The subharmonic response of a single-degree-of-freedom linear vibroimpact oscillator with a one-sided barrier to the narrow-band random excitation is investigated.The analysis is based on a special Zhuravlev transform...The subharmonic response of a single-degree-of-freedom linear vibroimpact oscillator with a one-sided barrier to the narrow-band random excitation is investigated.The analysis is based on a special Zhuravlev transformation,which reduces the system to the one without impacts or velocity jumps,and thereby permits the applications of asymptotic averaging over the period for slowly varying the inphase and quadrature responses.The averaged stochastic equations are exactly solved by the method of moments for the mean square response amplitude for the case of zero offset.A perturbation-based moment closure scheme is proposed for the case of nonzero offset.The effects of damping,detuning,and bandwidth and magnitudes of the random excitations are analyzed.The theoretical analyses are verified by the numerical results.The theoretical analyses and numerical simulations show that the peak amplitudes can be strongly reduced at the large detunings.展开更多
Earthquake is a violent and irregular ground motion that can severely damage structures. In this paper we subject a single-degree-of-freedom system, consisting of spring and damper, to an earthquake excitation, and me...Earthquake is a violent and irregular ground motion that can severely damage structures. In this paper we subject a single-degree-of-freedom system, consisting of spring and damper, to an earthquake excitation, and meanwhile investigate the response behavior from a novel theory about the dynamical system, by viewing the time-varying signum function of It can reflect the characteristic property of each earthquake through and the second component of f, where is a time-sampling record of the acceleration of a ground motion. The barcode is formed by plotting with respect to time. We analyze the complex jumping behavior in a barcode and an essential property of a high percentage occupation of the first set of dis-connectivity in the barcode from four strong earthquake records: 1940 El Centro earthquake, 1989 Loma earthquake, and two records of 1999 Chi-Chi earthquake. Through the comparisons of four earthquakes, we can observe that strong earthquake leads to large percentage of the first set of dis-connectivity.展开更多
Throughout the vehicle crash event, the interactions between vehicle, occupant, restraint system (VOR) are complicated and highly non-linear. CAE and physical tests are the most widely used in vehicle passive safety d...Throughout the vehicle crash event, the interactions between vehicle, occupant, restraint system (VOR) are complicated and highly non-linear. CAE and physical tests are the most widely used in vehicle passive safety development, but they can only be done with the detailed 3D model or physical samples. Often some design errors and imperfections are difficult to correct at that time, and a large amount of time will be needed. A restraint system concept design approach which based on single-degree-of-freedom occupant-vehicle model (SDOF) is proposed in this paper. The interactions between the restraint system parameters and the occupant responses in a crash are studied from the view of mechanics and energy. The discrete input and the iterative algorithm method are applied to the SDOF model to get the occupant responses quickly for arbitrary excitations (impact pulse) by MATLAB. By studying the relationships between the ridedown efficiency, the restraint stiffness, and the occupant response, the design principle of the restraint stiffness aiming to reduce occupant injury level during conceptual design is represented. Higher ridedown efficiency means more occupant energy absorbed by the vehicle, but the research result shows that higher ridedown efficiency does not mean lower occupant injury level. A proper restraint system design principle depends on two aspects. On one hand,the restraint system should lead to as high ridedown efficiency as possible, and at the same time, the restraint system should maximize use of the survival space to reduce the occupant deceleration level. As an example, an optimization of a passenger vehicle restraint system is designed by the concept design method above, and the final results are validated by MADYMO, which is the most widely used software in restraint system design, and the sled test. Consequently, a guideline and method for the occupant restraint system concept design is established in this paper.展开更多
The wave-particle duality of a single particle with an n-dimensional internal degree of freedom is re-examined theo- retically in a Mach-Zehnder interferometer. The famous duality relation D2 + V2 〈 1 is always vali...The wave-particle duality of a single particle with an n-dimensional internal degree of freedom is re-examined theo- retically in a Mach-Zehnder interferometer. The famous duality relation D2 + V2 〈 1 is always valid in this situation, where D is the distinguishability and V is the visibility. However, the sum of the particle information and the wave information, D2 V2, can be smaller than one for the input of a pure state if this initial pure state includes the internal degree of freedom of the particle, while the quantity D2~ V2 is always equal to one when the internal degree of freedom of the particle is excluded.展开更多
Because of hydraulic-electromagnetic double supporting forms,the supporting capacity and stiffness of magnetic-liquid double suspension bearing(MLDSB)can be improved sharply and then it is more suitable for medium spe...Because of hydraulic-electromagnetic double supporting forms,the supporting capacity and stiffness of magnetic-liquid double suspension bearing(MLDSB)can be improved sharply and then it is more suitable for medium speed,heavy load and frequent-starting occasions.Due to the multiple uncertainty,such as the coupling,the unmodeled dynamics,the parameter perturbation and the external disturbance perturbation,the robust stability and stiffness of control system of MLDSB are hard to meet the design requirements.Firstly,the structural features and the regulation mechanisms of MLDSB are presented and the radial 4-DOF kinetic equations are established.Secondly,the influence factors of the control system's coupling on unbalanced vibration caused by the deviation of the rotor center of mass are revealed,and then the weighting function of suppressing the unbalanced vibration can be obtained.Finally,H∞ controller of MLDSB is designed with H∞ mixed-sensitivity method,and the control performances of H∞ controller is compared with the state feedback controller.The simulation results show that single degree of freedom(DOF)supporting system of MLDSB with H∞ controller has good robust stability,stiffness and the ability to suppress unbalanced external disturbances.This study can provide the theoretical reference for stabilized suspension and control of MLDSB.展开更多
This paper presents a type of vibration energy harvester combining a piezoelectric cantilever and a single degree of freedom (SDOF) elastic system. The main function of the additional SDOF elastic system is to magnify...This paper presents a type of vibration energy harvester combining a piezoelectric cantilever and a single degree of freedom (SDOF) elastic system. The main function of the additional SDOF elastic system is to magnify vibration displacement of the piezoelectric cantilever to improve the power output. A mathematical model of the energy harvester is developed based on Hamilton's principle and Rayleigh-Ritz method. Furthermore, the effects of the structural parameters of the SDOF elastic system on the electromechanical outputs of the energy harvester are analyzed numerically. The accuracy of the output performance in the numerical solution is identified from the finite element method (FEM). A good agreement is found between the numerical results and FEM results. The results show that the power output can be increased and the frequency bandwidth can be improved when the SDOF elastic system has a larger lumped mass and a smaller damping ratio. The numerical results also indicate that a matching load resistance under the short circuit resonance condition can obtain a higher current output, and so is more suitable for application to the piezoelectric energy harvester.展开更多
建立具有设计意义的地震动总输入能量谱是实现结构能量设计的基础。根据中长周期段修正的加速度反应谱及地震动有效持时,提出了一种生成地震动输入能量谱的方法。统计270组人工波的时程分析结果,得到了以等效速度表征的四段式弹性单自由...建立具有设计意义的地震动总输入能量谱是实现结构能量设计的基础。根据中长周期段修正的加速度反应谱及地震动有效持时,提出了一种生成地震动输入能量谱的方法。统计270组人工波的时程分析结果,得到了以等效速度表征的四段式弹性单自由度(single degree of freedom,SDOF)体系总输入能量谱,并给出了不同场地类型、抗震设防烈度等设计条件下归一化等效速度谱的参数取值。在考虑延性系数及刚度折减系数的影响后,提出了弹塑性SDOF体系修正输入能量谱的等效速度谱,估算了引起结构损伤的滞回耗能占总能量的比值。该能量谱可为基于能量的结构设计及研究提供参考。展开更多
以4种场地土条件下40条强震记录为输入,分析了弹塑性单自由度(Single Degree of Freedom,SDOF)系统的地震输入能量谱,并对地震动强度和SDOF系统参数对地震输入能量谱的影响进行了研究。结果表明:能量谱峰值主要由地震动强度决定,阻尼比...以4种场地土条件下40条强震记录为输入,分析了弹塑性单自由度(Single Degree of Freedom,SDOF)系统的地震输入能量谱,并对地震动强度和SDOF系统参数对地震输入能量谱的影响进行了研究。结果表明:能量谱峰值主要由地震动强度决定,阻尼比和延性系数有很大影响。在长周期范围,延性系数一定时,随着阻尼比的增大,能量谱值也有所增大;随延性系数增大,能量谱值随阻尼比增加而增大的趋势有所减缓。采用归一化方法,根据能量谱的特征建议了简化三段式地震输入能量谱,并根据能量谱分析结果的统计,建议了弹塑性SDOF系统能量谱峰值和能量谱曲线参数的确定方法。展开更多
为了确定弹塑性单自由度(single degree of freedom,SDOF)体系地震输入能,分析了中美场地土剪切波速转换关系,将从美国PEER地震记录数据库选取的220条强震记录按中国场地土类型进行分类,基于能量平衡原理,采用归一化方法,建议了一种基...为了确定弹塑性单自由度(single degree of freedom,SDOF)体系地震输入能,分析了中美场地土剪切波速转换关系,将从美国PEER地震记录数据库选取的220条强震记录按中国场地土类型进行分类,基于能量平衡原理,采用归一化方法,建议了一种基于复合强度指标的弹性SDOF体系三段式等效速度谱.分析了5类场地土条件下SDOF体系系统参数对地震输入等效速度谱的影响.研究结果表明:刚度折减系数对等效速度谱无明显影响;延性系数和阻尼比增大均对等效速度谱峰值和下降段衰减速度有削弱作用.综合考虑各类影响因素,通过参数多次拟合,得出弹性SDOF体系归一化等效速度谱峰值段及下降段修正系数,提出了一种适用于我国场地土类型、可直接供设计使用的弹塑性SDOF体系归一化等效速度谱确定方法,并验证了其有效性.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 10772046 and 50978058)the Natural Science Foundation of Guangdong Province of China (Nos. 7010407 and 05300566)
文摘The subharmonic response of a single-degree-of-freedom linear vibroimpact oscillator with a one-sided barrier to the narrow-band random excitation is investigated.The analysis is based on a special Zhuravlev transformation,which reduces the system to the one without impacts or velocity jumps,and thereby permits the applications of asymptotic averaging over the period for slowly varying the inphase and quadrature responses.The averaged stochastic equations are exactly solved by the method of moments for the mean square response amplitude for the case of zero offset.A perturbation-based moment closure scheme is proposed for the case of nonzero offset.The effects of damping,detuning,and bandwidth and magnitudes of the random excitations are analyzed.The theoretical analyses are verified by the numerical results.The theoretical analyses and numerical simulations show that the peak amplitudes can be strongly reduced at the large detunings.
文摘Earthquake is a violent and irregular ground motion that can severely damage structures. In this paper we subject a single-degree-of-freedom system, consisting of spring and damper, to an earthquake excitation, and meanwhile investigate the response behavior from a novel theory about the dynamical system, by viewing the time-varying signum function of It can reflect the characteristic property of each earthquake through and the second component of f, where is a time-sampling record of the acceleration of a ground motion. The barcode is formed by plotting with respect to time. We analyze the complex jumping behavior in a barcode and an essential property of a high percentage occupation of the first set of dis-connectivity in the barcode from four strong earthquake records: 1940 El Centro earthquake, 1989 Loma earthquake, and two records of 1999 Chi-Chi earthquake. Through the comparisons of four earthquakes, we can observe that strong earthquake leads to large percentage of the first set of dis-connectivity.
基金supported by National Natural Science Foundation of China (Grant No. 51075180)Open Foundation of State Key Laboratory of Vehicle NVH and Safety Technology of China (Grant No.NVHSKL-201013)
文摘Throughout the vehicle crash event, the interactions between vehicle, occupant, restraint system (VOR) are complicated and highly non-linear. CAE and physical tests are the most widely used in vehicle passive safety development, but they can only be done with the detailed 3D model or physical samples. Often some design errors and imperfections are difficult to correct at that time, and a large amount of time will be needed. A restraint system concept design approach which based on single-degree-of-freedom occupant-vehicle model (SDOF) is proposed in this paper. The interactions between the restraint system parameters and the occupant responses in a crash are studied from the view of mechanics and energy. The discrete input and the iterative algorithm method are applied to the SDOF model to get the occupant responses quickly for arbitrary excitations (impact pulse) by MATLAB. By studying the relationships between the ridedown efficiency, the restraint stiffness, and the occupant response, the design principle of the restraint stiffness aiming to reduce occupant injury level during conceptual design is represented. Higher ridedown efficiency means more occupant energy absorbed by the vehicle, but the research result shows that higher ridedown efficiency does not mean lower occupant injury level. A proper restraint system design principle depends on two aspects. On one hand,the restraint system should lead to as high ridedown efficiency as possible, and at the same time, the restraint system should maximize use of the survival space to reduce the occupant deceleration level. As an example, an optimization of a passenger vehicle restraint system is designed by the concept design method above, and the final results are validated by MADYMO, which is the most widely used software in restraint system design, and the sled test. Consequently, a guideline and method for the occupant restraint system concept design is established in this paper.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB921603)the National Natural Science Foundation of China(Grant Nos.11125418 and 11364022)
文摘The wave-particle duality of a single particle with an n-dimensional internal degree of freedom is re-examined theo- retically in a Mach-Zehnder interferometer. The famous duality relation D2 + V2 〈 1 is always valid in this situation, where D is the distinguishability and V is the visibility. However, the sum of the particle information and the wave information, D2 V2, can be smaller than one for the input of a pure state if this initial pure state includes the internal degree of freedom of the particle, while the quantity D2~ V2 is always equal to one when the internal degree of freedom of the particle is excluded.
基金Supported by the National Nature Science Foundation of China(No.51705445,52075468)General Project of Natural Science Foundation of Hebei Province(E2020203052)+1 种基金Youth Fund Project of Scientific Research Project of Hebei University(QN202013)Open Project Funding of Jiangsu Provincial Key Laboratory of Advanced Manufacture and Process for Marine Mechanical Equipment and Open Project Funding of Fluid Power Transmission Control Laboratory of Yanshan University.
文摘Because of hydraulic-electromagnetic double supporting forms,the supporting capacity and stiffness of magnetic-liquid double suspension bearing(MLDSB)can be improved sharply and then it is more suitable for medium speed,heavy load and frequent-starting occasions.Due to the multiple uncertainty,such as the coupling,the unmodeled dynamics,the parameter perturbation and the external disturbance perturbation,the robust stability and stiffness of control system of MLDSB are hard to meet the design requirements.Firstly,the structural features and the regulation mechanisms of MLDSB are presented and the radial 4-DOF kinetic equations are established.Secondly,the influence factors of the control system's coupling on unbalanced vibration caused by the deviation of the rotor center of mass are revealed,and then the weighting function of suppressing the unbalanced vibration can be obtained.Finally,H∞ controller of MLDSB is designed with H∞ mixed-sensitivity method,and the control performances of H∞ controller is compared with the state feedback controller.The simulation results show that single degree of freedom(DOF)supporting system of MLDSB with H∞ controller has good robust stability,stiffness and the ability to suppress unbalanced external disturbances.This study can provide the theoretical reference for stabilized suspension and control of MLDSB.
基金Project supported by the National Natural Science Foundation of China (No. 51077018)the Science and Technology Planning Project of Qiqihar (No. GYGG2010-02-1), China
文摘This paper presents a type of vibration energy harvester combining a piezoelectric cantilever and a single degree of freedom (SDOF) elastic system. The main function of the additional SDOF elastic system is to magnify vibration displacement of the piezoelectric cantilever to improve the power output. A mathematical model of the energy harvester is developed based on Hamilton's principle and Rayleigh-Ritz method. Furthermore, the effects of the structural parameters of the SDOF elastic system on the electromechanical outputs of the energy harvester are analyzed numerically. The accuracy of the output performance in the numerical solution is identified from the finite element method (FEM). A good agreement is found between the numerical results and FEM results. The results show that the power output can be increased and the frequency bandwidth can be improved when the SDOF elastic system has a larger lumped mass and a smaller damping ratio. The numerical results also indicate that a matching load resistance under the short circuit resonance condition can obtain a higher current output, and so is more suitable for application to the piezoelectric energy harvester.
文摘建立具有设计意义的地震动总输入能量谱是实现结构能量设计的基础。根据中长周期段修正的加速度反应谱及地震动有效持时,提出了一种生成地震动输入能量谱的方法。统计270组人工波的时程分析结果,得到了以等效速度表征的四段式弹性单自由度(single degree of freedom,SDOF)体系总输入能量谱,并给出了不同场地类型、抗震设防烈度等设计条件下归一化等效速度谱的参数取值。在考虑延性系数及刚度折减系数的影响后,提出了弹塑性SDOF体系修正输入能量谱的等效速度谱,估算了引起结构损伤的滞回耗能占总能量的比值。该能量谱可为基于能量的结构设计及研究提供参考。
文摘以4种场地土条件下40条强震记录为输入,分析了弹塑性单自由度(Single Degree of Freedom,SDOF)系统的地震输入能量谱,并对地震动强度和SDOF系统参数对地震输入能量谱的影响进行了研究。结果表明:能量谱峰值主要由地震动强度决定,阻尼比和延性系数有很大影响。在长周期范围,延性系数一定时,随着阻尼比的增大,能量谱值也有所增大;随延性系数增大,能量谱值随阻尼比增加而增大的趋势有所减缓。采用归一化方法,根据能量谱的特征建议了简化三段式地震输入能量谱,并根据能量谱分析结果的统计,建议了弹塑性SDOF系统能量谱峰值和能量谱曲线参数的确定方法。
文摘为了确定弹塑性单自由度(single degree of freedom,SDOF)体系地震输入能,分析了中美场地土剪切波速转换关系,将从美国PEER地震记录数据库选取的220条强震记录按中国场地土类型进行分类,基于能量平衡原理,采用归一化方法,建议了一种基于复合强度指标的弹性SDOF体系三段式等效速度谱.分析了5类场地土条件下SDOF体系系统参数对地震输入等效速度谱的影响.研究结果表明:刚度折减系数对等效速度谱无明显影响;延性系数和阻尼比增大均对等效速度谱峰值和下降段衰减速度有削弱作用.综合考虑各类影响因素,通过参数多次拟合,得出弹性SDOF体系归一化等效速度谱峰值段及下降段修正系数,提出了一种适用于我国场地土类型、可直接供设计使用的弹塑性SDOF体系归一化等效速度谱确定方法,并验证了其有效性.