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A multiphase meshfree particle method for continuum-based modeling of dry and submerged granular flows

POWDER TECHNOLOGY 2018年 335卷 258-274页

作者： Nodoushan, E. Jafari Shakibaeinia, A. Hosseini, K. Polytech Montreal Dept Civil Geol & Min Engn Montreal PQ Canada Islamic Azad Univ Bijar Branch Dept Civil Engn Bijar Iran Semnan Univ Dept Civil Engn Semnan Iran

We develop and fully characterize a meshfree Lagrangian (particle) model for continuum-based numerical modeling of dry and submerged granular flows. The multiphase system of the granular material and the ambient fluid is treated as a multi-density multi-viscosity system in which the viscous behavior of the granular phase is predicted using a regularized viscoplastic rheological model with a pressure-dependent yield criterion. The numerical technique is based on the Weakly-Compressible Moving Particle Semi-implicit (WC-MPS) method. The required algorithms for approximation of the effective viscosity, effective pressure, and shear stress divergence are introduced. The capability of the model in dealing with the viscoplasticity is validated for the viscoplastic Poiseuille flow between parallel plates. The model is then applied and fully characterized (in respect to the various rheological and numerical parameters) for dry and submerged granular collapses with different aspect ratios. The numerical results are evaluated in comparison with the available experimental measurement from the literature as well as some complementary experimental measurements, performed in this study. The results show the capabilities of the presented model and its potential to deal with a broad range of dry and submerged granular flows. They also reveal the impotent role of the regularization, effective pressure, and shear stress divergence calculation methods on the accuracy of the results. For the case of the granular collapse the results characterize the shape, evolution, and flow regimes of granular deposit, as well as the important effect of the ambient fluid. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Multiphase granular flow continuum-based modeling Meshfree Lagrangian modeling WC-MPS method

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Development of a continuum-based, meshless, finite element modeling approach for representation of trabecular bone indentation

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JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS 2024年 159卷 106679页

作者： Benais, Remy Rycman, Aleksander Mclachlin, Stewart D. Univ Waterloo Dept Mech & Mechatron Engn Waterloo ON Canada

Implant subsidence into the underlying trabecular bone is a common problem in orthopaedic surgeries;however, the ability to pre-operatively predict implant subsidence remains limited. Current state-of-the-art computational models for predicting subsidence have issues addressing this clinical problem, often resulting from the size and complexity of existing subject-specific, image-based finite element (FE) models. The current study aimed to develop a simplified approach to FE modeling of subject-specific trabecular bone indentation resulting from implant penetration. Confined indentation experiments of human trabecular bone with flat- and sharp-tip indenters were simulated using FE analysis. A generalized continuum-level approach using a meshless smoothed particle hydrodynamics (SPH) approach and an isotropic crushable foam (CF) material model was developed for the trabecular bone specimens. Five FE models were generated with CF material parameters calibrated to cadaveric specimens spanning a range of bone mineral densities (BMD). Additionally, an alternative model configuration was developed that included consideration of bone marrow, with bone and marrow material parameters assigned to elements randomly according to bone volume (BV%) measurements of experimental specimens, owing to the non-uniform nature of trabecular bone tissue microstructure. Statistical analysis found significant correlation between the shapes of the numerical and experimental forcedisplacement curves. FE models accurately captured the bone densification patterns observed experimentally. Inclusion of marrow elements offered improved response prediction of the flat-tip indenter tests. Ultimately, the developed approach demonstrates the ability of a generalizable continuum-level SPH approach to capture bone variability using clinical bone imaging metrics without needing detailed image-based geometries, a significant step towards simplified subject-specific modeling of implant subsidence.

关键词： Finite element model Smoothed particle hydrodynamics Trabecular bone indentation Crushable foam continuum-based modeling Marrow

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The modeling of Magnetorheological Elastomers: A State-of-the-Art Review

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ADVANCED ENGINEERING MATERIALS 2023年第16期25卷 2300182-2300182页

作者： Saber, Amin Sedaghati, Ramin Concordia Univ Dept Mech Ind & Aerosp Montreal PQ H3G 1M8 Canada

The magnetorheological elastomers (MREs) are novel multifunctional materials wherein their viscoelastic properties can be varied instantly under an application of applied magnetic field. Due to their field-dependent stiffness and damping properties, MREs are widely used in the development and design of MRE-based adaptive vibration isolators and absorbers and also biomedical engineering. Moreover, MREs due to their inherent magnetostriction effect have enormous potential for the development of soft actuators. The dynamic behavior of MREs is affected by various material parameters (e.g., matrix and particle types, particle concentration, additives) as well as mechanical and magnetic loading parameters (e.g., frequency, amplitude, temperature, magnetic flux density). Understanding and predicting the effect of materials and loading parameters on the response behavior of MREs are of paramount importance for the design of MRE-based adaptive structures and systems. This review paper mainly aims to provide a comprehensive study of material constitutive models to predict the nonlinear magnetomechanical behavior of MREs. Particular emphasis is paid to physics-based models including continuum- and microstructure-based models. Moreover, phenomenological models describing the dynamic magnetoviscoelastic behavior of MREs as well as the effect of temperature on the magnetomechanical behavior of such materials are properly addressed.

关键词： continuum-based modeling magnetoelastic and magnetoviscoelastic magnetorheological elastomers microstructure-based modeling phenomenological modeling temperature-included modeling

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Surface elasticity-based modeling of rotating functionally graded nanoshafts in thermal environments

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JOURNAL OF THERMAL STRESSES 2016年第12期39卷 1483-1498页

作者： Kiani, Keivan KN Toosi Univ Technol Dept Civil Engn POB 15875-4416 Tehran Iran

Thermoelastic field analysis of a rotating functionally graded nanoshaft (RFGNS) in thermal environments is of interest. The governing equations of the rotating nanoshaft with varying material properties along the radial direction are obtained. Two nonclassical boundary conditions, namely, fixed-free and free-free, are established accounting for the surface energy effect. Using finite element method and Hamilton's principle, the thermoelastic field within RFGNS is evaluated. The effects of power-law index, aspect ratio, temperature, angular velocity of the RFGNS, and surface energy on the displacements and stresses are displayed in detail.

关键词： continuum-based modeling finite element method functionally graded materials rotating nanoshaft surface energy effect thermomechanical analysis

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Multiscale Nonlinear Constitutive modeling of Carbon Nanostructures based on Interatomic Potentials

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CMC-COMPUTERS MATERIALS & CONTINUA 2009年第1期10卷 41-64页

作者： Ghanbari, J. Naghdabadi, R. Sharif Univ Technol Dept Mech Engn Tehran Iran Sharif Univ Technol Inst Nano Sci & Technol Tehran Iran

continuum-based modeling of nanostructures is an efficient and suitable method to study the behavior of these Structures when the deformation can be considered homogeneous. This paper is concerned about multiscale nonlinear tensorial constitutive modeling of carbon nanostructures based on the interatomic potentials. The proposed constitutive model is a tensorial equation relating the second Piola-Kirchhoff stress tensor to Green-Lagrange strain tensor. For carbon nanotubes, some modifications are made on the planar representative volume element (RVE) to account for the curved atomic structure resulting a non-planar RVE. Using the proposed constitutive model, the elastic behavior of the graphene sheet and carbon nanotube are studied.

关键词： Multi scale modeling continuum-based modeling Constitutive modeling Carbon nanotubes Graphene sheet

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