of the volume fraction.By adjusting the parameters to an appropriate range,we achieve the final optimization results of the IEFG method without the checkerboard phenomenon.Comparative studies between the Element-Free Galerkin(EFG)and IEFG methods reveal that both methods yield consistent optimization results under identical parameter settings.However,the IEFG method significantly reduces computational time,highlighting its efficiency and suitability for orthotropic materials.展开更多
Transducing thermal energy into mechanical movements via molecular reconfigurations offers a cutting-edge approach to thermal actuating materials,which could be applied to sensors,energy harvesting and storage devices...Transducing thermal energy into mechanical movements via molecular reconfigurations offers a cutting-edge approach to thermal actuating materials,which could be applied to sensors,energy harvesting and storage devices[1].Thermal expansion is a pivotal aspect in solid state chemistry,intricately intertwined with various factors such as crystal structure,chemical composition,electronic configuration,microstructure,and defects.Most materials undergo isotropic and positive thermal expansion(PTE)because of the disharmonic vibrational amplitudes of their chemical bonds.Moreover,anisotropic thermal expansion(ATE)and negative thermal expansion(NTE)are fascinating physical attributes of solids,which can originate from electronic or magnetic mechanisms,as well as through a transverse phonon mechanism in insulating lattice solids.展开更多
为获得高速动车齿轮箱最优结构设计方案,针对目前国产高速动车牵引齿轮箱箱体特点及存在的问题,基于SIMP(solid isotropic material with penalization)材料插值模型及应变能理论,利用软件HyperMesh中的拓扑优化与形状优化模块对动车齿...为获得高速动车齿轮箱最优结构设计方案,针对目前国产高速动车牵引齿轮箱箱体特点及存在的问题,基于SIMP(solid isotropic material with penalization)材料插值模型及应变能理论,利用软件HyperMesh中的拓扑优化与形状优化模块对动车齿轮箱箱体结构进行拓扑优化和局部形状优化。优化结果表明:优化后的动车齿轮箱结构的最大变形和最大应力有大幅度降低,能有效提高齿轮箱箱体的刚度和强度。文中结果可为设计性能优异的国产化高速动车齿轮箱提供数据支持。展开更多
To deal with the numerical dispersion problem, by combining the staggeredgrid technology with the compact finite difference scheme, we derive a compact staggered- grid finite difference scheme from the first-order vel...To deal with the numerical dispersion problem, by combining the staggeredgrid technology with the compact finite difference scheme, we derive a compact staggered- grid finite difference scheme from the first-order velocity-stress wave equations for the transversely isotropic media. Comparing the principal truncation error terms of the compact staggered-grid finite difference scheme, the staggered-grid finite difference scheme, and the compact finite difference scheme, we analyze the approximation accuracy of these three schemes using Fourier analysis. Finally, seismic wave numerical simulation in transversely isotropic （VTI） media is performed using the three schemes. The results indicate that the compact staggered-grid finite difference scheme has the smallest truncation error, the highest accuracy, and the weakest numerical dispersion among the three schemes. In summary, the numerical modeling shows the validity of the compact staggered-grid finite difference scheme.展开更多
The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize...The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.展开更多
A thickness strain model of aluminium alloy plate under plastic deformation,based on thin plate assumption was proposed.It is found that when ratio of stress fractions is constant during in-plane loading,ratios of str...A thickness strain model of aluminium alloy plate under plastic deformation,based on thin plate assumption was proposed.It is found that when ratio of stress fractions is constant during in-plane loading,ratios of strain components under various loading conditions are linearly related and these points of ratios form a η-η line.Under these simple loadings,strains in thickness direction can be easily calculated by the η-η line equation without integral and differential work.When the plate is under more complicated loading conditions,the thickness can be computed by the proposed optimization and piecewise calculation model.Validation computations indicate that the relative error of the results of the presented model is less than 0.75% compared with the proven theories and FE simulation.Therefore,the developed model can be applied to engineering calculation,e.g.pre-stretching analysis of aerospace aluminium thick plate,with acceptable accuracy.展开更多
We have studied Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model filled with anisotropic fluid in general theory of relativity. The solutions of the field equations are obtained by using special ...We have studied Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model filled with anisotropic fluid in general theory of relativity. The solutions of the field equations are obtained by using special form of deceleration parameter which gives early deceleration and late time accelerating cosmological model. The geometrical and physical aspect of the model is also studied.展开更多
A series of experiments were pertbrmed to determine rock mechanical parameters related to hydraulic fracturing of coal. The effect of confining pressure and pore pressure on the strength of coal was stt, died. Experim...A series of experiments were pertbrmed to determine rock mechanical parameters related to hydraulic fracturing of coal. The effect of confining pressure and pore pressure on the strength of coal was stt, died. Experimental results show that the coal seam in the study areas has a relatively low elastic modulus, high Poisson＇s ratio, high fragility and is easily broken and compressed. The coal seam is considered as a transversely isotropic medium, since the physical properties in the direction of bedding plane and orthogonal to the bedding plane vary markedly. Based on the generalized plane strain model, stress distribution for an arbitrarily orientated wellbore in the coal seam was determined. In a horizontal well, hydraulic fracturing was lbund to initiate in the coal seam mass due to tensile failure, or from cleats due to shear or tensile failure. For those coal seams with abundant natural cleats, hydraulic fracture initiation can be induced by any of these mechanisms. In this study, hydraulic fracture initiation criteria tbr a horizontal well in a coal seam were established.展开更多
The unbonded flexible pipe of eight layers, in which all the layers except the carcass layer are assumed to have isotropic properties, has been analyzed. Specifically, the carcass layer shows the orthotropic character...The unbonded flexible pipe of eight layers, in which all the layers except the carcass layer are assumed to have isotropic properties, has been analyzed. Specifically, the carcass layer shows the orthotropic characteristics. The effective elastic moduli of the carcass layer have been developed in terms of the influence of deformation to stiffness. With consideration of the effective elastic moduli, the structure can be properly analyzed. Also the relative movements of tendons and relative displacements of wires in helical armour layer have been investigated. A three-dimensional nonlinear finite element model has been presented to predict the response of flexible pipes under axial force and torque. Further, the friction and contact of interlayer have been considered. Comparison between the finite element model and experimental results obtained in literature has been given and discussed, which might provide practical and technical support for the application of unbonded flexible pipes.展开更多
This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot＇s poroelastic theory and the constitutive relations of the transversely isotropic medium, th...This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot＇s poroelastic theory and the constitutive relations of the transversely isotropic medium, the dynamic governing equations of the outer and inner transversely isotropic saturated soil layers are derived. The Laplace transform is used to solve the governing equations of the outer and inner soil layers. The dynamic torsional response of the pipe pile in the frequency domain is derived utilizing 1D elastic theory and the continuous conditions at the interfaces between the pipe pile and the soils. The time domain solution is obtained by Fourier inverse transform. A parametric study is conducted to demonstrate the influence of the anisotropies of the outer and inner soil on the torsional dynamic response of the pipe pile.展开更多
基金supported by the National Natural Science Foundation of China(12372103)the Opening Fund of State Key Laboratory of Nonlinear Mechanics(Institute of Mechanics,CAS)the Fundamental Research Funds for Central Universities(Peking University).
文摘This work investigates the indentation response of an elastic plate resting upon a thin,transversely isotropic elastic layer supported by a rigid substrate.Such a scenario is encountered across a range of length scales from piezoresistive tests on graphite nanoflakes to the bending of floating ice shelves atop seabed,where the elastic layer commonly exhibits certain anisotropy.We first develop an approximate model to describe the elastic response of a transversely isotropic layer by exploiting the slenderness of the layer.We show that this approximate model can be reduced to the classic compressible Winkler foundation model as the elastic constants of the layer are set isotropic.We then investigate the combined response of an elastic plate on the transversely isotropic elastic layer.Facilitated by the simplicity of our proposed approximate model,we can derive simple analytical solutions for the cases of small and large indenter radi.The analytical results agree well with numerical calculations obtained via finite element methods,as long as the system is sufficiently slender in a mechanical sense.These results offer quantitative insights into the mechanical behavior of numerous semiconductor materials characterized by transverse isotropy and employed with slender geometries in various practical applications where the thin layer works as conductive and functional layers.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12272269, 11972257,11832014 and 11472193)the Shanghai Pilot Program for Basic Researchthe Shanghai Gaofeng Project for University Academic Program Development。
文摘Understanding the effects of point liquid loading on transversely isotropic poroelastic media is crucial for advancing geomechanics and biomechanics, where precise modeling of fluid-structure interactions is essential. This paper presents a comprehensive analysis of infinite transversely isotropic poroelasticity under a fluid source, based on Biot's theory, aiming to uncover new and previously unexplored insights in the literature. We begin our study by deriving a general solution for fluid-saturated, transversely isotropic poroelastic materials in terms of harmonic functions that satisfy sixth-order homogeneous partial differential equations, using potential theory and Almansi's theorem. Based on these general solutions and potential functions, we construct a Green's function for a point fluid source, introducing three new harmonic functions with undetermined constants. These constants are determined by enforcing continuity and equilibrium conditions. Substituting these into the general solution yields fundamental solutions for poroelasticity that provide crucial support for a wide range of project problems. Numerical results and comparisons with existing literature are provided to illustrate physical mechanisms through contour plots. Our observations reveal that all components tend to zero in the far field and become singular at the concentrated source. Additionally, the contours exhibit rapid changes near the point fluid source but display gradual variations at a distance from it. These findings highlight the intricate behavior of the system under point liquid loading, offering valuable insights for further research and practical applications.
基金supported by the Qingdao Postdoctoral Science Foundation(No.862205040054)the International Research Fellowship from the Japan Society for the Promotion of Science(Postdoctoral Fellowships for Research in Japan(Standard))the National Natural Science Foundation of China(No.52078093).
文摘The mechanical properties of bedding rock in cold regions are frequently affected by freeze-thaw(F-T)cycles and ani-sotropy.Research on the mechanical characteristics of rock damage under the combined action of F-T and bedding angles is limited,and most traditional rock damage models cannot accurately capture these characteristics.We performed axial compression tests to ex-plore the strength characteristics of bedding slates at the bedding angles ofβ=0°,30°,45°,60°,and 90°under various F-T cycles.The experimental findings suggest that the elastic modulus and uniaxial compressive strength of the slate declined exponentially as the number of F-T cycles increased.Axial compressive strength was characterized by a U-shaped tendency with the bedding angle.This study proposes a damage model for the uniaxial compressive strength of transversely isotropic rock,which integrates the F-T effect,utilizing the enhanced anisotropic Hoek-Brown strength criterion and a statistical damage model.This model was validated using experimental data.This statistical damage model can precisely capture the dual attributes of rock mass strength reduction with F-T cy-cles and variations arising from the loading direction.
文摘A solution for the lithospheric deformation of a uniform,elastically isotropic layer(EIL)of uniform thickness welded with a uniform,elastically orthotropic half-space(EOHS)due to a vertical tensile line fault(VTLF)with an opening in the horizontal direction located in the isotropic layer is derived in the integral form by employing Airy’s stress function approach for the plane strain case.The linear combination of exponential terms appearing in the denominator of the integral expressions of the deformation field of the EIL is expressed as a finite sum of exponential terms(FSET)by applying the method of least squares to analytically compute the deformation field.The displacement field is discussed in detail and computed numerically by considering the EOHS as olivine or barytes material or considering half-space to be isotropic.
基金supported by the National Natural Science Foun-dation of China(Grant No.92165107)the China Postdoctoral Science Foundation(Grant No.2022M723270)the National Defense Basic Scientific Research Pogram of China。
文摘Isotropic laser cooling(ILC)is widely recognized for its distinct advantages and demonstrates significant potential in quantum precision measurements and quantum sensing technologies.The morphology and density distribution of the cold atomic cloud generated by ILC are strongly influenced by the distribution of cooling light and the structural geometry of the cavity,making precise characterization and optimization of cold atom distribution essential for practical applications.In this paper,we present an innovative flat diffuse cavity design with the dimensions approximating a quasi-two-dimensional configuration,which generates a sheet-like isotropic laser field inside the cavity through diffuse reflections.We thoroughly characterized the system’s performance under different optical parameter settings.A two-dimensional(2D)movable detection system was employed to detect the quasi-two-dimensional distribution of cold atoms.These results demonstrate the ability of ILC to produce diverse morphological and density distributions of cold atoms,which we anticipate will be suitable for quantum sensing.
基金financially supported by the Liaoning Province Applied Fundamental Research Program (No.2023JH2/101700039)Liaoning Province Natural Science Foundation (No.2023-MSLH-328).
文摘Metallic lattice structures represent advanced architected materials delivering exceptional properties with promising lightweight potential.With the rapid advancement of additive manufacturing,these structures have garnered increasing research interest.However,most metallic lattice structures generally exhibit anisotropic characteristics,which limits their application ranges.Additionally,a limited number of studies have successfully developed precise mechanical models,which have undergone experimental validation,for the purpose of describing the mechanical response exhibited by additively manufactured metallic lattice structures.In this study,Kelvin lattice structures with varying porosities were systematically designed and fabricated using laser powder bed fusion(LPBF)technology.By integrating finite element simulations with experimental characterization,an enhanced mechanical model was developed through a modification of the Gibson-Ashby model,providing an accurate quantitative description of the relationship between porosity and mechanical properties.The results show that the revised mechanical model can accurately describe the relationship between the geometric parameters and properties of metallic lattice structures.Specifically,the designed Kelvin lattice structures exhibit a smooth stress-strain curve with an obvious yield platform,demonstrating isotropic mechanical properties in all the three spatial directions.This enhances their suitability for complex loading conditions.Meanwhile,the microstructure and manufacturing accuracy of the Kelvin lattice structures were observed and analyzed by micro computed tomography.The results show that the fabricated metallic lattice structures achieved precise dimensional control and optimal densification.This study presents the complete process involved in modeling the Kelvin structure,including its conceptualization,manufacturing,implementation,and ultimately,disposal.
基金supported by he National Natural Science Foundation of China(Grant Nos.12304359,12304398,12404382,12234009,12274215,and 12427808)the China Postdoctoral Science Foundation(Grant No.2023M731611)+4 种基金the Jiangsu Funding Program for Excellent Postdoctoral Talent(Grant No.2023ZB717)Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301400)Key R&D Program of Jiangsu Province(Grant No.BE2023002)Natural Science Foundation of Jiangsu Province(Grant Nos.BK20220759 and BK20233001)Program for Innovative Talents and Entrepreneurs in Jiangsu,and Key R&D Program of Guangdong Province(Grant No.2020B0303010001).
文摘As an emerging microscopic detection tool,quantum microscopes based on the principle of quantum precision measurement have attracted widespread attention in recent years.Compared with the imaging of classical light,quantum-enhanced imaging can achieve ultra-high resolution,ultra-sensitive detection,and anti-interference imaging.Here,we introduce a quantum-enhanced scanning microscope under illumination of an entangled NOON state in polarization.For the phase imager with NOON states,we propose a simple four-basis projection method to replace the four-step phase-shifting method.We have achieved the phase imaging of micrometer-sized birefringent samples and biological cell specimens,with sensitivity close to the Heisenberg limit.The visibility of transmittance-based imaging shows a great enhancement for NOON states.Besides,we also demonstrate that the scanning imaging with NOON states enables the spatial resolution enhancement of√N compared with classical measurement.Our imaging method may provide some reference for the practical application of quantum imaging and is expected to promote the development of microscopic detection.
基金National Natural Science Foundation of China under Grant No.U2139208。
文摘Natural soil generally exhibits significant transverse isotropy(TI)due to weathering and sedimentation,meaning that horizontal moduli differ from their vertical counterpart.The TI mechanical model is more appropriate for actual situations.Although soil exhibits material nonlinearity under earthquake excitation,existing research on the TI medium is limited to soil linearity and neglects the nonlinear response of TI sites.A 2D equivalent linear model for a layered TI half-space subjected to seismic waves is derived in the transformed wave number domain using the exact dynamic stiffness matrix of the TI medium.This study introduces a method for determining the effective shear strain of TI sites under oblique wave incidence,and further describes a systematic study on the effects of TI parameters and soil nonlinearity on site responses.Numerical results indicate that seismic responses of the TI medium significantly differ from those of isotropic sites and that the responses are highly dependent on TI parameters,particularly in nonlinear cases,while also being sensitive to incident angle and excitation intensity.Moreover,the differences in peak acceleration and waveform for various TI materials may also be amplified due to the strong nonlinearity.The study provides valuable insights for improving the accuracy of seismic response analysis in engineering applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.52038005 and 52201326)the fellowship of China Postdoctoral Science Foundation(Grant No.2022M721883)Tsinghua University Initiative Scientific Research Program.
文摘We present an assumed enhanced strain finite element framework for the simulation of tensile fracturing processes in transversely isotropic rocks.Fractures along the weak bedding planes and through the anisotropic rock matrix are treated with distinct enrichment,and a recently proposed dualmechanism tensile failure criterion for transversely isotropic rocks is adopted to determine crack initiation for the two failure modes.The cohesive crack model is adopted to characterize the response of embedded cracks.As for the numerical implementation of the proposed framework,both algorithms for the update of local history variables at Gauss points and of the global finite element system are derived.Four boundary-value problem simulations are carried out with the proposed framework,including uniaxial tension tests of Argillite,pre-notched square loaded in tension,three-point bending tests on Longmaxi shale,and simulations of tensile cracks induced by a strip load around a tunnel in transversely isotropic rocks.Simulation results reveal that the proposed framework can properly capture the tensile strength anisotropy and the anisotropic evolution of tensile cracks in transversely isotropic rocks.
基金supported by the Graduate Student Scientific Research Innovation Project through Research Innovation Fund for Graduate Students in Shanxi Province(Project No.2024KY648).
文摘In this paper,we develop an advanced computational framework for the topology optimization of orthotropic materials using meshless methods.The approximation function is established based on the improved moving least squares(IMLS)method,which enhances the efficiency and stability of the numerical solution.The numerical solution formulas are derived using the improved element-free Galerkin(IEFG)method.We introduce the solid isotropic microstructures with penalization(SIMP)model to formulate a mathematical model for topology opti-mization,which effectively penalizes intermediate densities.The optimization problem is defined with the numerical solution formula and volume fraction as constraints.The objective function,which is the minimum value of flexibility,is optimized iteratively using the optimization criterion method to update the design variables efficiently and converge to an optimal solution.Sensitivity analysis is performed using the adjoint method,which provides accurate and efficient gradient information for the optimization algorithm.We validate the proposed framework through a series of numerical examples,including clamped beam,cantilever beam,and simply supported beam made of orthotropic materials.The convergence of the objective function is demonstrated by increasing the number of iterations.Additionally,the stability of the iterative process is analyzed by examining the fluctuation law of the volume fraction.By adjusting the parameters to an appropriate range,we achieve the final optimization results of the IEFG method without the checkerboard phenomenon.Comparative studies between the Element-Free Galerkin(EFG)and IEFG methods reveal that both methods yield consistent optimization results under identical parameter settings.However,the IEFG method significantly reduces computational time,highlighting its efficiency and suitability for orthotropic materials.
基金supported by the National Natural Science Foundation of China(22171155)Natural Science Foundation of Shandong Province(ZR2022YQ07)Taishan Scholar Program(tsqn202306166).
文摘Transducing thermal energy into mechanical movements via molecular reconfigurations offers a cutting-edge approach to thermal actuating materials,which could be applied to sensors,energy harvesting and storage devices[1].Thermal expansion is a pivotal aspect in solid state chemistry,intricately intertwined with various factors such as crystal structure,chemical composition,electronic configuration,microstructure,and defects.Most materials undergo isotropic and positive thermal expansion(PTE)because of the disharmonic vibrational amplitudes of their chemical bonds.Moreover,anisotropic thermal expansion(ATE)and negative thermal expansion(NTE)are fascinating physical attributes of solids,which can originate from electronic or magnetic mechanisms,as well as through a transverse phonon mechanism in insulating lattice solids.
文摘为获得高速动车齿轮箱最优结构设计方案,针对目前国产高速动车牵引齿轮箱箱体特点及存在的问题,基于SIMP(solid isotropic material with penalization)材料插值模型及应变能理论,利用软件HyperMesh中的拓扑优化与形状优化模块对动车齿轮箱箱体结构进行拓扑优化和局部形状优化。优化结果表明:优化后的动车齿轮箱结构的最大变形和最大应力有大幅度降低,能有效提高齿轮箱箱体的刚度和强度。文中结果可为设计性能优异的国产化高速动车齿轮箱提供数据支持。
基金supported by the National High-Tech Research and Development Program of China(Grant No.2006AA06Z202)the Open Fund of the Key Laboratory of Geophysical Exploration of CNPC(Grant No.GPKL0802)+1 种基金the Graduate Student Innovation Fund of China University of Petroleum(East China)(Grant No.S2008-1)the Program for New Century Excellent Talents in University(Grant No.NCET-07-0845)
文摘To deal with the numerical dispersion problem, by combining the staggeredgrid technology with the compact finite difference scheme, we derive a compact staggered- grid finite difference scheme from the first-order velocity-stress wave equations for the transversely isotropic media. Comparing the principal truncation error terms of the compact staggered-grid finite difference scheme, the staggered-grid finite difference scheme, and the compact finite difference scheme, we analyze the approximation accuracy of these three schemes using Fourier analysis. Finally, seismic wave numerical simulation in transversely isotropic （VTI） media is performed using the three schemes. The results indicate that the compact staggered-grid finite difference scheme has the smallest truncation error, the highest accuracy, and the weakest numerical dispersion among the three schemes. In summary, the numerical modeling shows the validity of the compact staggered-grid finite difference scheme.
文摘The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.
基金Project(51475483)supported by the National Natural Science Foundation of ChinaProject(2014FJ3002)supported by Science and Technology Project of Hunan Province,ChinaProject supported by Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province,China
文摘A thickness strain model of aluminium alloy plate under plastic deformation,based on thin plate assumption was proposed.It is found that when ratio of stress fractions is constant during in-plane loading,ratios of strain components under various loading conditions are linearly related and these points of ratios form a η-η line.Under these simple loadings,strains in thickness direction can be easily calculated by the η-η line equation without integral and differential work.When the plate is under more complicated loading conditions,the thickness can be computed by the proposed optimization and piecewise calculation model.Validation computations indicate that the relative error of the results of the presented model is less than 0.75% compared with the proven theories and FE simulation.Therefore,the developed model can be applied to engineering calculation,e.g.pre-stretching analysis of aerospace aluminium thick plate,with acceptable accuracy.
文摘We have studied Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model filled with anisotropic fluid in general theory of relativity. The solutions of the field equations are obtained by using special form of deceleration parameter which gives early deceleration and late time accelerating cosmological model. The geometrical and physical aspect of the model is also studied.
基金the financial support from the National Natural Science Foundation of China(No.51204195,No.51074171 and No.51274216)
文摘A series of experiments were pertbrmed to determine rock mechanical parameters related to hydraulic fracturing of coal. The effect of confining pressure and pore pressure on the strength of coal was stt, died. Experimental results show that the coal seam in the study areas has a relatively low elastic modulus, high Poisson＇s ratio, high fragility and is easily broken and compressed. The coal seam is considered as a transversely isotropic medium, since the physical properties in the direction of bedding plane and orthogonal to the bedding plane vary markedly. Based on the generalized plane strain model, stress distribution for an arbitrarily orientated wellbore in the coal seam was determined. In a horizontal well, hydraulic fracturing was lbund to initiate in the coal seam mass due to tensile failure, or from cleats due to shear or tensile failure. For those coal seams with abundant natural cleats, hydraulic fracture initiation can be induced by any of these mechanisms. In this study, hydraulic fracture initiation criteria tbr a horizontal well in a coal seam were established.
基金supported by the "111" Project of China (Grant No. B07019)State Key Laboratory of Ocean Engineeringof Shanghai Jiao Tong University (Grant No. 1008)the Fundamental Research Funds for the Central University
文摘The unbonded flexible pipe of eight layers, in which all the layers except the carcass layer are assumed to have isotropic properties, has been analyzed. Specifically, the carcass layer shows the orthotropic characteristics. The effective elastic moduli of the carcass layer have been developed in terms of the influence of deformation to stiffness. With consideration of the effective elastic moduli, the structure can be properly analyzed. Also the relative movements of tendons and relative displacements of wires in helical armour layer have been investigated. A three-dimensional nonlinear finite element model has been presented to predict the response of flexible pipes under axial force and torque. Further, the friction and contact of interlayer have been considered. Comparison between the finite element model and experimental results obtained in literature has been given and discussed, which might provide practical and technical support for the application of unbonded flexible pipes.
基金The 111 Project under Grant No.B13024the National Natural Science Foundation of China under Grant Nos.U1134207 and 51378177the Program for New Century Excellent Talents in University under Grant No.NCET-12-0843
文摘This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot＇s poroelastic theory and the constitutive relations of the transversely isotropic medium, the dynamic governing equations of the outer and inner transversely isotropic saturated soil layers are derived. The Laplace transform is used to solve the governing equations of the outer and inner soil layers. The dynamic torsional response of the pipe pile in the frequency domain is derived utilizing 1D elastic theory and the continuous conditions at the interfaces between the pipe pile and the soils. The time domain solution is obtained by Fourier inverse transform. A parametric study is conducted to demonstrate the influence of the anisotropies of the outer and inner soil on the torsional dynamic response of the pipe pile.
