The precise computation of nanoelectromechanical switches’(NEMS)multi-physical interactions requires advanced numerical models and is a crucial part of the development of micro-and nano-systems.This paper presents a ...The precise computation of nanoelectromechanical switches’(NEMS)multi-physical interactions requires advanced numerical models and is a crucial part of the development of micro-and nano-systems.This paper presents a novel compound numerical method to study the instability of a functionally graded(FG)beam-type NEMS,considering surface elasticity effects as stated by Gurtin-Murdoch theory in an Euler-Bernoulli beam.The presented method is based on a combination of the Method of Adjoints(MoA)together with the Bézier-based multistep technique.By utilizing the MoA,a boundary value problem(BVP)is turned into an initial value problem(IVP).The resulting IVP is then solved by employing a cost-efficient multi-step process.It is demonstrated that the mentioned method can arrive at a high level of accuracy.Furthermore,it is revealed that the stability of the presented methodology is far better than that of other common multi-step methods,such as Adams-Bashforth,particularly at higher step sizes.Finally,the effects of axially functionally graded(FG)properties on the pull-in phenomenon and the main design parameters of NEMS,including the detachment length,are inspected.It was shown that the main parameter of design is the modulus of elasticity of the material,as Silver(Ag),which had better mechanical properties,showed almost a 6%improvement compared to aluminum(Al).However,by applying the correct amount of material with sturdier surface parameters,such as Aluminum(Al),at certain points,the nanobeams’functionality can be improved even further by around 1.5%.展开更多
The size-dependent elastic property of rectangular nanobeams （nanowires or nanoplates） induced by the surface elas- ticity effect is investigated by using a developed modified core-shell model. The effect of surface...The size-dependent elastic property of rectangular nanobeams （nanowires or nanoplates） induced by the surface elas- ticity effect is investigated by using a developed modified core-shell model. The effect of surface elasticity on the elastic modulus of nanobeams can be characterized by two surface related parameters, i.e., inhomogeneous degree constant and surface layer thickness. The analytical results show that the elastic modulus of the rectangular nanobeam exhibits a distinct size effect when its characteristic size reduces below 1 O0 nm. It is also found that the theoretical results calculated by a mod- ified core-shell model have more obvious advantages than those by other models （core-shell model and core-surface model） by comparing them with relevant experimental measurements and computational results, especially when the dimensions of nanostructures reduce to a few tens of nanometers.展开更多
This paper presents a novel surface model based on the Gurtin–Murdoch theory and Kerr-type differential relations,which is established and numerically simulated.By employing the principles of equivalent force and mec...This paper presents a novel surface model based on the Gurtin–Murdoch theory and Kerr-type differential relations,which is established and numerically simulated.By employing the principles of equivalent force and mechanical equilibrium,a differential equation for the contact pressure-deflection relationship between a rigid indenter and an elastic thin beam is derived.The study investigates pressure distribution within the contact area and deformation patterns outside this region.The relationship between indentation parameters is analyzed from two perspectives:clamped and simply-supported boundaries,with a detailed comparison to classical cases.The findings reveal that the normalized contact pressure and load–displacement relationship of elastic thin beams are influenced not only by the half-width ratio and indentation depth but also by the material’s surface elasticity.Similar to classical contact scenarios,an increase in surface elasticity leads to the separation of the indenter from the beam’s center when the contact half-width exceeds a certain threshold(e.g.,a ratio of 4 to the beam thickness).This results in a negative normalized contact pressure and the formation of two independent,symmetric contact strips.Notably,the relationship between displacement and contact half-width remains largely unaffected by surface elasticity,aligning with classical indentation contact results.The methodology and outcomes of this research provide a foundation for analyzing the structures and properties of nanostructured materials,offer insights for the design of future nanostructured devices,and present innovative approaches to addressing practical engineering challenges.展开更多
Atomic force microscope （AFM）, as an important instrument in micro/nano operation, has been widely used to measure sampie＇s height information. However, the so called compression effect, due to force aroused from t...Atomic force microscope （AFM）, as an important instrument in micro/nano operation, has been widely used to measure sampie＇s height information. However, the so called compression effect, due to force aroused from the contact of AFM tip with a sample surface, would result in imprecision of the surface＇s height measurement, i.e., the measured height is lower than expected. Up to now, there is not any effective and rapid method to attenuate this kind of measurement error. Thus, in this paper, an algorithm to obtain high accurate height measurement is proposed. Firstly, the concept of force curve is used to analyze the basic principle of the compression effect. Secondly, an automatic compensation method by fusing the height signal and the deflection signal is proposed. The proposed algorithm can also be used to obtain a surface elasticity image. Finally, in order to validate the proposed method, two experiments are conducted with respect to mufti-wall nano-carbon tubes on a silicon substrate and graphemes on a mica substrate.展开更多
The main goal of this paper is to present the free vibration and buckling of viscoelastic functionally graded porous(FGP)nanosheet based on nonlocal strain gradient(NSGT)and surface elasticity theories.The nanosheets ...The main goal of this paper is to present the free vibration and buckling of viscoelastic functionally graded porous(FGP)nanosheet based on nonlocal strain gradient(NSGT)and surface elasticity theories.The nanosheets are placed on a visco-Pasternak medium in a hygro-temperature environment with nonlinear rules.The viscoelastic material characteristics of nanosheets are based on Kelvin’s model.The unique point of this study is to consider the change of nonlocal and length-scale coefficients according to thickness,similar to the laws of the material properties.The Galerkin approach based on the Kirchhoff-love plate theory is applied to determine the natural frequency and critical buckling load of the viscoelastic FGP nanosheet with various boundary conditions.The accuracy of the proposed method is verified through reliable publications.The outcome of this study highlights the significant effects of the nonlocal and length-scale parameters on the vibration and buckling behaviors of viscoelastic FGP nanosheets.展开更多
Within the context of Gurtin-Murdoch surface elasticity theory,closed-form analytical solutions are derived for an isotropic elastic half-plane subjected to a concentrated/uniform surface load.Both the effects of resi...Within the context of Gurtin-Murdoch surface elasticity theory,closed-form analytical solutions are derived for an isotropic elastic half-plane subjected to a concentrated/uniform surface load.Both the effects of residual surface stress and surface elasticity are included.Airy stress function method and Fourier integral transform technique are used.The solutions are provided in a compact manner that can easily reduce to special situations that take into account either one surface effect or none at all.Numerical results indicate that surface effects generally lower the stress levels and smooth the deformation profiles in the half-plane.Surface elasticity plays a dominant role in the in-plane elastic fields for a tangentially loaded half-plane,while the effect of residual surface stress is fundamentally crucial for the out-of-plane stress and displacement when the half-plane is normally loaded.In the remaining situations,combined effects of surface elasticity and residual surface stress should be considered.The results for a concentrated surface force serve essentially as fundamental solutions of the Flamant and the half-plane Cerruti problems with surface effects.The solutions presented in this work may be helpful for understanding the contact behaviors between solids at the nanoscale.展开更多
This study is directed towards a comprehensive exploration on the deformation mechanism of the thin membrane transducer（TMT） caused by surface stress variation.We stress that the biomolecular interaction has changed...This study is directed towards a comprehensive exploration on the deformation mechanism of the thin membrane transducer（TMT） caused by surface stress variation.We stress that the biomolecular interaction has changed the magnitude of the surface stress;and when the surface stress exceeds a critical value the TMT will buckle and deform.Based upon Gurtin＇s theory of surface elasticity and principle of finite deformation,we abstract the TMT as a nanobeam with two clamped ends,and the close-formed governing equation set is derived accordingly.A computer code via the shooting method is developed to solve the presented two-point boundary value problem.In succession,the nanobeam deflection and critical parameters for buckling are quantitatively discussed.This investigation lays the theoretical foundation of TMTs;and it is also beneficial to gain deep insight into characterizing mechanical properties of nanomaterials and engineering nano-devices.展开更多
This work presents a theoretical study of contact problem. The Fourier integral transform method based on the surface elasticity theory is adopted to derive the fundamental solution for the contact problem with surfac...This work presents a theoretical study of contact problem. The Fourier integral transform method based on the surface elasticity theory is adopted to derive the fundamental solution for the contact problem with surface effects, in which both the surface tension and the surface elasticity are considered. As a special case, the deformation induced by a triangle distribution force is discussed in detail. The results are compared with those of the classical contact problem. At nano-scale, the contributions of the surface tension and the surface elasticity to the stress and displacement are not equal at the contact surface. The surface tension plays a major role to the normal stress, whereas the shear stress is mainly affected by the surface elasticity. In addition, the hardness of material depends strongly on the surface effects. This study is helpful to characterize and measure the mechanical properties of soft materials through nanoindentation.展开更多
In five-axis machining,tool orientation above a blade stream surface may lead to tool collision and a decrease in workpiece rigidity.Hence,collisionless tool orientation smoothing(TOS)becomes an important issue.On the...In five-axis machining,tool orientation above a blade stream surface may lead to tool collision and a decrease in workpiece rigidity.Hence,collisionless tool orientation smoothing(TOS)becomes an important issue.On the basis of a constant scallop height tool path,the triangular facets in the faces,vertices format are constructed from cutter contact(CC)using the Voronoi incremental algorithm.The cutter location(CL)points candidate set is represented by an oblique elliptic cone whose vertex lies at CC using NURBS envelope.Whether the CL point is above its CC is judged by the dot product between the normal vector and the point on triangulation nearest to the CL point.The curvatures at CC are obtained by fitting a moving least square(MLS) quadratic patch to the local neighborhood of a vertex and calculating eigenvectors and eigenvalues of the Hessian matrix.Triangular surface elastic energy is employed as the weight in selection from the NURBS envelope.The collision is judged by NURBS surface intersection.TOS can then be expressed by selecting a CL point for each CC point and converted into a numerical control(NC)code automatically according to the postprocessor type of the machine center.The proposed method is verified by finishing of a cryogenic turboexpander impeller of air separation equipment.展开更多
Piezoelectric semiconductors(PSCs)find extensive applications in modern smart electronic devices because of their dual properties of being piezoelectric and semiconductive.With the increasing demand for miniaturizatio...Piezoelectric semiconductors(PSCs)find extensive applications in modern smart electronic devices because of their dual properties of being piezoelectric and semiconductive.With the increasing demand for miniaturization of these devices,the performance of their components needs to be carefully designed and optimized,especially when reduced to nanosize.It has been shown that surface elastic properties play a substantial role in the mechanical performance of nanoscale materials and structures.Building on this understanding,the surface elastic effects,encompassing surface residual stress,surface membrane stiffness,and surface bending stiffness,are comprehensively taken into account to explore the electromechanical responses of a PSC nanobeam.Additionally,the flexoelectric effect on their responses is also systematically studied.The results of this work reveal that surface elastic properties predominantly influence mechanical performance,while the flexoelectric effect plays a more dominant role in electric-related quantities at the nanoscale.Notably,the significance of surface bending rigidity,which was often underestimated in the earlier literature,is demonstrated.Furthermore,owing to the flexoelectric effect,the linear distribution of electric potential and charge carriers along the length transforms into a nonlinear pattern.The distributions of electric potential and charge carriers across the cross section are also evidently impacted.Moreover,the size-dependent responses are evaluated.Our findings may provide valuable insights for optimizing electronic devices based on nanoscale PSCs.展开更多
A feasible method to improve the reliability and processing efficiency of large vibrating screen via the application of an elastic screen surface with multiple attached substructures （ESSMAS） was proposed. In the ES...A feasible method to improve the reliability and processing efficiency of large vibrating screen via the application of an elastic screen surface with multiple attached substructures （ESSMAS） was proposed. In the ESSMAS, every screen rod, with ends embedded into elastomer, is coupled to the main screen structure in a relatively flexible manner. The theoretical analysis was conducted, which consists of establishing dynamic model promoted from the fuzzy structure theory as well as calculating for the equivalent stiffness of each attached structure. According to the numerical simulation using the NEWMARK-fl integration method, this assembling pattern significantly leads to the screen surface/rod having larger vibration intensity than that of the corresponding position on screen structure, which specifically, with an averaged acceleration amplitude increasing ratio of 11.37% in theoretical analysis and 20.27% in experimental test. The experimental results, within a tolerant error, also confirm the established model and demonstrate the feasibility of ESSMAS.展开更多
A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were c...A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were coupled to the main screen structure with ends embedded into the elastomers, and the secondary robs were attached to adjacent two primary robs with elastic bands. The dynamic model of vibrating screen with NTESSMDF was established based on Lagrange's equation and the equivalent stiffnesses of the elastomer and elastic band were calculated. According to numerical simulation using the 4th order Runge-Kutta method, the vibration intensity of screen surface can be enhanced substantially with an averaged acceleration amplitude increasing ratio of 72.36%. The primary robs and secondary robs vibrate inversely in steady state, which would result in the friability of materials and avoid stoppage. The experimental results validate the dynamic characteristics with acceleration amplitude rising by62.93% on average, which demonstrates the feasibility of NTESSMDF.展开更多
A method to solve the elastic conjugate surfaces in multi-teeth meshing ispresented. In mechanical manufacturing and design, there exist a lot of problems relating toconjugate surfaces, such as three-dimensional engag...A method to solve the elastic conjugate surfaces in multi-teeth meshing ispresented. In mechanical manufacturing and design, there exist a lot of problems relating toconjugate surfaces, such as three-dimensional engagement, steel rolling and workpiece machining,which cause great effects on the quality of machining and performances of transmission. This methoddescribes relation between conjugate motion and elastic deformation in the process of mesh-in andmesh-out, and can be used to determine the profile of gear tooth by a certain given load sharing.展开更多
Removal of brittle materials in the brittle or ductile mode inevitably causes damaged or strained surface layers containing cracks, scratches or dislocations. Within elastic deformation, the arrangement of each atom c...Removal of brittle materials in the brittle or ductile mode inevitably causes damaged or strained surface layers containing cracks, scratches or dislocations. Within elastic deformation, the arrangement of each atom can be recovered back to its original position without any defects introduced. Based on surface hydroxylation and chemisorption theory, material removal mechanism of quartz glass in the elastic mode is analyzed to obtain defect-free surface. Elastic contact condition between nanoparticle and quartz glass surface is confirmed from the Hertz contact theory model. Atoms on the quartz glass surface are removed by chemical bond generated by impact reaction in the elastic mode, so no defects are generated without mechanical process. Experiment was conducted on a numerically controlled system for nanoparticle jet polishing, and one flat quartz glass was polished in the elastic mode. Results show that scratches on the sample surface are completely removed away with no mechanical defects introduced, and microroughness(Ra) is decreased from 1.23 nm to 0.47 nm. Functional group Ce — O — Si on ceria nanoparticles after polishing was detected directly and indirectly by FTIR, XRD and XPS spectra analysis from which the chemical impact reaction is validated.展开更多
This paper mainly studies the effects of surface elastic electrodes and electric loading on the nonlinear vibration of flexoelectric nanoplate.The governing equations are derived based on the von Karman type strain-di...This paper mainly studies the effects of surface elastic electrodes and electric loading on the nonlinear vibration of flexoelectric nanoplate.The governing equations are derived based on the von Karman type strain-displacement relations and the flexoelectricity theory.The nonlinear vibration equation is solved by an approximate method.Numerical results reveal that the surface elastic electrodes and the length-width ratio of flexoelectric nanoplate have a more significant effect on the nonlinear resonant frequency of simply-supported nanoplate than that of the all-edge-clamped nanoplate.Meanwhile,the effect of the graphene electrode on the nonlinear resonant frequency is more notable than that of the A1 electrode.Additionally,the applied electric loading can significantly affect the nonlinear resonant frequency of the flexoelectric nanoplate.For the nanoplates with different boundary conditions,the applied electric loading has different effects on the nonlinear resonant frequency.This study has certain research significance in the structure design and examination of the flexoelectric nanoplate with electrodes.展开更多
This paper investigates the photodetachment of the negative hydrogen ion H- near an elastic wall in a magnetic field. The magnetic field confines the perpendicular motion of the electron, which results in a real three...This paper investigates the photodetachment of the negative hydrogen ion H- near an elastic wall in a magnetic field. The magnetic field confines the perpendicular motion of the electron, which results in a real three-dimensional well for the detached electron. The analytical formulas for the cross section of the photodetachment in the three-dimensional quantum well are derived based on both the quantum approach and closed-orbit theory. The magnetic field and the elastic surface lead to two completely different modulations to the cross section of the photodetachment. The oscillation amplitude depends on the strength of the magnetic field, the ion-wall distance and the photon polarization as well. Specially, for the circularly polarized photon-induced photodetachment, the cross sections display a suppressed （E - Eth）1/2 threshold law with energy E in the vicinity above Landau energy Eta, contrasting with the （E - Eta）-1/2 threshold law in the presence of only the magnetic field. The semiclassical calculation fits the quantum result quite well, although there are still small deviations. The difference is attributed to the failure of semiclassical mechanics.展开更多
The current article discusses the heat transfer characteristics of ferromagnetic liquid over an elastic surface with the thermal radiation and non-Fourier heat flux.In most of the existing studies,the heat flux is con...The current article discusses the heat transfer characteristics of ferromagnetic liquid over an elastic surface with the thermal radiation and non-Fourier heat flux.In most of the existing studies,the heat flux is considered as constant,but whereas we incorporated the non-Fourier flux to get the exact performance of the flow.Also,we excluded the PWT and PHF cases to control the boundary layer of the flow.The governing equations related to our contemplate are changed into non-linear ordinary differential equations(ODE’s)by utilizing appropriate similarity changes,which are at the point enlightened by Runge–Kutta based shooting approach.The equations are broken down concerning boundary conditions and to be explained prescribed wall temperature(PWT)and prescribed heat flux(PHF)cases.The impacts of diverse non-dimensional physical parameters on velocity and temperature profiles are laid out graphically.Also,the assortment of skin friction and local Nusselt number for both PWT and PHF cases for various assessments of non-dimensional parameters have been sorted out.Towards the wrap-up of the examination,we suspect that the friction factor coefficient is higher in the PWT case compared to the PHF case.This result helps to conclude that the flux conditions are useful for cooling applications.展开更多
A flew numerical method for constructing a pressure distribution to calculate surface elastic deformationcaused by normal contact pressure is developed in this paper. The pressure distribution over one of nonequidista...A flew numerical method for constructing a pressure distribution to calculate surface elastic deformationcaused by normal contact pressure is developed in this paper. The pressure distribution over one of nonequidistantrectangles is fitted by an approximate tangent plane(ATP), which is formed by five pressure samples. Because thepressure distribution could be expressed as an one order linear polynomial, the iterative expression of elasticdeformation deduced by this method is simple, and the numerical accuracy is higher.展开更多
In the present paper, we study the torsional wave propagation along a micro-tube with clog- ging attached to its inner surface. The clogging accumulated on the inner surface of the tube is modeled as an ＂elastic memb...In the present paper, we study the torsional wave propagation along a micro-tube with clog- ging attached to its inner surface. The clogging accumulated on the inner surface of the tube is modeled as an ＂elastic membrane＂ which is described by the so-called surface elasticity. A power-series solution is particularly developed for the lowest order of wave propagation. The dispersion diagram of the lowest-order wave is numerically presented with the surface （clogging） effect.展开更多
Analysis of the mechanical behavior of nanos- tructures has been very challenging. Surface energy and non- local elasticity of materials have been incorporated into the traditional continuum analysis to create modifie...Analysis of the mechanical behavior of nanos- tructures has been very challenging. Surface energy and non- local elasticity of materials have been incorporated into the traditional continuum analysis to create modified continuum mechanics models. This paper reviews recent advancements in the applications of such modified continuum models in nanostructures such as nanotubes, nanowires, nanobeams, graphenes, and nanoplates. A variety of models for these nanostructures under static and dynamic loadings are men- tioned and reviewed. Applications of surface energy and nonlocal elasticity in analysis of piezoelectric nanomateri- als are also mentioned. This paper provides a comprehensive introduction of the development of this area and inspires fur- ther applications of modified continuum models in modeling nanomaterials and nanostructures.展开更多
文摘The precise computation of nanoelectromechanical switches’(NEMS)multi-physical interactions requires advanced numerical models and is a crucial part of the development of micro-and nano-systems.This paper presents a novel compound numerical method to study the instability of a functionally graded(FG)beam-type NEMS,considering surface elasticity effects as stated by Gurtin-Murdoch theory in an Euler-Bernoulli beam.The presented method is based on a combination of the Method of Adjoints(MoA)together with the Bézier-based multistep technique.By utilizing the MoA,a boundary value problem(BVP)is turned into an initial value problem(IVP).The resulting IVP is then solved by employing a cost-efficient multi-step process.It is demonstrated that the mentioned method can arrive at a high level of accuracy.Furthermore,it is revealed that the stability of the presented methodology is far better than that of other common multi-step methods,such as Adams-Bashforth,particularly at higher step sizes.Finally,the effects of axially functionally graded(FG)properties on the pull-in phenomenon and the main design parameters of NEMS,including the detachment length,are inspected.It was shown that the main parameter of design is the modulus of elasticity of the material,as Silver(Ag),which had better mechanical properties,showed almost a 6%improvement compared to aluminum(Al).However,by applying the correct amount of material with sturdier surface parameters,such as Aluminum(Al),at certain points,the nanobeams’functionality can be improved even further by around 1.5%.
基金Project supported by the National Natural Science Foundation of China (Grant No.11072104)the Scientific Research Program for Higher Schools of Inner Mongolia (Grant No.NJZY13013)
文摘The size-dependent elastic property of rectangular nanobeams （nanowires or nanoplates） induced by the surface elas- ticity effect is investigated by using a developed modified core-shell model. The effect of surface elasticity on the elastic modulus of nanobeams can be characterized by two surface related parameters, i.e., inhomogeneous degree constant and surface layer thickness. The analytical results show that the elastic modulus of the rectangular nanobeam exhibits a distinct size effect when its characteristic size reduces below 1 O0 nm. It is also found that the theoretical results calculated by a mod- ified core-shell model have more obvious advantages than those by other models （core-shell model and core-surface model） by comparing them with relevant experimental measurements and computational results, especially when the dimensions of nanostructures reduce to a few tens of nanometers.
基金Natural Science Foundation of Gansu Province,24JRRA182,Liyuan Wang,25JRRA802,zhiying ou。
文摘This paper presents a novel surface model based on the Gurtin–Murdoch theory and Kerr-type differential relations,which is established and numerically simulated.By employing the principles of equivalent force and mechanical equilibrium,a differential equation for the contact pressure-deflection relationship between a rigid indenter and an elastic thin beam is derived.The study investigates pressure distribution within the contact area and deformation patterns outside this region.The relationship between indentation parameters is analyzed from two perspectives:clamped and simply-supported boundaries,with a detailed comparison to classical cases.The findings reveal that the normalized contact pressure and load–displacement relationship of elastic thin beams are influenced not only by the half-width ratio and indentation depth but also by the material’s surface elasticity.Similar to classical contact scenarios,an increase in surface elasticity leads to the separation of the indenter from the beam’s center when the contact half-width exceeds a certain threshold(e.g.,a ratio of 4 to the beam thickness).This results in a negative normalized contact pressure and the formation of two independent,symmetric contact strips.Notably,the relationship between displacement and contact half-width remains largely unaffected by surface elasticity,aligning with classical indentation contact results.The methodology and outcomes of this research provide a foundation for analyzing the structures and properties of nanostructured materials,offer insights for the design of future nanostructured devices,and present innovative approaches to addressing practical engineering challenges.
基金supported by the CAS FEA International Partnership Program for Creative Research Teams
文摘Atomic force microscope （AFM）, as an important instrument in micro/nano operation, has been widely used to measure sampie＇s height information. However, the so called compression effect, due to force aroused from the contact of AFM tip with a sample surface, would result in imprecision of the surface＇s height measurement, i.e., the measured height is lower than expected. Up to now, there is not any effective and rapid method to attenuate this kind of measurement error. Thus, in this paper, an algorithm to obtain high accurate height measurement is proposed. Firstly, the concept of force curve is used to analyze the basic principle of the compression effect. Secondly, an automatic compensation method by fusing the height signal and the deflection signal is proposed. The proposed algorithm can also be used to obtain a surface elasticity image. Finally, in order to validate the proposed method, two experiments are conducted with respect to mufti-wall nano-carbon tubes on a silicon substrate and graphemes on a mica substrate.
文摘The main goal of this paper is to present the free vibration and buckling of viscoelastic functionally graded porous(FGP)nanosheet based on nonlocal strain gradient(NSGT)and surface elasticity theories.The nanosheets are placed on a visco-Pasternak medium in a hygro-temperature environment with nonlinear rules.The viscoelastic material characteristics of nanosheets are based on Kelvin’s model.The unique point of this study is to consider the change of nonlocal and length-scale coefficients according to thickness,similar to the laws of the material properties.The Galerkin approach based on the Kirchhoff-love plate theory is applied to determine the natural frequency and critical buckling load of the viscoelastic FGP nanosheet with various boundary conditions.The accuracy of the proposed method is verified through reliable publications.The outcome of this study highlights the significant effects of the nonlocal and length-scale parameters on the vibration and buckling behaviors of viscoelastic FGP nanosheets.
基金supported by the National Natural Science Foundation of China(12272126,12272127)the Doctoral Fund of HPU(B2015-64).
文摘Within the context of Gurtin-Murdoch surface elasticity theory,closed-form analytical solutions are derived for an isotropic elastic half-plane subjected to a concentrated/uniform surface load.Both the effects of residual surface stress and surface elasticity are included.Airy stress function method and Fourier integral transform technique are used.The solutions are provided in a compact manner that can easily reduce to special situations that take into account either one surface effect or none at all.Numerical results indicate that surface effects generally lower the stress levels and smooth the deformation profiles in the half-plane.Surface elasticity plays a dominant role in the in-plane elastic fields for a tangentially loaded half-plane,while the effect of residual surface stress is fundamentally crucial for the out-of-plane stress and displacement when the half-plane is normally loaded.In the remaining situations,combined effects of surface elasticity and residual surface stress should be considered.The results for a concentrated surface force serve essentially as fundamental solutions of the Flamant and the half-plane Cerruti problems with surface effects.The solutions presented in this work may be helpful for understanding the contact behaviors between solids at the nanoscale.
基金Project supported by National Natural Science Foundation of China(Nos.11272357 and 11320003)the Natural Science Fund for Distinguished Young Scholar of Shandong Province(No.JQ201302)
文摘This study is directed towards a comprehensive exploration on the deformation mechanism of the thin membrane transducer（TMT） caused by surface stress variation.We stress that the biomolecular interaction has changed the magnitude of the surface stress;and when the surface stress exceeds a critical value the TMT will buckle and deform.Based upon Gurtin＇s theory of surface elasticity and principle of finite deformation,we abstract the TMT as a nanobeam with two clamped ends,and the close-formed governing equation set is derived accordingly.A computer code via the shooting method is developed to solve the presented two-point boundary value problem.In succession,the nanobeam deflection and critical parameters for buckling are quantitatively discussed.This investigation lays the theoretical foundation of TMTs;and it is also beneficial to gain deep insight into characterizing mechanical properties of nanomaterials and engineering nano-devices.
文摘This work presents a theoretical study of contact problem. The Fourier integral transform method based on the surface elasticity theory is adopted to derive the fundamental solution for the contact problem with surface effects, in which both the surface tension and the surface elasticity are considered. As a special case, the deformation induced by a triangle distribution force is discussed in detail. The results are compared with those of the classical contact problem. At nano-scale, the contributions of the surface tension and the surface elasticity to the stress and displacement are not equal at the contact surface. The surface tension plays a major role to the normal stress, whereas the shear stress is mainly affected by the surface elasticity. In addition, the hardness of material depends strongly on the surface effects. This study is helpful to characterize and measure the mechanical properties of soft materials through nanoindentation.
基金Project supported by the National Basic Research Program (973) of China (No. 2011CB706506)the National Science and Technology Major Project of China (Nos. 2011ZX04014-131 and 2012ZX04010 011)the National Science Foundation for Young Scholars of China (No. 51005204)
文摘In five-axis machining,tool orientation above a blade stream surface may lead to tool collision and a decrease in workpiece rigidity.Hence,collisionless tool orientation smoothing(TOS)becomes an important issue.On the basis of a constant scallop height tool path,the triangular facets in the faces,vertices format are constructed from cutter contact(CC)using the Voronoi incremental algorithm.The cutter location(CL)points candidate set is represented by an oblique elliptic cone whose vertex lies at CC using NURBS envelope.Whether the CL point is above its CC is judged by the dot product between the normal vector and the point on triangulation nearest to the CL point.The curvatures at CC are obtained by fitting a moving least square(MLS) quadratic patch to the local neighborhood of a vertex and calculating eigenvectors and eigenvalues of the Hessian matrix.Triangular surface elastic energy is employed as the weight in selection from the NURBS envelope.The collision is judged by NURBS surface intersection.TOS can then be expressed by selecting a CL point for each CC point and converted into a numerical control(NC)code automatically according to the postprocessor type of the machine center.The proposed method is verified by finishing of a cryogenic turboexpander impeller of air separation equipment.
基金support of the National Natural Science Foundation of China[Grant number:11702076]the Natural Science Foundation of Anhui Province[Grant numbers:2208085MA17 and 2208085ME129].
文摘Piezoelectric semiconductors(PSCs)find extensive applications in modern smart electronic devices because of their dual properties of being piezoelectric and semiconductive.With the increasing demand for miniaturization of these devices,the performance of their components needs to be carefully designed and optimized,especially when reduced to nanosize.It has been shown that surface elastic properties play a substantial role in the mechanical performance of nanoscale materials and structures.Building on this understanding,the surface elastic effects,encompassing surface residual stress,surface membrane stiffness,and surface bending stiffness,are comprehensively taken into account to explore the electromechanical responses of a PSC nanobeam.Additionally,the flexoelectric effect on their responses is also systematically studied.The results of this work reveal that surface elastic properties predominantly influence mechanical performance,while the flexoelectric effect plays a more dominant role in electric-related quantities at the nanoscale.Notably,the significance of surface bending rigidity,which was often underestimated in the earlier literature,is demonstrated.Furthermore,owing to the flexoelectric effect,the linear distribution of electric potential and charge carriers along the length transforms into a nonlinear pattern.The distributions of electric potential and charge carriers across the cross section are also evidently impacted.Moreover,the size-dependent responses are evaluated.Our findings may provide valuable insights for optimizing electronic devices based on nanoscale PSCs.
基金Projects(50574091,50774084) supported by the National Natural Science Foundation of China
文摘A feasible method to improve the reliability and processing efficiency of large vibrating screen via the application of an elastic screen surface with multiple attached substructures （ESSMAS） was proposed. In the ESSMAS, every screen rod, with ends embedded into elastomer, is coupled to the main screen structure in a relatively flexible manner. The theoretical analysis was conducted, which consists of establishing dynamic model promoted from the fuzzy structure theory as well as calculating for the equivalent stiffness of each attached structure. According to the numerical simulation using the NEWMARK-fl integration method, this assembling pattern significantly leads to the screen surface/rod having larger vibration intensity than that of the corresponding position on screen structure, which specifically, with an averaged acceleration amplitude increasing ratio of 11.37% in theoretical analysis and 20.27% in experimental test. The experimental results, within a tolerant error, also confirm the established model and demonstrate the feasibility of ESSMAS.
基金Project(51221462)supported by the National Natural Science Foundation of China for Innovative Research GroupProject(20120095110001)supported by the Doctoral Fund of Ministry of Education of China+1 种基金Project supported by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,ChinaProject(CXJJ201303)supported by the Innovation Foundation of Xuyi Research and Development Center of Mining Equipment and Materials,China University of Mining and Technology,China
文摘A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were coupled to the main screen structure with ends embedded into the elastomers, and the secondary robs were attached to adjacent two primary robs with elastic bands. The dynamic model of vibrating screen with NTESSMDF was established based on Lagrange's equation and the equivalent stiffnesses of the elastomer and elastic band were calculated. According to numerical simulation using the 4th order Runge-Kutta method, the vibration intensity of screen surface can be enhanced substantially with an averaged acceleration amplitude increasing ratio of 72.36%. The primary robs and secondary robs vibrate inversely in steady state, which would result in the friability of materials and avoid stoppage. The experimental results validate the dynamic characteristics with acceleration amplitude rising by62.93% on average, which demonstrates the feasibility of NTESSMDF.
基金This project is supported by National Key Project of China (No. PD9521903) , National Natural Science Foundation of China (No. 50075031) and National Key Laboratory of Mechanical Transmission of China.
文摘A method to solve the elastic conjugate surfaces in multi-teeth meshing ispresented. In mechanical manufacturing and design, there exist a lot of problems relating toconjugate surfaces, such as three-dimensional engagement, steel rolling and workpiece machining,which cause great effects on the quality of machining and performances of transmission. This methoddescribes relation between conjugate motion and elastic deformation in the process of mesh-in andmesh-out, and can be used to determine the profile of gear tooth by a certain given load sharing.
基金Projects(51305450,51275521)supported by the National Natural Science Foundation of China
文摘Removal of brittle materials in the brittle or ductile mode inevitably causes damaged or strained surface layers containing cracks, scratches or dislocations. Within elastic deformation, the arrangement of each atom can be recovered back to its original position without any defects introduced. Based on surface hydroxylation and chemisorption theory, material removal mechanism of quartz glass in the elastic mode is analyzed to obtain defect-free surface. Elastic contact condition between nanoparticle and quartz glass surface is confirmed from the Hertz contact theory model. Atoms on the quartz glass surface are removed by chemical bond generated by impact reaction in the elastic mode, so no defects are generated without mechanical process. Experiment was conducted on a numerically controlled system for nanoparticle jet polishing, and one flat quartz glass was polished in the elastic mode. Results show that scratches on the sample surface are completely removed away with no mechanical defects introduced, and microroughness(Ra) is decreased from 1.23 nm to 0.47 nm. Functional group Ce — O — Si on ceria nanoparticles after polishing was detected directly and indirectly by FTIR, XRD and XPS spectra analysis from which the chemical impact reaction is validated.
文摘This paper mainly studies the effects of surface elastic electrodes and electric loading on the nonlinear vibration of flexoelectric nanoplate.The governing equations are derived based on the von Karman type strain-displacement relations and the flexoelectricity theory.The nonlinear vibration equation is solved by an approximate method.Numerical results reveal that the surface elastic electrodes and the length-width ratio of flexoelectric nanoplate have a more significant effect on the nonlinear resonant frequency of simply-supported nanoplate than that of the all-edge-clamped nanoplate.Meanwhile,the effect of the graphene electrode on the nonlinear resonant frequency is more notable than that of the A1 electrode.Additionally,the applied electric loading can significantly affect the nonlinear resonant frequency of the flexoelectric nanoplate.For the nanoplates with different boundary conditions,the applied electric loading has different effects on the nonlinear resonant frequency.This study has certain research significance in the structure design and examination of the flexoelectric nanoplate with electrodes.
基金supported by the National Natural Science Foundation of China (Grant No. 10774162)
文摘This paper investigates the photodetachment of the negative hydrogen ion H- near an elastic wall in a magnetic field. The magnetic field confines the perpendicular motion of the electron, which results in a real three-dimensional well for the detached electron. The analytical formulas for the cross section of the photodetachment in the three-dimensional quantum well are derived based on both the quantum approach and closed-orbit theory. The magnetic field and the elastic surface lead to two completely different modulations to the cross section of the photodetachment. The oscillation amplitude depends on the strength of the magnetic field, the ion-wall distance and the photon polarization as well. Specially, for the circularly polarized photon-induced photodetachment, the cross sections display a suppressed （E - Eth）1/2 threshold law with energy E in the vicinity above Landau energy Eta, contrasting with the （E - Eta）-1/2 threshold law in the presence of only the magnetic field. The semiclassical calculation fits the quantum result quite well, although there are still small deviations. The difference is attributed to the failure of semiclassical mechanics.
文摘The current article discusses the heat transfer characteristics of ferromagnetic liquid over an elastic surface with the thermal radiation and non-Fourier heat flux.In most of the existing studies,the heat flux is considered as constant,but whereas we incorporated the non-Fourier flux to get the exact performance of the flow.Also,we excluded the PWT and PHF cases to control the boundary layer of the flow.The governing equations related to our contemplate are changed into non-linear ordinary differential equations(ODE’s)by utilizing appropriate similarity changes,which are at the point enlightened by Runge–Kutta based shooting approach.The equations are broken down concerning boundary conditions and to be explained prescribed wall temperature(PWT)and prescribed heat flux(PHF)cases.The impacts of diverse non-dimensional physical parameters on velocity and temperature profiles are laid out graphically.Also,the assortment of skin friction and local Nusselt number for both PWT and PHF cases for various assessments of non-dimensional parameters have been sorted out.Towards the wrap-up of the examination,we suspect that the friction factor coefficient is higher in the PWT case compared to the PHF case.This result helps to conclude that the flux conditions are useful for cooling applications.
文摘A flew numerical method for constructing a pressure distribution to calculate surface elastic deformationcaused by normal contact pressure is developed in this paper. The pressure distribution over one of nonequidistantrectangles is fitted by an approximate tangent plane(ATP), which is formed by five pressure samples. Because thepressure distribution could be expressed as an one order linear polynomial, the iterative expression of elasticdeformation deduced by this method is simple, and the numerical accuracy is higher.
文摘In the present paper, we study the torsional wave propagation along a micro-tube with clog- ging attached to its inner surface. The clogging accumulated on the inner surface of the tube is modeled as an ＂elastic membrane＂ which is described by the so-called surface elasticity. A power-series solution is particularly developed for the lowest order of wave propagation. The dispersion diagram of the lowest-order wave is numerically presented with the surface （clogging） effect.
基金project was supported the National Natural Science Foundation of China (Grant 11372086)the Natural Science Foundation of Guangdong Province of China (Grant 2014A030313696)
文摘Analysis of the mechanical behavior of nanos- tructures has been very challenging. Surface energy and non- local elasticity of materials have been incorporated into the traditional continuum analysis to create modified continuum mechanics models. This paper reviews recent advancements in the applications of such modified continuum models in nanostructures such as nanotubes, nanowires, nanobeams, graphenes, and nanoplates. A variety of models for these nanostructures under static and dynamic loadings are men- tioned and reviewed. Applications of surface energy and nonlocal elasticity in analysis of piezoelectric nanomateri- als are also mentioned. This paper provides a comprehensive introduction of the development of this area and inspires fur- ther applications of modified continuum models in modeling nanomaterials and nanostructures.
