Accepted Manuscripts

Chao Liu, Amin Mehrabian and Younane Abousleiman
J. Appl. Mech   doi: 10.1115/1.4040890
The linear theory of dual-porosity and dual-permeability poro-chemo-electro-elasticity is presented. The theory outlines the dual-continuum formulation of multiple coupled processes involving solid deformation, pore fluid flow, and electrically-charged species transport, within and in between two coexisting porosity systems of a fluid-saturated, poroelastic medium. The described formulation is used to derive the analytical solutions to the inclined wellbore problem and axisymmetric Mandel-Type problem of dual-porosity, dual-permeability poro-chemo-electro-elasticity. The effects of chemical and electrical potentials on the distributions of stress and pore pressure are demonstrated by numerical examples pertaining to the considered problems. It is shown that the fully-coupled nature of the solutions rigorously captures the seemingly anomalous time variations of the effective stress as driven by the pore fluid pressure disturbances, as well as distribution and movement of anions/cations within the dual-porosity porous medium. The existing subset of published solutions on the subject is successfully reproduced as special cases of the solutions presented in this paper.
TOPICS: Deformation, Permeability, Porosity, Elasticity, Stress, Porous materials, Fluids, Pressure, Fluid pressure, Fluid dynamics
Qinyi Huang, Yihui Pan and Zheng Zhong
J. Appl. Mech   doi: 10.1115/1.4040777
In this paper, an acoustomechanical constitutive model is developed to describe the heating effect of a tissue-mimicking gel by cavitation in exposure to high-intensity focused ultrasound (HIFU). An internal variable, representing the evolution of cavitation process, is introduced into the Helmholtz free energy under the framework of thermodynamics that combines the acoustic radiation stress theory and the nonlinear elasticity theory together. Thus, the internal variable is related to the cavitation process and the mechanical energy dissipation of a tissue-mimicking gel from a macroscopic viewpoint. Since the temperature rise of cavitation phenomenon is more remarkable than that of heating waves, the temperature inside the tissue-mimicking gel rises rapidly mainly due to large amounts of cavitation bubbles. This phenomenon can be quantitatively described by the present model, which fits the existing experimental data well.
TOPICS: Cavitation, Ultrasound, Constitutive equations, Biological tissues, Heating, Temperature, Radiation (Physics), Acoustics, Stress, Waves, Energy dissipation, Elasticity, Thermodynamics, Bubbles
Matteo Filippi, Alfonso Pagani and Erasmo Carrera
J. Appl. Mech   doi: 10.1115/1.4040693
Nonlinear dynamics and mode aberration of rotating plates and shells are discussed in this work. The mathematical formalism is based on the one-dimensional Carrera Unified Formulation (CUF), which enables to express the governing equations and related finite element arrays as independent of the theory approximation order. As a consequence, three-dimensional solutions accounting for couplings due to geometry, material and inertia can be included with ease and with low computational costs. Geometric nonlinearities are incorporated in a total Lagrangian scenario and the full Green-Lagrange strains are employed to outline accurately the equilibrium path of structures subjected to inertia, centrifugal forces and Coriolis effect. A number of representative numerical examples are discussed, including multi-section blades and shells with different radii of curvature. Particular attention is focussed on the capabilities of the present formulation to deal with nonlinear effects, and comparison with s simpler linearized approach shows evident differences, particularly in the case of deep shells.
TOPICS: Rotating blades, Nonlinear dynamics, Shells, Inertia (Mechanics), Coriolis force, Centrifugal force, Equilibrium (Physics), Finite element analysis, Plates (structures), Approximation, Blades, Couplings, Geometry, Accounting
Xiongfei Lv, Liwu Liu, Yanju Liu and Jinsong Leng
J. Appl. Mech   doi: 10.1115/1.4040405
Dielectric elastomer (DE) is a promising electroactive polymer. As DE material, rubbers are often filled with functional particles to improve their electromechanical coupling performance. However, the filled particles also bring stress softening, which is known as Mullins effect. In this paper, we prepared the carbon nanotube filled silicone elastomer as dielectric elastomer composite, and used the pseudo-elastic theory to model its Mullins effect. Then the thermodynamics and pseudo-elastic theory were combined to predict the idealized electromechanical softening behavior. Two cases are considered: linear dielectric and saturated dielectric. For linear dielectric with an initial force, the voltage-controlled unloading remains "residual strain" after every cycle and reloading may eliminate instability. For saturated dielectric, we assume it is all linear before polarization saturation. After saturation, the material response changes a lot, which also affects the following softening behavior. At last, viscoelasticity was further incorporated to account for rate-dependent softening deformation, and we also carried out some simply electromechanical experiments on VHB 4910 to explore its softening behavior. This work may lead to a better understanding of the softening behavior in dielectric elastomers undergoing electromechanical coupling situations.
TOPICS: Elastomers, Modeling, Particulate matter, Carbon nanotubes, Cycles, Silicones, Conducting polymers, Polarization (Electricity), Stress, Viscoelasticity, Polarization (Light), Deformation, Thermodynamics, Polarization (Waves), Composite materials

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