Uncertain parameters are widespread in engineering systems.This study investigates the modal analysis of a fluid-conveying pipe subjected to elastic supports with unknown-but-bound parameters.The governing equation fo...Uncertain parameters are widespread in engineering systems.This study investigates the modal analysis of a fluid-conveying pipe subjected to elastic supports with unknown-but-bound parameters.The governing equation for the elastically supported fluid-conveying pipe is transformed into ordinary differential equations using the Galerkin truncation method.The Chebyshev interval approach,integrated with the assumed mode method is then used to investigate the effects of uncertainties of support stiffness,fluid speed,and pipe length on the natural frequencies and mode shapes of the pipe.Additionally,both symmetrical and asymmetrical support stiffnesses are discussed.The accuracy and effectiveness of the Chebyshev interval approach are verified through comparison with the Monte Carlo method.The results reveal that,for the same deviation coefficient,uncertainties in symmetrical support stiffness have a greater impact on the first four natural frequencies than those of the asymmetrical one.There may be significant differences in the sensitivity of natural frequencies and mode shapes of the same order to uncertain parameters.Notably,mode shapes susceptible to uncertain parameters exhibit wider fluctuation intervals near the elastic supports,requiring more attention.展开更多
In this study,a human-sensitive frequency band vibration isolator(HFBVI)with quasi-zero stiffness(QZS)characteristics for heavy-duty truck seats is designed to improve the comfort of heavy-duty truck drivers on uneven...In this study,a human-sensitive frequency band vibration isolator(HFBVI)with quasi-zero stiffness(QZS)characteristics for heavy-duty truck seats is designed to improve the comfort of heavy-duty truck drivers on uneven roads.First,the analytical expressions for the force and displacement of the HFBVI are derived with the Lagrange equation and d'Alembert's principle,and are validated through the prototype restoring force testing.Second,the harmonic balance method(HBM)is used to obtain the dynamic responses under harmonic excitation,and further the influence of pre-stretching on the dynamic characteristics and transmissibility is discussed.Finally,the experimental prototype of the HFBVI is fabricated,and vibration experiments are conducted under harmonic excitation to verify the vibration isolation performance(VIP)of the proposed vibration isolator.The experimental results indicate that the HFBVI can effectively suppress the frequency band(4-8 Hz)to which the human body is sensitive to vertical vibration.In addition,under real random road spectrum excitation,the HFBVI can achieve low-frequency vibration isolation close to 2 Hz,providing new prospects for ensuring the health of heavy-duty truck drivers.展开更多
As the proton transport channel and binder within the catalytic layer(CL),the physicochemical properties of the ionomer can affect the CL microstructure and performance of the membrane electrode assembly.In this paper...As the proton transport channel and binder within the catalytic layer(CL),the physicochemical properties of the ionomer can affect the CL microstructure and performance of the membrane electrode assembly.In this paper,we select ionomers with different side-chain lengths and investigate the effects of the side-chain structure and content of the ionomers on the performance of membrane electrode assembly(MEA).Electrochemical tests show that at a mass ratio of 10 wt.%of ionomer/Ir(I/Ir),long-side-chain(LSC)ionomer exhibits the best performance(2.141 V@2.00 A/cm^(2),while short-side-chain(SSC)ionomer is 2.208 V@2.00 A/cm^(2)).The MEA containing LSC ionomer shows better electrochemical performance than the SSC at the same I/Ir mass ratio,especially at high current density.The MEA containing LSC ionomer has a larger average pore size and porosity,which indicates that it may have better mass-transfer properties.From the analysis of voltage loss,it can be seen that LSC ionomers have a smaller ohmic impedance and mass transfer resistance than SSC ionomers.In conclusion,LSC ionomers are more conducive to water-gas transport,which can provide excellent water electrolysis performance.This article focuses on the optimization of ionomer side chains and content,which can enhance PEM water electrolysis performance at lower cost.展开更多
Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In...Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In this study,a machine learning(ML)-assisted weak vibration design method under harsh environmental excitations is proposed.The dynamic model of a typical pipe is developed using the absolute nodal coordinate formulation(ANCF)to determine its vibrational characteristics.With the harsh vibration environments as the preserved frequency band(PFB),the safety design is defined by comparing the natural frequency with the PFB.By analyzing the safety design of pipes with different constraint parameters,the dataset of the absolute safety length and the absolute resonance length of the pipe is obtained.This dataset is then utilized to develop genetic programming(GP)algorithm-based ML models capable of producing explicit mathematical expressions of the pipe's absolute safety length and absolute resonance length with the location,stiffness,and total number of retaining clips as design variables.The proposed ML models effectively bridge the dataset with the prediction results.Thus,the ML model is utilized to stagger the natural frequency,and the PFB is utilized to achieve the weak vibration design.The findings of the present study provide valuable insights into the practical application of weak vibration design.展开更多
Pipes have been extensively utilized in the aerospace,maritime,and other engineering sectors.However,the vibrations of pipes can significantly affect the system reliability and even lead to accidents.Visco-hyperelasti...Pipes have been extensively utilized in the aerospace,maritime,and other engineering sectors.However,the vibrations of pipes can significantly affect the system reliability and even lead to accidents.Visco-hyperelastic materials can enhance the dissipative effect,and reduce the vibrations of pipes.However,the mechanism based on the constitutive model for visco-hyperelastic materials is not clear.In this study,the damping effect of a visco-hyperelastic material on the outer surface of a plain steel pipe is investigated.The nonlinear constitutive relation of the visco-hyperelastic material is introduced into the governing equation of the system for the first time.Based on this nonlinear constitutive model,the governing model for the forced vibration analysis of a simply-supported laminated pipe is established.The Galerkin method is used to analyze the effects of the visco-hyperelastic parameters and structural parameters on the natural characteristics of the fluid-conveying pipes.Subsequently,the harmonic balance method(HBM)is used to investigate the forced vibration responses of the pipe.Finally,the differential quadrature element method(DQEM)is used to validate these results.The findings demonstrate that,while the visco-hyperelastic material has a minimal effect on the natural characteristics,it effectively dampens the vibrations in the pipe.This research provides a theoretical foundation for applying vibration damping materials in pipe vibration control.展开更多
Fluid-conveying pipes generally face combined excitations caused by periodic loads and random noises.Gaussian white noise is a common random noise excitation.This study investigates the random vibration response of a ...Fluid-conveying pipes generally face combined excitations caused by periodic loads and random noises.Gaussian white noise is a common random noise excitation.This study investigates the random vibration response of a simply-supported pipe conveying fluid under combined harmonic and Gaussian white noise excitations.According to the generalized Hamilton’s principle,the dynamic model of the pipe conveying fluid under combined harmonic and Gaussian white noise excitations is established.Subsequently,the averaged stochastic differential equations and Fokker–Planck–Kolmogorov(FPK)equations of the pipe conveying fluid subjected to combined excitations are acquired by the modified stochastic averaging method.The effectiveness of the analysis results is verified through the Monte Carlo method.The effects of fluid speed,noise intensity,amplitude of harmonic excitation,and damping factor on the probability density functions of amplitude,displacement,as well as velocity are discussed in detail.The results show that with an increase in fluid speed or noise intensity,the possible greatest amplitude for the fluid-conveying pipe increases,and the possible greatest displacement and velocity also increase.With an increase in the amplitude of harmonic excitation or damping factor,the possible greatest amplitude for the pipe decreases,and the possible greatest displacement and velocity also decrease.展开更多
Research on pipe dynamics primarily focuses on in-plane vibration.However,pipes simultaneously experience in-plane and out-of-plane vibrations.Therefore,a three-dimensional dynamic model using the absolute nodal coord...Research on pipe dynamics primarily focuses on in-plane vibration.However,pipes simultaneously experience in-plane and out-of-plane vibrations.Therefore,a three-dimensional dynamic model using the absolute nodal coordinate formulation(ANCF)method is established and the dynamic characteristics of a planar L-shaped pipe are analyzed.Firstly,the dynamic equations of the pipe element are derived,and then the overall equations of the pipe model are composed by matrix assembly.By solving equations,it is found that static deformation caused by fluid velocity occurs in the plane,with larger deformations at higher fluid velocities.Additionally,the study observes coupling between different modes and variations in modal shapes.Variations in arc segment structural parameters result in non-uniform changes in natural frequencies,with out-of-plane vibration presenting even more complexity,and the results are verified by ANSYS simulation.Subsequently,a comparison between experimental and theoretical results is conducted across three sets of structural parameters,the consistency between these results validates the engineering significance of the theoretical model.展开更多
This work discusses the strain and acceleration suppression of a flexible beam subjected to different supports analytically.As classical protection,the beam is mounted on a vertical linear spring together with a linea...This work discusses the strain and acceleration suppression of a flexible beam subjected to different supports analytically.As classical protection,the beam is mounted on a vertical linear spring together with a linear damper in parallel.This is called linear isolation.To enhance isolation performance,nonlinearity is employed in the boundary.In addition,quasi-zero isolation is established based on the non-linearly enhanced one by adjusting the installation length of the horizontal spring.To discuss their performance fully and fairly,the amplitude,the acceleration,the potential energy of the beam,the input work of the excitation,the dissipation work of the beam,and the dynamics stress along the beam are investigated based on the same parameters.The comparison shows that all these isolations can protect the beam with high efficiency,even when the basement excitation is tiny.Although the linear isolation and the nonlinearly enhanced one will arouse two resonance peaks on both sides of the primary resonance of the beam without isolation,the maximum amplitudes of them are reduced a lot.But for the low frequency excitation,the quasi-zero isolation has the best performance as it drives the primary resonance to the high frequency region.The simulation shows that the beam needs a relatively soft isolation to avoid the damage caused by the shock vibration,including the quasi-zero one.In general,the quasi-zero isolation shows the best performance.The nonlinearly enhanced one is the suboptimal choice.The present work shows the capacities of three isolations for a flexible beam by the steady-state response and the shock vibration.It provides design suggestions for the isolation of flexible beams.展开更多
Designing,modeling,and analyzing novel nonlinear elastic elements for the nonlinear energy sink(NES)have long been an attractive research topic.Since gravity is difficult to overcome,previous NES research mainly focus...Designing,modeling,and analyzing novel nonlinear elastic elements for the nonlinear energy sink(NES)have long been an attractive research topic.Since gravity is difficult to overcome,previous NES research mainly focused on horizontal vibration suppression.This study proposes an origami-inspired NES.A stacked Miura-origami(SMO)structure,consisting of two Miura-ori sheets,is adopted to construct a nonlinear elastic element.By adjusting the initial angle and the connecting crease torsional stiffness,the quasi-zero stiffness(QZS)and load-bearing capacity can be customized to match the corresponding mass,establishing the vertical SMO-NES.The dynamic model of the SMO-NES coupled with a linear oscillator(LO)is derived for vibrations in the vertical direction.The approximate analytical solutions of the dynamic equation are obtained by the harmonic balance method(HBM),and the solutions are verified numerically.The parameter design principle of the SMO-NES is provided.Finally,the vibration reduction performance of the SMO-NES is studied.The results show that the proposed SMONES can overcome gravity and achieve quasi-zero nonlinear restoring force.Therefore,the SMO-NES has the ability of wide-frequency vibration reduction,and can effectively suppress vertical vibrations.By adjusting the initial angle and connecting the crease torsional stiffness of the SMO,the SMO-NES can be achieved with different loading weights,effectively suppressing the vibrations with different primary system masses and excitation amplitudes.In conclusion,with the help of popular origami structures,this study proposes a novel NES,and starts the research of combining origami and NES.展开更多
Suppressing micro-amplitude vibrations is a critical issue in aerospace engineering.While nonlinear energy sinks(NES)are effective for passive vibration damping,their performance diminishes for micro-amplitude vibrati...Suppressing micro-amplitude vibrations is a critical issue in aerospace engineering.While nonlinear energy sinks(NES)are effective for passive vibration damping,their performance diminishes for micro-amplitude vibrations.This paper introduces a motion-amplified NES(MANES)to address this challenge.The system’s governing equations are derived using Hamilton’s principle,and an approximate analytical solution is validated by numerical methods.The effects of various parameters are explored,with higher vibration reduction efficiency achievable through parameter adjustments.Compared to cubic NES,MANES shows superior vibration suppression and a broader reduction bandwidth for micro-amplitude excitations.Additionally,MANES enters the effective vibration reduction range at lower excitation levels,indicating a reduced threshold for vibration suppression.This study provides insight into the vibration suppression mechanism of MANES,offering a theoretical foundation for mitigating micro-amplitude vibrations in engineering applications.展开更多
Nonlinear vibration absorbers have been widely used for vibration suppression of elastic structures,but they were usually placed within the structures.However,designing such a vibration damping device within an engine...Nonlinear vibration absorbers have been widely used for vibration suppression of elastic structures,but they were usually placed within the structures.However,designing such a vibration damping device within an engineering structure is possibly difficult.In this paper,an inertial nonlinear energy sinks(NES)is mounted on the boundaries of the elastic beam to suppress its vibration.Although this vibration suppression approach is more in line with engineering requirements,it introduces nonlinear oscillators at boundaries.This brings certain difficulties to the structural vibration analysis and the optimal absorber design.An approximate analytical approach for the steady-state response is developed in this work and verified by numerical solutions.The comparison with the uncontrolled system demonstrates the high-efficiency vibration suppression of the inertial NES installed on the boundary.Besides,the optimization of the NES parameters is performed.Resonance amplitude of the elastic structure can be reduced by 98%with the optimized NES.In summary,this paper proposes a novel approach to suppress the bending vibration of elastic structures through boundary NESs.The vibration reduction effect is very significant,and it is more feasible to implement.Therefore,this work is helpful to study the vibration of elastic structures with nonlinear boundaries and to promote the application of nonlinear vibration absorbers.展开更多
Fluid-conveying pipes are widely used to transfer bulk fluids from one point to another in many engineering applications.They are subject to various excitations from the conveying fluids,the supporting structures,and ...Fluid-conveying pipes are widely used to transfer bulk fluids from one point to another in many engineering applications.They are subject to various excitations from the conveying fluids,the supporting structures,and the working environment,and thus are prone to vibrations such as flow-induced vibrations and acoustic-induced vibrations.Vibrations can generate variable dynamic stress and large deformation on fluid-conveying pipes,leading to vibration-induced fatigue and damage on the pipes,or even leading to failure of the entire piping system and catastrophic accidents.Therefore,the vibration control of fluid-conveying pipes is essential to ensure the integrity and safety of pipeline systems,and has attracted considerable attention from both researchers and engineers.The present paper aims to provide an extensive review of the state-of-the-art research on the vibration control of fluid-conveying pipes.The vibration analysis of fluid-conveying pipes is briefly discussed to show some key issues involved in the vibration analysis.Then,the research progress on the vibration control of fluid-conveying pipes is reviewed from four aspects in terms of passive control,active vibration control,semi-active vibration control,and structural optimization design for vibration reduction.Furthermore,the main results of existing research on the vibration control of fluid-conveying pipes are summarized,and future promising research directions are recommended to address the current research gaps.This paper contributes to the understanding of vibration control of fluid-conveying pipes,and will help the research work on the vibration control of fluidconveying pipes attract more attention.展开更多
Impact dampers are usually used to suppress single mode resonance. The goal of this paper is to clarify the difference when the impact damper suppresses the resonances of different modes. A cantilever beam equipped wi...Impact dampers are usually used to suppress single mode resonance. The goal of this paper is to clarify the difference when the impact damper suppresses the resonances of different modes. A cantilever beam equipped with the impact damper is modeled. The elastic contact of the ball and the cantilever beam is described by using the Hertz contact model. The viscous damper between the ball and the cantilever beam is modeled to consume the vibrational energy of the cantilever beam. A piecewise ordinary differential-partial differential equation of the cantilever beam is established, including equations with and without the impact damper. The vibration responses of the cantilever beam with and without the impact damper are numerically calculated. The effects of the impact absorber parameters on the vibration reduction are examined. The results show that multiple resonance peaks of the cantilever beam can be effectively suppressed by the impact damper. Specifically, all resonance amplitudes can be reduced by a larger weight ball. Moreover, the impacting gap is very effective in suppressing the vibration of the cantilever beam. More importantly, there is an optimal impacting gap for each resonance mode of the cantilever beam, but the optimal gap for each mode is different.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12272211,12072181,and 12121002).
文摘Uncertain parameters are widespread in engineering systems.This study investigates the modal analysis of a fluid-conveying pipe subjected to elastic supports with unknown-but-bound parameters.The governing equation for the elastically supported fluid-conveying pipe is transformed into ordinary differential equations using the Galerkin truncation method.The Chebyshev interval approach,integrated with the assumed mode method is then used to investigate the effects of uncertainties of support stiffness,fluid speed,and pipe length on the natural frequencies and mode shapes of the pipe.Additionally,both symmetrical and asymmetrical support stiffnesses are discussed.The accuracy and effectiveness of the Chebyshev interval approach are verified through comparison with the Monte Carlo method.The results reveal that,for the same deviation coefficient,uncertainties in symmetrical support stiffness have a greater impact on the first four natural frequencies than those of the asymmetrical one.There may be significant differences in the sensitivity of natural frequencies and mode shapes of the same order to uncertain parameters.Notably,mode shapes susceptible to uncertain parameters exhibit wider fluctuation intervals near the elastic supports,requiring more attention.
基金supported by the National Natural Science Foundation of China(No.12172226)。
文摘In this study,a human-sensitive frequency band vibration isolator(HFBVI)with quasi-zero stiffness(QZS)characteristics for heavy-duty truck seats is designed to improve the comfort of heavy-duty truck drivers on uneven roads.First,the analytical expressions for the force and displacement of the HFBVI are derived with the Lagrange equation and d'Alembert's principle,and are validated through the prototype restoring force testing.Second,the harmonic balance method(HBM)is used to obtain the dynamic responses under harmonic excitation,and further the influence of pre-stretching on the dynamic characteristics and transmissibility is discussed.Finally,the experimental prototype of the HFBVI is fabricated,and vibration experiments are conducted under harmonic excitation to verify the vibration isolation performance(VIP)of the proposed vibration isolator.The experimental results indicate that the HFBVI can effectively suppress the frequency band(4-8 Hz)to which the human body is sensitive to vertical vibration.In addition,under real random road spectrum excitation,the HFBVI can achieve low-frequency vibration isolation close to 2 Hz,providing new prospects for ensuring the health of heavy-duty truck drivers.
基金Project(52271013)supported by the National Natural Science Foundation of ChinaProject(23DZ1200600)supported by the Science and Technology Innovation Action Plan of Shanghai,China。
文摘As the proton transport channel and binder within the catalytic layer(CL),the physicochemical properties of the ionomer can affect the CL microstructure and performance of the membrane electrode assembly.In this paper,we select ionomers with different side-chain lengths and investigate the effects of the side-chain structure and content of the ionomers on the performance of membrane electrode assembly(MEA).Electrochemical tests show that at a mass ratio of 10 wt.%of ionomer/Ir(I/Ir),long-side-chain(LSC)ionomer exhibits the best performance(2.141 V@2.00 A/cm^(2),while short-side-chain(SSC)ionomer is 2.208 V@2.00 A/cm^(2)).The MEA containing LSC ionomer shows better electrochemical performance than the SSC at the same I/Ir mass ratio,especially at high current density.The MEA containing LSC ionomer has a larger average pore size and porosity,which indicates that it may have better mass-transfer properties.From the analysis of voltage loss,it can be seen that LSC ionomers have a smaller ohmic impedance and mass transfer resistance than SSC ionomers.In conclusion,LSC ionomers are more conducive to water-gas transport,which can provide excellent water electrolysis performance.This article focuses on the optimization of ionomer side chains and content,which can enhance PEM water electrolysis performance at lower cost.
基金Project supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.12421002)the National Science Funds for Distinguished Young Scholars of China(No.12025204)+1 种基金the National Natural Science Foundation of China(No.12372015)China Scholarship Council(No.202206890065)。
文摘Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In this study,a machine learning(ML)-assisted weak vibration design method under harsh environmental excitations is proposed.The dynamic model of a typical pipe is developed using the absolute nodal coordinate formulation(ANCF)to determine its vibrational characteristics.With the harsh vibration environments as the preserved frequency band(PFB),the safety design is defined by comparing the natural frequency with the PFB.By analyzing the safety design of pipes with different constraint parameters,the dataset of the absolute safety length and the absolute resonance length of the pipe is obtained.This dataset is then utilized to develop genetic programming(GP)algorithm-based ML models capable of producing explicit mathematical expressions of the pipe's absolute safety length and absolute resonance length with the location,stiffness,and total number of retaining clips as design variables.The proposed ML models effectively bridge the dataset with the prediction results.Thus,the ML model is utilized to stagger the natural frequency,and the PFB is utilized to achieve the weak vibration design.The findings of the present study provide valuable insights into the practical application of weak vibration design.
基金supported by the National Natural Science Foundation of China(Nos.12372015 and12421002)the National Science Fund for Distinguished Young Scholars of China(No.12025204)。
文摘Pipes have been extensively utilized in the aerospace,maritime,and other engineering sectors.However,the vibrations of pipes can significantly affect the system reliability and even lead to accidents.Visco-hyperelastic materials can enhance the dissipative effect,and reduce the vibrations of pipes.However,the mechanism based on the constitutive model for visco-hyperelastic materials is not clear.In this study,the damping effect of a visco-hyperelastic material on the outer surface of a plain steel pipe is investigated.The nonlinear constitutive relation of the visco-hyperelastic material is introduced into the governing equation of the system for the first time.Based on this nonlinear constitutive model,the governing model for the forced vibration analysis of a simply-supported laminated pipe is established.The Galerkin method is used to analyze the effects of the visco-hyperelastic parameters and structural parameters on the natural characteristics of the fluid-conveying pipes.Subsequently,the harmonic balance method(HBM)is used to investigate the forced vibration responses of the pipe.Finally,the differential quadrature element method(DQEM)is used to validate these results.The findings demonstrate that,while the visco-hyperelastic material has a minimal effect on the natural characteristics,it effectively dampens the vibrations in the pipe.This research provides a theoretical foundation for applying vibration damping materials in pipe vibration control.
基金supported by the National Natural Science Foundation of China(Nos.12272211 and 12072181).
文摘Fluid-conveying pipes generally face combined excitations caused by periodic loads and random noises.Gaussian white noise is a common random noise excitation.This study investigates the random vibration response of a simply-supported pipe conveying fluid under combined harmonic and Gaussian white noise excitations.According to the generalized Hamilton’s principle,the dynamic model of the pipe conveying fluid under combined harmonic and Gaussian white noise excitations is established.Subsequently,the averaged stochastic differential equations and Fokker–Planck–Kolmogorov(FPK)equations of the pipe conveying fluid subjected to combined excitations are acquired by the modified stochastic averaging method.The effectiveness of the analysis results is verified through the Monte Carlo method.The effects of fluid speed,noise intensity,amplitude of harmonic excitation,and damping factor on the probability density functions of amplitude,displacement,as well as velocity are discussed in detail.The results show that with an increase in fluid speed or noise intensity,the possible greatest amplitude for the fluid-conveying pipe increases,and the possible greatest displacement and velocity also increase.With an increase in the amplitude of harmonic excitation or damping factor,the possible greatest amplitude for the pipe decreases,and the possible greatest displacement and velocity also decrease.
基金supported by the China National Funds for Distinguished Young Scholars(Grant No.12025204)the project of the National Natural Science Foundation of China(Grant No.12072181)the YEQISUN Joint Funds of the National Science Foundation of China(Grant No.U2341231).
文摘Research on pipe dynamics primarily focuses on in-plane vibration.However,pipes simultaneously experience in-plane and out-of-plane vibrations.Therefore,a three-dimensional dynamic model using the absolute nodal coordinate formulation(ANCF)method is established and the dynamic characteristics of a planar L-shaped pipe are analyzed.Firstly,the dynamic equations of the pipe element are derived,and then the overall equations of the pipe model are composed by matrix assembly.By solving equations,it is found that static deformation caused by fluid velocity occurs in the plane,with larger deformations at higher fluid velocities.Additionally,the study observes coupling between different modes and variations in modal shapes.Variations in arc segment structural parameters result in non-uniform changes in natural frequencies,with out-of-plane vibration presenting even more complexity,and the results are verified by ANSYS simulation.Subsequently,a comparison between experimental and theoretical results is conducted across three sets of structural parameters,the consistency between these results validates the engineering significance of the theoretical model.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12002195 and 12372015)the National Science Fund for Distinguished Young Scholars(Grant No.12025204)the Program of Shanghai Municipal Education Commission(Grant No.2019-01-07-00-09-E00018).
文摘This work discusses the strain and acceleration suppression of a flexible beam subjected to different supports analytically.As classical protection,the beam is mounted on a vertical linear spring together with a linear damper in parallel.This is called linear isolation.To enhance isolation performance,nonlinearity is employed in the boundary.In addition,quasi-zero isolation is established based on the non-linearly enhanced one by adjusting the installation length of the horizontal spring.To discuss their performance fully and fairly,the amplitude,the acceleration,the potential energy of the beam,the input work of the excitation,the dissipation work of the beam,and the dynamics stress along the beam are investigated based on the same parameters.The comparison shows that all these isolations can protect the beam with high efficiency,even when the basement excitation is tiny.Although the linear isolation and the nonlinearly enhanced one will arouse two resonance peaks on both sides of the primary resonance of the beam without isolation,the maximum amplitudes of them are reduced a lot.But for the low frequency excitation,the quasi-zero isolation has the best performance as it drives the primary resonance to the high frequency region.The simulation shows that the beam needs a relatively soft isolation to avoid the damage caused by the shock vibration,including the quasi-zero one.In general,the quasi-zero isolation shows the best performance.The nonlinearly enhanced one is the suboptimal choice.The present work shows the capacities of three isolations for a flexible beam by the steady-state response and the shock vibration.It provides design suggestions for the isolation of flexible beams.
基金Project supported by the National Science Fund for Distinguished Young Scholars(No.12025204)the China Scholarship Council(No.202206890066)。
文摘Designing,modeling,and analyzing novel nonlinear elastic elements for the nonlinear energy sink(NES)have long been an attractive research topic.Since gravity is difficult to overcome,previous NES research mainly focused on horizontal vibration suppression.This study proposes an origami-inspired NES.A stacked Miura-origami(SMO)structure,consisting of two Miura-ori sheets,is adopted to construct a nonlinear elastic element.By adjusting the initial angle and the connecting crease torsional stiffness,the quasi-zero stiffness(QZS)and load-bearing capacity can be customized to match the corresponding mass,establishing the vertical SMO-NES.The dynamic model of the SMO-NES coupled with a linear oscillator(LO)is derived for vibrations in the vertical direction.The approximate analytical solutions of the dynamic equation are obtained by the harmonic balance method(HBM),and the solutions are verified numerically.The parameter design principle of the SMO-NES is provided.Finally,the vibration reduction performance of the SMO-NES is studied.The results show that the proposed SMONES can overcome gravity and achieve quasi-zero nonlinear restoring force.Therefore,the SMO-NES has the ability of wide-frequency vibration reduction,and can effectively suppress vertical vibrations.By adjusting the initial angle and connecting the crease torsional stiffness of the SMO,the SMO-NES can be achieved with different loading weights,effectively suppressing the vibrations with different primary system masses and excitation amplitudes.In conclusion,with the help of popular origami structures,this study proposes a novel NES,and starts the research of combining origami and NES.
基金supported by the China National Funds for Distinguished Young Scholars(Grant No.12025204)the Shanghai Municipal Education Commission(Grant No.2019-01-07-00-09-E00018)。
文摘Suppressing micro-amplitude vibrations is a critical issue in aerospace engineering.While nonlinear energy sinks(NES)are effective for passive vibration damping,their performance diminishes for micro-amplitude vibrations.This paper introduces a motion-amplified NES(MANES)to address this challenge.The system’s governing equations are derived using Hamilton’s principle,and an approximate analytical solution is validated by numerical methods.The effects of various parameters are explored,with higher vibration reduction efficiency achievable through parameter adjustments.Compared to cubic NES,MANES shows superior vibration suppression and a broader reduction bandwidth for micro-amplitude excitations.Additionally,MANES enters the effective vibration reduction range at lower excitation levels,indicating a reduced threshold for vibration suppression.This study provides insight into the vibration suppression mechanism of MANES,offering a theoretical foundation for mitigating micro-amplitude vibrations in engineering applications.
基金The authors gratefully acknowledge the support of the National Natural Science Foundation of China(Grants 12025204 and 12002217)the Program of Shanghai Municipal Education Commission(Grant 2019-01-07-00-09-E00018)the Key Research Projects of Shanghai Science and Technology Commission(Grant 18010500100).
文摘Nonlinear vibration absorbers have been widely used for vibration suppression of elastic structures,but they were usually placed within the structures.However,designing such a vibration damping device within an engineering structure is possibly difficult.In this paper,an inertial nonlinear energy sinks(NES)is mounted on the boundaries of the elastic beam to suppress its vibration.Although this vibration suppression approach is more in line with engineering requirements,it introduces nonlinear oscillators at boundaries.This brings certain difficulties to the structural vibration analysis and the optimal absorber design.An approximate analytical approach for the steady-state response is developed in this work and verified by numerical solutions.The comparison with the uncontrolled system demonstrates the high-efficiency vibration suppression of the inertial NES installed on the boundary.Besides,the optimization of the NES parameters is performed.Resonance amplitude of the elastic structure can be reduced by 98%with the optimized NES.In summary,this paper proposes a novel approach to suppress the bending vibration of elastic structures through boundary NESs.The vibration reduction effect is very significant,and it is more feasible to implement.Therefore,this work is helpful to study the vibration of elastic structures with nonlinear boundaries and to promote the application of nonlinear vibration absorbers.
基金Project supported by the China National Funds for Distinguished Young Scholars(No.12025204)the Shanghai Municipal Education Commission(No.2019-01-07-00-09-E00018)。
文摘Fluid-conveying pipes are widely used to transfer bulk fluids from one point to another in many engineering applications.They are subject to various excitations from the conveying fluids,the supporting structures,and the working environment,and thus are prone to vibrations such as flow-induced vibrations and acoustic-induced vibrations.Vibrations can generate variable dynamic stress and large deformation on fluid-conveying pipes,leading to vibration-induced fatigue and damage on the pipes,or even leading to failure of the entire piping system and catastrophic accidents.Therefore,the vibration control of fluid-conveying pipes is essential to ensure the integrity and safety of pipeline systems,and has attracted considerable attention from both researchers and engineers.The present paper aims to provide an extensive review of the state-of-the-art research on the vibration control of fluid-conveying pipes.The vibration analysis of fluid-conveying pipes is briefly discussed to show some key issues involved in the vibration analysis.Then,the research progress on the vibration control of fluid-conveying pipes is reviewed from four aspects in terms of passive control,active vibration control,semi-active vibration control,and structural optimization design for vibration reduction.Furthermore,the main results of existing research on the vibration control of fluid-conveying pipes are summarized,and future promising research directions are recommended to address the current research gaps.This paper contributes to the understanding of vibration control of fluid-conveying pipes,and will help the research work on the vibration control of fluidconveying pipes attract more attention.
基金the National Natural Science Foundation of China(No.11772181)the Program of Shanghai Municipal Education Commission(No.2019-01-07-00-09-E0018)the Key Research Projects of Shanghai Science and Technology Commission(No.18010500100)。
文摘Impact dampers are usually used to suppress single mode resonance. The goal of this paper is to clarify the difference when the impact damper suppresses the resonances of different modes. A cantilever beam equipped with the impact damper is modeled. The elastic contact of the ball and the cantilever beam is described by using the Hertz contact model. The viscous damper between the ball and the cantilever beam is modeled to consume the vibrational energy of the cantilever beam. A piecewise ordinary differential-partial differential equation of the cantilever beam is established, including equations with and without the impact damper. The vibration responses of the cantilever beam with and without the impact damper are numerically calculated. The effects of the impact absorber parameters on the vibration reduction are examined. The results show that multiple resonance peaks of the cantilever beam can be effectively suppressed by the impact damper. Specifically, all resonance amplitudes can be reduced by a larger weight ball. Moreover, the impacting gap is very effective in suppressing the vibration of the cantilever beam. More importantly, there is an optimal impacting gap for each resonance mode of the cantilever beam, but the optimal gap for each mode is different.
