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Effects of thermo-magneto-electro nonlinearity characteristics on the stability of functionally graded piezoelectric beam

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Applied Mathematics and Mechanics(English Edition) 2020年第2期41卷 313-326页

作者： Haohao BI Bo WANG Zichen DENG Shuodao WANG Department of Applied Mathematics Northwestern Polytechnical UniversityXi’an 710072China Ministry of Industry and Information Technology Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China Department of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China School of Mechanical and Aerospace Engineering Oklahoma State UniversityOklahoma 74078U.S.A.

Due to the increasing interests in using functionally graded piezoelectric materials(FGPMs) in the design of advanced micro-electro-mechanical systems, it is important to understand the stability behaviors of the FGPM beams. In this study, considering the effects of geometrical nonlinearity, temperature, and electricity in the constitutive relations and the effect of the magnetic field on the FGPM beam, the Euler-Bernoulli beam model is adopted, and the nonlinear governing equation of motion is derived via Hamilton's principle. A perturbation method, which can decompose the deflection into static and dynamic components, is utilized to linearize the nonlinear governing equation. Then,a dynamic stability analysis is carried out, and the approximate analytical solutions for the nonlinear frequency and boundary frequencies of the unstable region are *** examples are performed to verify the present analysis. The effects of the static deflection, the static load factor, the temperature change, and the magnetic field flux on the stability behaviors of the FGPM beam are discussed. From the proposed analytical solutions and numerical results, one can easily and clearly find the effects of various controlled parameters, such as geometric and physical properties of the system, on the mechanical behaviors of structures, and the conclusions are very important and useful for the design of micro-devices.

关键词： functionally graded piezoelectric material(FGPM) geometrical nonlinearity stability analysis

Multidirectional 3D printed functionally graded modular joint actuated by TCPFL muscles for soft robots

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Bio-Design and Manufacturing 2019年第4期2卷 256-268页

作者： Armita Hamidi Yara Almubarak Yonas Tadesse Humanoid Bio-robotics and Smart Systems(HBS)LaboratoryMechanical Engineering DepartmentThe University of Texas at DallasRichardsonTX 75080USA

Highly deformable bodies are essential for numerous types of applications in all sorts of environments. Joint-like structures comprising a ball and socket joint have many degrees of freedom that allow mobility of many biomimetic structures. Recently, soft robots are favored over rigid structures for their highly compliant material, high-deformation properties at low forces, and ability to operate in di fficult environments. However, it is still challenging to fabricate complex designs that satisfy application constraints due to the combined e ffects of material properties, actuation method, and structural geometry on the performance of the soft robot. Therefore, a combination of a rigid joint and a soft body can help achieve modular robots with fully functional body morphology. Yet, the fabrication of soft parts requires extensive molding for complex shapes, which comprises several processes and can be time-consuming. In addition, molded connections between extremely soft materials and hard materials can be critical failing points. In this paper, we present a functionally graded 3D-printed joint-like structure actuated by novel contractile actuators. Functionally graded materials (FGMs) via 3D printing allow for extensive material property enhancement and control which warrant tunable functionalities of the system. The 3D-printed structure is made of 3 rigid ball and socket joints connected in series and actuated by integrating twisted and coiled polymer fishing line ( TCPFL) actuators, which are con fined in the FGM accordion-shaped channels. The implementation of the untethered T CPFL actuation system can be highly bene ficial for deployment in environments that require low vibrations and silent actuation. The fishing line TCP actuators produce an actuation strain up to 40% and bend the joint up to 40° in any direction. The T CPFL can be actuated individually or as a group to control the bending trajectory of the modular joint, which is bene ficial when deployed i

关键词： Functionally graded 3D-printed Joint Multidirectional Fishing line TCP

Bio-inspiration as a Concept for Sustainable Constructions Illustrated on graded Concrete

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Journal of Bionic Engineering 2019年第4期16卷 742-753页

作者： Rafael Horn Stefan Albrecht Walter Haase Max Langer Daniel Schmeer Werner Sobek Olga Speck Philip Leistner Fraunhofer Institute for Building Physics IBP GaBi Stuttgart 70563Germany Institute for Lightweight Structures and Conceptual Design(ILEK’) University of StuttgartStuttgart 70569Germany Plant Biomechanics Group Botanic GardenUniversity of FreiburgFreiburg 79104Germany Institute for Acoustics and Building Physics University of StuttgartStuttgart 70569Germany

The building industry is one of the main contributors to worldwide resource consumption and anthropogenic climate ***,sustainable solutions in construction are particularly *** by the success principles of living nature,biologists and engineers present here an interdisciplinary work:The sustainability assessment of a bio-inspired material technology called graded concrete,which was developed at *** structural materials can be found in plants on different hierarchical levels,providing a multitude of creative solutions for *** concrete applies this biological concept of structural optimization to the interior structure of concrete components to minimize material and resource *** evaluate the sustainability of this innovation,a newly developed quantitative Bio-inspired Sustainability Assessment(BiSA)method is *** focuses on the relationship of environmental,social and economic functions and the corresponding burdens quantified basing on life cycle *** BiSA of graded concrete slabs shows significant improvements over conventional concrete for the applied use *** an overall reduction of environmental burdens by 13%is expected,economic burdens can be reduced by up to 40%and social burdens by 35.7%.The assessment of the graded concrete technology identifies its potential with regard to sustainable *** presented work provides a blueprint for the interdisciplinary,integrative work on sustainable,bio-inspired *** shows that the synergies of bio-inspiration and BiSA within technical product development can be fruitful.

关键词： sustainability assessment bio-inspired sustainability graded concrete biomimetic promise BiSA

Nonlinear dynamic behavior of inhomogeneous functional plates composed of sigmoid graded metal-ceramic materials

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Science China(Technological Sciences) 2018年第11期61卷 1654-1665页

作者： WANG YanQing ZU Jean W. Department of Mechanics Northeastern University Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines Northeastern University Department of Mechanical and Industrial Engineering University of Toronto

This paper presents a study on nonlinear vibration of inhomogeneous functional plates composed of sigmoid graded metalceramic materials. The material properties vary continuously along the thickness direction according to a sigmoid distribution rule, which is defined by piecewise functions to ensure smooth distribution of stress among all the interfaces. The geometric nonlinearity is considered by adopting the von Kármán geometrical relations. Based on the d'Alembert's principle, the nonlinear out-of-plane equation of motion of the plates is developed. The Galerkin method is employed to discretize the motion equation to a series of ordinary differential ones, which are subsequently analyzed via the use of the method of harmonic balance. Then, the analytical results are validated by the comparison to numerical solutions, which are obtained by using the adaptive step-size fourth-order Runge-Kutta method. The stability of the steady-state response is examined by the perturbation technique. Results show the first and third modes are both activated while the second mode is not activated for the plates under harmonic point excitation. The frequency response relationships of activated modes exhibit very complicated curves due to the nonlinear modal interaction. In addition, influences of key system parameters on nonlinear vibrational characteristics of the present inhomogeneous plates are illustrated.

关键词： inhomogeneous functional plates sigmoid graded metal-ceramic material nonlinear vibration response harmonic balance method

Coupling Magneto-Electro-Elastic node-based smoothed radial point interpolation method for free vibration and transient analysis of Functionally graded Magneto-Electro-Elastic structures

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Chinese Journal of Aeronautics 2020年第1期33卷 227-243页

作者： Liming ZHOU Shuhui REN Bin NIE Guikai GUO Xiangyang CUI School of Mechanical and Aerospace Engineering Jilin UniversityChangchun 130025China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082China

A Coupling Magneto-Electro-Elastic(MEE)Node-based Smoothed Radial Point Interpolation Method(CM-NS-RPIM)was proposed to solve the free vibration and transient responses of Functionally graded Magneto-Electro-Elastic(FGMEE)*** introducing the modified Newmark method,the displacement,electrical potential and magnetic potential of the structures under transient mechanical loading were *** on G space theory and the weakened weak(W2)formulation,the equations of the multi-physics coupling problems were *** triangular background elements,the free vibration and transient responses of three numerical examples were *** proved that CM-NS-RPIM performed better than the standard FEM by reducing the overly-stiff of ***,CM-NS-RPIM could reduce the number of nodes while guaranteeing the ***,triangular elements could be generated automatically even for complex ***,the effectiveness and validity of CM-NS-RPIM were demonstrated,which were valuable for the design of intelligence devices,such as energy harvesters and sensors.

关键词： Coupling Magneto-Electro-Elastic node-based smoothed radial point interpolation method Functionally graded Magneto-Electro-Elastic Gradient smoothing technique Rayleigh damping Transient responses

Thermo-magnetic analysis of thick-walled spherical pressure vessels made of functionally graded materials

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Applied Mathematics and Mechanics(English Edition) 2019年第6期40卷 751-766页

作者： M. A. NEMATOLLAHI A. DINI M. HOSSEINI Department of Biosystems Engineering College of AgricultureShiraz UniversityShiraz 71441-65186Iran Department of Mechanical Engineering Ferdowsi University of MashhadMashhad 91775-1111Iran Department of Mechanical Engineering Sirjan University of TechnologySirjan 78137-33385Iran

This study presents an analytical solution of thermal and mechanical displacements, strains, and stresses for a thick-walled rotating spherical pressure vessel made of functionally graded materials (FGMs). The pressure vessel is subject to axisymmetric mechanical and thermal loadings within a uniform magnetic field. The material properties of the FGM are considered as the power-law distribution along the thickness. Navier’s equation, which is a second-order ordinary differential equation, is derived from the mechanical equilibrium equation with the consideration of the thermal stresses and the Lorentz force resulting from the magnetic field. The distributions of the displacement, strains, and stresses are determined by the exact solution to Navier’s equation. Numerical results clarify the influence of the thermal loading, magnetic field, non-homogeneity constant, internal pressure, and angular velocity on the magneto-thermo-elastic response of the functionally graded spherical vessel. It is observed that these parameters have remarkable effects on the distributions of radial displacement, radial and circumferential strains, and radial and circumferential stresses.

关键词： analytical solution magnetic field thermal loading rotating thick-walled spherical pressure vessel functionally graded material (FGM)

Fracture analysis of a functionally graded interfacial zone between two dissimilar homogeneous materials

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Science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 540-552页

作者： CHENG Zhanqi1,2 & ZHONG Zheng1 1. School of Aerospace Engineering and Applied mechanics, Tongji University, Shanghai 200092, China 2. College of Civil Engineering, Zhengzhou University, Zhengzhou 450002, China School of Aerospace Engineering and Applied mechanics Tongji University Shanghai China College of Civil Engineering Zhengzhou University Zhengzhou China

In this paper the plane elasticity problem for a functionally graded interfacial zone containing a crack between two dissimilar homogeneous materials has been considered. It is assumed that in the interfacial zone the reciprocal of the shear modulus is a linear function of the coordinate, while Possion’s ratio keeps constant. By utilizing the Fourier transformation technique and the transfer matrix method, the mixed boundary problem is reduced to a system of singular integral equations that are solved numerically. The influences of the geometric parameters and the graded parameter on the stress intensity factors are investigated. The numerical results show that the graded parameters, the thickness of interfacial zone, the crack size and location have significant effects on the stress intensity factors.

关键词： functionally graded material interfacial zone fracture stress intensity factor

Large deformation analysis of a cantilever beam made of axially functionally graded material by homotopy analysis method

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Applied Mathematics and Mechanics(English Edition) 2019年第10期40卷 1375-1386页

作者： Xin LIN Yixin HUANG Yang ZHAO Tianshu WANG School of Astronautics Harbin Institute of TechnologyHarbin 150001China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

Large deformation of a cantilever axially functionally graded (AFG) beam subject to a tip load is analytically studied using the homotopy analysis method (HAM). It is assumed that its Young’s modulus varies along the longitudinal direction according to a power law. Taking the solution of the corresponding homogeneous beam as the initial guess and obtaining a convergence region by adjusting an auxiliary parameter, the analytical expressions for large deformation of the AFG beam are provided. Results obtained by the HAM are compared with those obtained by the finite element method and those in the previous works to verify its validity. Good agreement is observed. A detailed parametric study is carried out. The results show that the axial material variation can greatly change the deformed configuration, which provides an approach to control and manage the deformation of beams. By tailoring the axial material distribution, a desired deformed configuration can be obtained for a specific load. The analytical solution presented herein can be a helpful tool for this procedure.

关键词： large deformation beam axially functionally graded (AFG) material Euler-Bernoulli beam homotopy analysis method (HAM)

Electro-mechanical response of functionally graded beams with imperfectly integrated surface piezoelectric layers

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Science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 513-525页

作者： YAN Wei1 & CHEN Weiqiu1,2 1. Department of Civil Engineering, Zhejiang University, Hangzhou 310027, China 2. State Key Lab of CAD & CG, Zhejiang University, Hangzhou 310027, China Department of Civil Engineering Zhejiang University Hangzhou China State Key Lab of CAD & CG Zhejiang University Hangzhou China

The time-dependent behavior of a simply-supported functionally graded beam bonded with piezoelectric sensors and actuators is studied using the state-space method. The creep behavior of bonding adhesives between piezoelectric layers and beam is characterized by a Kelvin-Voigt viscoelastic model, which is practical in a high temperature circumstance. Both the host elastic functionally graded beam and the piezoelectric layers are orthotropic and in a state of plane stress, with the former being inhomogeneous along the thickness direction. A laminate model is employed to approximate the host beam. Moreover, the coupling effect between the elastic deformation and electric field in piezoelectric layers is considered. Results indicate that the viscoelastic property of interfacial adhesives has a significant effect on the function of bonded actuators and sensors with time elapsing.

关键词： functionally graded beam piezoelectric layers Kelvin-Voigt model state-space method