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Ultra-wide band gap and wave attenuation mechanism of a novel star-shaped chiral metamaterial

Applied Mathematics and Mechanics(English Edition) 2024年第7期45卷 1261-1278页

作者： Shuo WANG Anshuai WANG Yansen WU Xiaofeng LI Yongtao SUN Zhaozhan ZHANG Qian DING G.D.AYALEW Yunxiang MA Qingyu LIN Department of Mechanics Tianjin University tianjin key laboratory of nonlinear dynamics and control Tianjin University State key laboratory of Metastable Materials Science and Technology Yanshan University

A novel hollow star-shaped chiral metamaterial(SCM) is proposed by incorporating chiral structural properties into the standard hollow star-shaped metamaterial, exhibiting a wide band gap over 1 500 Hz. To broaden the band gap,solid single-phase and two-phase SCMs are designed and simulated, which produce two ultra-wide band gaps(approximately 5 116 Hz and 6 027 Hz, respectively). The main reason for the formation of the ultra-wide band gap is that the rotational vibration of the concave star of two novel SCMs drains the energy of an elastic wave. The impacts of the concave angle of a single-phase SCM and the resonator radius of a two-phase SCM on the band gaps are studied. Decreasing the concave angle leads to an increase in the width of the widest band gap, and the width of the widest band gap increases as the resonator radius of the two-phase SCM increases. Additionally,the study on elastic wave propagation characteristics involves analyzing frequency dispersion surfaces, wave propagation directions, group velocities, and phase velocities. Ultimately, the analysis focuses on the transmission properties of finite periodic structures. The solid single-phase SCM achieves a maximum vibration attenuation over 800, while the width of the band gap is smaller than that of the two-phase SCM. Both metamaterials exhibit high vibration attenuation capabilities, which can be used in wideband vibration reduction to satisfy the requirement of ultra-wide frequencies.

关键词： metamaterial ultra-wide band gap wave propagation vibration suppression O421 + .5 74H45

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An electromagnetic semi-active dynamic vibration absorber for thin-walled workpiece vibration suppression in mirror milling

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Applied Mathematics and Mechanics(English Edition) 2024年第8期45卷 1315-1334页

作者： Jianghua KONG Bei DING Wei WANG Zhixia WANG Juliang XIAO Hongyun QIU School of Mechanical Engineering Tianjin University tianjin key laboratory of nonlinear dynamics and control key laboratory of Modern Mechanisms and Equipment Design of the State Ministry of Education Tianjin University

As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness. To address these challenges, we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA), which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling. This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process. Additionally, the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator, which alters the distance between magnets. This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference. The frequency shift characteristics and vibration absorption performance are comprehensively investigated. Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool, resulting in a vibration suppression rate of approximately 47.57%. Moreover, the roughness of the machined surface decreases by18.95%, significantly enhancing the surface quality. The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.

关键词： 70J35 mirror milling O326 self-sensing semi-active dynamic vibration absorber (SADVA) thin-walled workpiece vibration absorption tuning

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考虑各向异性变形的人耳鼓膜纤维增强细观本构模型

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Acta Mechanica Sinica 2024年第5期40卷 184-197页

作者：向书毅杜智博施汇斌严子铭孙永涛王杰柳占立 School of Aerospace Engineering Tsinghua University Beijing China Department of Mechanics and tianjin key Lab of nonlinear dynamics and control Tianjin University Tianjin China Department of Otorhinolaryngology Head and Neck Surgery Beijing Tongren Hospital Capital Medical University Beijing China Beijing Engineering Research Center of Audiological Technology Beijing China

鼓膜是听觉系统的重要组成部分,位于外耳道末端,是一种含胶原的多层软组织膜。鼓膜的纤维沿着径向和环向方向高度取向,其独特而复杂的超微结构使得力学行为呈现各向异性非线性,这对于声音传输很重要.然而,同时包含这两个特征的鼓膜本构... 详细信息

鼓膜是听觉系统的重要组成部分,位于外耳道末端,是一种含胶原的多层软组织膜。鼓膜的纤维沿着径向和环向方向高度取向,其独特而复杂的超微结构使得力学行为呈现各向异性非线性,这对于声音传输很重要.然而,同时包含这两个特征的鼓膜本构模型尚未提出.在本研究中,我们建立了考虑鼓膜纤维分布的细观本构模型,模型能够同时捕捉各向异性和非线性弹性力学行为.鼓膜被认为是包含两族胶原纤维的连续纤维增强复合材料,并通过整合沿厚度方向异质材料性质建立整体力学性质.均匀化的力学性质被假定沿着厚度方向均匀分布,并由径向胶原纤维,环向胶原纤维和等效各向同性基质的三个非耦合弹性贡献叠加组成.通过逆方法并使用文献数据校准模型.仿真结果表明,特定的胶原纤维排列是鼓膜条带试样变形呈现显著空间非均匀性及各向异性的原因。通过与纤维变形相关的强度准则,可以捕获在实验中观察到的鼓膜条带各向异性局部化失效模式。胶原纤维束的旋转和非线性性质是单轴加载下鼓膜条带非线性力学行为的起源.该细观本构模型为鼓膜的各向异性和非线性弹性力学行为提供了不同的视角.这项研究提高了我们对鼓膜力学行为的理解,并有助于仿生移植物的发展.

关键词：非线性弹性力学胶原纤维细观本构模型移植物空间非均匀性非线性性质听觉系统非线性力学行为

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Uncertainty and disturbance estimator-based model predictive control for wet flue gas desulphurization system

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Chinese Journal of Chemical Engineering 2024年第3期67卷 182-194页

作者： Shan Liu Wenqi Zhong Li Sun Xi Chen Rafal Madonski School of Energy and Environment Key Laboratory of Energy Thermal Conversion and Control of Ministry of EducationSoutheast UniversityNanjing 210096China Faculty of Automatic control Electronics and Computer ScienceSilesian University of TechnologyGliwise 44-100Poland

Wet flue gas desulphurization technology is widely used in the industrial process for its capability of efficient pollution *** desulphurization control system,however,is subjected to complex reaction mechanisms and severe disturbances,which make for it difficult to achieve certain practically relevant control goals including emission and economic performances as well as system *** address these challenges,a new robust control scheme based on uncertainty and disturbance estimator(UDE)and model predictive control(MPC)is proposed in this *** UDE is used to estimate and dynamically compensate acting disturbances,whereas MPC is deployed for optimal feedback regulation of the resultant *** viewing the system nonlinearities and unknown dynamics as disturbances,the proposed control framework allows to locally treat the considered nonlinear plant as a linear *** obtained simulation results confirm that the utilization of UDE makes the tracking error negligibly small,even in the presence of unmodeled *** the conducted comparison study,the introduced control scheme outperforms both the standard MPC and PID(proportional-integral-derivative)control strategies in terms of transient performance and ***,the results reveal that a lowpass-filter time constant has a significant effect on the robustness and the convergence range of the tracking error.

关键词： Desulphurization system Disturbance rejection Model predictive control Uncertainty and disturbance estimator nonlinear system

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Adaptive fault-tolerant control for non-minimum phase hypersonic vehicles based on adaptive dynamic programming

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Chinese Journal of Aeronautics 2024年第3期37卷 290-311页

作者： Le WANG Ruiyun QI Bin JIANG State key laboratory of Mechanics and control for Aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China College of Automation Engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China

In this paper,a novel adaptive Fault-Tolerant control(FTC)strategy is proposed for non-minimum phase Hypersonic Vehicles(HSVs)that are affected by actuator faults and parameter *** strategy is based on the output redefinition method and Adaptive Dynamic Programming(ADP).The intelligent FTC scheme consists of two main parts:a basic fault-tolerant and stable controller and an ADP-based supplementary *** the basic FTC part,an output redefinition approach is designed to make zero-dynamics stable with respect to the new ***,Ideal Internal Dynamic(IID)is obtained using an optimal bounded inversion approach,and a tracking controller is designed for the new output to realize output tracking of the nonminimum phase HSV *** the ADP-based compensation control part,an ActionDependent Heuristic Dynamic Programming(ADHDP)adopting an actor-critic learning structure is utilized to further optimize the tracking performance of the HSV control ***,simulation results are provided to verify the effectiveness and efficiency of the proposed FTC algorithm.

关键词： Hypersonic vehicle Fault-tolerant control Non-minimum phase system Adaptive control nonlinear control Adaptive dynamic programming

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Theoretical and experimental investigations on an X-shaped vibration isolator with active controlled variable stiffness

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Applied Mathematics and Mechanics(English Edition) 2024年第8期45卷 1371-1386页

作者： Zeyu CHAI J.T.HAN Xuyuan SONG Jian ZANG Yewei ZHANG Zhen ZHANG College of Aerospace Engineering Shenyang Aerospace University Jacobs School of Engineering University of California San Diego key laboratory of Vibration and control of Aero-Propulsion System Ministry of EducationNortheastern University

A novel X-shaped variable stiffness vibration isolator(X-VSVI) is *** Runge-Kutta method, harmonic balance method, and wavelet transform spectra are introduced to evaluate the performance of the X-VSVI under various excitations. The layer number, the installation angle of the X-shaped structure, the stiffness, and the active control parameters are systematically analyzed. In addition, a prototype of the X-VSVI is manufactured, and vibration tests are carried out. The results show that the proposed X-VSVI has a superior adaptability to that of a traditional X-shaped mechanism, and shows excellent vibration isolation performance in response to different amplitudes and forms of excitations. Moreover, the vibration isolation efficiency of the device can be improved by appropriate adjustment of parameters.

关键词： 70J35 70K30 70K50 bionic vibration isolation nonlinear dynamics O322 prototype experiment variable stiffness structure X-shaped structure

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Dirac method for nonlinear and non-homogenous boundary value problems of plates

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 15-38页

作者： Xiaoye MAO Jiabin WU Junning ZHANG Hu DING Liqun CHEN Shanghai key laboratory of Mechanics in Energy Engineering Shanghai Frontier Science Center of MechanoinformaticsShanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200444China Shanghai Institute of Aircraft Mechanics and control Shanghai 200092China

The boundary value problem plays a crucial role in the analytical investigation of continuum dynamics. In this paper, an analytical method based on the Dirac operator to solve the nonlinear and non-homogeneous boundary value problem of rectangular plates is proposed. The key concept behind this method is to transform the nonlinear or non-homogeneous part on the boundary into a lateral force within the governing function by the Dirac operator, which linearizes and homogenizes the original boundary, allowing one to employ the modal superposition method for obtaining solutions to reconstructive governing equations. Once projected into the modal space, the harmonic balance method(HBM) is utilized to solve coupled ordinary differential equations(ODEs)of truncated systems with nonlinearity. To validate the convergence and accuracy of the proposed Dirac method, the results of typical examples, involving nonlinearly restricted boundaries, moment excitation, and displacement excitation, are compared with those of the differential quadrature element method(DQEM). The results demonstrate that when dealing with nonlinear boundaries, the Dirac method exhibits more excellent accuracy and convergence compared with the DQEM. However, when facing displacement excitation, there exist some discrepancies between the proposed approach and simulations;nevertheless, the proposed method still accurately predicts resonant frequencies while being uniquely capable of handling nonuniform displacement excitations. Overall, this methodology offers a convenient way for addressing nonlinear and non-homogenous plate boundaries.

关键词： rectangular plate Dirac operator nonlinear boundary time-dependent boundary boundary value problem

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Resilient control of flexible hypersonic vehicles against unmatched distributed faults

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Chinese Journal of Aeronautics 2024年第5期37卷 60-70页

作者： Dong ZHAO Wenjing REN School of Artificial Intelligence Anhui UniversityHefei 230601China key laboratory of System control and Information Processing Ministry of EducationShanghai Jiao Tong UniversityShanghai 200240China School of Electrical Engineering and Automation Hefei University of TechnologyHefei 230009China

This paper studies a robust fault compensation and vibration suppression problem of flexible hypersonic *** controlled plant is represented by a cascade system composed of a nonlinear Ordinary Differential Equation(ODE)and an Euler-Bernoulli Beam Equation(EBBE),in which the vibration dynamics is coupled with the rigid dynamics and suffers from distributed faults.A state differential transformation is introduced to transfer distributed faults to an EBBE boundary and a longitudinal dynamics is refined by utilizing T-S fuzzy IF-THEN rules.A novel T-S fuzzy based fault-tolerant control algorithm is developed and related stability conditions are *** robust exponential stability and well-posedness are proved by using the modified l_(0)-semigroup based Lyapunov direct approach.A simulation study on the longitudinal dynamics of flexible hypersonic vehicles effectively verifies the validity of the developed theoretical results.

关键词： Flexible hypersonic vehicles ODE-EBBE cascade Robust exponential stability Unmatched distributed fault compensation Vibration suppression

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Relations of Microstructural Attributes and Strength-Ductility of Zirconium Alloys with Hydrides

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Chinese Journal of Mechanical Engineering 2023年第4期36卷 407-419页

作者： Chao Fang Xiang Guo Jianghua Li Gang Chen School of Mechanical Engineering Tianjin UniversityTianjin 300354China tianjin key laboratory of nonlinear dynamics and control Tianjin 300072China State key laboratory of nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China

As the first safety barrier of nuclear reactors,zirconium alloy cladding tubes have attracted extensive attention because of its good mechanical *** strength and ductility of zirconium alloy are of great significance to the service process of cladding tubes,while brittle hydrides precipitate and thus deteriorate the overall *** on the cohesive finite element method,the effects of cohesive strength,interfacial characteristics,and hydrides geometric characteristics on the strength and ductility of two-phase material(zirconium alloy with hydrides)are numerically *** results show that the fracture behavior is significantly affected by the cohesive strength and that the overall strength and ductility are sensitive to the cohesive strength of the zirconium ***,the interface is revealed to have prominent effects on the overall fracture *** the cohesive strength and fracture energy of the interface are higher than those of the hydride phase,fracture initiates in the hydrides,which is consistent with the experimental *** addition,it is found that the number density and arrangement of hydrides play important roles in the overall strength and *** simulation provides theoretical support for the performance analysis of hydrogenated zirconium alloys during nuclear reactor operation.

关键词： Zirconium alloy Hydride Strength and ductility Cohesive finite element method Microcrack initiation and propagation

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nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film-shaped memory alloy composite plate subjected to in-plane stochastic excitation

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Chinese Physics B 2014年第8期23卷 165-171页

作者：竺致文张庆昕许佳 Department of Mechanics Tianjin University tianjin key laboratory of nonlinear dynamics and chaos control

The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared based on an SMA plate, and combined into a GMF-SMA composite plate. The Van der Pol item is improved to explain the hysteretic phenomena of GMF and SMA, and the nonlinear dynamics model of a GMF-SMA composite cantilever plate subjected to in-plane stochastic excitation is developed. The stochastic stability of the system is analyzed, and the steady-state probability density function of the dynamic response of the system is obtained. The condition of stochastic Hopf bifurcation is discussed, the reliability function of the system is provided, and then the probability density of the first-passage time is given. Finally, the stochastic optimal control strategy is proposed by the stochastic dynamic programming method. Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the system＇s reliability is improved through stochastic optimal control, and the first- passage time is delayed. A GMF-SMA composite plate combines the advantages of GMF and SMA, and can reduce vibration through passive control and active control effectively. The results are helpful for the engineering applications of GMF-SMA composite plates.

关键词： giant magnetostrictive film shape memory alloy composite cantilever plate stochastic Hopf bifurcation optimal control

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