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Localization of elastic waves in one-dimensional detuned phononic crystals with flexoelectric effect

International Journal of Smart and Nano Materials 2022年第2期13卷 244-262页

作者： Cheng Shen Yifan Kong Tian Jian Lu Shasha Yang State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjingPRChina MIIT Key Laboratory of Multifunctional Lightweight Materials and Structures Nanjing University of Aeronautics and AstronauticsNanjingPRChina Space Structure and Mechanism Technology Laboratory of China Aerospace Science and Technology Group Co.Ltd ShanghaiP.R China School of Mechanical Engineering Nanjing Vocational University of Industry TechnologyNanjingP.R China

Although forbidden band effect in perfectly periodic phononic crystals(PC)is very attractive,random disordered(***)phenomenon is inevitable in engineering processing,thus explor-ing the effect of detuning on the wave characteristics of PC becomes a *** this study,fundamental governing equa-tions and boundary conditions are derived from the principle of virtual *** characteristics and localization factor of one-dimensional(1D)detuned nano-PC are investigated based on the transfer matrix method,with flexoelectric effect duly accounted ***,with BaTiO_(3)􀀀SrTiO_(3) nano-PC taken for illustration,forbidden band properties and localization factor of 1D elastic waves in harmonic and detuned states are systematically *** is demonstrated that localization factor can characterize the energy band structure of 1D PC *** effect tends to widen the width of forbidden band with increasing detuning,and detuning is linearly related to the *** forbidden band is more sensitive to flexoelectric coefficient detuning than thickness *** research results provide useful theoretical guidance for designing high-frequency nanoscaled devices with the function of filtering based on band gap effect of nano-PC.

关键词： flexoelectric effect phononic crystal detuning localization factor forbidden band

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Theoretical analysis of the influence of flexoelectric effect on the defect site in nematic inversion walls

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Chinese Physics B 2016年第3期25卷 270-276页

作者：郑桂丽张辉叶文江张志东宋宏伟宣丽 State Key Laboratory of Applied Optics Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Changchun 130033 China University of Chinese Academy of Sciences Beijing 100049 China School of Sciences Hebei University of Technology Tianjin 300401 China College of Electronic Science and Engineering Jilin University Changchun 130021 China

Based on the experimental phenomena of flexoelectric response at defect sites in nematic inversion walls conducted by Kumar et al., we gave the theoretical analysis using the Frank elastic theory. When a direct-current electric field normal to the plane of the substrate is applied to the parallel aligned nematic liquid crystal cell with weak anchoring, the rotation of 4-1 defects in the narrow inversion walls can be exhibited. The free energy of liquid crystal molecules around the ＋1 and - 1 defect sites in the nematic inversion walls under the electric field was formulated and the electric-field-driven structural changes at the defect site characterized by polar and azimuthal angles of the local director were simulated. The results reveal that the deviation of azimuthal angle induced by flexoelectric effect are consistent with the switching of extinction brushes at the - 1 and -1 defects obtained in the experiment conducted by Kumar et al.

关键词： liquid crystal flexoelectric effect zk 1 defects Frank theory

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Variational principles and governing equations in nano-dielectrics with the flexoelectric effect

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Science China(Physics,Mechanics & Astronomy) 2010年第8期53卷 1497-1504页

作者： HU ShuLing SHEN ShengPing MOE Key Laboratory for Strength and Vibration School of AerospaceXi’an Jiaotong UniversityXi’an 710049China

The flexoelectric effect is very strong and coupled with large strain gradients for nanoscale dielectrics. At the nanoscale, the electrostatic force cannot be ignored. In this paper, we have established the electric enthalpy variational principle for nanosized dielectrics with the strain gradient and the polarization gradient effect, as well as the effect of the electrostatic force. The complete governing equations, which include the effect of the electrostatic force, are derived from this variational principle, and based on the principle the generalized electrostatic stress is obtained, the generalized electrostatic stress contains the Maxwell stress corresponding to the polarization and strain, and stress related to the polarization gradient and strain gradient. This work provides the basis for the analysis and computations for the electromechanical problems in nanosized dielectric materials.

关键词： flexoelectric effect variational principle governing equations dielectrics electrostatic stress nanoscale

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flexoelectric effect Based on a Bent Piezoelectric Semiconductive Nanowire

Flexoelectric Effect Based on a Bent Piezoelectric Semicondu...

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2011年全国压电和声波理论及器件应用研讨会

作者： Ying XU Shengping SHEN MOE Key Laboratory for Strength and Vibration,School of Aerospace,Xi''an Jiaotong University,28 West Xianning Road.Xi''an,Shaanxi 710049,PR China

＜正＞For nanodevices,the effect of the coupling of strain gradient and polarization gradient can no longer be *** this paper,direct flexoelectric effect is taken into account while calculating the electric potential ... 详细信息

关键词： flexoelectric effect ZnO Nanowire Size effect Piezoelectric Semiconductor

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An isogeometric approach to static and transient analysis of fluid-infiltrated porous metal foam piezoelectric nanoplates with flexoelectric effects and variable nonlocal parameters

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Frontiers of Structural and Civil Engineering 2024年第3期18卷 461-489页

作者： Quoc-Hoa PHAM Van Ke Tran Phu-Cuong Nguyen Faculty of Engineering and Technology Nguyen Tat Thanh UniversityHo Chi Minh City 700000Vietnam Faculty of Mechanical Engineering Le Quy Don Technical UniversityHanoi 100000Vietnam Advanced Structural Engineering Laboratory Department of Structural EngineeringFaculty of Civil EngineeringHo Chi Minh City Open UniversityHo Chi Minh City 700000Vietnam

In this work,a novel refined higher-order shear deformation plate theory is integrated with nonlocal elasticity theory for analyzing the free vibration,bending,and transient behaviors of fluid-infiltrated porous metal foam piezoelectric nanoplates resting on Pasternak elastic foundation with flexoelectric *** analysis(IGA)and the Navier solution are applied to the *** innovation in the present study is that the influence of the in-plane variation of the nonlocal parameter on the free and forced vibration of the piezoelectric nanoplates is investigated for the first *** nonlocal parameter and material characteristics are assumed to be material-dependent and vary gradually over the thickness of *** on Hamilton’s principle,equations of motion are built,then the IGA approach combined with the Navier solution is used to analyze the static and dynamic response of the ***,we investigate the effects of the porosity coefficients,flexoelectric parameters,elastic stiffness,thickness,and variation of the nonlocal parameters on the mechanical behaviors of the rectangular and elliptical piezoelectric nanoplates.

关键词： isogeometric analysis fluid-infiltrated porous piezoelectric nanoplates static and transient analysis flexoelectric effect variable nonlocal parameters

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WAVE PROPAGATION IN PIEZOELECTRIC LAYERED STRUCTURE WITH flexoelectric effect TAKEN INTO CONSIDERATION

WAVE PROPAGATION IN PIEZOELECTRIC LAYERED STRUCTURE WITH FLE...

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2016年全国压电和声波理论及器件应用研讨会

作者： Feng-yu JIAO Pei-jun WEI Yue-qiu LI Department of applied mechanics University of Science and Technology Beijing Department of applied mathmatics Qiqihar University

Background, Motivation and Objective In the classical piezoelectric elastic theory, the stress at a piezoelectric material point is assumed to be dependent upon the strain and electric field at same piezoelectric material point, and no characteristic length is included in the constitutive relations. Therefore, the classical piezoelectric elastic theory cannot describe the mechanical and electrical behave of piezoelectric material at the micro or nano scale and size effects. The find of the flexoelectric effects in piezoelectric solids and the potential applications at nanoscale electromechanical system make the investigation of acoustic wave propagation in the piezoelectric solid with the flexoelectric effects taken into consideration necessary. The influences of the flexoelectric effects on the wave propagation mode and the dispersive relations of these waves are therefore interesting. Statement of Contribution/Methods The reflection and transmission phenomenon of acoustic propagation at a piezoelectric half-space and through layered structure are considered. The piezoelectric solids are modeled by the generalized elastic theory with the strain gradient terms included in the constitutive relations to reflect the flexoelectric effects. Due to the flexoelectric effects, there are five kinds of wave propagation modes appeared instead of three propagation modes in the classic piezoelectric solids. Not only that, the traditional surface tractions should be modified as the monopolar surface tractions and the dipolar surface tractions. Accordingly, the traditional surface/interface conditions are replaced by the new surface/interface conditions when the flexoelectric effects are taken into consideration. Results Two boundary conditions(traction-free and electrically shorted/charge-free) and interface conditions with mechanically and dielectrically perfect and imperfect are considered in the present work. The amplitude ratios and energy flux ratios of the reflection waves

关键词： flexoelectric effect Dipolar traction Strain gradient Reflection and transmission Energy flux ratio

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A multi-field coupling theoretical framework considering flexoelectric effect and finite element implementation for ferroelectric domain evolution

A multi-field coupling theoretical framework considering fle...

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第十三届全国物理力学学术会议

作者： L.M.Jiang Y.C.Zhou J.Y.Tang Q.Yang Y.Zhang Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education Xiangtan University Faculty of Materials Optoelectronics and PhysicsXiangtan University

A multi-field coupling theoretical framework of flexoelectric effect on ferroelectric domain evolution is developed based on the phase-field *** forms are derived and implemented in a finite element formulation for numerically solving the model equations in higher *** strain and polarization distributions in an epitaxial ferroelectric Pb Ti O3 film are *** found that the dislocation-free ferroelastically twinned films exhibit intrinsic elastic strain gradients of06 m-1 inside c domains and 107-108 m-1 at domain walls,sufficient to produce significant flexoelectric *** magnitudes of remnant polarizations and coercive field decrease and eventually become zero as the horizontal flexoelectricity increases.A large horizontal flexoelectricity beyond a critical value may lead to the formation of an incommensurate state,which shows antiferroelectric-like double hysteresis loops under a high electric field.

关键词： Multi-field coupling flexoelectric effect Domain structure Finite element method Phase-field method

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flexoelectricity in oxide thin films

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Journal of Advanced Dielectrics 2024年第1期14卷 1-24页

作者： Guoyang Shen Renhong Liang Zhiguo Wang Zhiyong Liu Longlong Shu School of Physics and Materials Science Nanchang University Nanchang 330031 P.R.China School of Materials Science and Engineering Nanchang Hangkong University Nanchang 330063P.R.China

flexoelectric effect describes the electromechanical coupling between the strain gradient and its internal polarization in all *** this universality,the resulting flexoelectric field remains small at the macroscopic ***,in nanosystems,the size-dependent effect of flexoelectricity becomes increasingly significant,leading to a notable flexoelectric field that can strongly influence the material’s physical *** review aims to explore the flexoelectric effect specifically at the *** achieve this by examining strain gradients generated through two distinct methods:internal inhomogeneous strain and external *** addition,advanced synthesis techniques are utilized to enhance the properties and functionalities associated with ***,we delve into other coupled phenomena observed in thin films,including the coupling and utilization of flexomagnetic and flexophotovoltaic *** review presents the latest advancements in these areas and highlights their role in driving further breakthroughs in the field of flexoelectricity.

关键词： flexoelectric effect strain gradient polarization nano-thin film flexomagnetic flexophotovoltaic

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Magnetically induced electric potential in first-order composite beams incorporating couple stress and its flexoelectric effects

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Acta Mechanica Sinica 2021年第10期37卷 1509-1519,I0002页

作者： Gongye Zhang Yilin Qu Ziwen Guo Feng Jin Jiangsu Key Laboratory of Engineering Mechanics School of Civil EngineeringSoutheast UniversityNanjing210096China State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China

A new model of a first-order composite beam with flexoelectric and piezomagnetic layers is *** new model is under a transverse magnetic field and can capture the couple stress and its flexoelectric *** governing equations are obtained through a variational *** illustrate the new model,the static bending problem is analytically solved based on a Navier’s *** numerical results reveal that the extension,deflection,and shear deformation of the current or couple stress relevant flexoelectric model are always smaller than those of classical models at very small *** is also found that the electric potentials only appear with the presence of the flexoelectric effect for this non-piezoelectric composite beam ***,various electric potential distributions can be manipulated by the particular magnetic fields,and remote/non-contact control at micro-and nano-scales can be realized by current functional composite beams.

关键词： flexoelectric effect Couple stress theory Microstructure effect First-order beam Piezomagnetic layer Static bending

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An artificial neural network model for multi-flexoelectric actuation of Plates

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International Journal of Smart and Nano Materials 2022年第4期13卷 713-734页

作者： Mu Fan Pengcheng Yu Zhongmin Xiao State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjingChina Interdisciplinary Research Institute of Aeronautics and Astronautics College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjingChina School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore

flexoelectric effect can be used to design actuators to control engi-neering structures including beams,plates,and *** flexo-electric actuators method has the advantage of less stress concentration and better control effect,but the mode-dependent optimal actuator locations could influence the flexoelectric actuation effect *** this work,a neural network model is established to study the optimal combinations of multiple flexoelectric actuators on a rectangular *** the physical model,an atomic force micro-scope(AFM)probe was employed to generate an electric field gradient in the flexoelectric patch,so that flexoelectric control force and moment can be *** flexoelectric actuators on the plate was *** studies showed that the flexoelectricity induced stress mainly concentrate near the probe,the size and shape of the flexoelectric patch have limited effect on the actuation,hence,only the actuator positions were choosing as the input of the ANN *** the prediction of the neural network model,the driving effect of a large number of actuators at different positions can be quickly obtained,and the optimal position of the actuator can be analyzed more accurately.

关键词： smart structure flexoelectric effect vibration of thin plate Artificial neural network

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