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Formation adaptation in obstacle-cluttered environments via MPC-based trajectory planning

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Science China(Information Sciences) 2024年第7期67卷 321-323页

作者： Yuda CHEN Zhongkui LI department of mechanics and engineering Science College of Engineering Peking University

Formation is a typical collective behavior in multiagent systems utilized in areas such as inspection, surveillance, and transportation. Commonly-used approaches to achieve formation include virtual structure [1], con...

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A design and manufacturing methodology for encoded soft-textile robots

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Science China(Physics,mechanics & Astronomy) 2024年第5期67卷 212-213页

作者： Yihui Zhang Applied mechanics Laboratory Department of Engineering MechanicsTsinghua UniversityBeijing 100084China

The development of programmable soft robots with bioinspired morphing capabilities has attracted considerable *** mode and complexity of morphing capabilities are essential to the manipulation and movement abilities o... 详细信息

关键词： environments robots manipulation

Granular collapse in fluids:Dynamics and flow regime identification

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Particuology 2024年第9期92卷 30-41页

作者： Hu Tang Bisong Lin Dengming Wang department of mechanics and engineering Science School of Civil Engineering and MechanicsKey Laboratory of Mechanics on Disaster and Environment in Western China of Ministry of EducationLanzhou UniversityLanzhou730000China

The collapse of granular material in fluids is a prevalent phenomenon in both natural and industrial processes,displaying a notable sensitivity to initial configuration of the *** study is specifically oriented towards falling process of collapsing material under various fluid conditions,employing the computational fluid dynamics-discrete element method(CFD-DEM)to primarily investigate the dynamics and scaling laws of deposit morphology of collapsed *** a comprehensive analysis of particle sedimentation in fluids,we introduce a refined inertial characteristic time for granular collapse within the inertial ***,we propose modifications to conventional fluid-particle density ratio and Reynolds number,aiming to enhance the accuracy of depicting collapse dynamics and identifying flow regimes across diverse column heights and fluid ***,we construct a phase diagram of flow regimes using modified dimensionless numbers,emphasizing the role of column height in transition between viscous and inertial *** parameters demonstrate enhanced relevance in governing the collapse of immersed granular columns,thereby contributing to a more nuanced understanding of fluid-particle interations in dense granular flows under different regimes.

关键词： Immersed granular material Collapse Dynamic Flow regime Computational fluid dynamics-discrete element method

Enhanced Flexoelectric Response from Functionally Gradient Electrets Undergoing Crumpling Deformation

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Acta Mechanica Solida Sinica 2024年第4期37卷 541-554页

作者： Jianhua Ma Jinrui Xu Jun Li Binglei Wang department of engineering mechanics Shandong UniversityJinan250061China

Non-uniform deformation of the dielectric subjected to external forces can induce the flexoelectric effect, a phenomenon that couples electrical polarization to strain gradients. However, limited by the size effects, flexoelectricity is not significant at the macroscale and only becomes catchable at the microscale and nanoscale. In recent work, we obtained a considerable flexoelectric-like response by crumpling the dielectric embedded with charges, i.e., the electret, which significantly improved the flexoelectric effect at the macroscale. In this work, we further optimize the macroscopic performance of the flexoelectric response by applying gradient treatment to the electret films. Specifically, we analytically derive the electromechanical coupling of crumpled electret films with gradients of different thicknesses, charge densities, and Young’s moduli as key design variables. It is shown that the gradient-oriented electret film can be tuned to nearly five times that of a uniform electret film.

关键词： Functionally gradient electret Size effects Crumpling Flexoelectric-like response

Analysis of piezoelectric semiconductor fibers under gradient temperature changes

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Applied Mathematics and mechanics(English Edition) 2024年第2期45卷 311-320页

作者： Shuangpeng LI Ruoran CHENG Nannan MA Chunli ZHANG department of engineering mechanics Zhejiang UniversityHangzhou 310027China

Piezoelectric semiconductors(PSs)possess both semiconducting properties and piezoelectric coupling effects,making them optimal building blocks for semiconductor *** fiber-like structures have wide applications in multi-functional semiconductor *** this paper,a one-dimensional(1D)theoretical model is established to describe the piezotronic responses of a PS fiber under gradient temperature *** theoretical model aims to explain the mechanism behind the resistance change caused by such gradient temperature *** results demonstrate that a gradient temperature change significantly affects the physical fields within the PS fiber,and can induce changes in its surface *** provides important theoretical guidance on the development of piezotronic devices that are sensitive to temperature effects.

关键词： piezoelectric semiconductor(PS)fiber one-dimensional(1D)model piezotronic effect gradient temperature change

Control and vibration analyses of a sandwich doubly curved micro-composite shell with honeycomb, truss, and corrugated cores based on the fourth-order shear deformation theory

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Applied Mathematics and mechanics(English Edition) 2024年第10期45卷 1773-1790页

作者： F.SHIRDELAN M.MOHAMMADIMEHR F.BARGOZINI department of Solid mechanics Faculty of Mechanical Engineering University of Kashan

Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures, flexibility, and attractive appearance. However, the inability of controlling and regulating vibrations and destroying them afterward is a challenge to scientists. In this paper, the curve shell equations and a linear quadratic regulator are adopted for the state feedback design to manage the structure vibrations in state space forms. A five-layer sandwich doubly curved micro-composite shell, comprising two piezoelectric layers for the sensor and actuator, is modeled by the fourth-order shear deformation theory. The core(honeycomb, truss, and corrugated) is analyzed for the bearing of transverse shear forces. The results show that the honeycomb core has a greater effect on the vibrations. When the parameters related to the core and the weight percentage of graphene increase, the frequency increases. The uniform distribution of graphene platelets results in the lowest natural frequency while the natural frequency increases. Furthermore, without taking into account the piezoelectric layers,the third-order shear deformation theory(TSDT) and fourth-order shear deformation theory(FOSDT) align closely. However, when the piezoelectric layers are incorporated,these two theories diverge significantly, with the frequencies in the FOSDT being lower than those in the TSDT.

关键词： 74F15 corrugate core doubly curved shell honeycomb micro-composite O343 truss vibration and control

Bioinspired 3D flexible devices and functional systems

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National Science Review 2024年第3期11卷 271-295页

作者： Xu Cheng Zhangming Shen Yihui Zhang Applied mechanics Laboratory Department of Engineering Mechanics Tsinghua University Laboratory of Flexible Electronics Technology Tsinghua University

Flexible devices and functional systems with elaborated three-dimensional(3D) architectures can endow better mechanical/electrical performances, more design freedom, and unique functionalities, when compared to their two-dimensional(2D) counterparts. Such 3D flexible devices/systems are rapidly evolving in three primary directions, including the miniaturization, the increasingly merged physical/artificial intelligence and the enhanced adaptability and capabilities of heterogeneous *** challenges exist in this emerging research area, such as relatively poor controllability in the locomotion of soft robotic systems, mismatch of bioelectronic interfaces, and signal coupling in multi-parameter sensing. By virtue of long-time–optimized materials, structures and processes, natural organisms provide rich sources of inspiration to address these challenges, enabling the design and manufacture of many bioinspired 3D flexible devices/systems. In this Review, we focus on bioinspired 3D flexible devices and functional systems, and summarize their representative design concepts, manufacturing methods, principles of structure-function relationship and broad-ranging applications. Discussions on existing challenges, potential solutions and future opportunities are also provided to usher in further research efforts toward realizing bioinspired 3D flexible devices/systems with precisely programmed shapes,enhanced mechanical/electrical performances, and high-level physical/artificial intelligence.

关键词： bioinspired designs biomimetic 3D structures 3D flexible electronics 3D functional systems direct 3D manufacture 2D-to-3D assembly

New Insight into the Flexoelectricity in the View of mechanics of Materials:Prismatic Beams Subjected to Bending

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Acta Mechanica Solida Sinica 2024年第4期37卷 555-569页

作者： Xu Yang Lingling Chen Shengyou Yang department of engineering mechanics School of Civil EngineeringShandong UniversityJinan250061China

Flexoelectricity is a fascinating electromechanical phenomenon that occurs in non-homogeneously deformed dielectric *** piezoelectricity,the flexoelectric effect is highly dependent on both the material scale and the deformation *** several theoretical models have been proposed to explain the mechanism of flexoelectricity,these models can be rather complicated for those who are interested in studying the *** paper aims to simplify the understanding of flexoelectricity by focusing on the bending behavior of a prismatic dielectric beam from a mechanics of material *** avoid using complicated mathematical formulations based on continuum mechanics,including advanced tensor algebra and calculus of *** formulation clearly explains how inhomogeneous deformations and material size affect the electromechanical coupling,changing the effective bending stiffness,deflection,and rotation angles of a bending *** hope this paper can help undergraduate students and researchers,who are unfamiliar with the electromechanical coupling in flexoelectricity,to develop an understanding of this phenomenon and encourage further research in this area.

关键词： bending formulation dielectric

Theoretical and experimental study of a bi-stable piezoelectric energy harvester under hybrid galloping and band-limited random excitations

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Applied Mathematics and mechanics(English Edition) 2024年第3期45卷 461-478页

作者： Haitao LI Tianyu ZHENG Weiyang QIN Ruilan TIAN Hu DING J.C.JI Liqun CHEN department of engineering mechanics North University of ChinaTaiyuan 030051China department of engineering mechanics Northwestern Polytechnical UniversityXi'an 710072China department of engineering mechanics Shijiazhuang Tiedao UniversityShijiazhuang 050043China Shanghai Key Laboratory of mechanics in Energy engineering Shanghai Frontier Science Center of MechnoinformaticsShanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China School of Mechanical and Mechatronic engineering University of Technology SydneyNew South Wales 2007Australia

In the practical environment,it is very common for the simultaneous occurrence of base excitation and *** the combined energy of vibration and wind with a single energy harvesting structure is *** this purpose,the effects of the wind speed and random excitation level are investigated with the stochastic averaging method(SAM)based on the energy *** results of the analytical prediction are verified with the Monte-Carlo method(MCM).The numerical simulation shows that the introduction of wind can reduce the critical excitation level for triggering an inter-well jump and make a bi-stable energy harvester(BEH)realize the performance enhancement for a weak base ***,as the strength of the wind increases to a particular level,the influence of the random base excitation on the dynamic responses is weakened,and the system exhibits a periodic galloping response.A comparison between a BEH and a linear energy harvester(LEH)indicates that the BEH demonstrates inferior performance for high-speed *** experiments are conducted to investigate the validity of the theoretical prediction and numerical *** experimental findings also show that strong random excitation is favorable for the BEH in the range of low wind ***,as the speed of the incoming wind is up to a particular level,the disadvantage of the BEH becomes clear and evident.

关键词： bi-stability inter-well response galloping band-limited random