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Electro-mechanical bending analysis of ionic polymer metal nanocomposites (IPMNCs)
, Article Mechanics Research Communications ; Vol. 62 , December , 2014 , pp. 77-82 ; ISSN: 00936413 ; Baghani, M ; Naghdabadi, R ; Sharif University of Technology
Abstract
A nonlinear electro-elasticity formulation for a cantilever beam made of IPMNC is used to obtain constitutive equations. Using the measured experimental data, the constitutive parameters connecting the free energy to the beam characteristics are calibrated. The results show that the constitutive equations are able to include the softening behavior of the material under applied voltages as well as the shift of the bending neutral axis from the geometrical midline of the beam by a closed-form solution which bridges between macroscopic and microscopic scales. The equations consider large deformations of thin and thick beams
Strain gradient thermoelasticity of functionally graded cylinders
, Article Scientia Iranica ; Volume 21, Issue 4 , 2014 , Pages 1415-1423 ; ISSN: 10263098 ; Baghani, M ; Naghdabadi, R ; Sharif University of Technology
Abstract
In this paper, strain gradient thermo-elasticity formulation for axisymmetric Functionally Graded (FG) thick-walled cylinders is presented. For this purpose, the elastic strain energy density function is considered to be a function of gradient of strain tensor in addition to the strain tensor. The material properties are assumed to vary according to a power law in radial direction. Using the constitutive equations and equation of equilibrium in the cylindrical coordinates, a fourth order non-homogenous governing equation for thermo-elastic analysis of thick-walled FG cylinders subjected to thermal and mechanical loadings is obtained and solved numerically. Results show that the intrinsic...
Finite strain numerical analysis of elastomeric bushings under multi-axial loadings: A compressible visco-hyperelastic approach
, Article International Journal of Mechanics and Materials in Design ; Volume 9, Issue 4 , December , 2013 , Pages 385-399 ; 15691713 (ISSN) ; Baghani, M ; Naghdabadi, R ; Sharif University of Technology
2013
Abstract
Elastomers have wide and ever increasing applications in several industries. In this work a compressible visco-hyperelastic approach is employed to investigate the behavior of elastomeric materials. The time-discrete form of the material model is developed to be used in numerical simulations. This formulation provides a recursive relation to update the stress in any time step regarding the deformation history. By means of analytical solutions derived for pure torsion of a solid circular cylinder, the numerical implementation is validated and then, the response of an elastomeric bushing is investigated in torsional, axial and combined deformations. These bushings are used in suspension...
A viscoelastic constitutive model for compressible polymers based on logarithmic strain and its finite element implementation
, Article Finite Elements in Analysis and Design ; Volume 62 , 2012 , Pages 18-27 ; 0168874X (ISSN) ; Baghani, M ; Arghavani, J ; Sharif University of Technology
2012
Abstract
In this paper, employing the logarithmic (or Hencky) strain as a more physical measure of strain, the time-dependent response of compressible viscoelastic materials is investigated. In this regard, we present a phenomenological finite strain viscoelastic constitutive model, developed within the framework of irreversible thermodynamics with internal variables. The formulation is based on the multiplicative decomposition of the deformation gradient into elastic and viscoelastic parts, together with the use of the isotropic property of the Helmholtz strain energy function. Making use of a logarithmic mapping, we present an appropriate form of the proposed constitutive equations in the...
Strain gradient elasticity solution for functionally graded micro-cylinders
, Article International Journal of Engineering Science ; Volume 50, Issue 1 , January , 2012 , Pages 22-30 ; 00207225 (ISSN) ; Baghani, M ; Naghdabadi, R ; Sharif University of Technology
2012
Abstract
In this paper, strain gradient elasticity formulation for analysis of FG (functionally graded) micro-cylinders is presented. The material properties are assumed to obey a power law in radial direction. The governing differential equation is derived as a fourth order ODE. A power series solution for stresses and displacements in FG micro-cylinders subjected to internal and external pressures is obtained. Numerical examples are presented to study the effect of the characteristic length parameter and FG power index on the displacement field and stress distribution in FG cylinders. It is observed that the characteristic length parameter has a considerable effect on the stress distribution of FG...
Inhomogeneous and homogeneous swelling behavior of temperature-sensitive poly-(N-isopropylacrylamide) hydrogels
, Article Journal of Intelligent Material Systems and Structures ; Volume 27, Issue 3 , 2016 , Pages 324-336 ; 1045389X (ISSN) ; Baghani, M ; Naghdabadi, R ; Sharif University of Technology
SAGE Publications Ltd
Abstract
The aim of this work is to develop a model to continuously predict inhomogeneous and homogeneous swelling behavior of temperature-sensitive poly-(N-isopropylacrylamide) hydrogels. Employing this model, some benchmark homogeneous problems such as free, unidirectional constrained and biaxial constrained swelling as well as swelling of core-shell structures are investigated. The main advantage of the model is its ability to solve inhomogeneous deformations due to a stable behavior in the vicinity of the phase transition temperature. Therefore, inhomogeneous swelling of a spherical shell on a hard core with application to microfluidics is analytically and numerically investigated for various...
A time-dependent finite element formulation for thick shape memory polymer beams considering shear effects
, Article International Journal of Applied Mechanics ; Volume 10, Issue 4 , 2018 ; 17588251 (ISSN) ; Baghani, M ; Sohrabpour, S ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2018
Abstract
In this paper, employing a thermomechanical small strain constitutive model for shape memory polymers (SMP), a beam element made of SMPs is presented based on the kinematic assumptions of Timoshenko beam theory. Considering the low stiffness of SMPs, the necessity for developing a Timoshenko beam element becomes more prominent. This is due to the fact that relatively thicker beams are required in the design procedure of smart structures. Furthermore, in the design and optimization process of these structures which involves a large number of simulations, we cannot rely only on the time consuming 3D finite element analyses. In order to properly validate the developed formulations, the numeric...
A combined experimental and numerical study of the effect of surface roughness on nanoindentation
, Article International Journal of Applied Mechanics ; Volume 11, Issue 7 , 2019 ; 17588251 (ISSN) ; Chamani, M ; Baghani, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2019
Abstract
Gold and copper thin films are widely used in microelectromechanical system (MEMS) and nanoelectromechanical system (NEMS) devices. Nanoindentation has been developed in mechanical characterization of thin films in recent years. Several researchers have examined the effect of surface roughness on nanoindentation results. It is proved that the surface roughness has great importance in nanoindentation of thin films. In this paper, the surface topography of thin films is simulated using the extracted data from the atomic force microscopy (AFM) images. Nanoindentation on a rough surface is simulated using a three-dimensional finite-element model. The results are compared with the results of...
Gaseous slip flow mixed convection in vertical microducts with constant axial energy input
, Article Journal of Heat Transfer ; Vol. 136, issue. 3 , 2014 ; ISSN: 00221481 ; Baghani, M ; Saidi, M. H ; Sharif University of Technology
Abstract
The present investigation is devoted to the fully developed slip flow mixed convection in vertical microducts of two different cross sections, namely, polygon, with circle as a limiting case, and rectangle. The two axially constant heat flux boundary conditions of H1 and H2 are considered in the analysis. The velocity and temperature discontinuities at the boundary are incorporated into the solutions using the first-order slip boundary conditions. The method considered is mainly analytical in which the governing equations in cylindrical coordinates along with the symmetry conditions and finiteness of the flow parameter at the origin are exactly satisfied. The first-order slip boundary...
Gaseous slip flow forced convection through ordered microcylinders
, Article Microfluidics and Nanofluidics ; Volume 15, Issue 1 , 2013 , Pages 73-85 ; 16134982 (ISSN) ; Baghani, M ; Saidi, M. H ; Sharif University of Technology
2013
Abstract
This is a theoretical study dealing with longitudinal gaseous slip flow forced convection between a periodic bunch of microcylinders arranged in regular array. The selected geometry has applications in microscale pin fin heat sinks used for cooling of microchips. The flow is considered to be hydrodynamically and thermally fully developed. The two axially constant heat flux boundary conditions of H1 and H2 are considered in the analysis. The velocity and temperature discontinuities at the boundary are incorporated into the solutions using the first order slip boundary conditions. The method considered is mainly analytical in which the governing equations and three of the boundary conditions...
Inhomogeneous swelling behavior of temperature sensitive PNIPAM hydrogels in micro-valves: Analytical and numerical study
, Article Smart Materials and Structures ; Volume 24, Issue 4 , February , 2015 ; 09641726 (ISSN) ; Baghani, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
In this work, inhomogeneous swelling of the temperature-sensitive PNIPAM hydrogel is investigated with application to micro-valves. In this regard, a modified model is considered, and an analytical solution of the inhomogeneous swelling of a hydrogel jacket coated on a rigid pillar is performed, which is valuable for the conceptual design of the micro-valve. Then, finite element implementation of the modified model is carried out, and its validity is verified by both the analytical and experimental results. Thereafter, thermo-mechanical behavior of the micro-valve is investigated considering the coupling between the inhomogeneous swelling of the jacket and contact problems due to the...
Entropy generation in thermally developing laminar forced convection through a slit microchannel
, Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010, Montreal, QC ; Issue PARTS A AND B , 2010 , Pages 515-526 ; 9780791854501 (ISBN) ; Baghani, M ; Saidi, M. H ; Sharif University of Technology
2010
Abstract
The issue of entropy generation in laminar forced convection of a Newtonian fluid through a slit microchannel is analytically investigated by taking the viscous dissipation effect, the slip velocity and the temperature jump at the wall into account. Flow is considered to be hydrodynamically fully developed but thermally developing. The energy equation is solved by means of integral transform. The results demonstrate that to increase Knudsen number is to decrease entropy generation, while the effect of increasing values of Brinkman number and the group parameter is to increase entropy generation. Also it is disclosed that in the thermal entrance region the average entropy generation number...
Thermo-elastic analysis of thick-walled cylinders made of Functionally Graded materials using the strain gradient elasticity
, Article ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2010, 28 September 2010 through 1 October 2010 ; Volume 2 , 2010 , Pages 1-6 ; 9780791844168 (ISBN) ; Baghani, M ; Naghdabadi, R ; Aerospace Division ; Sharif University of Technology
Abstract
In this paper, strain gradient thermo-elasticity formulation for Functionally Graded (FG) thick-walled cylinders is presented. Elastic strain energy density function is considered to be a function of gradient of strain tensor in addition to the strain tensor. The material properties are assumed to vary according to power law in radial direction. Using the constitutive equations and equation of equilibrium in the cylindrical coordinates, fourth order non-homogenous governing equation for thermo-elastic analysis of thick-walled FG cylinders subjected to thermal and mechanical loadings is obtained and solved numerically. Results show that the intrinsic length parameter affects the stress...
A finite deformation viscoelastic-viscoplastic constitutive model for self-healing materials
, Article Smart Materials and Structures ; Volume 25, Issue 12 , 2016 , Pages 1DUMMY- ; 09641726 (ISSN) ; Naghdabadi, R ; Baghani, M ; Sohrabpour, S ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
In this paper, employing the Hencky strain, viscoelastic-viscoplastic response of self-healing materials is investigated. Considering the irreversible thermodynamics and using the effective configuration in the Continuum Damage-Healing Mechanics (CDHM), a phenomenological finite strain viscoelastic-viscoplastic constitutive model is presented. Considering finite viscoelastic and viscoplastic deformations, total deformation gradient is multiplicatively decomposed into viscoelastic and viscoplastic parts. Due to mathematical advantages and physical meaning of Hencky strain, this measure of strain is employed in the constitutive model development. In this regard, defining the damage and healing...
A viscoelastic-viscoplastic constitutive model considering damage evolution for time dependent materials: Application to asphalt mixes
, Article International Journal of Damage Mechanics ; Volume 25, Issue 7 , 2016 , Pages 921-942 ; 10567895 (ISSN) ; Naghdabadi, R ; Baghani, M ; Sohrabpour, S ; Sharif University of Technology
SAGE Publications Ltd
Abstract
In this paper, employing the definition of an effective configuration in the continuum damage mechanics, mechanical response of a compressible viscoelastic-viscoplastic material is investigated. We present a phenomenological viscoelastic-viscoplastic-viscodamage constitutive model, developed within the framework of irreversible thermodynamics. The formulation is based on the additive decomposition of the total strain into elastic, viscoelastic, and viscoplastic parts in the effective configuration. Thus, the Helmholtz energy is partitioned into elastic, elastic-viscoelastic, and viscoplastic parts. Then, each one is divided into deviatoric and volumetric energies. Considering the...
Continuum damage-healing constitutive modeling for concrete materials through stress spectral decomposition
, Article International Journal of Damage Mechanics ; Volume 25, Issue 6 , 2016 , Pages 900-918 ; 10567895 (ISSN) ; Baghani, M ; Sohrabpour, S ; Naghdabadi, R ; Sharif University of Technology
SAGE Publications Ltd
2016
Abstract
Self-healing concrete materials have the capability to recover a part of the weakened mechanical properties induced by damage. In this paper, a constitutive model is proposed to investigate damage and healing phenomena in concrete materials. In order to consider the different behavior of concretes in tension and compression, a spectral decomposition of the stress is utilized. In addition, employing the Clausius-Duhem inequality and considering the irreversible thermodynamics, conjugate forces of the damage and healing are expressed. The Gibbs potential energy is decomposed into three parts: elastic, damage and healing. In this regard, damage and healing behavior are distinguished from the...
Coupling behavior of the pH/temperature sensitive hydrogels for the inhomogeneous and homogeneous swelling
, Article Smart Materials and Structures ; Volume 25, Issue 8 , 2016 ; 09641726 (ISSN) ; Baghani, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
In this work, a model is developed to continuously predict homogeneous and inhomogeneous swelling behavior of pH/temperature sensitive PNIPAM hydrogels. Employing the model, homogeneous swelling of the pH/temperature sensitive hydrogel is investigated for free and biaxial constrained swelling cases. Comparing the model results with the experimental data available in the literature, the validity of the model is confirmed. The model is then employed to investigate inhomogeneous swelling of a spherical shell on a hard core both analytically and numerically for pH or temperature variations. In this regard, numerical tools are developed via preparing a user defined subroutine in ABAQUS software....
A thermodynamically consistent viscoelastic–viscoplastic constitutive model for self-healing materials
, Article Journal of Intelligent Material Systems and Structures ; Volume 29, Issue 6 , 2018 , Pages 1065-1080 ; 1045389X (ISSN) ; Baghani, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
Self-healing materials, as a class of intelligent materials, are capable to recover a part of the weakened mechanical properties induced by damage. In this article, based on the thermodynamics of irreversible processes, employing the effective configuration in the continuum damage-healing mechanics, a viscoelastic–viscoplastic constitutive model is presented. In the constitutive model development, we adopt an additive decomposition of the total strain into elastic, viscoelastic, and viscoplastic parts. In this regard, defining the damage and healing variables and employing the strain energy equivalence hypothesis, stress and strain tensors in the effective configuration are obtained....
Second law analysis for extended graetz problem including viscous dissipation in microtubes
, Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2010 Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, Montreal, QC, 1 August 2010 through 5 August 2010 ; Issue PARTS A AND B , 2010 , Pages 503-514 ; 9780791854501 (ISBN) ; Baghani, M ; Saidi, M. H ; Fluids Engineering Division ; Sharif University of Technology
2010
Abstract
The entropy generation rate has become a useful tool for evaluating the intrinsic irreversibilities associated with a given process or device. This work presents an analytical solution for entropy generation in hydrodynamically fully developed thermally developing laminar flow in a microtube. The rarefaction effects as well as viscous heating effects are taken into consideration, but axial conduction is neglected. Using fully developed velocity profile, the energy equation is solved by means of integral transform. The solution is validated by comparing the local Nusselt numbers against existing literature data. From the results it is realized that the entropy generation decreases as Knudsen...
An investigation on thermomechanical flexural response of shape-memory-polymer beams
, Article International Journal of Applied Mechanics ; Volume 8, Issue 5 , 2016 ; 17588251 (ISSN) ; Heydarzadeh, N ; Baghani, M ; Eskandari, A. H ; Baniassadi, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2016
Abstract
In this paper, the predictions of different beam theories for the behavior of a shape memory polymer (SMP) beam in different steps of a thermomechanical cycle are compared. Employing the equilibrium equations, the governing equations of the deflection of a SMP beam in the different steps of a thermomechanical cycle, for higher order beam theories (Timoshenko Beam Theory and von-Kármán Beam Theory), are developed. For the Timoshenko Beam Theory, a closed form analytical solution for various steps of the thermomechanical cycle is presented. The nonlinear governing equations in von-Kármán Beam theory are numerically solved. Results reveal that in the various beam length to beam thickness...