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Total 134 records

    On the static pull-in of circular microplates under capillary force

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 ; Volume 11 , 2011 , Pages 401-405 ; 9780791854976 (ISBN) Kahrobaiyan, M. H ; Fallah, A ; Bozorgzadeh, S ; Firoozbakhsh, K ; Ahmadian, M. T ; Sharif University of Technology
    Abstract
    In this paper, the static pull-in phenomenon is investigated in circular micro-plates subjected to capillary force. The capillary force appears in micro-scale structures due to presence of a liquid bridge. The governing equation of a circular micro-plate subjected to capillary force is presented and the static deflection of a fully-clamped circular plate is evaluated. Moreover, the effect of the normalized adhesion tension caused due to the capillary force on the static pull-in of the micro-plate is assessed  

    Bending analysis of thin skew plates using extended Kantorovich method

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 2 , 2010 , Pages 39-44 ; 9780791849163 (ISBN) Kargarnovin, M. H ; Joodaky, A ; Sharif University of Technology
    2010
    Abstract
    An accurate approximate closed-form solution is presented for bending of thin skew plates with clamped edges subjected to uniform loading using the extended Kantorovich method (EKM). Successive application of EKM together with the idea of weighted residual technique (Galerkin method) converts the governing forth-order partial differential equation (PDE) to two separate ordinary differential equations (ODE) in terms of oblique coordinates system. The obtained ODE systems are then solved iteratively with very fast convergence. In every iteration step, exact closed-form solutions are obtained for two ODE systems. It is shown that some parameters such as angle of skew plate have an important... 

    Seismic rehabilitation of exterior RC beam-column joints using steel plates, angles, and posttensioning rods

    , Article Journal of Performance of Constructed Facilities ; Volume 30, Issue 1 , 2016 ; 08873828 (ISSN) Arzeytoon, A ; Hosseini, A ; Goudarzi, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    Abstract
    The presented studies have been conducted on the scope and magnitude of damages inflicted by earthquakes over the years. Many RC buildings, designed and constructed in the 1960s and 1970s, have serious structural deficiencies, especially in their beam-column joints. Such deficiencies result from inadequate joint shear strength or confinement of column reinforcement. The joints require elaborate retrofit measures to ensure the performances comparable to those of new designed structures. In this research, a new seismic retrofitting method is presented for beam-column joints based on the two-dimensional enlargement of the joint by using steel plate, angles, and posttensioning rods. The seismic... 

    The effect of gusset plate in moment-rotation behavior of double-web angle connection in braced frames

    , Article Scientia Iranica ; Volume 24, Issue 6 , 2017 , Pages 2712-2725 ; 10263098 (ISSN) Mofid, M ; Wayghan, A. R. T ; Sharif University of Technology
    Abstract
    Double-web angle connection is one of the most rudimentary connections in simple structural systems such as braced frame system. It is essentially presumed in conventional designs that double-web angle connection behaves as a hinge connection. However, in braced frames, due to existence of braces in some bays, in specified locations where gusset plates of brace are placed with beam-to-column connection in one joint, this assumption may not be accurate. This is due to the restraining of the beam from rotation by gusset plates that are placed either on the top and bottom of the beam or only on one side. In such cases, the simple beam-to-column connection may be transformed into a semi-hinge or... 

    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
    Abstract
    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... 

    Post-buckling analysis of piezo-magnetic nanobeams with geometrical imperfection and different piezoelectric contents

    , Article Microsystem Technologies ; Volume 25, Issue 9 , 2019 , Pages 3477-3488 ; 09467076 (ISSN) Mirjavadi, S. S ; Forsat, M ; Barati, M. R ; Abdella, G. M ; Hamouda, A. M. S ; Mohasel Afshari, B ; Rabby, S ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    Thermal post-buckling behavior of a geometrically imperfect/perfect piezo-magnetic nano-scale beams made of two-phase composites is analyzed in the present paper based on nonlocal elasticity theory. For the first time, the material properties of the nanobeam are considered as functions of piezoelectric phase percentage. All previous investigations on piezo-magnetic nanobeams neglect the effect of geometrical imperfection which is very important since the nanobeams are not always ideal or perfect. The post-buckling problem of such nanobeams is solved by introducing an analytical approach to derive buckling temperatures. The present solution is simple and easily understandable. For both... 

    Nonlinear free and forced vibrations of graphene nanoplatelet reinforced microbeams with geometrical imperfection

    , Article Microsystem Technologies ; Volume 25, Issue 8 , 2019 , Pages 3137-3150 ; 09467076 (ISSN) Mirjavadi, S. S ; Mohasel Afshari, B ; Barati, M. R ; Hamouda, A. M. S ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    Nonlinear free/forced vibration of a functionally graded graphene nanoplatelet (GNP) reinforced microbeam having geometrical imperfection which is rested on a non-linear elastic substrate have been studied in the present research. Graphene Platelets have been uniformly and non-uniformly scattered in the cross section area of the microbeam. Non-uniform distribution of GNPs is considered to be linear or non-linear type. Geometric imperfection is considered similar to the first vibration mode of microbeam. Size effects due to micro-rotations are captured in this study by means of modified couple stress elasticity. In the case of forced vibration, a uniform harmonic load is exerted to the top... 

    Non-linear thermo-mechanical cylindrical bending of functionally graded plates

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 222, Issue 3 , 2008 , Pages 305-318 ; 09544062 (ISSN) Fallah, F ; Nosier, A ; Sharif University of Technology
    2008
    Abstract
    Based on the first-order non-linear von Karman theory, cylindrical bending of functionally graded (FG) plates subjected to mechanical, thermal, and combined thermo-mechanical loadings are investigated. Analytical solutions are obtained for an FG plate with various clamped and simply-supported boundary conditions. The closed form solutions obtained are very simple to be used in design purposes. The material properties are assumed to vary continuously through the thickness of the plate according to a power-law distribution of the volume fraction of the constituents. The effects of non-linearity, material property, and boundary conditions on various response quantities are studied and... 

    Parametric analyses on the initial stiffness of flush end-plate splice connections using FEM

    , Article Journal of Constructional Steel Research ; Volume 64, Issue 10 , 2008 , Pages 1129-1141 ; 0143974X (ISSN) Mohamadi shooreh, M. R ; Mofid, M ; Sharif University of Technology
    Elsevier BV  2008
    Abstract
    Existing design procedures for steel frames have been modified during the last three decades to incorporate the semi-rigid behavior of the connections into the frame design advancement. Knowledge in initial rotational stiffness of a connection is important for the global elastic analysis of frame structures. This paper presents the results of several parametric analyses on the Initial Rotational Stiffness (IRS or Sini) of Bolted Flush End-plate Beam (BFEB) splice connections using Finite Element Modeling (FEM). The FEMs have taken into account material behavior, geometrical discontinuities and large displacements. The analyses have been calibrated to experimental results that are also... 

    Nonlinear flutter of three dimensional general laminated composite plates

    , Article 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Waikiki, HI, 23 April 2007 through 26 April 2007 ; Volume 8 , 2007 , Pages 7518-7529 ; 02734508 (ISSN); 1563478927 (ISBN); 9781563478925 (ISBN) Kouchakzadeh, M. A ; Rasekh, M ; Guran, A ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2007
    Abstract
    The nonlinear aeroelastic behavior of a three-dimensional general laminated composite plate at high supersonic Mach numbers is investigated using von Karman's large deflection plate theory and quasisteady aerodynamic theory. Galerkin's method is used to reduce the governing equations to a system of nonlinear ordinary differential equations in time, which are then solved by a direct numerical integration method. Nonlinear flutter results are presented with the effects of in-plane force, static pressure differential, fiber orientation and aerodynamic damping  

    Dynamic analysis of orthotropic laminated composite plates under axial load on elastic foundation

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ahmadian, M. T ; Pirbodaghi, T ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    In this paper, free vibration analysis of laminated composite plates is carried out using first shear deformation theory and finite element method. Effect of axial tension and compression forces on the natural frequencies of the structure is investigated. Applying elastic foundation under the laminated composite plates has enabled us to achieve desired frequencies. The displacements are based C0 - nine plate bending element and each node has three degree of freedom. The equations of motion are derived using Hamilton's principle. Results indicate the tension forces will increase the natural frequency while the compression force reduces the natural frequency. The buckling force of plate is... 

    Dynamics of multi layer microplates considering nonlinear squeeze film damping

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 1096665X (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ahmadian, M. T ; Moghimi Zand, M ; Borhan, H ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    This paper presents a model to analyze pull-in phenomenon and dynamics of multi layer microplates using coupled finite element and finite difference methods. Firstorder shear deformation theory is used to model dynamical system using finite element method, while Finite difference method is applied to solve the nonlinear Reynolds equation of squeeze film damping. Using this model, Pull-in analysis of single layer and multi layer microplates are studied. The results of pull-in analysis are in good agreement with literature. Validating our model by pull-in results, an algorithm is presented to study dynamics of microplates. These simulations have many applications in designing multi layer... 

    Online prediction of plate deformations under external forces using neural networks

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ahmadian, M. T ; Mobini, A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    Recently online prediction of plate deformations in modern systems have been considered by many researchers, common standard methods are highly time consuming and powerful processors are needed for online computation of deformations. Artificial neural networks have capability to develop complex, nonlinear functional relationships between input and output patterns based on limited data. A good trained network could predict output data very fast with acceptable accuracy. This paper describes the application of an artificial neural network to identify deformation pattern of a four-side clamped plate under external loads. In this paper the distributed loads are approximated by a set of... 

    Detection of delamination in composite laminated plates using filtered mode shapes

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 226, Issue 12 , 2012 , Pages 2902-2911 ; 09544062 (ISSN) Bazardehi, S. R. K ; Kouchakzadeh, M. A ; Sharif University of Technology
    2012
    Abstract
    Filtered mode shapes are used to detect the presence, location, size and shape of the delaminations in composite laminated plates with various boundary conditions. This method is the extension of a previous study by the authors on the delamination detection in the beams using irregularities of the mode shapes. The mode shapes are filtered to separate the smooth and irregular parts. Presence and situation of delamination affects these separated parts, and these effects are used to detect the delamination. Here, two new indicators, named 'slope of smooth part' and 'irregularities in the slope of smooth part', are introduced to increase the clarity of detected damage and reduce the noisy... 

    Dynamic analysis of microrobots with Coulomb friction using harmonic balance method

    , Article Nonlinear Dynamics ; Volume 67, Issue 2 , 2012 , Pages 1357-1371 ; 0924090X (ISSN) Eigoli, A. K ; Vossoughi, G. R ; Sharif University of Technology
    Abstract
    In this paper, we investigate the dynamic analysis of a strongly nonlinear microrobot using a three-term harmonic balance method. The employed locomotion concept, namely "friction drive principle," is based on the superposition of a horizontal vibration at the interface between the robot and work floor and an active variation of friction force, obtained by the vertical vibration of the base at the same interface. The equation of motion for the system reveals a parametrically excited oscillator with discontinuity for which the elastic force term is proportional to a signum function. The obtained periodic solution not only is of high accuracy, but also can predict the contribution of the... 

    Experimental investigation of RCS connections performance using self-consolidated concrete

    , Article Journal of Constructional Steel Research ; Volume 114 , November , 2015 , Pages 204-216 ; 0143974X (ISSN) Alizadeh, S ; Attari, N. K. A ; Kazemi, M. T ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    The cyclic behavior of RCS connection consisted of Reinforced Concrete (RC) columns and Steel (S) beams is studied in this paper. Two interior connections are investigated experimentally. The joint of the first specimen is designed according to ASCE 1994 guideline, while the second specimen has a new proposed joint detail. Self-consolidating concrete is used in both specimens. Self-consolidating concrete could improve constructability of the congested joint of RCS frames. The specimens detail include steel band plates, face bearing plates, L-shaped joint stirrups, and steel doubler plate for the panel zone. The proposed joint detail consists of additional bearing plates, which cause an... 

    Post-buckling behavior of functionally graded circular plates under asymmetric transverse and in-plane loadings

    , Article Composite Structures ; Volume 125 , 2015 , Pages 477-488 ; 02638223 (ISSN) Fallah, F ; Vahidipoor, M. K ; Nosier, A ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    Based on the first-order nonlinear von Karman theory, the post-buckling analysis of FG circular plates under asymmetric transverse and in-plane loadings are presented. The nonlinear governing equations are reformulated using a stress function and a boundary layer function, and solved by employing a multi-parameter perturbation technique and Fourier series method. The material properties are assumed to vary through the plate thickness according to a power-law distribution of the volume fractions of the constituents. The results are verified with the known results in the literature. The effects of loading, material properties, and boundary conditions on different response quantities are... 

    Parallel-plate waveguide integrated filters and lenses realized by metallic posts for terahertz applications

    , Article International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, 25 September 2016 through 30 September 2016 ; Volume 2016-November , 2016 ; 21622027 (ISSN) ; 9781467384858 (ISBN) Ahmadi Boroujeni, M ; Sharif University of Technology
    IEEE Computer Society  2016
    Abstract
    In this paper, we report on the design and analysis of filters and lenses realized by an array of metallic posts integrated in a parallel-plate waveguide (PPWG). The design methodology of these components is inferred from the modal analysis of a spoof surface plasmonic waveguide composed of metallic posts arranged in a 1D periodic structure inside PPWG. Samples of the proposed devices are analyzed using a full-wave analysis method and their performance is assessed. We show that the mentioned structure can be used to realize all-metallic band-pass filters and lenses for mm-wave and terahertz applications  

    On the energy harvesting via doubly curved piezoelectric panels

    , Article Journal of Intelligent Material Systems and Structures ; Volume 27, Issue 19 , 2016 , Pages 2692-2706 ; 1045389X (ISSN) Sayyaadi, H ; Rahnama, F ; Sharif University of Technology
    SAGE Publications Ltd 
    Abstract
    This article presents an analytical solution for power output from a doubly curved piezoelectric energy harvester. The energy harvester is made of an elastic core layer coupled with one or two surface-bonded piezoelectric layers. Five mechanical equations of motion together with Gauss's equation are derived on the basis of first-order shell theory and solved simultaneously for simply supported mechanical boundary conditions. The influence of structural damping is taken into account using Rayleigh damping. The electromechanical frequency response functions that relate the power output and circuit load resistance are identified from the exact solutions. Finally, the performance of the system... 

    Numerical study of flow-induced oscillations of two rigid plates elastically hinged at the two ends of a stationary plate in a cross-flow

    , Article Journal of Fluids and Structures ; Volume 66 , 2016 , Pages 147-169 ; 08899746 (ISSN) Darbandi, M ; Fouladi, N ; Sharif University of Technology
    Academic Press  2016
    Abstract
    The flow-induced oscillation (FIO) of bluff bodies is commonly encountered in the fluid structure interaction (FSI) problems. In this study, we use an unstructured moving grid strategy and simulate the FIO of two rigid plates, which are elastically hinged at the two ends of a fixed flat plate in a cross-flow. We use a hybrid finite-element-volume (FEV) method in an arbitrary Lagrangian–Eulerian (ALE) framework to study FIO of the two hinged plates. The current simulations are carried out for wide ranges of flow Reynolds number (50–175), spring stiffness coefficient, and the two hinged plates’ moment of inertia magnitudes. The influences of these parameters are investigated on the magnitudes...