We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement an...We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement and electric potential for the electromechanical coupling analysis, and additional independent fields to address the incompressible constraint of the hyperelastic material. Linearization of the variational form and finite element discretization are adopted for the numerical implementation. A general FEM program framework is devel- oped using C＋＋ based on the open-source finite element library deal.II to implement this proposed algorithm. Numerical examples demonstrate the accuracy, convergence properties, mesh-independence properties, and scalability of this method. We also use the method for eigenvalue analysis of a dielectric elastomer actuator subject to electromechanical loadings. Our finite element implementation is available as an online supplementary material.展开更多
We present a finite element method for dielectric elastomer （DE） transducers based on the nonlinear field theory of DE. The method is implemented in the commercial finite element software ABAQUS, which provides a la...We present a finite element method for dielectric elastomer （DE） transducers based on the nonlinear field theory of DE. The method is implemented in the commercial finite element software ABAQUS, which provides a large library functions to describe finite elasticity. This method can be used to solve electromechanical coupling problems of DE transducers with complex configurations and under inhomogeneous deformation.展开更多
Propagation characteristics of surface acoustic waves（SAWs） in ZnO films/glass substrates are theoretically investigated by the three-dimensional（3D） finite element method. At first, for（11ˉ20） ZnO films/glass ...Propagation characteristics of surface acoustic waves（SAWs） in ZnO films/glass substrates are theoretically investigated by the three-dimensional（3D） finite element method. At first, for（11ˉ20） ZnO films/glass substrates, the simulation results confirm that the Rayleigh waves along the [0001] direction and Love waves along the [1ˉ100] direction are successfully excited in the multilayered structures. Next, the crystal orientations of the ZnO films are rotated, and the influences of ZnO films with different crystal orientations on SAW characterizations, including the phase velocity, electromechanical coupling coefficient, and temperature coefficient of frequency, are investigated. The results show that at appropriate h/λ, Rayleigh wave has a maximum k^2 of 2.4% in（90°, 56.5°, 0°） ZnO film/glass substrate structure; Love wave has a maximum k^2 of 3.81% in（56°, 90°, 0°） ZnO film/glass substrate structure. Meantime, for Rayleigh wave and Love wave devices, zero temperature coefficient of frequency（TCF） can be achieved at appropriate ratio of film thickness to SAW wavelength. These results show that SAW devices with higher k^2 or lower TCF can be fabricated by flexibly selecting the crystal orientations of ZnO films on glass substrates.展开更多
The dielectric elastomer(DE)has attracted significant attention due to its desired features,including large deformation,fast response,and high energy density.However,for a DE actuator(DEA)utilizing a snap-through defo...The dielectric elastomer(DE)has attracted significant attention due to its desired features,including large deformation,fast response,and high energy density.However,for a DE actuator(DEA)utilizing a snap-through deformation mode,most existing theoretical models fail to predict its deformation path.This paper develops a new finite element method(FEM)based on the three-parameter Gent-Gent model suitable for capturing strain-stiffening behaviors.The simulation results are verified by experiments,indicating that the FEM can accurately characterize the snap-through path of a DE.The method proposed in this paper provides theoretical guidance and inspiration for designing and applying DEs and bistable electroactive actuators.展开更多
To simulate the nonlinear behavior of ferroelectric structures and devices under non-uniform electromechanical loadings,a domain-switching embedded electromechanical finite element method is developed in this paper.Fo...To simulate the nonlinear behavior of ferroelectric structures and devices under non-uniform electromechanical loadings,a domain-switching embedded electromechanical finite element method is developed in this paper.Following continuum assumption,the electromechanical behavior of each representative material point can be obtained by averaging the behavior of the local corresponding microstructure,e.g.42 domains used in this work.A new Double Gibbs free energy criterion for domain-switching is proposed to ensure the convergence and stability of the simulations on ferroelectrics under non-uniform field.Several computational examples are given to demonstrate that this nonlinear finite element method can yield reasonable and stable simulation results which can be used to explain some experimental results and assist the design of ferroelectric devices.展开更多
A nonlinear finite element （FE） model based on domain switching was proposed to study the electromechanical behavior of ferroelectric ceramics. The incremental FE formulation was improved to avoid any calculation in...A nonlinear finite element （FE） model based on domain switching was proposed to study the electromechanical behavior of ferroelectric ceramics. The incremental FE formulation was improved to avoid any calculation instability. The problems of mesh sensitivity and convergence, and the efficiency of the proposed nonlinear FE technique have been assessed to illustrate the versatility and potential accuracy of the said technique. The nonlinear electromechanical behavior, such as the hysteresis loops and butterfly curves, of ferroelectric ceramics subjected to both a uniform electric field and a point electric potential has been studied numerically. The results obtained are in good agreement with those of the corresponding theoretical and experimental analyses. Furthermore, the electromechanical coupling fields near （a） the boundary of a circular hole, （b） the boundary of an elliptic hole and （c） the tip of a crack, have been analyzed using the proposed nonlinear finite element method （FEM）. The proposed nonlinear electromechanically coupled FEM is useful for the analysis of domain switching, deformation and fracture of ferroelectric ceramics.展开更多
Soft machines are combinations of hard and soft active materials, thus the coupling and interaction between soft and hard components dictate the performance of soft machines. Structural optimization has been intensive...Soft machines are combinations of hard and soft active materials, thus the coupling and interaction between soft and hard components dictate the performance of soft machines. Structural optimization has been intensively used for design of conventional hard machines, while, to our best knowledge, few attempts have been made towards optimal design of soft machines. Here, we describe the sizing optimization problem of a dielectric elastomer(DE) actuated mechanical amplifier, and achieve the optimal design through combination of a commercial finite element method(FEM) software and an optimization automation software.We then design, fabricate and demonstrate a locomotive soft machine driven by DE actuator with amplified displacement output.The methodology and results present here open the door towards optimal designs of active materials based soft machines.展开更多
The considerable electric-induced shape change,together with the attributes of lightweight,high efficiency,and inexpensive cost,makes dielectric elastomer,a promising soft active material for the realization of actuat...The considerable electric-induced shape change,together with the attributes of lightweight,high efficiency,and inexpensive cost,makes dielectric elastomer,a promising soft active material for the realization of actuators in broad applications.Although,a number of prototype devices have been demonstrated in the past few years,the further development of this technology necessitates adequate analytical and numerical tools.Especially,previous the-oretical studies always neglect the influence of surrounding med-ium.Due to the large deformation and nonlinear equations of states involved in dielectric elastomer,finite element method(FEM)is anticipated;however,the few available formulations employ homemade codes,which are inconvenient to implement.The aim of this work is to present a numerical approach with the commercial FEM package COMSOL to investigate the nonlinear response of dielectric elastomer under electric stimulation.The influence of surrounding free space on the electric field is analyzed and the corresponding electric force is taken into account through an electric surface traction on the circumstances edge.By employ-ing Maxwell stress tensor as actuation pressure,the mechanical and electric governing equations for dielectric elastomer are coupled,and then solved simultaneously with the Gent model of stain energy to derive the electric induced large deformation as well as the electromechanical instability.The finite element imple-mentation presented here may provide a powerful computational tool to help design and optimize the engineering applications of dielectric elastomer.展开更多
基金the support under A*STAR SERC grant (132-183-0025)
文摘We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement and electric potential for the electromechanical coupling analysis, and additional independent fields to address the incompressible constraint of the hyperelastic material. Linearization of the variational form and finite element discretization are adopted for the numerical implementation. A general FEM program framework is devel- oped using C＋＋ based on the open-source finite element library deal.II to implement this proposed algorithm. Numerical examples demonstrate the accuracy, convergence properties, mesh-independence properties, and scalability of this method. We also use the method for eigenvalue analysis of a dielectric elastomer actuator subject to electromechanical loadings. Our finite element implementation is available as an online supplementary material.
基金supported by the National Natural Science Foundation of China (No. 10832009)the Program for New Century Excellent Talents in University (NCET-08-0480)+1 种基金the Fundamental Research Funds for the Central Universities,and MRSEC at Harvard Universitysupport by the China Scholarship Council Foundation and Harvard University through the sponsoring of a nine-month visit at Harvard University
文摘We present a finite element method for dielectric elastomer （DE） transducers based on the nonlinear field theory of DE. The method is implemented in the commercial finite element software ABAQUS, which provides a large library functions to describe finite elasticity. This method can be used to solve electromechanical coupling problems of DE transducers with complex configurations and under inhomogeneous deformation.
基金supported by the National Natural Science Foundation of China(Grant No.11304160)the Natural Science Foundation of Jiangsu Provincial Higher Education Institutions,China(Grant No.13KJB140008)the Foundation of Nanjing University of Posts and Telecommunications,China(Grant No.NY213018)
文摘Propagation characteristics of surface acoustic waves（SAWs） in ZnO films/glass substrates are theoretically investigated by the three-dimensional（3D） finite element method. At first, for（11ˉ20） ZnO films/glass substrates, the simulation results confirm that the Rayleigh waves along the [0001] direction and Love waves along the [1ˉ100] direction are successfully excited in the multilayered structures. Next, the crystal orientations of the ZnO films are rotated, and the influences of ZnO films with different crystal orientations on SAW characterizations, including the phase velocity, electromechanical coupling coefficient, and temperature coefficient of frequency, are investigated. The results show that at appropriate h/λ, Rayleigh wave has a maximum k^2 of 2.4% in（90°, 56.5°, 0°） ZnO film/glass substrate structure; Love wave has a maximum k^2 of 3.81% in（56°, 90°, 0°） ZnO film/glass substrate structure. Meantime, for Rayleigh wave and Love wave devices, zero temperature coefficient of frequency（TCF） can be achieved at appropriate ratio of film thickness to SAW wavelength. These results show that SAW devices with higher k^2 or lower TCF can be fabricated by flexibly selecting the crystal orientations of ZnO films on glass substrates.
基金Project supported by the National Key Research and Development Program of China(No.2019YFB1311600)the National Natural Science Foundation of China(Nos.11902248 and 52075411)+1 种基金the Shaanxi Key Research and Development Program of China(No.2020ZDLGY06-11)the State Key Laboratory for Strength and Vibration of Mechanical Structures of China(No.SV2018-KF-08)。
文摘The dielectric elastomer(DE)has attracted significant attention due to its desired features,including large deformation,fast response,and high energy density.However,for a DE actuator(DEA)utilizing a snap-through deformation mode,most existing theoretical models fail to predict its deformation path.This paper develops a new finite element method(FEM)based on the three-parameter Gent-Gent model suitable for capturing strain-stiffening behaviors.The simulation results are verified by experiments,indicating that the FEM can accurately characterize the snap-through path of a DE.The method proposed in this paper provides theoretical guidance and inspiration for designing and applying DEs and bistable electroactive actuators.
基金supported by the National Natural Science Foundation of China(Grant Nos. 10702034,10732050,90816006 and 10820101048)the National Basic Research Program of China(Grant Nos.2007CB936803 and 2010CB832701)
文摘To simulate the nonlinear behavior of ferroelectric structures and devices under non-uniform electromechanical loadings,a domain-switching embedded electromechanical finite element method is developed in this paper.Following continuum assumption,the electromechanical behavior of each representative material point can be obtained by averaging the behavior of the local corresponding microstructure,e.g.42 domains used in this work.A new Double Gibbs free energy criterion for domain-switching is proposed to ensure the convergence and stability of the simulations on ferroelectrics under non-uniform field.Several computational examples are given to demonstrate that this nonlinear finite element method can yield reasonable and stable simulation results which can be used to explain some experimental results and assist the design of ferroelectric devices.
基金The project supported by the National Natural Science Foundation of China(10025209,10132010 90208002)the Research Grants of the Council of the Hong Kong Special Administrative Region,China(HKU7086/02E)the Key Grant Project of the Chinese Ministr
文摘A nonlinear finite element （FE） model based on domain switching was proposed to study the electromechanical behavior of ferroelectric ceramics. The incremental FE formulation was improved to avoid any calculation instability. The problems of mesh sensitivity and convergence, and the efficiency of the proposed nonlinear FE technique have been assessed to illustrate the versatility and potential accuracy of the said technique. The nonlinear electromechanical behavior, such as the hysteresis loops and butterfly curves, of ferroelectric ceramics subjected to both a uniform electric field and a point electric potential has been studied numerically. The results obtained are in good agreement with those of the corresponding theoretical and experimental analyses. Furthermore, the electromechanical coupling fields near （a） the boundary of a circular hole, （b） the boundary of an elliptic hole and （c） the tip of a crack, have been analyzed using the proposed nonlinear finite element method （FEM）. The proposed nonlinear electromechanically coupled FEM is useful for the analysis of domain switching, deformation and fracture of ferroelectric ceramics.
基金supported by the National Natural Science Foundation of China(Grant Nos.11472210 and 11372239)
文摘Soft machines are combinations of hard and soft active materials, thus the coupling and interaction between soft and hard components dictate the performance of soft machines. Structural optimization has been intensively used for design of conventional hard machines, while, to our best knowledge, few attempts have been made towards optimal design of soft machines. Here, we describe the sizing optimization problem of a dielectric elastomer(DE) actuated mechanical amplifier, and achieve the optimal design through combination of a commercial finite element method(FEM) software and an optimization automation software.We then design, fabricate and demonstrate a locomotive soft machine driven by DE actuator with amplified displacement output.The methodology and results present here open the door towards optimal designs of active materials based soft machines.
基金This work was supported by NSFC under Grant(11321062 and 11402186,11402185)China Postdoctoral Science Foundation under Grant(2015M572548).
文摘The considerable electric-induced shape change,together with the attributes of lightweight,high efficiency,and inexpensive cost,makes dielectric elastomer,a promising soft active material for the realization of actuators in broad applications.Although,a number of prototype devices have been demonstrated in the past few years,the further development of this technology necessitates adequate analytical and numerical tools.Especially,previous the-oretical studies always neglect the influence of surrounding med-ium.Due to the large deformation and nonlinear equations of states involved in dielectric elastomer,finite element method(FEM)is anticipated;however,the few available formulations employ homemade codes,which are inconvenient to implement.The aim of this work is to present a numerical approach with the commercial FEM package COMSOL to investigate the nonlinear response of dielectric elastomer under electric stimulation.The influence of surrounding free space on the electric field is analyzed and the corresponding electric force is taken into account through an electric surface traction on the circumstances edge.By employ-ing Maxwell stress tensor as actuation pressure,the mechanical and electric governing equations for dielectric elastomer are coupled,and then solved simultaneously with the Gent model of stain energy to derive the electric induced large deformation as well as the electromechanical instability.The finite element imple-mentation presented here may provide a powerful computational tool to help design and optimize the engineering applications of dielectric elastomer.
