Search for: elastic-moduli
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    Preparation of highly rubber-toughened nylons

    , Article Iranian Polymer Journal (English Edition) ; Volume 16, Issue 7 , 2007 , Pages 459-468 ; 10261265 (ISSN) Bordbar, H ; Yousefi, A. A ; Ramezani saadatabadi, A ; Sharif University of Technology
    Nylon 6 and 66 were toughened with EPDM-g-MA and SEBS-g-MA and steadystate rheological behaviour of rubbers, nylons and their blends and mechanical properties of nylons and their rubber-toughened blends were investigated. The EPDM maleic grafting preparation was performed In the framework of this study where SEBS-g-MA was obtained from a commercial source. The results showed the ultratoughened SEBS-g-MA blends, whereas EPDM blends under the same blending conditions did not show a significant improvement in toughness. In case of EPDM toughened blends an average of some micrometers was observed for the dispersed EPDM particles. Impact and tensile properties of the toughened blend with 20% of... 

    Mechanical properties of graphene oxide: A molecular dynamics study

    , Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 24, Issue 9 , 2016 , Pages 594-603 ; 1536383X (ISSN) Khoei, A. R ; Sarkari Khorrami, M ; Sharif University of Technology
    Taylor and Francis Inc 
    In this paper, the mechanical properties of graphene oxide are obtained using the molecular dynamics analysis, including the ultimate stress, Young modulus, shear modulus and elastic constants, and the results are compared with those of pristine graphene. It is observed that the increase of oxide agents (–O) and (–OH) leads to the increase of C–C bond length at each hexagonal lattice and as a result, alter the mechanical properties of the graphene sheet. It is shown that the elasticity modulus and ultimate tensile strength of graphene oxides (–O) and (–OH) decrease significantly causing the failure behavior of graphene sheet changes from the brittle to ductile. The results of shear loading... 

    Elastic moduli tensors, ideal strength, and morphology of stanene based on an enhanced continuum model and first principles

    , Article Mechanics of Materials ; Volume 110 , 2017 , Pages 1-15 ; 01676636 (ISSN) Shodja, H. M ; Ojaghnezhad, F ; Etehadieh, A ; Tabatabaei, M ; Sharif University of Technology
    Elsevier B.V  2017
    The present work aims to provide an accurate description of the tensile behavior of the planar as well as low-buckled stanene and to capture their ideal strength in armchair (AC)- and zigzag (ZZ)-directions. For an accurate description of anisotropic response of such hyperelastic materials as stanene, consideration of a highly nonlinear constitutive model in which up to the fourth power of strains is incorporated is inevitable. By utilizing first principles calculations based on density functional theory (DFT), the second, third, fourth, and fifth order elastic moduli tensors corresponding to both planar and low-buckled states are obtained. Moreover, the morphology of the free-standing... 

    Molecular dynamics study on axial elastic modulus of carbon nanoropes

    , Article Archives of Civil and Mechanical Engineering ; Volume 19, Issue 4 , 2019 , Pages 1127-1134 ; 16449665 (ISSN) Mehralian, F ; Firouz Abadi, R. D ; Norouzi, M ; Sharif University of Technology
    Elsevier B.V  2019
    Carbon nanoropes (CNRs) are of interest for a wide variety of nanotechnological applications. Since little attention has been paid to mechanical properties of CNRs, their axial elastic modulus is explored herein. Molecular dynamics (MDs) simulations are adopted for analysis of Young's modulus of CNRs. It is also shown that increase in the initial helical angle decreases Young's modulus; however, by increase in the number of CNTs and strands, different influence on Young's modulus emerges. Therefore, the highest value of Young's modulus obtained at the lower value of initial helical angle and consequently, Young's modulus of bundle of straight CNTs is higher than CNRs with hierarchical... 

    Estimation of modulus of elasticity for closed-cell aluminum foam

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3, Issue PARTS A, B, AND C , 2012 , Pages 1285-1289 ; 9780791845196 (ISBN) Ahmadian, M. T ; Gobal, A ; Alkhani, R ; Sharif University of Technology
    Monodisperse closed cell aluminum foam was analyzed numerically to determine the relationship between its elastic modulus, porosity and pore diameter. It was found a nonlinear relationship exists between porosity, pore diameter and modulus of elasticity. In this regard, an empirical equation is developed and implemented for the prediction of modulus of elasticity versus porosity and pore diameter. Comparing experimental and analytical approaches by other researchers with those obtained in this research shows agreement exists within 1 to 3 percent  

    Evaluation of dynamic properties of cement-admixed clay using neural network and dynamic triaxial test results

    , Article Annual Conference of the Canadian Society for Civil Engineering 2007: Where the Road Ends, Ingenuity Begins, Yellowknife, NT, 6 June 2007 through 9 June 2007 ; Volume 1 , 2007 , Pages 215-223 Bahador, M ; Reinforced Earth Company Ltd.; First Air; Dillon Consulting; FSC Architects and Engineers; DIAVIK Diamond Mines; et al ; Sharif University of Technology
    In this paper dynamic property of Cement-Admixed clay under a wide range of strains were studied considering the effect of different mixing ratio and the change of confining pressures through dynamic triaxial test. Triaxial tests were conducted on untreated and cement treated soils and the results were then analyzed to study the variations in dynamic elastic modulus (Ed) and the damping ratio (D) of soil specimens at different cement ratio. Increasing cement ratio has a significant effect on Ed of the treated soils, and increases it. In contrast, increasing cement ratio decreases D; however, the rate of decreasing D with increasing cement ratio is not considerable. The feed-forward... 

    A general unified treatment of lamellar inhomogeneities

    , Article Engineering Fracture Mechanics ; Volume 74, Issue 9 , 2007 , Pages 1499-1510 ; 00137944 (ISSN) Shodja, H. M ; Ojaghnezhad, F ; Sharif University of Technology
    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  

    Thermoelastic fields of a functionally graded coated lnhomogeneity with sliding/perfect interlaces

    , Article Journal of Applied Mechanics, Transactions ASME ; Volume 74, Issue 3 , 2007 , Pages 389-398 ; 00218936 (ISSN) Hatami Marbini, H ; Shodja, H. M ; Sharif University of Technology
    The determination of the thermo-mechanical stress field in and around a spherical/ cylindrical inhomogeneity surrounded by a functionally graded (FG) coating, which in turn is embedded in an infinite medium, is of interest. The present work, in the frame work of Boussinesq/Papkovich-Neuber displacement potentials method, discovers the potential functions by which not only the relevant boundary value problems (BVPs) in the literature, but also the more complex problem of the coated inhomogeneities with FG coating and sliding interfaces can be treated in a unified manner. The thermo-elastic fields pertinent to the inhomogeneities with multiple homogeneous coatings and various combinations of... 

    Composites of rice husk/wheat straw with pMDI resin and polypropylene

    , Article Polymers and Polymer Composites ; Volume 15, Issue 8 , 2007 , Pages 619-626 ; 09673911 (ISSN) Frounchi, M ; Dadbin, S ; Jahanbakhsh, J ; Janat Alipour, M ; Sharif University of Technology
    Rapra Technology Ltd  2007
    The application of agricultural fibers for making particleboards has been studied in two types of composites: (i) type I particleboards were composites of wheat straw and rice husk fibers with polymeric methylene di-phenyl diisocyanate resin (pMDI) as a binder made by compression moulding; (ii) type II particleboards were composites of rice husk and polypropylene made by extrusion and injection moulding. In type I particleboards, the effects of varying the resin content and various combinations of wheat straw/rice husk fibers were investigated and characterised in terms of physical and mechanical properties of particle boards such as modulus of rupture, modulus of elasticity, compression... 

    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) Behfar, K ; Seifi, P ; Naghdabadi, R ; Ghanbari, J ; Sharif University of Technology
    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... 

    Modeling and analysis of AN ultra light slow flyer with variable shape control surfaces using shape memory alloy actuators

    , Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 2 , 2004 , Pages 153-162 ; 0791841731 (ISBN); 9780791841730 (ISBN) Alasty, A ; Alemohamad, S. H ; Khiabani, R. H ; Khalighi, Y ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    Applying flexible variable shape control surfaces (wing and elevator) structures is a way to increase efficiency and maneuverability of the planes, which is recently under research. In this paper, modeling of the flight of an unmanned ultra light plane is discussed. The modeling is done based on a real ultra light plane presented recently. To increase maneuverability of the plane, flexible variable shape structures are designed for the wing and the elevator. In design procedure, having an ultra light plane is considered. The elevator and the wing are used as control surfaces for longitudinal and lateral maneuvers respectively. Shape memory alloys (SMA) are used for reshaping the flexible... 

    Comparison of the experimental behavior of a shape memory alloy in compression and tension

    , Article 2003 ASME International Mechanical Engineering Congress, Washington, DC., 15 November 2003 through 21 November 2003 ; Volume 68 , 2003 , Pages 471-478 ; 07334230 (ISSN) Hesse, T ; Ghorashi, M ; Inman, D. J ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2003
    The concept of Shape Memory Alloy (SMA) has been a subject of extensive research in the recent few years. In many SMA applications, wire elements have been used in order to control structural specifications like shape and stiffness. Since a wire can only be subjected to tensile forces, the available theoretical models for SMA discuss only the tensile loading. The present paper is an endeavor to overcome this shortcoming. It gives experimental results for tension and compression tests on specimens (having different geometries) made of an identical shape memory alloy. The corresponding results are compared with each other. Using stress-strain diagrams, several important material properties are... 

    Coupled effects of suction and degree of saturation on large strain shear modulus of unsaturated sands

    , Article Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 ; Vol. 2, issue , July , 2014 , p. 1559-1564 ; 978-1-138-00150-3 Jafarzadeh, F ; Ahmadinezhad, A ; Sadeghi, H ; Sharif University of Technology
    Predictions of soil behavior in response to dynamic loads require an understanding of dynamic properties of soil. Studies on dynamic properties of unsaturated soils at large-strains are quite limited, while some dynamic loadings, like earthquakes, are in the medium to large-strain ranges. A cyclic simple shear apparatus was developed to measure large-strain shear modulus and damping ratio under different matric suction or degree of saturation. Six cyclic tests, with referring to the soil-water retention curve, were conducted on clean medium sand. Results indicated that shear modulus slightly increases when suction varies from zero up to the air entry value. Approaching the residual value, a... 

    Numerical modeling of piles in sandy soils considering stress dependent modulus of elasticity

    , Article Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014, 22 September 2014 through 25 September 2014, Kyoto ; 2015 , Pages 973-977 ; 9781138001480 (ISBN) Ahmadi, M. M ; Abadi, S. M ; Sharif University of Technology
    Taylor and Francis - Balkema  2015
    Pile Foundations are used to transfer loads from superstructures to the underlying competent soil layers. Predicting pile bearing capacity is among the most interesting subjects for geotechnical engineers. In this study, a single pile is modeled in axisymmetric condition. The soil is considered to be a sandy soil. Then, results of the model were verified with a full scale pile load test performed by previous researchers. In order to take into consideration the real behavior of sandy soils, a variation of modulus of elasticity with respect to the changes in the mean effective stress was taken into account. The dependency of soil modulus to the mean effective stress makes the model more... 

    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) Ahmadi, S ; Sadrnezhad, S. K ; Sharif University of Technology
    Elsevier Ltd 
    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... 

    Development of an accurate finite element model for N-layer MR-laminated beams using a layerwise theory

    , Article Mechanics of Advanced Materials and Structures ; Volume 25, Issue 13 , 2018 , Pages 1148-1155 ; 15376494 (ISSN) Momeni, S ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Laminated composite beams incorporated with magneto-rheological fluid are being used in variety of critical applications. An N-layer magneto-rheological-laminated beam based on layerwise theory has been developed to study the dynamic characteristics. For simulation purpose, an MR-laminated beam with five layers is considered in which two layers filled with magneto-rheological and three layers are made of composite materials. The results of simulations are compared with existing layerwise, first-order shear-deformation theory and experimental tests where it shows the accuracy and functionality of the present model. The complex shear modulus of magneto-rheological fluid has been determined... 

    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) Ali Shafiei, M ; Sharif University of Technology
    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  

    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) Mohammadi, M ; Farrahi, G. H ; Hoseini, S. H ; Sharif University of Technology
    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... 

    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) Mohammadi, Z ; Ziaei Moayyed, A. A ; Mesgar, A. S. M ; Sharif University of Technology
    Elsevier  2007
    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... 

    Numerical simulation of three-dimensional flow and analysis of filling process in compression resin transfer moulding

    , Article Composites Part A: Applied Science and Manufacturing ; Volume 37, Issue 9 , 2006 , Pages 1434-1450 ; 1359835X (ISSN) Shojaei, A ; Sharif University of Technology
    In compression resin transfer moulding (CRTM), resin flows inside a mould filled with fibrous reinforcement as a result of resin injection and mould compression. This process facilitates the resin flow through the fibrous reinforcement particularly for high fiber content parts. This paper presents the numerical simulation of filling process of CRTM in full three-dimensional domain. A mathematical model of three-dimensional resin flow inside the CRTM mould is presented. An effective elastic modulus is introduced for multi-layer preforms connecting the mould closing speed to deformation rate of individual layers. Control volume/finite element method (CV/FEM) is used and the numerical algorithm...