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Two Kinds Equal Frequency Circuits to Achieve Locally Resonant Band Gap of a Circular Plate Attached Alternately by Piezoelectric Unimorphs

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Acta Mechanica Solida Sinica 2016年第5期29卷 502-513页

作者： Longxiang Dai Hongping Hu Shan Jiang xuedong chen Department of Mechanics Huazhong University of Science and Technology Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment Huazhong University of Science and Technology State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology

A circular thin plate is proposed for vibration attenuation,which is attached alternately by annular piezoelectric unimorphs with resonant shunt *** kinds of equal frequency resonant shunt circuits are designed to achieve an integrated locally resonant（LR）band gap（BG） with a much smaller transmission factor：（1） the structure is arrayed periodically while the resonant shunt circuits are aperiodic;（2） the resonant shunt circuits are periodic while the structure is *** transmission factor curve is calculated,which is validated by the finite element *** of the LR BG performance upon the geometric and electric parameters are also analyzed.

关键词： resonant piezoelectric periodically shunt circuits circular validated locally patches connected

DYNAMIC CHARACTERISTIC ANALY-SIS OF PRECISE LONG STROKE LINEAR MOTOR WITH AIR-BEARING IN OPTICAL LITHOGRAPHY

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Chinese Journal of Mechanical Engineering 2008年第2期21卷 17-22页

作者： chen xuedong YU Xianzhong HE Xueming YAN Tianhong State Key Laboratory of Digital Manufacturing Equipment ＆ Technology Huazhong University of Science and Technology Wuhan 430074 China National Optical Lithography Equipment R ＆ D Center Shanghai 201203 China

Dynamic characteristic is presented by identifying the model and the dynamic parameters of a precise long stroke linear motor （PLSLM） with the air-bearing in optical lithography. The PLSLM is supported by air-bearing on the stator, and is driven by on-board two large linear motors in a cross-configuration. Firstly, a model of the PLSLM is established by finite element method （FEM）. Secondly, based on the model, the natural frequencies and model shapes are discusse＆ And the contribution of each active mode is evaluated by computing the modal participation factors （MPF）, which indicates the major vibration direction. Furthermore, by the experimental modal analysis, the experimental results are in agreement with simulation results, which it is sure that the FEM is reasonable. What＇s more, comparing with the effects on the frequency due to the air-bearing stiffness, the relations of the natural frequencies with the air-bearing stiffness are found. It is found that the frequency response curve is fluctuant with the air-bearing stiffness in each direction. Finally, it is conclusion that the natural frequency of the PLSLM is largely affected by the air-bearing stiffness variety. This research is contributed to the dynamic characteristics resulted from the air-beating stiffness. Further work will include better optimization on the dynamic parameter in the controller design through the control algorithm for the precise long stroke motor.

关键词： Dynamic analysis Air-bearing stiffness Precise long stroke linear motor Frequency response

Design of a combined magnetic negative stiffness mechanism with high linearity in a wide working region

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Science China(Technological Sciences) 2022年第9期65卷 2127-2142页

作者： WU JiuLin CHE JiXing chen xuedong JIANG Wei State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

Combining magnetic negative stiffness mechanism(NSM) in parallel with positive stiffness has been considered to be an effective approach to realize the quasi-zero stiffness(QZS) characteristic,thus resolving the contradiction between high load capacity and(ultra-) low-frequency vibration isolation ***,the remarkable stiffness nonlinearity of common magnetic NSMs restricts the displacement region with reliable negative stiffness,resulting in considerable nonlinear behavior,poor vibration attenuation performance,and probable instability under large amplitude vibrations.A novel combined negative stiffness mechanism(CNSM) with attractive magnetic NSM(ANSM) and repulsive magnetic NSM(RNSM) in parallel is proposed in this *** stiffness nonlinearities of the ANSM and RNSM in the CNSM are counteracted through the parallel configuration such that the displacement region with reliable linear stiffness of the CNSM is widened by several *** analytical model of the CNSM is established by the magnetic charge model and verified by simulation on ANSYS *** studies are then conducted to investigate the effects of design parameters on the stiffness characteristic,providing guidelines for the optimal design of the ***,the stiffness and nonlinearity of the CNSM are compared with that of a single ANSM and *** and dynamic experiments are finally conducted on the proposed test *** results demonstrated the validity of the established model and the effectiveness of the CNSM in generating high linear stiffness within a wide displacement region and lowering the resonance ***,the proposed CNSM can be applied in(ultra-) low-frequency vibration isolation under large amplitude excitations.

关键词： vibration isolation quasi-zero stiffness combined negative stiffness mechanism high linearity

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Modeling and Experimental Analysis of Roughness Effect on Ultrasonic Nondestructive Evaluation of Micro-crack

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Chinese Journal of Mechanical Engineering 2021年第6期34卷 126-137页

作者： Zhe Wang Zhichao Fan xuedong chen Yihua Kang Jingwei cheng Wei chen National Safety Engineering Technology Research Center for Pressure Vessels and Pipeline Hefei General Machinery Research Institute Co.LtdHefei230031China State Key Lab of Digital Manufacturing Equipment&Technology Huazhong University of Science and TechnologyWuhan430074China

A high-precision evaluation of ultrasonic detection sensitivity for a micro-crack can be restricted by a corroded rough surface when the surface microtopography is of the same order of magnitude as the crack *** this study,a back-surface micro-crack is considered as a research target.A roughness-modified ultrasonic testing model for micro-cracks is established based on a multi-Gaussian beam model and the principle of phase-screen *** echo signals of micro-cracks and noises corresponding to different rough front surfaces and rough back surfaces are obtained based on a reference reflector signal acquired from a two-dimensional simulation *** compari-son between the analytical and numerical models shows that the responses of micro-cracks under the effects of dif-ferent corroded rough surfaces can be accurately *** numerical and analytical results show that the echo signal amplitude of the micro-crack decreases significantly with an increase in roughness,whereas the noise ampli-tude slightly ***,the effect of the rough front surface on the echo signal of the micro-crack is greater than that of the rough back *** the root-mean-square(RMS)height of the surface microtopography is less than 15μm,the two rough surfaces have less influence on the echo signals detected by a focused transducer with a frequency of 5 MHz and diameter of 6 mm.A method for predicting and evaluating the detection accuracy of micro-cracks under different rough surfaces is proposed by combining the theoretical model and a finite element ***,a series of rough surface samples containing different micro-cracks are fabricated to experimentally validate the evaluation method.

关键词： Surface roughness Micro-crack Ultrasonic testing model Detection accuracy Evaluation method

Experimental and numerical studies of impact on filament-wound composite cylinder

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Acta Mechanica Solida Sinica 2017年第5期30卷 540-549页

作者： Qiaoguo Wu xuedong chen Zhichao Fan Yong Jiang Defu Nie National Safety Engineering Technology Research Center for Pressure Vessels and Pipelines Anhui Key Laboratory of Composite Technology for General Machinery Hefei General Machinery Research Institute Hefei 230031 China

This study focused on the impact behavior of carbon-fiber-wrapped composite cylinders subjected to impact from flat-ended, hemispherical-nosed and conical-nosed impactors. Damage morphologies of the cylinders and mechanisms of the damage were analyzed. Change laws of the maximum impact forces, durations of impact processes and energies absorbed by the cylinders after impact with different impactors and impact energies were obtained. A finite element model was developed and the simulation results were in reason- able agreement with the tests. Finally, taking the flat-ended impactor as an example, stress distributions of the cylinders under pressurization and impact were discussed.

关键词： Composite cylinderImpact testingNumerical simulationDamage behaviorImpact curve

Folding beam-type piezoelectric phononic crystal with low-frequency and broad band gap

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Applied Mathematics and Mechanics(English Edition) 2017年第3期38卷 411-422页

作者： Shan JIANG Longxiang DAI Hao chen Hongping HU Wei JIANG xuedong chen Department of Mechanics Huazhong University of Science and Technology Wuhan 430074 China Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment Huazhong University of Science and Technology Wuhan 430074 China State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China

A folding beam-type piezoelectric phononic crystal model is proposed to isolate vibration. Two piezoelectric bimorphs are joined by two masses as a folding structure to comprise each unit cell of the piezoelectric phononic crystal. Each bimorph is connected independently by a resistive-inductive resonant shunting circuit. The folding structure extends the propagation path of elastic waves, while its structure size remains quite small. Propagation of coupled extension-flexural elastic waves is studied by the classical laminated beam theory and transfer matrix method. The theoretical model is further verified with the finite element method(FEM). The effects of geometrical and circuit parameters on the band gaps are analyzed. With only 4 unit cells, the folding beam-type piezoelectric phononic crystal generates two Bragg band gaps of 369 Hz to1 687 Hz and 2 127 Hz to 4 000 Hz. In addition, between these two Bragg band gaps, a locally resonant band gap is induced by resonant shunting circuits. Appropriate circuit parameters are used to join these two Bragg band gaps by the locally resonant band ***, a low-frequency and broad band gap of 369 Hz to 4 000 Hz is obtained.

关键词： folding beam-type structure phononic crystal band gap wave propagation piezoelectric

Consistency and asymptotic normality of profilekernel and backfitting estimators in semiparametric reproductive dispersion nonlinear models

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Science China Mathematics 2009年第4期52卷 757-770页

作者： TANG NianSheng chen xuedong WANG XueRen Department of Statistics Yunnan UniversityKunming 650091China Faculty of Science Huzhou Normal CollegeHuzhou 313000China

Semiparametric reproductive dispersion nonlinear model (SRDNM) is an extension of nonlinear reproductive dispersion models and semiparametric nonlinear regression models, and includes semiparametric nonlinear model and semiparametric generalized linear model as its special cases. Based on the local kernel estimate of nonparametric component, profile-kernel and backfitting estimators of parameters of interest are proposed in SRDNM, and theoretical comparison of both estimators is also investigated in this paper. Under some regularity conditions, strong consistency and asymptotic normality of two estimators are proved. It is shown that the backfitting method produces a larger asymptotic variance than that for the profile-kernel method. A simulation study and a real example are used to illustrate the proposed methodologies.

关键词： asymptotic normality backfitting method consistency profile-kernel method semiparametric reproductive dispersion nonlinear models 62G05 62G08 62G20

Analysis of complex intermittency in Boost converter from a bifurcation control viewpoint

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Science in China(Series F) 2008年第12期51卷 2135-2149页

作者： ZHOU YuFei JIANG xuedong chen JunNing School of Electronic Science and Technology Anhui University Hefei 230039 China

Due to undesirable interference via unintended coupling paths, switching converters may exhibit complex intermittency, which appears as a form of bifurcation undergoing regular operation, subharmonics, and chaos orderly and repeatedly for a long period of time. Such intermittent operation, being an unwanted operating state, should normally be avoided in power converters. This paper expounds the mechanism and conditions for the emergence of intermittency in a common current-mode controlled Boost converter. It is found that interference at frequencies near the switching frequency or its rational multiples may induce intermittent operation. The strengths and frequencies of the interfering signals determine the type and period of intermittency. The problem is analyzed by transforming the time-bifurcation analysis to a conventional parameter-bifurcation analysis. Based on this transformation, intermittency can be investigated from the bifurcation control viewpoint. Furthermore, the critical circuit parameter conditions for the emergence of intermittency can be predicted and compared with those from circuit simulation.

关键词： power converter intermittency bifurcation bifurcation control

An improved piezoelectric harvester available in scavenging-energy from the operating environment with either weaker or stronger vibration levels

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Science China(Physics,Mechanics & Astronomy) 2009年第2期52卷 218-225页

作者： XUE Huan HU HongPing HU YuanTai chen xuedong Department of Mechanics Huazhong University of Science and TechnologyWuhan 430074China

An improved harvester available in scavenging energy from the operating environment with either weaker or stronger vibration levels is studied. To ensure the optimal harvester performance, a Cuk dc-dc converter is employed into the modulating circuit. This paper reports how this harvester scav- enges maximal energy from varying-level vibrations and store energy into an electrochemical battery. Dependence of the duty cycle upon the external vibration level is calculated, and it is found that: 1) for weaker vibrations, the charging current into the battery is smaller than the allowable current, and thus all the optimal output power of the harvesting structure can be absorbed by the battery. In this case, the duty cycle should be fixed at 1.86%; 2) for stronger external forcing, the allowable charging current of the battery is smaller than the optimal harvested current. This indicates that just a portion of the sca- venged energy can be accepted by the battery. Thus, the duty cycle should be decreased gradually with the increase of the vibration level. Finally the energy transmission process and the roles of each elec- tronic element are analyzed. It is shown that a Cuk converter can greatly raise the efficiency of such a harvester, particularly when subjected to a weaker ambient vibration.

关键词： piezoelectric harvester scavenging energy Cuk converter duty cycle