The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification metho...The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification method for the TDSS based on vibration response analysis.Based on the Johnson-Cook constitutive model and failure criteria,the ballistic impact finite element simulation model is established,which is verified by the ballistic impact experiment of the Tail Drive Shaft(TDS).Considering the ballistic impact excitation force,the dynamic model of the TDSS with ballistic impact is established,which is verified by finite element commercial software.If a bullet hits the TDS,the bending vibration displacement increases sharply at a certain moment and then significantly increases but remains stable.Meanwhile,the critical speed component appears in the frequency-domain response of bending vibration,and then the speed component significantly increases but remains stable.What's more,the axis trajectory exhibits a sudden,large-scale,and irregular whirling motion at a certain moment,followed by a significant increase but remains stable.Furthermore,if the axial vibration response is small,the bullet core shooting should be considered vertically or at a small incident angle,otherwise,it should be considered at a large incident angle.展开更多
A new quadrilateral finite element IQ4 is developed for the free vibration of carbon nanotube-reinforced composite(CNTRC)perforated plates with a central cutout.By enriching the membrane part and incorporating a proje...A new quadrilateral finite element IQ4 is developed for the free vibration of carbon nanotube-reinforced composite(CNTRC)perforated plates with a central cutout.By enriching the membrane part and incorporating a projected shear technique,the IQ4 element is proposed to address the known limitations of the standard Q4 element,such as shear locking and limited consistency in the coupling ofmembrane-bending components.The proposed element is formulated within the FSDT-based framework and assessed through benchmark tests to verify its convergence and accuracy.The governing equations are obtained via theweak formofHamilton’s principle.Particular attention is given to the influence of carbon nanotube volume fraction,distribution patterns,and boundary conditions on the fundamental frequency response of CNTRC plates with cutouts.In addition,a parametric study is conducted to assess the influence of cutout geometric configuration,shape,and size ratios on the vibrational response of the CNTRC plate.The numerical results demonstrate that the formulated IQ4 element provides stable and accurate estimations of natural frequencies,even in the presence of a cutout and the coupled effects of the non-uniform distribution of reinforcement through the plate thickness.The developed formulation is expected to contribute to the structural design and optimization of advanced lightweight systems,particularly in aerospace and mechanical engineering applications.展开更多
The vibrational frequency analysis of finite elastic tube filled with compressible viscous fluid has received plenty of attention in recent years. To apply frequency analysis to defect detection for example, it is nec...The vibrational frequency analysis of finite elastic tube filled with compressible viscous fluid has received plenty of attention in recent years. To apply frequency analysis to defect detection for example, it is necessary to investigate the vibrational behavior under appropriate boundary conditions. In this paper, we present a detailed theoretical study of the three dimensional modal analysis of compressible fluid within an elastic cylinder. The dispersion equations of flexura], torsional and longitudinal modes are derived by elastodynamic theory and the unsteady Stokes equation. The symbolic software Mathematica is used in order to find the coupled vibration frequencies. The dispersion equation is deduced and analytically solved. The finite element results are compared with the present method for validation and an acceptable match between them are obtained.展开更多
We present the numerical simulation results of a model granular assembly formed by spherical particles with tIertzian interaction subjected to a simple shear in the athermal quasi-static limit. The stress-strain curve...We present the numerical simulation results of a model granular assembly formed by spherical particles with tIertzian interaction subjected to a simple shear in the athermal quasi-static limit. The stress-strain curve is shown to separate into smooth, elastic branches followed by a subsequent plastic event. Mode analysis shows that the lowest-frequency vibrational mode is more localized, and eigenvalues and participation ratios of low- frequency modes exhibit similar power-law behavior as the system approaches plastic instability, indicating that the nature of plastic events in the granular system is also a saddle node bifurcation. The analysis of projection and spatial structure shows that over 75% contributions to the non-affine displacement field at a plastic instability come from the lowest-frequency mode, and the lowest-frequency mode is strongly spatially correlated with local plastic rearrangements, inferring that the lowest-frequency mode could be used as a predictor for future plastic rearrangements in the disordered system jammed marginally.展开更多
It is well known that boron exists as polyborate anions in aqueous solution.Boron atom can coordinates to three or four oxygen atoms and borate can exist as not only the monomer but also the polymer.The polymerization
The vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4 000~400and 4 000~400cm-1 respectively,for N-[4-[1-hydroxy-2-[(1-methyl ethyl)amino]ethyl]phenyl]methane sulfona...The vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4 000~400and 4 000~400cm-1 respectively,for N-[4-[1-hydroxy-2-[(1-methyl ethyl)amino]ethyl]phenyl]methane sulfonamide(HPAEPMS)molecule.Theoretical calculations were performed by ab initio Density Functional Theory(DFT)method using 6-31G(d,p)basis set.The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution(PED).The results of the calculations were applied to simulated spectra of the title compound,which show excellent agreement.展开更多
Argyris'natural approach is employed to analyze vibranon mode of multilayered composite plates and shells.The shells can be either symmetric or unsymmetric.The spectral transformation Lanczos method with selective...Argyris'natural approach is employed to analyze vibranon mode of multilayered composite plates and shells.The shells can be either symmetric or unsymmetric.The spectral transformation Lanczos method with selective or fully orthogonalization is used to solve the eigenvalue problem of pencil(K,M).Some problems on shift,which is essential for the success of this method, are discussed.A few numerical examples, including composite square plates and conical shells,are presented. The results show that the method in this paper is efficient and reliable for vibration mode analysis.展开更多
The dynamics of quantum entanglement described by the yon Neumann entropy is studied for the localized states of Fermi-resonance coupling vibrations in molecule CS2, where the interacting energy between the stretching...The dynamics of quantum entanglement described by the yon Neumann entropy is studied for the localized states of Fermi-resonance coupling vibrations in molecule CS2, where the interacting energy between the stretching and the bending modes is considered to establish a connection between entanglement and energy. It is shown that entanglement reveals dominant anti-correlation with the interacting energy for the stretch-localized state, while that exhibits dominantly positive correlation for the bend-localized state. The entanglement and the energy for the dislocalized states are discussed as well. Those are useful for molecular quantum computing and quantum information in high dimensional states.展开更多
This paper studies the coupling mechanism between the nonlinear stiffness and damping coefficients of Active Elastic Support/Dry Friction Damper(AESDFD)and rotor system.First,parameters for evaluating the vibration re...This paper studies the coupling mechanism between the nonlinear stiffness and damping coefficients of Active Elastic Support/Dry Friction Damper(AESDFD)and rotor system.First,parameters for evaluating the vibration reduction characteristics are proposed to facilitate the design of the AESDFD.To achieve this,the nonlinear friction force is initially represented as equivalent stiffness and damping coefficients,based on the ball-plate friction model.Second,three evaluation parameters—optimal slipping displacement,loss factor,and controllability—are proposed to reveal the vibration reduction characteristics of the AESDFD,alongside determining the optimal normal force.Subsequently,the finite element method,in conjunction with the ball-plate friction model,is introduced to formulate the governing equation of a low-pressure rotor system equipped with AESDFDs.The steady-state responses of the AESDFDs-rotor system are solved using the harmonic balance method combined with an efficient iteration method.Finally,the solutions are validated on the AESDFDs-rotor system both numerically and experimentally.The results indicate that controllability effectively assesses the vibration reduction performance of the AESDFD and is relatively insensitive to variations in low normal force.Away from the critical speed,the AESDFD suppresses vibration by altering the resonance position of the rotor system through its stiffness coefficient.Near the critical speed,vibration reduction is achieved primarily through energy dissipation by the damping coefficient.If the loss factor is less than one,the stiffness coefficient can diminish the vibration reduction effect of the damping coefficient.Notably,the optimal normal force of the AESDFD achieves optimal vibration reduction effect.This study reveals that changes in rotor system unbalance do not affect the vibration reduction characteristics of the AESDFD,with the same upper limit to the vibration reduction effect of the AESDFD.展开更多
The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction...The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction system,making it essential for ensuring the safety of this emerging towing-out mode.In this paper,the frequency evolutionary tendency of the traction system is studied and obtained considering the variation of nonlinear contact stiffness for the first time.A novel modal analysis method,based on a derived nonlinear contact relationship,is proposed to investigate the vibration characteristics for mechanical system.Frequency veering and mode exchange phenomena in the low-order modes are observed due to the variation of nonlinear contact stiffness.These findings are further validated by the experimental results of a scaled-down model.In addition,it is also found that the veering critical point will be shifted with the external loads.The study provides valuable insights into the vibration characteristics and frequency veering behavior of similar mechanism-based systems,such as towbarless traction system,and has important implications for improving their design and operational performance.展开更多
Skin panels on supersonic vehicles are subjected to aero-thermo-acoustic loads,resulting in a well-known multi-physics dynamic problem.The high-frequency dynamic response of these panels significantly impacts the stru...Skin panels on supersonic vehicles are subjected to aero-thermo-acoustic loads,resulting in a well-known multi-physics dynamic problem.The high-frequency dynamic response of these panels significantly impacts the structural safety of supersonic vehicles,but it has been rarely investigated.Given that existing methods are inefficient for high-frequency dynamic analysis in multi-physics fields,the present work addresses this challenge by proposing a Stochastic Energy Finite Element Method(SEFEM).SEFEM uses energy density instead of displacement to describe the dynamic response,thereby significantly enhancing its efficiency.In SEFEM,the effects of aerodynamic and thermal loads on the energy propagation characteristics are studied analytically and incorporated into the energy density governing equation.These effects are also considered when calculating the input power generated by the acoustic load,and two effective approaches named Frequency Response Function Method(FRFM)and Mechanical Impedance Method(MIM)are developed accordingly and integrated into SEFEM.The good accuracy,applicability,and high efficiency of the proposed SEFEM are demonstrated through numerical simulations performed on a two-dimensional panel under aero-thermoacoustic loads.Additionally,the effects and underlying mechanisms of aero-thermo-acoustic loads on the high-frequency response are explored.This work not only presents an efficient approach for predicting high-frequency dynamic response of panels subjected to aero-thermo-acoustic loads,but also provides insights into the high-frequency dynamic characteristics in multi-physics fields.展开更多
This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FG...This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP)materials.The strain potential and kinetic energies of each beam along with the work done by the external force are calculated.Additionally,a higher-order beam element is introduced to derive stiffness and mass matrices,along with the force vector.The curved and straight beams are discretized,and their assembled stiffness,mass matrices,and force vectors,are obtained.Continuity conditions at the joints are used to derive the total matrices of the entire structure.Subsequently,the natural frequencies and transient response of the system are determined.The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANSYS,demonstrating excellent agreement.Furthermore,a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.展开更多
A U(2) algebraic model is introduced for the spectrum of a molecule XY4, where the interactions between the stretch and bend modes are described by Td symmetric Fermi resonance terms. The presented algebraic model in ...A U(2) algebraic model is introduced for the spectrum of a molecule XY4, where the interactions between the stretch and bend modes are described by Td symmetric Fermi resonance terms. The presented algebraic model in a limit corresponds to another model in recent literature. The vibrational spectrum of methane (CH4) measured recently with modern spectroscopy techniques is employed to test those models. The obtained standard deviation between the observed and the calculated vibrational energy levels in the algebraic model is smaller than that in the corresponding model.展开更多
Shape control and free vibration analysis of piezolaminated plates subjected to electro mechanical loading are evaluated using finite element method. First order shear deformation theory is employed in the analysis. B...Shape control and free vibration analysis of piezolaminated plates subjected to electro mechanical loading are evaluated using finite element method. First order shear deformation theory is employed in the analysis. Both extensions as well as shear actuators are considered for piezolaminated plates. Rectangular four node isoparametric element is used in the finite element formulation. Variation of temperature is neglected for the orthotropic layers of the laminate and for piezolayer. Annular circular plates and rectangular plates with piezoelectric layers mounted and/or integrated are analysed for various parameters. Numerical results are presented for varying the actuator voltage for annular plates with different thicknesses of piezo patches. In case of rectangular plate shear actuator is considered for vibration analysis.展开更多
Vibrations in aircraft hydraulic pipeline system,due to multi-source excitation of high fluid pressure fluctuation and serious vibration environment of airframe,can cause the pipeline system vibration failures through...Vibrations in aircraft hydraulic pipeline system,due to multi-source excitation of high fluid pressure fluctuation and serious vibration environment of airframe,can cause the pipeline system vibration failures through overload in engineering field.Controlling the vibrations in hydraulic pipeline is a challenging work to ensure the flight safety of aircraft.The common vibration control technologies have been demonstrated to be effective in typical structures such as aerospace structures,shipbuilding structures,marine offshore structures,motor structures,etc.However,there are few research literatures on vibration control strategies of aircraft hydraulic pipeline.Combining with the development trend of aircraft hydraulic pipeline system and the requirement of vibration control technologies,this paper provides a detailed review on the current vibration control technologies in hydraulic pipeline system.A review of the general approaches following the passive and active control technologies are presented,which are including optimal layout technique of pipeline and clamps,constrained layer damping technique,vibration absorber technique,hydraulic hose technique,optimal pump structure technique,and active vibration control technique of pipeline system.Finally,some suggestions for the application of vibration control technologies in engineering field are given.展开更多
A bimorph piezoelectric beam with periodically variable cross-sections is used for the vibration energy harvesting. The effects of two geometrical parameters on the first band gap of this periodic beam are investigate...A bimorph piezoelectric beam with periodically variable cross-sections is used for the vibration energy harvesting. The effects of two geometrical parameters on the first band gap of this periodic beam are investigated by the generalized differential quadrature rule （GDQR） method. The GDQR method is also used to calculate the forced vibration response of the beam and voltage of each piezoelectric layer when the beam is subject to a sinusoidal base excitation. Results obtained from the analytical method are compared with those obtained from the finite element simulation with ANSYS, and good agreement is found. The voltage output of this periodic beam over its first band gap is calculated and compared with the voltage output of the uniform piezoelectric beam. It is concluded that this periodic beam has three advantages over the uniform piezoelectric beam, i.e., generating more voltage outputs over a wide frequency range, absorbing vibration, and being less weight.展开更多
The design strategies for powertrain mounting systems play an important role in the reduction of vehicular vibration and noise. As stiffness and damping elements connecting the transmission system and vehicle body, th...The design strategies for powertrain mounting systems play an important role in the reduction of vehicular vibration and noise. As stiffness and damping elements connecting the transmission system and vehicle body, the rubber mount exhibits better vibration isolation performance than the rigid connection. This paper presents a complete design process of the mounting system, including the vibration decoupling, vibration simulation analysis, topology optimization, and experimental verification. Based on the 6?degrees?of?freedom vibration coupling model of the powertrain mounting system, an optimization algorithm is used to extract the best design parameters of each mount, thus rendering the mounting system fully decoupled and the natural frequency well configured, and the optimal parameters are used to design the mounting system. Subsequently, vibration simulation analysis is applied to the mounting system, considering both transmission and road excitations. According to the results of finite element analysis, the topological structure of the metal frame of the front mount is optimized to improve the strength and dynamic characteristics of the mounting system. Finally, the vibration bench test is used to verify the availability of the optimization design with the analysis of acceleration response and vibration transmissibility of the mounting system. The results show that the vibration isolation performance of the mounting system can be improved effectively using the vibration optimal decoupling method, and the structural modification of the metal frame can well promote the dynamic characteristics of the mounting system.展开更多
A new wavelet finite element method(WFEM)is constructed in this paper and two elements for bending and free vibration problems of a stiffened plate are analyzed.By means of generalized potential energy function and vi...A new wavelet finite element method(WFEM)is constructed in this paper and two elements for bending and free vibration problems of a stiffened plate are analyzed.By means of generalized potential energy function and virtual work principle,the formulations of the bending and free vibration problems of the stiffened plate are derived separately.Then,the scaling functions of the B-spline wavelet on the interval(BSWI)are introduced to discrete the solving field variables instead of conventional polynomial interpolation.Finally,the corresponding two problems can be resolved following the traditional finite element frame.There are some advantages of the constructed elements in structural analysis.Due to the excellent features of the wavelet,such as multi-scale and localization characteristics,and the excellent numerical approximation property of the BSWI,the precise and efficient analysis can be achieved.Besides,transformation matrix is used to translate the meaningless wavelet coefficients into physical space,thus the resolving process is simplified.In order to verify the superiority of the constructed method in stiffened plate analysis,several numerical examples are given in the end.展开更多
Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform...Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.展开更多
Space robotics has been used extensively in complex space missions. Rigid-manipulator space robots may suffer from rigid-body collisions with targets. This collision is likely to cause damage to the space robot and th...Space robotics has been used extensively in complex space missions. Rigid-manipulator space robots may suffer from rigid-body collisions with targets. This collision is likely to cause damage to the space robot and the target. To overcome such a problem, a novel ContinuumManipulator Space Robot(CMSR) for performing on-orbit servicing missions is proposed in this paper. Compared with rigid-manipulator space robots, CMSRs are able to perform compliant operations and avoid rigid-body collisions with a target. The CMSR consists of two kinds of flexible components, including solar arrays and continuum manipulators. The elastic vibrations of these flexible components disturb the position and attitude of CMSRs. The beating phenomenon introduced by the energy transfer among these flexible components can cause damage to solar arrays.The complicated dynamic coupling poses enormous challenges in dynamic modeling and vibration analysis. The dynamic model for CMSRs is derived and the mechanism of the beating phenomenon is analyzed in this paper. Simulation results show that an obvious beating phenomenon occurs and the amplitude of the solar arrays increases significantly when the natural frequencies of two kinds of flexible components are close. A method is provided to avoid the beating phenomenon.展开更多
基金co-supported by the National Natural Science Foundation of China(No.52275061)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.KYCX24_0562)。
文摘The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification method for the TDSS based on vibration response analysis.Based on the Johnson-Cook constitutive model and failure criteria,the ballistic impact finite element simulation model is established,which is verified by the ballistic impact experiment of the Tail Drive Shaft(TDS).Considering the ballistic impact excitation force,the dynamic model of the TDSS with ballistic impact is established,which is verified by finite element commercial software.If a bullet hits the TDS,the bending vibration displacement increases sharply at a certain moment and then significantly increases but remains stable.Meanwhile,the critical speed component appears in the frequency-domain response of bending vibration,and then the speed component significantly increases but remains stable.What's more,the axis trajectory exhibits a sudden,large-scale,and irregular whirling motion at a certain moment,followed by a significant increase but remains stable.Furthermore,if the axial vibration response is small,the bullet core shooting should be considered vertically or at a small incident angle,otherwise,it should be considered at a large incident angle.
文摘A new quadrilateral finite element IQ4 is developed for the free vibration of carbon nanotube-reinforced composite(CNTRC)perforated plates with a central cutout.By enriching the membrane part and incorporating a projected shear technique,the IQ4 element is proposed to address the known limitations of the standard Q4 element,such as shear locking and limited consistency in the coupling ofmembrane-bending components.The proposed element is formulated within the FSDT-based framework and assessed through benchmark tests to verify its convergence and accuracy.The governing equations are obtained via theweak formofHamilton’s principle.Particular attention is given to the influence of carbon nanotube volume fraction,distribution patterns,and boundary conditions on the fundamental frequency response of CNTRC plates with cutouts.In addition,a parametric study is conducted to assess the influence of cutout geometric configuration,shape,and size ratios on the vibrational response of the CNTRC plate.The numerical results demonstrate that the formulated IQ4 element provides stable and accurate estimations of natural frequencies,even in the presence of a cutout and the coupled effects of the non-uniform distribution of reinforcement through the plate thickness.The developed formulation is expected to contribute to the structural design and optimization of advanced lightweight systems,particularly in aerospace and mechanical engineering applications.
文摘The vibrational frequency analysis of finite elastic tube filled with compressible viscous fluid has received plenty of attention in recent years. To apply frequency analysis to defect detection for example, it is necessary to investigate the vibrational behavior under appropriate boundary conditions. In this paper, we present a detailed theoretical study of the three dimensional modal analysis of compressible fluid within an elastic cylinder. The dispersion equations of flexura], torsional and longitudinal modes are derived by elastodynamic theory and the unsteady Stokes equation. The symbolic software Mathematica is used in order to find the coupled vibration frequencies. The dispersion equation is deduced and analytically solved. The finite element results are compared with the present method for validation and an acceptable match between them are obtained.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11272048 and 51239006the European Commission Marie Curie Actions under Grant No IRSES-294976
文摘We present the numerical simulation results of a model granular assembly formed by spherical particles with tIertzian interaction subjected to a simple shear in the athermal quasi-static limit. The stress-strain curve is shown to separate into smooth, elastic branches followed by a subsequent plastic event. Mode analysis shows that the lowest-frequency vibrational mode is more localized, and eigenvalues and participation ratios of low- frequency modes exhibit similar power-law behavior as the system approaches plastic instability, indicating that the nature of plastic events in the granular system is also a saddle node bifurcation. The analysis of projection and spatial structure shows that over 75% contributions to the non-affine displacement field at a plastic instability come from the lowest-frequency mode, and the lowest-frequency mode is strongly spatially correlated with local plastic rearrangements, inferring that the lowest-frequency mode could be used as a predictor for future plastic rearrangements in the disordered system jammed marginally.
基金Financial supports from the NNSFCs (Grants 201276194 and 201306136)the Funds of Tianjin Key Laboratory of Marine Resources and Chemistry in TUST (Grants 201303 and 201206)the Natural Science Fund of TUST (Grant 20130112)
文摘It is well known that boron exists as polyborate anions in aqueous solution.Boron atom can coordinates to three or four oxygen atoms and borate can exist as not only the monomer but also the polymer.The polymerization
文摘The vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4 000~400and 4 000~400cm-1 respectively,for N-[4-[1-hydroxy-2-[(1-methyl ethyl)amino]ethyl]phenyl]methane sulfonamide(HPAEPMS)molecule.Theoretical calculations were performed by ab initio Density Functional Theory(DFT)method using 6-31G(d,p)basis set.The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution(PED).The results of the calculations were applied to simulated spectra of the title compound,which show excellent agreement.
文摘Argyris'natural approach is employed to analyze vibranon mode of multilayered composite plates and shells.The shells can be either symmetric or unsymmetric.The spectral transformation Lanczos method with selective or fully orthogonalization is used to solve the eigenvalue problem of pencil(K,M).Some problems on shift,which is essential for the success of this method, are discussed.A few numerical examples, including composite square plates and conical shells,are presented. The results show that the method in this paper is efficient and reliable for vibration mode analysis.
基金This work was supported by the National Natural Science Foundation of China （No.11174099）.
文摘The dynamics of quantum entanglement described by the yon Neumann entropy is studied for the localized states of Fermi-resonance coupling vibrations in molecule CS2, where the interacting energy between the stretching and the bending modes is considered to establish a connection between entanglement and energy. It is shown that entanglement reveals dominant anti-correlation with the interacting energy for the stretch-localized state, while that exhibits dominantly positive correlation for the bend-localized state. The entanglement and the energy for the dislocalized states are discussed as well. Those are useful for molecular quantum computing and quantum information in high dimensional states.
基金supported by the National Science and Technology Major Project,China,the China Scholarship Council(No.202306290109)National Natural Science Foundation of China(Nos.52472456 and 52361165620)。
文摘This paper studies the coupling mechanism between the nonlinear stiffness and damping coefficients of Active Elastic Support/Dry Friction Damper(AESDFD)and rotor system.First,parameters for evaluating the vibration reduction characteristics are proposed to facilitate the design of the AESDFD.To achieve this,the nonlinear friction force is initially represented as equivalent stiffness and damping coefficients,based on the ball-plate friction model.Second,three evaluation parameters—optimal slipping displacement,loss factor,and controllability—are proposed to reveal the vibration reduction characteristics of the AESDFD,alongside determining the optimal normal force.Subsequently,the finite element method,in conjunction with the ball-plate friction model,is introduced to formulate the governing equation of a low-pressure rotor system equipped with AESDFDs.The steady-state responses of the AESDFDs-rotor system are solved using the harmonic balance method combined with an efficient iteration method.Finally,the solutions are validated on the AESDFDs-rotor system both numerically and experimentally.The results indicate that controllability effectively assesses the vibration reduction performance of the AESDFD and is relatively insensitive to variations in low normal force.Away from the critical speed,the AESDFD suppresses vibration by altering the resonance position of the rotor system through its stiffness coefficient.Near the critical speed,vibration reduction is achieved primarily through energy dissipation by the damping coefficient.If the loss factor is less than one,the stiffness coefficient can diminish the vibration reduction effect of the damping coefficient.Notably,the optimal normal force of the AESDFD achieves optimal vibration reduction effect.This study reveals that changes in rotor system unbalance do not affect the vibration reduction characteristics of the AESDFD,with the same upper limit to the vibration reduction effect of the AESDFD.
基金co-supported by the Key Projects of the Civil Aviation Joint Fund of the National Natural Science Foundation of China(No.U2033208)。
文摘The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction system,making it essential for ensuring the safety of this emerging towing-out mode.In this paper,the frequency evolutionary tendency of the traction system is studied and obtained considering the variation of nonlinear contact stiffness for the first time.A novel modal analysis method,based on a derived nonlinear contact relationship,is proposed to investigate the vibration characteristics for mechanical system.Frequency veering and mode exchange phenomena in the low-order modes are observed due to the variation of nonlinear contact stiffness.These findings are further validated by the experimental results of a scaled-down model.In addition,it is also found that the veering critical point will be shifted with the external loads.The study provides valuable insights into the vibration characteristics and frequency veering behavior of similar mechanism-based systems,such as towbarless traction system,and has important implications for improving their design and operational performance.
基金financially supported by the National Natural Science Foundation of China(Nos.12302228 and 12372170)。
文摘Skin panels on supersonic vehicles are subjected to aero-thermo-acoustic loads,resulting in a well-known multi-physics dynamic problem.The high-frequency dynamic response of these panels significantly impacts the structural safety of supersonic vehicles,but it has been rarely investigated.Given that existing methods are inefficient for high-frequency dynamic analysis in multi-physics fields,the present work addresses this challenge by proposing a Stochastic Energy Finite Element Method(SEFEM).SEFEM uses energy density instead of displacement to describe the dynamic response,thereby significantly enhancing its efficiency.In SEFEM,the effects of aerodynamic and thermal loads on the energy propagation characteristics are studied analytically and incorporated into the energy density governing equation.These effects are also considered when calculating the input power generated by the acoustic load,and two effective approaches named Frequency Response Function Method(FRFM)and Mechanical Impedance Method(MIM)are developed accordingly and integrated into SEFEM.The good accuracy,applicability,and high efficiency of the proposed SEFEM are demonstrated through numerical simulations performed on a two-dimensional panel under aero-thermoacoustic loads.Additionally,the effects and underlying mechanisms of aero-thermo-acoustic loads on the high-frequency response are explored.This work not only presents an efficient approach for predicting high-frequency dynamic response of panels subjected to aero-thermo-acoustic loads,but also provides insights into the high-frequency dynamic characteristics in multi-physics fields.
文摘This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP)materials.The strain potential and kinetic energies of each beam along with the work done by the external force are calculated.Additionally,a higher-order beam element is introduced to derive stiffness and mass matrices,along with the force vector.The curved and straight beams are discretized,and their assembled stiffness,mass matrices,and force vectors,are obtained.Continuity conditions at the joints are used to derive the total matrices of the entire structure.Subsequently,the natural frequencies and transient response of the system are determined.The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANSYS,demonstrating excellent agreement.Furthermore,a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.
文摘A U(2) algebraic model is introduced for the spectrum of a molecule XY4, where the interactions between the stretch and bend modes are described by Td symmetric Fermi resonance terms. The presented algebraic model in a limit corresponds to another model in recent literature. The vibrational spectrum of methane (CH4) measured recently with modern spectroscopy techniques is employed to test those models. The obtained standard deviation between the observed and the calculated vibrational energy levels in the algebraic model is smaller than that in the corresponding model.
文摘Shape control and free vibration analysis of piezolaminated plates subjected to electro mechanical loading are evaluated using finite element method. First order shear deformation theory is employed in the analysis. Both extensions as well as shear actuators are considered for piezolaminated plates. Rectangular four node isoparametric element is used in the finite element formulation. Variation of temperature is neglected for the orthotropic layers of the laminate and for piezolayer. Annular circular plates and rectangular plates with piezoelectric layers mounted and/or integrated are analysed for various parameters. Numerical results are presented for varying the actuator voltage for annular plates with different thicknesses of piezo patches. In case of rectangular plate shear actuator is considered for vibration analysis.
基金the National Natural Science Foundation of China(No.51805462)。
文摘Vibrations in aircraft hydraulic pipeline system,due to multi-source excitation of high fluid pressure fluctuation and serious vibration environment of airframe,can cause the pipeline system vibration failures through overload in engineering field.Controlling the vibrations in hydraulic pipeline is a challenging work to ensure the flight safety of aircraft.The common vibration control technologies have been demonstrated to be effective in typical structures such as aerospace structures,shipbuilding structures,marine offshore structures,motor structures,etc.However,there are few research literatures on vibration control strategies of aircraft hydraulic pipeline.Combining with the development trend of aircraft hydraulic pipeline system and the requirement of vibration control technologies,this paper provides a detailed review on the current vibration control technologies in hydraulic pipeline system.A review of the general approaches following the passive and active control technologies are presented,which are including optimal layout technique of pipeline and clamps,constrained layer damping technique,vibration absorber technique,hydraulic hose technique,optimal pump structure technique,and active vibration control technique of pipeline system.Finally,some suggestions for the application of vibration control technologies in engineering field are given.
文摘A bimorph piezoelectric beam with periodically variable cross-sections is used for the vibration energy harvesting. The effects of two geometrical parameters on the first band gap of this periodic beam are investigated by the generalized differential quadrature rule （GDQR） method. The GDQR method is also used to calculate the forced vibration response of the beam and voltage of each piezoelectric layer when the beam is subject to a sinusoidal base excitation. Results obtained from the analytical method are compared with those obtained from the finite element simulation with ANSYS, and good agreement is found. The voltage output of this periodic beam over its first band gap is calculated and compared with the voltage output of the uniform piezoelectric beam. It is concluded that this periodic beam has three advantages over the uniform piezoelectric beam, i.e., generating more voltage outputs over a wide frequency range, absorbing vibration, and being less weight.
基金Supported by National Natural Science Foundation of China(Grant Nos.51375047,51775040)
文摘The design strategies for powertrain mounting systems play an important role in the reduction of vehicular vibration and noise. As stiffness and damping elements connecting the transmission system and vehicle body, the rubber mount exhibits better vibration isolation performance than the rigid connection. This paper presents a complete design process of the mounting system, including the vibration decoupling, vibration simulation analysis, topology optimization, and experimental verification. Based on the 6?degrees?of?freedom vibration coupling model of the powertrain mounting system, an optimization algorithm is used to extract the best design parameters of each mount, thus rendering the mounting system fully decoupled and the natural frequency well configured, and the optimal parameters are used to design the mounting system. Subsequently, vibration simulation analysis is applied to the mounting system, considering both transmission and road excitations. According to the results of finite element analysis, the topological structure of the metal frame of the front mount is optimized to improve the strength and dynamic characteristics of the mounting system. Finally, the vibration bench test is used to verify the availability of the optimization design with the analysis of acceleration response and vibration transmissibility of the mounting system. The results show that the vibration isolation performance of the mounting system can be improved effectively using the vibration optimal decoupling method, and the structural modification of the metal frame can well promote the dynamic characteristics of the mounting system.
基金This work was supported by the National Natural Science Foundation of China(Nos.51405370&51421004)the National Key Basic Research Program of China(No.2015CB057400)+2 种基金the project supported by Natural Science Basic Plan in Shaanxi Province of China(No.2015JQ5184)the Fundamental Research Funds for the Central Universities(xjj2014014)Shaanxi Province Postdoctoral Research Project.
文摘A new wavelet finite element method(WFEM)is constructed in this paper and two elements for bending and free vibration problems of a stiffened plate are analyzed.By means of generalized potential energy function and virtual work principle,the formulations of the bending and free vibration problems of the stiffened plate are derived separately.Then,the scaling functions of the B-spline wavelet on the interval(BSWI)are introduced to discrete the solving field variables instead of conventional polynomial interpolation.Finally,the corresponding two problems can be resolved following the traditional finite element frame.There are some advantages of the constructed elements in structural analysis.Due to the excellent features of the wavelet,such as multi-scale and localization characteristics,and the excellent numerical approximation property of the BSWI,the precise and efficient analysis can be achieved.Besides,transformation matrix is used to translate the meaningless wavelet coefficients into physical space,thus the resolving process is simplified.In order to verify the superiority of the constructed method in stiffened plate analysis,several numerical examples are given in the end.
基金The authors would like to thank the Iranian Nanotechnology Development Committee for their financial support.
文摘Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.
基金supported by the National Natural Science Foundation of China(Nos.91748203,11922203,11772074)。
文摘Space robotics has been used extensively in complex space missions. Rigid-manipulator space robots may suffer from rigid-body collisions with targets. This collision is likely to cause damage to the space robot and the target. To overcome such a problem, a novel ContinuumManipulator Space Robot(CMSR) for performing on-orbit servicing missions is proposed in this paper. Compared with rigid-manipulator space robots, CMSRs are able to perform compliant operations and avoid rigid-body collisions with a target. The CMSR consists of two kinds of flexible components, including solar arrays and continuum manipulators. The elastic vibrations of these flexible components disturb the position and attitude of CMSRs. The beating phenomenon introduced by the energy transfer among these flexible components can cause damage to solar arrays.The complicated dynamic coupling poses enormous challenges in dynamic modeling and vibration analysis. The dynamic model for CMSRs is derived and the mechanism of the beating phenomenon is analyzed in this paper. Simulation results show that an obvious beating phenomenon occurs and the amplitude of the solar arrays increases significantly when the natural frequencies of two kinds of flexible components are close. A method is provided to avoid the beating phenomenon.
