Accepted Manuscripts

Binghe Liu, Xu Wang, Haosen Chen, Sen Chen, Hongxin Yang, Jun Xu, Hanqing Jiang and Daining Fang
J. Appl. Mech   doi: 10.1115/1.4042432
The increasing significance on the development of high-performance lithium-ion (Li-ion) batteries is calling for new battery materials, theoretical models, and simulation tools. Lithiation induced deformation in electrodes calls attention to study the multiphysics coupling between mechanics and electrochemistry. In this paper, a simultaneous multiscale and multiphysics model to study the coupled electrochemistry and mechanics in the continuum battery cell level and the microscale particle level was developed and implemented in COMSOL Multiphysics. In the continuum scale, the porous electrode theory and the classical mechanics model were applied. In the microscale, the specific particle structure has been incorporated into the model. This model was demonstrated to study the effects of mechanical constraints, charging rate, and silicon/C ratio, on the electrochemical performance. This model provides a powerful tool to perform simultaneous multiscale and multiphysics design on Li-ion batteries, from the particle level to full-cell level.
TOPICS: Lithium, Shells, Particulate matter, Electrodes, Microscale devices, Batteries, Electrochemistry, Lithium-ion batteries, Silicon, Classical mechanics, Deformation, Simulation, Degrees of freedom, Design
Jianyong Chen, Hailong Wang, Kim M. Liew and Shengping Shen
J. Appl. Mech   doi: 10.1115/1.4042431
Based on the irreversible thermodynamics, a fully coupled chemomechanical model, i.e., the reaction-diffusion-stress model, is proposed and implemented numerically into the finite element method with UEL (user-defined element) subroutines in ABAQUS. Compositional stress and growth stress are induced by the diffusion and chemical reactions in the solid, and in turn, both the diffusion and chemical reactions are stress-dependent. By providing specialization of the chemical reaction and free energy function, the specialized constitutive equations are introduced, which are highly coupled and nonlinear. The finite element formulations are derived from the standard Galerkin approach and implemented via UEL subroutines in ABAQUS. Several illustrative numerical simulation examples are shown. The results demonstrate the validity and capability of the UEL subroutines, and show the interactions among mechanical deformation, diffusion and chemical reaction.
TOPICS: Finite element methods, Chemical reactions, Diffusion (Physics), Stress, Deformation, Computer simulation, Nonequilibrium thermodynamics, Constitutive equations, Finite element analysis
Hassan Bahaloo and Yaning Li
J. Appl. Mech   doi: 10.1115/1.4042428
Based on micropolar continuum theory, the closed-form stiffness tensor of auxetic chiral lattices with V-shaped wings and rotational joints were derived. Representative Volume Element (RVE) of the chiral lattice was decomposed into V-shape wings with four-fold symmetry. A unified V-beam finite element was developed to reduce the nodal Degrees of Freedoms (DOFs) of the RVE to enable closed-form analytical solutions. The elasticity constants were derived as functions of the angle of the V-shaped wings, non-dimensional in-plane thickness of the ribs, and the stiffness of the rotational joints. The influences of these parameters on the coupled chiral and auxetic effects were systematically explored. The results show that the elastic moduli were significantly influenced by all three parameters, while the Poisson's ratio was barely influenced by the in-plane thickness of the ribs but is sensitive to the angle of the V-shaped wings and the stiffness of the rotational springs. There is a transition region out of which, the spring stiffness does not considerably affect the auxeticity and the overall lattice stiffness.
TOPICS: Rotation, Poisson ratio, Tensors, Finite element analysis, Modeling, Elastic constants, Elastic moduli, Shapes, Springs, Stiffness, Wings
Xinyu Liao and Prashant K Purohit
J. Appl. Mech   doi: 10.1115/1.4042429
Irradiation induced oxidation of lipid membranes is implicated in diseases and has been harnessed in medical treatments. Irradiation induces the formation of oxidative free radicals which attack double-bonds in the hydrocarbon chains of lipids. Studies of the kinetics of this reaction suggest that the result of the first stage of oxidation is a structural change in the lipid that causes an increase in the area per molecule in a vesicle. Since area changes are directly connected to membrane tension, irradiation induced oxidation affects the mechanical behavior of a vesicle. Here we analyze shape changes of axisymmetric vesicles that are under simultaneous influence of adhesion, micropipette aspiration and irradiation. We study both the equilibrium and kinetics of shape changes and compare our results with experiments. The tension-area relation of a membrane which is derived by accounting for thermal fluctuations plays an important role in our analysis. Our model is an example of the coupling of mechanics and chemistry which is ubiquitous in biology.
TOPICS: Irradiation (Radiation exposure), Membranes, oxidation, Shapes, Tension, Biomedicine, Biology, Accounting, Equilibrium (Physics), Fluctuations (Physics), Chain, Mechanical behavior, Chemistry, Diseases, Adhesion
Jerome M. Colin, Mohsen Darayi and Maria Holland
J. Appl. Mech   doi: 10.1115/1.4042430
In this manuscript, we study the wrinkling instability of two layers embedded in a homogeneous matrix of infinite size. Using a linear stability analysis, we characterize the wrinkling of the two layers as a function of the layer spacing and the shear moduli ratio between the two materials. When the layers are stiffer than the surrounding matrix, stiffness contrast largely determines the stability behavior of the system. When the layers are softer than the surrounding matrix, stiffness contrast and layer spacing interact to determine critical threshold strain and wavelength, and result in striking discontinuities in wavelength between regimes. When the layers are close to each other, the system has a strong preference for the symmetric wrinkling mode, but as the distance between the two layers increases, the anti-symmetric mode may emerge.
TOPICS: Separation (Technology), Stiffness, Stability, Wavelength, Shear modulus, Preferences
Richard M. Christensen
J. Appl. Mech   doi: 10.1115/1.4042291
The recently developed theory for isotropic materials failure is briefly outlined. The many steps and stages of the verification process for the theory are fully documented so that it can be used with assurance in a wide variety of directions. Then the failure theory is used to develop a new measure or index for the degree of ductility of materials failure in any state of stress. This new failure property is named the ductility number, Nd. It is rigorously derived, intuitively compatible, and very easy to use. Applications and interpretations of Nd are given.
TOPICS: Ductility, Failure, Stress
Giovanni Formica, Michela Taló, Giulia Lanzara and Walter Lacarbonara
J. Appl. Mech   doi: 10.1115/1.4042137
Hysteresis due to stick-slip energy dissipation in carbon nanotubes (CNT) nanocomposites is experimentally observed, measured and identified through a 1D phenomenological model obtained via reduction of a full 3D mesoscale model. The ensuing model is shown to describe well the nanocomposite hysteretic response which features the transition from the purely elastic to the post-stick-slip behavior characterized by the interfacial frictional sliding motion between the polymer chains and the CNTs. Sensitivity analyses shed light onto the physical meaning of each model parameter and the influence on the material constitutive response. The model parameters are determined by fitting the experimentally acquired force-displacement curves of CNT/polymer nanocomposites using a differential evolution algorithm. Nanocomposite beam-like samples made of a high performance engineering polymer and high aspect ratio CNTs are fabricated and tested in bending mode at increasing displacement amplitudes. The entire time histories of the restoring force are fitted by the model through a unique set of parameters. The parameters identification is carried out for nanocomposites with various CNTs weight fractions, so as to highlight the model capability to identify a large variety of nanocomposites hysteretic behaviors through a fine tuning of its constitutive parameters. By exploiting the proposed model, a multi-scale material model design and optimization are made possible towards the exploitation of these promising materials for engineering applications.
TOPICS: Carbon nanotubes, Nanocomposites, Displacement, Evolutionary algorithms, Fittings, Weight (Mass), Polymer engineering, Energy dissipation, Design, Engineering systems and industry applications, Optimization, Sensitivity analysis, Stick-slip, Polymer chains, Polymer nanocomposites
Jae-Ha Lee, Hyunho Shin, Jong-Bong Kim, Ju-Young Kim, Sung-Taek Park, Gwang-Lyeon Kim and Kyeongwon Oh
J. Appl. Mech   doi: 10.1115/1.4042138
The load-displacement curves of an aluminum alloy and tantalum were determined using a hat-type specimen in the compression test. Based on the results of finite element analysis, the employed geometry of the hat-type specimen was found to yield a load-displacement curve that is nearly independent of the friction between the specimen and platen. The flow stress-strain curves of the alloy and tantalum were modelled using the Ludwik and Voce constitutive laws, respectively; furthermore, simulation of the compression event of the hat-type specimen was performed by assuming appropriate constitutive parameters. The constitutive parameters were varied via an optimization function built in MATLAB until the simulated load-displacement curves reasonably fit the experimental curve. The optimized constitutive parameters obtained in this way were then used to construct friction-free flow stress-strain curves of the two materials.
TOPICS: Flow (Dynamics), Aluminum alloys, Stress, Testing, Compression, Displacement, Tantalum, Stress-strain curves, Friction, Alloys, Simulation, Constitutive equations, Finite element analysis, Optimization, Geometry, Matlab
Emily Guzas, Sachin Gupta, Joseph M Ambrico, James M. LeBlanc and Arun Shukla
J. Appl. Mech   doi: 10.1115/1.4042046
This paper details a numerical study of the stability of a cylinder under combined hydrostatic and dynamic pressure loading within a tubular environment. Simulations are executed using a Eulerian-Lagrangian scheme, with the DYSMAS code, to model the (1) structural response of an unstiffened cylindrical shell to dynamic pressure and (2) the fluid flow within the surrounding environment during the collapse. Simulations involve an aluminum 6061-T6 cylinder structure with a length-to-diameter ratio of 9.6. The cylinder is 31.8 mm (1.25-in) in diameter, and concentrically and longitudinally centered within the outer tube. Simulations are run at four hydrostatic tank pressures, categorized by percentage of collapse pressure, Pc: 66% Pc, 80% Pc, 85% Pc, and 90%Pc. The shell is subjected to shock loading created by the detonation of a blasting cap at a standoff to the structure. Simulated pressure histories are compared to experimental pressure data at gage locations. The simulations produce the same overall result for three of four cases, survive/implode. For the 80%Pc case, the overall result differs in that the specimen in the experiment survives but the simulated cylinder implodes. The discrepancy between the overall experimental result and corresponding simulation is not deemed a failure for the 80%Pc case; instead, this signifies a transitional case for the dynamic stability of the shell structure (collapse is sensitive to small deviations from assumed conditions).
TOPICS: Pressure, Stability, Fluid dynamics, Hydrostatics, Aluminum, Explosions, Gages, Computer simulation, Simulation, Blasting, Shock (Mechanics), Engineering simulation, Pipes, Collapse, Cylinders, Dynamic stability, Failure, Shells

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