The problems associated with vibrations of viaducts and low-frequency structural noise radiation caused by train excitation continue to increase in importance.A new floating-slab track vibration isolator-non-obstructi...The problems associated with vibrations of viaducts and low-frequency structural noise radiation caused by train excitation continue to increase in importance.A new floating-slab track vibration isolator-non-obstructive particle damping-phononic crystal vibration isolator is proposed herein,which uses the particle damping vibration absorption technology and bandgap vibration control theory.The vibration reduction performance of the NOPD-PCVI was analyzed from the perspective of vibration control.The paper explores the structure-borne noise reduction performance of the NOPD-PCVIs installed on different bridge structures under varying service conditions encountered in practical engineering applications.The load transferred to the bridge is obtained from a coupled train-FST-bridge analytical model considering the different structural parameters of bridges.The vibration responses are obtained using the finite element method,while the structural noise radiation is simulated using the frequency-domain boundary element method.Using the particle swarm optimization algorithm,the parameters of the NOPD-PCVI are optimized so that its frequency bandgap matches the dominant bridge structural noise frequency range.The noise reduction performance of the NOPD-PCVIs is compared to the steel-spring isolation under different service conditions.展开更多
High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate tor...High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate torsional vibration. This paper presents the construction of a highly compact HSLDS torsional vibration isolator by connecting positive and negative stiffness components in paral lel. Based on mechanical model analysis, the restoring torque of negative stiffness components is de rived from their springs and connecting rods, while that of positive stiffness components is obtained through their circular section flexible rods. The quasizero stiffness characteristics of the HSLDS iso lator are achieved through a combination of static structural simulation and experimental test. The tor sional vibration isolation performance is assessed by means of numerical simulation and theory analy sis. Finally, the frequency-sweep vibration test is conducted. The test results indicate that the HSLDS torsional vibration isolator exhibits superior low-frequency isolation performance compared to its linear counterpart, rendering it a promising solution for mitigating low-frequency torsional vi bration in ship shafting.展开更多
The micromation and precision of the Micro-Electromechanical System demand that its manufacturing, measuring and assembling must work in a micro-manufacturing platform with good ability to isolate vibrations. This pap...The micromation and precision of the Micro-Electromechanical System demand that its manufacturing, measuring and assembling must work in a micro-manufacturing platform with good ability to isolate vibrations. This paper develops a vibration isolation system of micro-manufacturing platform. The brains of many kinds of birds can isolate vibrations well, such as woodpecker’s brain. When a woodpecker pecks the wood at the speed as 1.6 times as the velocity of sound, its brain will tolerate the wallop 1 500 times of the weight of itself without any damage. The isolation mechanics and organic texture of woodpecker’s brain that has good isolation characteristics were studied. A structure model of vibration isolation system for the micro-manufacturing platform is established based on the bionics of the bird’s brain vibration isolation mechanism. In order to isolate effectively the high frequency vibrations from the ground, a rubber layer is used to isolate vibrations passively between the micro-manufacturing platform’s pedestal and the ground. This layer corresponds to the cartilage and muscles in the outer meninges of the bird’s brain. The active vibration isolation technique is adopted to isolate vibrations between the micro-manufacturing platform and the pedestal. Air springs are used as elastic components, which correspond to the interspaces between the outer meninges and the encephala of the bird’s brain. Actuators are made of giant magnetostrictive material, and it corresponds to the nerves and neural muscles linking the meninges and the encephala. The actuators and air springs are arranged vertically in parallel to make use of the giant magnetostrictive actuators effectively. The air springs support almost all weight of the micro-manufacturing platform and the giant magnetostrictive actuators support almost no weight. In order to realize high performance to isolate complex micro-vibration, the control method using a three-layer neural network is presented. This vibration control system takes into account the floor disturbance and the direct disturbance acting on the micro-manufacturing platform. The absolute acceleration of the micro-manufacturing platform is used as the performance index of vibration control. The performance of the control system is tested by numerical simulation. Simulation results show that the active vibration isolation system has good isolation performance against the floor disturbance and the direct disturbance acting on the micro-manufacturing platform in all the frequency range.展开更多
A feedforword neural network of multi-layer topologies for systems with hysteretic nonlinearity is constructed based on Bouce Wen differential model. It not only reflects the hysteresis force characteristics of the Bo...A feedforword neural network of multi-layer topologies for systems with hysteretic nonlinearity is constructed based on Bouce Wen differential model. It not only reflects the hysteresis force characteristics of the Bouce Wen model, but also determines its corresponding parameters. The simulation results show that restoring forceedisplacement curve hysteresis loop is very close to the real curve. The model trained can accurately predict the time response of system. The model is checked under the noise level. The result shows that the model has higher modeling precision, good generalization capability and a certain anti-interference ability.展开更多
Three dimensional analysis was performed by regarding vibration isolation performance cast-in-place concrete thin-wall pipe pile (PCC) and using the finite element analysis software ANSYS. The ground vertical amplitud...Three dimensional analysis was performed by regarding vibration isolation performance cast-in-place concrete thin-wall pipe pile (PCC) and using the finite element analysis software ANSYS. The ground vertical amplitude was analyzed behind the single row cast-in-place concrete thin-wall pipe pile after the source vibration, and the influencing factors were also studied. The results indicate that in the one time of wavelength before the barrier, the oscillation amplitude is weakened; meanwhile the range which covers 4 times wavelength behind the barrier has a good vibration isolation effect, when the distance is larger than the barrier latter 4 times wavelength vibration isolation expiration.展开更多
Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attr...Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system.展开更多
The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equival...The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.展开更多
The lifetime of metal rubber isolator and its characteristics during lifetime experiment were studied. The stepped-up test principle was adopted to study the lifetime of resonant frequency, the breakage form of metal ...The lifetime of metal rubber isolator and its characteristics during lifetime experiment were studied. The stepped-up test principle was adopted to study the lifetime of resonant frequency, the breakage form of metal rubber isolator was obtained, and the relation between the energy dissipation, resonant frequency and stiffness was obtained in (available) lifetime of the isolator. Furthermore, the reason for the changes of properties of metal rubber isolator was analyzed with contact model of metal rubber material. The results show that if the resonant amplitude is large, the stiffness of metal rubber isolator will be kept steadily for a long time, its resonant frequency will be stable and the effective working time in the protecting area will be long. The lifetime of metal rubber isolator is more than 1376 h in the experiment. The main failure forms of metal rubber isolator are accumulative wear and breaking of metal wires and spirals. In protecting area the metal rubber isolator can work effectively for a long time, and the effective working time depends on the concrete working condition.展开更多
The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly ...The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.展开更多
基金Project(51978585)supported by the National Natural Science Foundation,ChinaProject(2022YFB2603404)supported by the National Key Research and Development Program,China+1 种基金Project(U1734207)supported by the High-speed Rail Joint Fund Key Projects of Basic Research,ChinaProject(2023NSFSC1975)supported by the Sichuan Nature and Science Foundation Innovation Research Group Project,China。
文摘The problems associated with vibrations of viaducts and low-frequency structural noise radiation caused by train excitation continue to increase in importance.A new floating-slab track vibration isolator-non-obstructive particle damping-phononic crystal vibration isolator is proposed herein,which uses the particle damping vibration absorption technology and bandgap vibration control theory.The vibration reduction performance of the NOPD-PCVI was analyzed from the perspective of vibration control.The paper explores the structure-borne noise reduction performance of the NOPD-PCVIs installed on different bridge structures under varying service conditions encountered in practical engineering applications.The load transferred to the bridge is obtained from a coupled train-FST-bridge analytical model considering the different structural parameters of bridges.The vibration responses are obtained using the finite element method,while the structural noise radiation is simulated using the frequency-domain boundary element method.Using the particle swarm optimization algorithm,the parameters of the NOPD-PCVI are optimized so that its frequency bandgap matches the dominant bridge structural noise frequency range.The noise reduction performance of the NOPD-PCVIs is compared to the steel-spring isolation under different service conditions.
文摘High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate torsional vibration. This paper presents the construction of a highly compact HSLDS torsional vibration isolator by connecting positive and negative stiffness components in paral lel. Based on mechanical model analysis, the restoring torque of negative stiffness components is de rived from their springs and connecting rods, while that of positive stiffness components is obtained through their circular section flexible rods. The quasizero stiffness characteristics of the HSLDS iso lator are achieved through a combination of static structural simulation and experimental test. The tor sional vibration isolation performance is assessed by means of numerical simulation and theory analy sis. Finally, the frequency-sweep vibration test is conducted. The test results indicate that the HSLDS torsional vibration isolator exhibits superior low-frequency isolation performance compared to its linear counterpart, rendering it a promising solution for mitigating low-frequency torsional vi bration in ship shafting.
文摘The micromation and precision of the Micro-Electromechanical System demand that its manufacturing, measuring and assembling must work in a micro-manufacturing platform with good ability to isolate vibrations. This paper develops a vibration isolation system of micro-manufacturing platform. The brains of many kinds of birds can isolate vibrations well, such as woodpecker’s brain. When a woodpecker pecks the wood at the speed as 1.6 times as the velocity of sound, its brain will tolerate the wallop 1 500 times of the weight of itself without any damage. The isolation mechanics and organic texture of woodpecker’s brain that has good isolation characteristics were studied. A structure model of vibration isolation system for the micro-manufacturing platform is established based on the bionics of the bird’s brain vibration isolation mechanism. In order to isolate effectively the high frequency vibrations from the ground, a rubber layer is used to isolate vibrations passively between the micro-manufacturing platform’s pedestal and the ground. This layer corresponds to the cartilage and muscles in the outer meninges of the bird’s brain. The active vibration isolation technique is adopted to isolate vibrations between the micro-manufacturing platform and the pedestal. Air springs are used as elastic components, which correspond to the interspaces between the outer meninges and the encephala of the bird’s brain. Actuators are made of giant magnetostrictive material, and it corresponds to the nerves and neural muscles linking the meninges and the encephala. The actuators and air springs are arranged vertically in parallel to make use of the giant magnetostrictive actuators effectively. The air springs support almost all weight of the micro-manufacturing platform and the giant magnetostrictive actuators support almost no weight. In order to realize high performance to isolate complex micro-vibration, the control method using a three-layer neural network is presented. This vibration control system takes into account the floor disturbance and the direct disturbance acting on the micro-manufacturing platform. The absolute acceleration of the micro-manufacturing platform is used as the performance index of vibration control. The performance of the control system is tested by numerical simulation. Simulation results show that the active vibration isolation system has good isolation performance against the floor disturbance and the direct disturbance acting on the micro-manufacturing platform in all the frequency range.
文摘A feedforword neural network of multi-layer topologies for systems with hysteretic nonlinearity is constructed based on Bouce Wen differential model. It not only reflects the hysteresis force characteristics of the Bouce Wen model, but also determines its corresponding parameters. The simulation results show that restoring forceedisplacement curve hysteresis loop is very close to the real curve. The model trained can accurately predict the time response of system. The model is checked under the noise level. The result shows that the model has higher modeling precision, good generalization capability and a certain anti-interference ability.
基金Project(50679017) supported by the National Natural Science Foundation of China
文摘Three dimensional analysis was performed by regarding vibration isolation performance cast-in-place concrete thin-wall pipe pile (PCC) and using the finite element analysis software ANSYS. The ground vertical amplitude was analyzed behind the single row cast-in-place concrete thin-wall pipe pile after the source vibration, and the influencing factors were also studied. The results indicate that in the one time of wavelength before the barrier, the oscillation amplitude is weakened; meanwhile the range which covers 4 times wavelength behind the barrier has a good vibration isolation effect, when the distance is larger than the barrier latter 4 times wavelength vibration isolation expiration.
基金the support from SOLVE: The Virtual Lab @ NITK (Grant number: No.F.16-35/2009-DL, Ministry of Human Resources Development)
文摘Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system.
基金Project(51375226)supported by the National Natural Science Foundation of ChinaProject(20113218110017)supported by the Doctoral Program Foundation of Institutions of Higher Education of China+2 种基金Project(PAPD)supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,ChinaProject(CXZZ11_0199)supported by the Funding of Jiangsu Innovation Program for Graduate Education,ChinaProject(2014)supported by the the Fundamental Research Funds for the Central Universities,China
文摘The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.
基金Project(50075017) supported by the National Natural Sceince Foundation of China
文摘The lifetime of metal rubber isolator and its characteristics during lifetime experiment were studied. The stepped-up test principle was adopted to study the lifetime of resonant frequency, the breakage form of metal rubber isolator was obtained, and the relation between the energy dissipation, resonant frequency and stiffness was obtained in (available) lifetime of the isolator. Furthermore, the reason for the changes of properties of metal rubber isolator was analyzed with contact model of metal rubber material. The results show that if the resonant amplitude is large, the stiffness of metal rubber isolator will be kept steadily for a long time, its resonant frequency will be stable and the effective working time in the protecting area will be long. The lifetime of metal rubber isolator is more than 1376 h in the experiment. The main failure forms of metal rubber isolator are accumulative wear and breaking of metal wires and spirals. In protecting area the metal rubber isolator can work effectively for a long time, and the effective working time depends on the concrete working condition.
基金Project(KYLX15_0256)supported by the Funding of Jiangsu Innovation Program for Graduate Education,ChinaProject(SV2015-KF-01)supported by the Open Project of State Key Laboratory for Strength and Vibration of Mechanical Structures,ChinaProject(XZA15003)supported by the Fundamental Research Funds for the Central Universities,China
文摘The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.
