Flexible damping technology considering aseismic materials and aseismic structures seems be a good solution for engineering structures.In this study,a constrained damping structure for underground tunnel lining,using ...Flexible damping technology considering aseismic materials and aseismic structures seems be a good solution for engineering structures.In this study,a constrained damping structure for underground tunnel lining,using a rubber-sand-concrete(RSC)as the aseismic material,is proposed.The aseismic performances of constrained damping structure were investigated by a series of hammer impact tests.The damping layer thickness and shape effects on the aseismic performance such as effective duration and acceleration amplitude of time-domain analysis,composite loss factor and damping ratio of the transfer function analysis,and total vibration level of octave spectrum analysis were discussed.The hammer impact tests revealed that the relationship between the aseismic performance and damping layer thickness was not linear,and that the hollow damping layer had a better aseismic performance than the flat damping layer one.The aseismic performances of constrained damping structure under different seismicity magnitudes and geological conditions were investigated.The effects of the peak ground acceleration(PGA)and tunnel overburden depth on the aseismic performances such as the maximum principal stress and equivalent plastic strain(PEEQ)were discussed.The numerical results show the constrained damping structure proposed in this paper has a good aseismic performance,with PGA in the range(0.2-1.2)g and tunnel overburden depth in the range of 0-300 m.展开更多
This paper investigates how the magnetic constrained layer damping (MCLD) treat- ment suppresses the displacement and acceleration resonant peak of a clamped-clamped beam. Because MCLD treatment reduces input work a...This paper investigates how the magnetic constrained layer damping (MCLD) treat- ment suppresses the displacement and acceleration resonant peak of a clamped-clamped beam. Because MCLD treatment reduces input work and gives more dissipation energy, the vibration from external excitation can be e?ectively suppressed.The vibration reduction e?ects of MCLD and other conventional constrained damping treatments are also evaluated. In many cases, using MCLD treatments can yield smaller displacement and acceleration resonant peak especially in mode 1 compared to the other treatments without greatly changing the natural frequencies of the base beam.展开更多
For the best dynamic performance of a co-cured composite damping instrument panel with light weight and high strength, a multilayer sandwich structure with polymethaerylimide (PMI) foam combined with embedded and co...For the best dynamic performance of a co-cured composite damping instrument panel with light weight and high strength, a multilayer sandwich structure with polymethaerylimide (PMI) foam combined with embedded and co-cured composite damping structure is proposed. The struetue can maintain the excellent mechanical properties of composite materials, and achieve the damping and light effect at the same time. Input variables which may affect the dynamic performance of the instrument panel were selected and variance based importance measure was analyzed through multi- finite element method (FEM) analysis. Using the results of the importance measure analysis, with other design requirements, the important design variable was optimized and an instrument panel with the best dynamic performance under the requirements of light weight and high strength was obtained. The structure of the instrument panel can provide reference for the design of precision, high speed, and dynamic composite component. The importance measure analysis of dynamic performance of the instrument panel can provide a reference for relative design.展开更多
The design and analysis of an intelligent vehicle suspension with MR dampers should address hybrid semi-active control goals, such as rejection of current-switching discontinuity and MR-damper hysteresis, asymmetric d...The design and analysis of an intelligent vehicle suspension with MR dampers should address hybrid semi-active control goals, such as rejection of current-switching discontinuity and MR-damper hysteresis, asymmetric damping from the symmetric MR-damper design, robustness on the vehicle operation parameter uncertainties and consideration of essential multiple suspension goals. Following the proposed skyhook-based asymmetric semi-active controller (Part I ) for achieving the above goals, herein, a set of suspension performance measures and three kinds of varying amplitude harmonic, rounded pulse and really measured random excitations are systematically defined, and the sensitivity of quarter-vehicle MR-suspension performance to variations in operating conditions is thoroughly analyzed. The results illustrate that the proposed skyhook-based semi-active MR-suspension in the asymmetric mode yields relatively superior dynamic responses to meet the multiple suspension performances of ride, rattle space, road-holding and dynamic tire force transmitted to the pavement, and has desirable robustness on variations in operating conditions of vehicle load and speed and the road roughness.展开更多
The hydrodynamic performance of a bottom-hinged flap wave energy converter (WEC) is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solutio...The hydrodynamic performance of a bottom-hinged flap wave energy converter (WEC) is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solution, as well as the qualitative analysis on the dynamic response of avibrating system. The concept of "optimum density" of the bottom-hinged flap is proposed, and its analytic expression is derived as well. The frequency interval in which the optimum density exists is also obtained. The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC. Some basic dynamic properties involving natural period, excitation moment, pitch amplitude, and optimum damping coefficient are analyzed and discussed in detail. In addition, this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters. The results indicate that "the optimum linear damping period of 5.0 s" is the most ideal option in the short wave sea states with the wave period below 6.0 s. Shallow water depth, large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture. In the sea state with water depth of 5.0 m and wave period of 5.0 s, the results of parametric optimization suggest a flap with the width of 8.0 m, thickness of 1.6 m, and with the density as little as possible when the optimum power take-off (PTO) damping coefficient is adopted.展开更多
Semi-active dampers are used in base-isolation to reduce the seismic response of civil engineering structures. In the present study, a new semi-active damping system using variable amplification will be investigated f...Semi-active dampers are used in base-isolation to reduce the seismic response of civil engineering structures. In the present study, a new semi-active damping system using variable amplification will be investigated for adaptive baseisolation. It uses a novel variable amplification device (VAD) connected in series with a passive damper. The VAD is capable of producing multiple amplification factors, each corresponding to a different amplification state. Forces from the damper are amplified to the structure according to the current amplification state, which is selected via a semi-active control algorithm specifically tailored to the system's tmique damping characteristics. To demonstrate the effectiveness of the VAD-damper system for adaptive base-isolation, numerical simulations are conducted for three and seven-story base-isolated buildings subject to both far and near-field ground motions. The results indicate that the system can achieve significant reductions in response compared to the base-isolated buildings with no damper. The proposed system is also found to perform well compared to a typical semi-active damper.展开更多
Three design modes of seat suspension,i.e.,negative stiffness elements(NSEs),damping elements(DEs),and negative stiffness-damping elements(NSDEs),are proposed to evaluate the ride performance of a vehicle.Based on a d...Three design modes of seat suspension,i.e.,negative stiffness elements(NSEs),damping elements(DEs),and negative stiffness-damping elements(NSDEs),are proposed to evaluate the ride performance of a vehicle.Based on a dynamic model of a seat suspension and indexes of the root mean square deformation and acceleration of the seat suspension(x RMS)and driver s seat(a RMS),the influence of the design parameters of the NSEs,DEs,and NSDEs on the driver s ride comfort is evaluated.A genetic algorithm is then applied to optimize the parameters of the NSEs,DEs,and NSDEs.The study results indicate that the design parameters of the NSEs and NSDEs remarkably influence x RMS and a RMS,whereas those of the DEs insignificantly influence x RMS and a RMS.Based on the optimal results of the NSEs,DEs,and NSDEs,the damping force of the DEs is 98.3%lower than the restoring force of the NSEs.Therefore,the DEs are ineffective in decreasing x RMS and a RMS.Conversely,the NSEs combined with the damping coefficient of the seat suspension strongly reduce x RMS and a RMS.Consequently,the NSEs can be added to the seat suspension,and the damping coefficient of the seat suspension can also be optimized or controlled to further enhance the vehicle s ride performance.展开更多
基金supported by the National Natural Science Foundation of China(No.52079133)CRSRI Open Research Program(Program SN:CKWV2019746/KY)+1 种基金the project of Key Laboratory of Water Grid Project and Regulation of Ministry of Water Resources(QTKS0034W23291)the Youth Innovation Promotion Association CAS.
文摘Flexible damping technology considering aseismic materials and aseismic structures seems be a good solution for engineering structures.In this study,a constrained damping structure for underground tunnel lining,using a rubber-sand-concrete(RSC)as the aseismic material,is proposed.The aseismic performances of constrained damping structure were investigated by a series of hammer impact tests.The damping layer thickness and shape effects on the aseismic performance such as effective duration and acceleration amplitude of time-domain analysis,composite loss factor and damping ratio of the transfer function analysis,and total vibration level of octave spectrum analysis were discussed.The hammer impact tests revealed that the relationship between the aseismic performance and damping layer thickness was not linear,and that the hollow damping layer had a better aseismic performance than the flat damping layer one.The aseismic performances of constrained damping structure under different seismicity magnitudes and geological conditions were investigated.The effects of the peak ground acceleration(PGA)and tunnel overburden depth on the aseismic performances such as the maximum principal stress and equivalent plastic strain(PEEQ)were discussed.The numerical results show the constrained damping structure proposed in this paper has a good aseismic performance,with PGA in the range(0.2-1.2)g and tunnel overburden depth in the range of 0-300 m.
文摘This paper investigates how the magnetic constrained layer damping (MCLD) treat- ment suppresses the displacement and acceleration resonant peak of a clamped-clamped beam. Because MCLD treatment reduces input work and gives more dissipation energy, the vibration from external excitation can be e?ectively suppressed.The vibration reduction e?ects of MCLD and other conventional constrained damping treatments are also evaluated. In many cases, using MCLD treatments can yield smaller displacement and acceleration resonant peak especially in mode 1 compared to the other treatments without greatly changing the natural frequencies of the base beam.
文摘For the best dynamic performance of a co-cured composite damping instrument panel with light weight and high strength, a multilayer sandwich structure with polymethaerylimide (PMI) foam combined with embedded and co-cured composite damping structure is proposed. The struetue can maintain the excellent mechanical properties of composite materials, and achieve the damping and light effect at the same time. Input variables which may affect the dynamic performance of the instrument panel were selected and variance based importance measure was analyzed through multi- finite element method (FEM) analysis. Using the results of the importance measure analysis, with other design requirements, the important design variable was optimized and an instrument panel with the best dynamic performance under the requirements of light weight and high strength was obtained. The structure of the instrument panel can provide reference for the design of precision, high speed, and dynamic composite component. The importance measure analysis of dynamic performance of the instrument panel can provide a reference for relative design.
基金Senior Visiting Scholarship of Chinese Scholarship Council (No.20H05002)Jiangsu Provincial Natural Science Foundation of Education Commission of China (No.03KJB510072)Jiangsu Provincial Six Categories of Summit Talents of China (No.2OO6194)
文摘The design and analysis of an intelligent vehicle suspension with MR dampers should address hybrid semi-active control goals, such as rejection of current-switching discontinuity and MR-damper hysteresis, asymmetric damping from the symmetric MR-damper design, robustness on the vehicle operation parameter uncertainties and consideration of essential multiple suspension goals. Following the proposed skyhook-based asymmetric semi-active controller (Part I ) for achieving the above goals, herein, a set of suspension performance measures and three kinds of varying amplitude harmonic, rounded pulse and really measured random excitations are systematically defined, and the sensitivity of quarter-vehicle MR-suspension performance to variations in operating conditions is thoroughly analyzed. The results illustrate that the proposed skyhook-based semi-active MR-suspension in the asymmetric mode yields relatively superior dynamic responses to meet the multiple suspension performances of ride, rattle space, road-holding and dynamic tire force transmitted to the pavement, and has desirable robustness on variations in operating conditions of vehicle load and speed and the road roughness.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41206074 and 51205346)the Special Fund for Marine Renewable Energy (Grant Nos. GHME2011CX01 and GHME2011ZC05)
文摘The hydrodynamic performance of a bottom-hinged flap wave energy converter (WEC) is investigated through a frequency domain numerical model. The numerical model is verified through a two-dimensional analytic solution, as well as the qualitative analysis on the dynamic response of avibrating system. The concept of "optimum density" of the bottom-hinged flap is proposed, and its analytic expression is derived as well. The frequency interval in which the optimum density exists is also obtained. The analytic expression of the optimum linear damping coefficient is obtained by a bottom-hinged WEC. Some basic dynamic properties involving natural period, excitation moment, pitch amplitude, and optimum damping coefficient are analyzed and discussed in detail. In addition, this paper highlights the analysis of effects on the conversion performance of the device exerted by some important parameters. The results indicate that "the optimum linear damping period of 5.0 s" is the most ideal option in the short wave sea states with the wave period below 6.0 s. Shallow water depth, large flap thickness and low flap density are advised in the practical design of the device in short wave sea states in order to maximize power capture. In the sea state with water depth of 5.0 m and wave period of 5.0 s, the results of parametric optimization suggest a flap with the width of 8.0 m, thickness of 1.6 m, and with the density as little as possible when the optimum power take-off (PTO) damping coefficient is adopted.
文摘Semi-active dampers are used in base-isolation to reduce the seismic response of civil engineering structures. In the present study, a new semi-active damping system using variable amplification will be investigated for adaptive baseisolation. It uses a novel variable amplification device (VAD) connected in series with a passive damper. The VAD is capable of producing multiple amplification factors, each corresponding to a different amplification state. Forces from the damper are amplified to the structure according to the current amplification state, which is selected via a semi-active control algorithm specifically tailored to the system's tmique damping characteristics. To demonstrate the effectiveness of the VAD-damper system for adaptive base-isolation, numerical simulations are conducted for three and seven-story base-isolated buildings subject to both far and near-field ground motions. The results indicate that the system can achieve significant reductions in response compared to the base-isolated buildings with no damper. The proposed system is also found to perform well compared to a typical semi-active damper.
基金The National Key Research and Development Plan(No.2019YFB2006402)the Talent Introduction Fund Project of Hubei Polytechnic University(No.19XJK20R)the Key Scientific Research Project of Hubei Polytechnic University(No.22xjz02A)。
文摘Three design modes of seat suspension,i.e.,negative stiffness elements(NSEs),damping elements(DEs),and negative stiffness-damping elements(NSDEs),are proposed to evaluate the ride performance of a vehicle.Based on a dynamic model of a seat suspension and indexes of the root mean square deformation and acceleration of the seat suspension(x RMS)and driver s seat(a RMS),the influence of the design parameters of the NSEs,DEs,and NSDEs on the driver s ride comfort is evaluated.A genetic algorithm is then applied to optimize the parameters of the NSEs,DEs,and NSDEs.The study results indicate that the design parameters of the NSEs and NSDEs remarkably influence x RMS and a RMS,whereas those of the DEs insignificantly influence x RMS and a RMS.Based on the optimal results of the NSEs,DEs,and NSDEs,the damping force of the DEs is 98.3%lower than the restoring force of the NSEs.Therefore,the DEs are ineffective in decreasing x RMS and a RMS.Conversely,the NSEs combined with the damping coefficient of the seat suspension strongly reduce x RMS and a RMS.Consequently,the NSEs can be added to the seat suspension,and the damping coefficient of the seat suspension can also be optimized or controlled to further enhance the vehicle s ride performance.