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
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
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
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
A 3D finite element model of the Huaiyin third pumping station of the Eastern Route of the South-to-North Water Transfer is described in this paper. Two methods were used in the calculation and vibration analysis of t...A 3D finite element model of the Huaiyin third pumping station of the Eastern Route of the South-to-North Water Transfer is described in this paper. Two methods were used in the calculation and vibration analysis of the pumping station in both the time domain and the frequency domain. The pressure pulsation field of the whole flow passage was structured on the basis of pressure pulsations recorded at some locations of the physical model test. Dynamic time-history analysis of the pump house under pressure pulsations was carried out. At the same time, according to spectrum characteristics of the pressure pulsations at measuring points and results of free vibration characteristics analysis of the pump house, the spectrum analysis method of random vibration was used to calculate dynamic responses of the pump house. Results from both methods are consistent, which indicates that they are both reasonable. The results can be used for reference in anti-vibration safety evaluation of the Huaiyin third pumping station.展开更多
We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle ...We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.展开更多
Free vibration analysis of symmetrically laminated composite plates resting on Pasternak elastic support and coupled with an ideal, incompressible and inviscid fluid is the objective of the present work. The fluid dom...Free vibration analysis of symmetrically laminated composite plates resting on Pasternak elastic support and coupled with an ideal, incompressible and inviscid fluid is the objective of the present work. The fluid domain is considered to be infinite in the length direction but bounded in the depth and width directions. In order to derive the eigenvalue equation, Rayleigh-Ritz method is applied for the fluid-plate-foundation system. The efficiency of the method is proved by comparison studies with those reported in the open literature. At the end, parametric studies are carried out to examine the impact of different parameters on the natural frequencies.展开更多
The microvibrations produced by momentum wheel assemblies（MWA） can degrade the performance of instruments with high pointing precision and stability on spacecraft.This paper concentrates on analyzing and testing the...The microvibrations produced by momentum wheel assemblies（MWA） can degrade the performance of instruments with high pointing precision and stability on spacecraft.This paper concentrates on analyzing and testing the microvibrations produced by MWA.We analyze the disturbance sources produced by mass imbalance,structural mode,bearing irregularity and nonlinear stiffness,and random noise;then,test a well-balanced MWA by a highly sensitive measurement system consisting of a Kistler table and an optical tabletop.The results show that the test system has a resolution of less than 0.003 N in the frequency range of 3-300 Hz.The dynamic imbalance of the MWA cannot excite the radial rocking mode,but there are dynamic amplifications when the poly-harmonic disturbances intersect with the structural modes.Especially at high rotational speed（〉3 000 rev/min）,the main disturbance sources of the MWA come from the bearing irregularity interacting with radial translation mode in the high frequency range.Thus,bearing noise deserves more attention for the well-balanced MWA,and alternative of high quality bearings are proposed to reduce the microvibrations.展开更多
This paper is concerned with the free vibration analysis of open circular cylindrical shells with either the two straight edges or the two curved edges simply supported and the remaining two edges supported by arbitra...This paper is concerned with the free vibration analysis of open circular cylindrical shells with either the two straight edges or the two curved edges simply supported and the remaining two edges supported by arbitrary classical boundary conditions. Based on the Donnell-Mushtari-Vlasov thin shell theory, an analytical solution of the traveling wave form along the simply supported edges and the modal wave form along the remaining two edges is obtained. With such a unidirectional traveling wave form solution, the method of the reverberation-ray matrix is introduced to derive the equation of natural frequencies of the shell with different classical boundary conditions. The exact solutions for natural frequencies of the open circular cylindrical shell are obtained with the employment of a golden section search algorithm. The calculation results are compared with those obtained by the finite element method and the methods in the available literature. The influence of length, thickness, radius, included angle, and the boundary conditions of the open circular cylindrical shell on the natural frequencies is investigated. The exact calculation results can be used as benchmark values for researchers to check their numerical methods and for engineers to design structures with thin shell components.展开更多
Soft nonlinear support is a major engineering project,but there are few relevant studies.In this paper,a dynamic pipeline model with soft nonlinear supports at both ends is established.By considering the influence of ...Soft nonlinear support is a major engineering project,but there are few relevant studies.In this paper,a dynamic pipeline model with soft nonlinear supports at both ends is established.By considering the influence of the Coriolis force and centrifugal force,the dynamical coupling equation of fluid-structure interaction is derived with extended Hamilton’s principle.Then,the approximate analytical solutions are sought via the harmonic balance method.The amplitude-frequency response curves show that different effects can be determined by approximate analysis.It is demonstrated that the increase in the fluid velocity can increase the amplitude of the pipeline system.The frequency range of unstable response increases when the fluid pressure raises.The combination of the soft nonlinear clamp and the large geometrical deformation of the pipeline affects the nonlinear vibration characteristic of the system,and the external excitation force and damping have significant effects on the stability.展开更多
In this research, vibration and wave propagation analysis of a twisted micro- beam on Pasternak foundation is investigated. The strain-displacement relations （kine-matic equations） are calculated by the displacement...In this research, vibration and wave propagation analysis of a twisted micro- beam on Pasternak foundation is investigated. The strain-displacement relations （kine-matic equations） are calculated by the displacement fields of the twisted micro-beam. The strain gradient theory （SGT） is used to implement the size dependent effect at micro-scale. Finally, using an energy method and Hamilton＇s principle, the governing equations of motion for the twisted micro-beam are derived. Natural frequencies and the wave prop- agation speed of the twisted micro-beam are calculated with an analytical method. Also, the natural frequency, the phase speed, the cut-off frequency, and the wave number of the twisted micro-beam are obtained by considering three material length scale parameters, the rate of twist angle, the thickness, the length of twisted micro-beam, and the elastic medium. The results of this work indicate that the phase speed in a twisted micro-beam increases with an increase in the rate of twist angle. Moreover, the wave number is in- versely related with the thickness of micro-beam. Meanwhile, it is directly related to the wave propagation frequency. Increasing the rate of twist angle causes the increase in the natural frequency especially with higher thickness. The effect of the twist angle rate on the group velocity is observed at a lower wave propagation frequency.展开更多
In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation...In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation mathematical model of fluid-structure interaction(FSI)was developed.Then,the transfer matrix method(TMM)was used to calculate the modal frequency,modal shape and frequency response.The results were compared with that in experiment to verify the correctness of the TMM and the results show that the fluid-structure coupling has a greater impact on the modal frequencies than the modal shape.Finally,the influence on the response spectrum of different damping ratios was studied and the results show that the natural frequency under different damping ratios has changed little but there is a big difference for the pressure spectrum.With the decreasing of damping ratio,the damping of the system on frequency spectrum is more and more significant and the dispersion and dissipation is more and more apparent.Therefore the appropriate damping ratio should be selected to minimize the effects of the vibration of the FSI.The results provide references for the theory research of FSI in the transient process.展开更多
Based on Kirchhoff plate theory and the Rayleigh-Ritz method,the model for free vibration of rectangular plate with rectangular cutouts under arbitrary elastic boundary conditions is established by using the improved ...Based on Kirchhoff plate theory and the Rayleigh-Ritz method,the model for free vibration of rectangular plate with rectangular cutouts under arbitrary elastic boundary conditions is established by using the improved Fourier series in combination with the independent coordinate coupling method(ICCM).The effect of the cutout is taken into account by subtracting the energies of the cutouts from the total energies of the whole plate.The vibration displacement function of the hole domain is based on the coordinate system of the hole domain in this method.From the continuity condition of the vibration displacement function at the cutout,the transition matrix between the two coordinate systems is constructed,and the mass and stiffness matrices are completely obtained.As a result,the calculation is simplified and the computational efficiency of the solution is improved.In this paper,numerical examples and modal experiments are presented to validate the effectiveness of the modeling methods,and parameters related to influencing factors of the rectangular plate are analyzed to study the vibration characteristics.展开更多
In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temper...In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.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
A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading ...A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading cycle due to fluctuating wind load.Consequently,wind turbine blade design is governed by fatigue rather than ultimate load considerations.Previous studies have adopted many different beam theories,using different techniques and codes,to model the National Renewable Energy Laboratory(NREL)5MWoffshore wind turbine blade.There are differences,from study to study,in the free vibration results and the dynamic response.The contribution of this study is to apply the code written by the authors to the different beam theories used with the aim of comparing the different beam theories presented in the literature and that developed by the authors.This paper reports the investigation of the effects of deformation parameters on the dynamic characteristics of the NREL 5 MW offshore wind turbine blades predicted by the different beam theories.The investigation of free vibrations is a fundamental step in the analysis of structural dynamics,and this study compares different computational structural methods and investigates their effect on the predicted dynamic response.The modal characteristics of every model examined have been combined with strip theory to determine the dynamic response of the blade.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 Science and Technology Support Program of China (Program for theEleventh Five-Year Plan, Grant No. 2006BAB04A03)the National Natural Science Foundation of China(Grant No. 10702019)
文摘A 3D finite element model of the Huaiyin third pumping station of the Eastern Route of the South-to-North Water Transfer is described in this paper. Two methods were used in the calculation and vibration analysis of the pumping station in both the time domain and the frequency domain. The pressure pulsation field of the whole flow passage was structured on the basis of pressure pulsations recorded at some locations of the physical model test. Dynamic time-history analysis of the pump house under pressure pulsations was carried out. At the same time, according to spectrum characteristics of the pressure pulsations at measuring points and results of free vibration characteristics analysis of the pump house, the spectrum analysis method of random vibration was used to calculate dynamic responses of the pump house. Results from both methods are consistent, which indicates that they are both reasonable. The results can be used for reference in anti-vibration safety evaluation of the Huaiyin third pumping station.
基金Project supported by the National High Technology Research and Developmem Program of China ~Grant No. 2013AA030901）.
文摘We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.
文摘Free vibration analysis of symmetrically laminated composite plates resting on Pasternak elastic support and coupled with an ideal, incompressible and inviscid fluid is the objective of the present work. The fluid domain is considered to be infinite in the length direction but bounded in the depth and width directions. In order to derive the eigenvalue equation, Rayleigh-Ritz method is applied for the fluid-plate-foundation system. The efficiency of the method is proved by comparison studies with those reported in the open literature. At the end, parametric studies are carried out to examine the impact of different parameters on the natural frequencies.
文摘The microvibrations produced by momentum wheel assemblies（MWA） can degrade the performance of instruments with high pointing precision and stability on spacecraft.This paper concentrates on analyzing and testing the microvibrations produced by MWA.We analyze the disturbance sources produced by mass imbalance,structural mode,bearing irregularity and nonlinear stiffness,and random noise;then,test a well-balanced MWA by a highly sensitive measurement system consisting of a Kistler table and an optical tabletop.The results show that the test system has a resolution of less than 0.003 N in the frequency range of 3-300 Hz.The dynamic imbalance of the MWA cannot excite the radial rocking mode,but there are dynamic amplifications when the poly-harmonic disturbances intersect with the structural modes.Especially at high rotational speed（〉3 000 rev/min）,the main disturbance sources of the MWA come from the bearing irregularity interacting with radial translation mode in the high frequency range.Thus,bearing noise deserves more attention for the well-balanced MWA,and alternative of high quality bearings are proposed to reduce the microvibrations.
基金Project supported by the National Natural Science Foundation of China （Nos. 51209052, 51279038, and 51479041）, the Natural Sci- ence Foundation of Heilongjiang Province （No. QC2011C013）, and the Opening Funds of State Key Laboratory of Ocean Engineering of Shanghai Jiao Tong University （No. 1307）, China
文摘This paper is concerned with the free vibration analysis of open circular cylindrical shells with either the two straight edges or the two curved edges simply supported and the remaining two edges supported by arbitrary classical boundary conditions. Based on the Donnell-Mushtari-Vlasov thin shell theory, an analytical solution of the traveling wave form along the simply supported edges and the modal wave form along the remaining two edges is obtained. With such a unidirectional traveling wave form solution, the method of the reverberation-ray matrix is introduced to derive the equation of natural frequencies of the shell with different classical boundary conditions. The exact solutions for natural frequencies of the open circular cylindrical shell are obtained with the employment of a golden section search algorithm. The calculation results are compared with those obtained by the finite element method and the methods in the available literature. The influence of length, thickness, radius, included angle, and the boundary conditions of the open circular cylindrical shell on the natural frequencies is investigated. The exact calculation results can be used as benchmark values for researchers to check their numerical methods and for engineers to design structures with thin shell components.
基金supported by the National Natural Science Foundation of China(No.11972112)the Fundamental Research Funds for the Central Universities of China(Nos.N2103024 and N2003014)the National Science and Technology Major Project of China(No.J2019-I-0008-0008)。
文摘Soft nonlinear support is a major engineering project,but there are few relevant studies.In this paper,a dynamic pipeline model with soft nonlinear supports at both ends is established.By considering the influence of the Coriolis force and centrifugal force,the dynamical coupling equation of fluid-structure interaction is derived with extended Hamilton’s principle.Then,the approximate analytical solutions are sought via the harmonic balance method.The amplitude-frequency response curves show that different effects can be determined by approximate analysis.It is demonstrated that the increase in the fluid velocity can increase the amplitude of the pipeline system.The frequency range of unstable response increases when the fluid pressure raises.The combination of the soft nonlinear clamp and the large geometrical deformation of the pipeline affects the nonlinear vibration characteristic of the system,and the external excitation force and damping have significant effects on the stability.
基金Project supported by the Iranian Nanotechnology Development Committee and the University of Kashan(No.463855/11)
文摘In this research, vibration and wave propagation analysis of a twisted micro- beam on Pasternak foundation is investigated. The strain-displacement relations （kine-matic equations） are calculated by the displacement fields of the twisted micro-beam. The strain gradient theory （SGT） is used to implement the size dependent effect at micro-scale. Finally, using an energy method and Hamilton＇s principle, the governing equations of motion for the twisted micro-beam are derived. Natural frequencies and the wave prop- agation speed of the twisted micro-beam are calculated with an analytical method. Also, the natural frequency, the phase speed, the cut-off frequency, and the wave number of the twisted micro-beam are obtained by considering three material length scale parameters, the rate of twist angle, the thickness, the length of twisted micro-beam, and the elastic medium. The results of this work indicate that the phase speed in a twisted micro-beam increases with an increase in the rate of twist angle. Moreover, the wave number is in- versely related with the thickness of micro-beam. Meanwhile, it is directly related to the wave propagation frequency. Increasing the rate of twist angle causes the increase in the natural frequency especially with higher thickness. The effect of the twist angle rate on the group velocity is observed at a lower wave propagation frequency.
文摘In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation mathematical model of fluid-structure interaction(FSI)was developed.Then,the transfer matrix method(TMM)was used to calculate the modal frequency,modal shape and frequency response.The results were compared with that in experiment to verify the correctness of the TMM and the results show that the fluid-structure coupling has a greater impact on the modal frequencies than the modal shape.Finally,the influence on the response spectrum of different damping ratios was studied and the results show that the natural frequency under different damping ratios has changed little but there is a big difference for the pressure spectrum.With the decreasing of damping ratio,the damping of the system on frequency spectrum is more and more significant and the dispersion and dissipation is more and more apparent.Therefore the appropriate damping ratio should be selected to minimize the effects of the vibration of the FSI.The results provide references for the theory research of FSI in the transient process.
基金support of this work by the National Natural Science Foundation of China(No.51405096)the Fundamental Research Funds for the Central Universities(HEUCF210710).
文摘Based on Kirchhoff plate theory and the Rayleigh-Ritz method,the model for free vibration of rectangular plate with rectangular cutouts under arbitrary elastic boundary conditions is established by using the improved Fourier series in combination with the independent coordinate coupling method(ICCM).The effect of the cutout is taken into account by subtracting the energies of the cutouts from the total energies of the whole plate.The vibration displacement function of the hole domain is based on the coordinate system of the hole domain in this method.From the continuity condition of the vibration displacement function at the cutout,the transition matrix between the two coordinate systems is constructed,and the mass and stiffness matrices are completely obtained.As a result,the calculation is simplified and the computational efficiency of the solution is improved.In this paper,numerical examples and modal experiments are presented to validate the effectiveness of the modeling methods,and parameters related to influencing factors of the rectangular plate are analyzed to study the vibration characteristics.
基金the Iranian Nanotechnology Development Committee for their financial supportthe University of Kashan (463855/7)
文摘In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.
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.
文摘A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading cycle due to fluctuating wind load.Consequently,wind turbine blade design is governed by fatigue rather than ultimate load considerations.Previous studies have adopted many different beam theories,using different techniques and codes,to model the National Renewable Energy Laboratory(NREL)5MWoffshore wind turbine blade.There are differences,from study to study,in the free vibration results and the dynamic response.The contribution of this study is to apply the code written by the authors to the different beam theories used with the aim of comparing the different beam theories presented in the literature and that developed by the authors.This paper reports the investigation of the effects of deformation parameters on the dynamic characteristics of the NREL 5 MW offshore wind turbine blades predicted by the different beam theories.The investigation of free vibrations is a fundamental step in the analysis of structural dynamics,and this study compares different computational structural methods and investigates their effect on the predicted dynamic response.The modal characteristics of every model examined have been combined with strip theory to determine the dynamic response of the blade.
