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elastic-moduli
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A combined first principles and analytical treatment for determination of the surface elastic constants: Application to Si(001) ideal and reconstructed surfaces
, Article Philosophical Magazine Letters ; Volume 92, Issue 1 , Sep , 2012 , Pages 7-19 ; 09500839 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2012
Abstract
Behavior of nanostructures, which are characterized by a large surface-to-volume ratio, is greatly influenced by their surface parameters, such as surface elastic moduli tensor. Accurate determination of the surface elastic constants by first principles is of particular interest. To this end, through consideration of the fundamental thermodynamic arguments for free solid surfaces, an analytical formulation for the change in specific Helmholtz surface free energy is developed. Relating this formulation to the corresponding energy calculated via first principles leads to the determination of the surface elastic moduli tensor. The surface mechanical properties, namely surface energy, surface...
A comprehensive mathematical simulation of the composite size-dependent rotary 3D microsystem via two-dimensional generalized differential quadrature method
, Article Engineering with Computers ; 2021 ; 01770667 (ISSN) ; Zhao, Y ; Pishbin, M ; Habibi, M ; Bashir, M. O ; Issakhov, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
In this study, frequency simulation and critical angular velocity of a size-dependent laminated rotary microsystem using modified couple stress theory (MCST) as the higher-order elasticity model is undertaken. The centrifugal and Coriolis impacts due to the spinning are taken into account. The size-dependent thick annular microsystem's computational formulation, non-classical governing equations, and corresponding boundary conditions are obtained by using the higher-order stress tensors and symmetric rotation gradient to the strain energy. By using a single material length scale factor, the most recent non-classical approach captures the size-dependency in the annular laminated microsystem....
A comprehensive mathematical simulation of the composite size-dependent rotary 3D microsystem via two-dimensional generalized differential quadrature method
, Article Engineering with Computers ; Volume 38 , 2022 , Pages 4181-4196 ; 01770667 (ISSN) ; Zhao, Y ; Pishbin, M ; Habibi, M ; Bashir, M. O ; Issakhov, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
In this study, frequency simulation and critical angular velocity of a size-dependent laminated rotary microsystem using modified couple stress theory (MCST) as the higher-order elasticity model is undertaken. The centrifugal and Coriolis impacts due to the spinning are taken into account. The size-dependent thick annular microsystem's computational formulation, non-classical governing equations, and corresponding boundary conditions are obtained by using the higher-order stress tensors and symmetric rotation gradient to the strain energy. By using a single material length scale factor, the most recent non-classical approach captures the size-dependency in the annular laminated microsystem....
Adhesive and cohesive properties by indentation method of plasma-sprayed hydroxyapatite coatings
, Article Applied Surface Science ; Volume 253, Issue 11 , 2007 , Pages 4960-4965 ; 01694332 (ISSN) ; Ziaei Moayyed, A. A ; Mesgar, A. S. M ; Sharif University of Technology
Elsevier
2007
Abstract
Adhesive and cohesive properties of the plasma-sprayed hydroxyapatite (HA) coatings, deposited on Ti-6Al-4V substrates by varying the plasma power level and spray distance (SD), were evaluated by an indentation method. The crystallinity and the porosity decreased with increasing both of these two parameters. The microhardness value, Young's modulus (E) and coating fracture toughness (K C ) were found to increase with a combinational increase in spray power and SD. The Knoop and Vickers indentation methods were used to estimate E and K C , respectively. The critical point at which no crack appears at the interface was determined by the interface indentation test. This was used to define the...
A general unified treatment of lamellar inhomogeneities
, Article Engineering Fracture Mechanics ; Volume 74, Issue 9 , 2007 , Pages 1499-1510 ; 00137944 (ISSN) ; Ojaghnezhad, F ; Sharif University of Technology
2007
Abstract
Consider a lamellar inhomogeneity embedded in an unbounded isotropic elastic medium. When the elastic moduli of the lamellar inhomogeneity are zero it is a crack, if its elastic moduli are infinite it is an anticrack, and when its elastic moduli are finite it is called a quasicrack. Based on the Eshelby's equivalent inclusion method (EIM), the present paper develops a unified approach for determination of the exact closed-form expressions for modes I, II, and III stress intensity factors (SIFs) at the tips of lamellar inhomogeneities under a remote applied polynomial loading. © 2006 Elsevier Ltd. All rights reserved
An analytical approach to determination of bending modulus of a multi-layered graphene sheet
, Article Thin Solid Films ; Volume 496, Issue 2 , 2006 , Pages 475-480 ; 00406090 (ISSN) ; Seifi, P ; Naghdabadi, R ; Ghanbari, J ; Sharif University of Technology
2006
Abstract
In this paper, the bending modulus of a multi-layered graphene sheet is investigated using a geometrically based analytical approach. For this purpose, a bending potential energy is derived, based on the van der Waals interactions of atoms belonging to the two neighboring sheets of a double-layered graphene sheet. The inter-atomic spacing between the adjacent layers is determined along the line of action of the applied bending moments. The bending potential of the double-layered sheet is calculated by summing up the potentials at discrete hexagons over the length and width of the sheet. A multi-layered graphene sheet is considered as consisting of many stacking double-layers. It is observed...
A new model for the effect of grain size on the elastic modulus of nanocrystalline materials
, Article Materials Science- Poland ; Volume 27, Issue 1 , 2009 , Pages 279-285 ; 01371339 (ISSN) ; Sharif University of Technology
2009
Abstract
A new model is developed for the structure of nanocrystalline materials. Based on the developed model, a new approach for investigating the effect of grain size on the elastic moduli of nanocrystalline materials is introduced. The predictions of the model are strongly correlated with the experimental results reported in the existing literature
An exact analysis for the hoop elasticity and pressure-induced twist of CNT-nanovessels and CNT-nanopipes
, Article Mechanics of Materials ; Volume 82 , 2015 , Pages 47-62A ; 01676636 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier
2015
Abstract
Carbon nanotubes (CNTs) with and without end caps may be used for fluid storage and transport, respectively, referred to as CNT-nanovessel and CNT-nanopipe. The determination of the stiffness in the hoop (circumferential) and radial directions, ideal hoop strength, and hoop stress-strain curve of such nanostructures is of particular interest. Due to the proposed viewpoint, a chiral free-standing single-walled CNT (SWCNT) has a natural angle of twist and natural extension along the axis of the tube. For example, for the SWCNT (9,3) with diameter of 0.85 nm and chirality angle of 13.9°, the natural angle of twist per unit length is 1.45×10-3 rad/nm. Previously, only Vercosa et al. (2010) who...
A novel method for production of foamy core@compact shell Ti6Al4V bone-like composite
, Article Journal of Alloys and Compounds ; Volume 656 , 2016 , Pages 416-422 ; 09258388 (ISSN) ; Sadrnezhad, S. K ; Sharif University of Technology
Elsevier Ltd
Abstract
This paper presents a novel method for fabrication of bone-like Ti6Al4V foamy core@compact shell composite for utilization as substitutive implant for cortical bone having porous core. Seven prototypes with core-diameters of 0, 6, 8, 10, 12, 14 and 16 mm surrounded by dense shells of respective thicknesses 8, 5, 4, 3, 2, 1 and 0 were produced by an innovative two-stage packing/compaction sintering method. Density, porosity, Young's modulus and compression strength of the prototypes depended on the core diameter. Mechanical strength and Young's modulus of 10@16 (10 mm core, 16 mm diameter prototypes) resembled that of the human ulna bone. Creation of foam at the center was achieved by...
A novel nonlinear constitutive relation for graphene and its consequence for developing closed-form expressions for Young's modulus and critical buckling strain of single-walled carbon nanotubes
, Article Acta Mechanica ; Volume 222, Issue 1-2 , 2011 , Pages 91-101 ; 00015970 (ISSN) ; Delfani, M. R ; Sharif University of Technology
2011
Abstract
Carbon nanotubes (CNTs) are viewed as rolled graphene. Thus, an appropriate formulation describing the behavior of CNTs must contain the key information about both their initial configuration as graphene and final configuration as CNT.On this note, to date, somemodels, in particular based on the Cauchy- Born rule, for the description of CNTs behavior exist. A simplifying assumption in some of these models is that the length and perimeter of the CNT equal the corresponding dimensions of the unrolled initial configuration, thus neglecting the induced hoop and longitudinal strains. On the other hand, the present work offers a purely nonlinear continuum model suitable for the description of the...
A novel procedure for micromechanical characterization of white matter constituents at various strain rates
, Article Scientia Iranica ; Volume 27, Issue 2 , 2021 , Pages 784-794 ; 10263098 (ISSN) ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
Sharif University of Technology
2021
Abstract
Optimal hyperplastic coeficients of the micromechanical constituents of the human brain stem were investigated. An evolutionary optimization algorithm was combined with a Finite Element (FE) model of a Representative Volume Element (RVE) to nd the optimal material properties of axon and Extra Cellular Matrix (ECM). The tension and compression test results of a previously published experiment were used for optimizing the material coeficients, and the shear experiment was used for the validation of the resulting constitutive model. The optimization algorithm was used to search for optimal shear moduli and ber sti ness of axon and ECM by tting the average stress in the axonal direction with the...
Antioxidant, antifungal, water binding, and mechanical properties of poly(vinyl alcohol) film incorporated with essential oil as a potential wound dressing material
, Article Journal of Applied Polymer Science ; Vol. 131, issue. 20 , 2014 ; Nateghpoor, B ; Dadfar, S. M. M ; Dadfar, S. M. A ; Sharif University of Technology
Abstract
In this study, the properties of poly (vinyl alcohol)(PVA) films incorporated with Zataria multiflora essential oil (ZMO) as a potential antioxidant/antibacterial material was investigated. PVA films were prepared from PVA solutions (2% w/v) containing different concentrations of ZMO. Water solubility, moisture absorption, water swelling, and water vapor permeability for pure PVA films were 57 ± 1.1, 99 ± 3.2%, 337 ± 8%, and 0.453 ± 0.015 g mm/m2 h, respectively. Incorporation of ZMO into PVA films caused a significant decrease in water swelling and moisture absorption and increase in solubility and water vapor permeability. Tensile strength, elastic modulus, and elongation at break for pure...
A proposal for distributed humidity sensor based on the induced LPFG in a periodic polymer coated fiber structure
, Article Optics and Laser Technology ; Volume 117 , 2019 , Pages 126-133 ; 00303992 (ISSN) ; Esmailzadeh Noghani, F ; Bahrampour, A ; Bahrampour, A. R ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this paper, a distributed relative humidity (RH) or moisture sensor is proposed. The proposed structure is a single mode telecommunication optical fiber coated by humidity sensitive and insensitive polymers periodically. The polymer coated fiber is surrounded by a high Young's modulus material such as stainless steel mesh. The swelling of the coated Humidity Sensitive Polymers (HSPs) as a result of moisture absorption induces fiber gratings in the single mode fiber. Depending on the coating period relative to the light wavelength, the induced fiber grating can be Fiber Bragg Grating (FBG) or Long Period Fiber Grating (LPFG). The light reflected by the induced FBG or losses due to the...
A single cone-cap plasticity with an isotropic hardening rule for powder materials
, Article International Journal of Mechanical Sciences ; Volume 47, Issue 1 , 2005 , Pages 94-109 ; 00207403 (ISSN) ; Azami, A. R ; Sharif University of Technology
2005
Abstract
In this paper, a new single cone-cap plasticity with an isotropic hardening rule is presented for powder materials. A general form is developed for the cap plasticity, which can be compared with some common double-surface plasticity models proposed for powders in literature. The constitutive elasto-plastic matrix and its components are derived based on the definition of yield surface, hardening parameter and nonlinear elastic behavior, as a function of relative density of powder. Different aspects of the model are illustrated and the procedure for determination of powder parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of...
Atomistic simulations of mechanical properties and fracture of graphene: A review
, Article Computational Materials Science ; Volume 210 , 2022 ; 09270256 (ISSN) ; Kouchakzadeh, M. A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Material properties and fracture characteristics are among the most prominent parameters that should be considered for a wide range of graphene applications. This article reviews recent advances in theoretical studies on the mechanical properties and fracture behaviors of graphene, focusing on the effect of various simulation models. Most studies investigated single-layer graphene sheets (SLGSs) under uniaxial tensile tests using different common interatomic potentials, particularly AIREBO. Although researchers have examined a similar problem, specifically for pristine graphene, the differences in the reported values are considerable. These discrepancies are most evident in fracture...
Atomistic study of the effect of crystallographic orientation on the twinning and detwinning behavior of NiTi shape memory alloys
, Article Computational Materials Science ; Volume 203 , 2022 ; 09270256 (ISSN) ; Izadifar, M ; Dolado, J. S ; Ramazani, A ; Sadrnezhaad, S. K ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Understanding the effect of crystallographic orientation on the twinnin/detwinning mechanisms in NiTi shape memory alloys at an atomistic scale can help to control and tune the mechanical properties and failure behavior of such materials. In this work, we employed classical molecular dynamics (MD) and density functional theory (DFT) computational methods to better understand how twinning and detwinning occurs through a combination of slip, twin, and shuffle on 〈0 1 0〉, 〈1 1 0〉, and 〈1 1 1〉 crystallographic orientations under uniaxial tensile test. Elastic constants including Young's Modulus (E), Bulk modulus (B), Poisson's ratio (ν), and Shear Modulus (G) are obtained and computed for...
Bauschinger effect investigation of an aluminum alloy, and its application in autofrettaged and compound tubes
, Article 2007 ASME Pressure Vessels and Piping Conference, PVP 2007, San Antonio, TX, 22 July 2007 through 26 July 2007 ; Volume 6 , 2008 , Pages 629-637 ; 0277027X (ISSN); 0791842843 (ISBN); 9780791842843 (ISBN) ; Farrahi, G. H ; Hoseini, S. H ; Sharif University of Technology
2008
Abstract
For characterizing Bauschinger effect factor (BEF) and Bauschinger modulus reduction of an A5083 aluminum alloy experimentally, several uniaxial tension- compression tests carried out in different pre-strain levels using INSTRON testing machine. BEF was investigated using both Welter and Milligan's definitions for various offset values. It was observed that Milligan's definition predicts BEF less than Welter's definition for all offset values. In addition, real loading-unloading behavior of such alloy was recorded to predict residual stresses resulting from autofrettage and shrink fit processes. Variable material properties (VMP) method, which is capable of incorporating real unloading...
Biodegradable ionic liquids: effects of temperature, alkyl side-chain length, and anion on the thermodynamic properties and interaction energies as determined by molecular dynamics simulations coupled with ab initio calculations
, Article Industrial and Engineering Chemistry Research ; Volume 54, Issue 46 , November , 2015 , Pages 11678-11700 ; 08885885 (ISSN) ; Gholami, M. R ; Sharif University of Technology
American Chemical Society
2015
Abstract
The effects of incorporating the ester functional group (-C=OO-) into the side chain of the 1-alkyl-3-methylimidazolium cation ([C1COOCnC1im]+, n = 1, 2, 4) paired with [Br]-, [NO3]-, [BF4]-, [PF6]-, [TfO]-, and [Tf2N]- anions on the various thermodynamic properties and interaction energies of these biodegradable ionic liquids (ILs) were investigated by means of molecular dynamics (MD) simulations combined with ab initio calculations in the temperature range of 298-550 K. Excluding the simulated density, the highest values of the volumetric properties such as molar volume, isobaric expansion coefficient, and isothermal compressibility coefficient can be attributed to the largest cation...
Calculation of thermodynamic properties of Ni nanoclusters via selected equations of state based on molecular dynamics simulations
, Article Solid State Communications ; Volume 151, Issue 14-15 , 2011 , Pages 965-970 ; 00381098 (ISSN) ; Abroshan, H ; Taherkhani, F ; Parsafar, G. A ; Sharif University of Technology
2011
Abstract
We present an approach for constant-pressure molecular dynamics simulations. This approach is especially designed for finite systems, for which no periodic boundary condition applies. A molecular dynamics (MD) simulation for Ni nanoclusters is used to calculate their pressurevolumetemperature (pvT) data for the temperature range 200 K≤T≤400 K, and pressures up to 600 kbar. Isothermal sets of pvT data were generated by the simulation; each set was fitted by three equations of state (EoSs): Linear Isotherm Regularity-II (LIRII), BirchMurnaghan (BM), and EOS III. It is found that the MD data are satisfactorily reproduced by the EoSs with reasonable precision. Some features of the EoSs criteria,...
Characterizing the effect of fines content on the small strain shear modulus of sand-silt mixtures during hydraulic hysteresis
, Article 4th International Conference on Transportation Geotechnics, ICTG 2021, 23 May 2021 through 26 May 2021 ; Volume 165 , 2022 , Pages 837-849 ; 23662557 (ISSN); 9783030772338 (ISBN) ; Mohsen Haeri, S ; Khosravi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Small strain shear modulus, Gmax, is one of the most important parameters for the characterization of the behavior of earth structures subjected to static or dynamic loading conditions. This research presents an experimental laboratory study on the effect of non-plastic fines content and hydraulic hysteresis on the Gmax of unsaturated sandy soils. In this regard, clean Firoozkuh No. 161 silica sand which is classified as poorly graded sand was mixed with different percentages of non-plastic Firoozkuh silt. A set of bender element tests were carried out using two modified triaxial devices. The modifications on these two apparatus were to add HAV ceramic discs for air–water control of...