Search for: viscoelasticity
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    An Analytical Approach to Nonlinear Vibrations of a Three-Layered Sandwich Beam with a Viscoelastic Core, under the Effects of Internal Resonance, Employing MMS

    , M.Sc. Thesis Sharif University of Technology PashaJavid, Babak (Author) ; Haddadpour, Hassan (Supervisor)
    Vibrations with high amplitudes in continuous systems and models with multiple degrees of freedom, in specific conditions, is concomitant with a phenomenon called internal resonance. In the presence of this phenomenon, energy is transferred from one directly excited mode to the other vibrating modes of the structure results in response of the structure to be combination of the excited modes. In that situation occurrence of the internal resonance may decrease the level of undesired vibrations of the structure. This behavior is of interest especially in sandwich structures with viscoelastic cores that are designated to improve the damping characteristics of the structure and the property may... 

    Investigation of Mechanical Properties of Healthy Red Blood Cells using Optical Tweezers

    , M.Sc. Thesis Sharif University of Technology Azadbakht, Ali (Author) ; Seyed Reihani, Nader (Supervisor) ; Moosavi-Movahhedi, Ali Akbar (Co-Advisor)
    Red blood cells (RBC, erythrocytes) are cells with an average diameter of 8 microns, the thickness of 2-3 microns and the volume of 90 fl. The biconcave shape of red blood cells,together with cell membrane flexibility, enables them to pass the capillaries whose diameter is considerably less than 8 micrometers. Mechanical properties of RBC are related to their membrane and cytoskeleton, which consists of spectrin network. Optical tweezers is able to exert very precise forces to erythrocytes using beed as a handle. In this report, we studied mechanical properties of RBC such as elasticity and viscoelasticity using single trap optical tweezers with beads with antibody coated in order to attach... 

    Flow of Saliva in a Lab-on-a-chip under Electrokinetic Body Force

    , M.Sc. Thesis Sharif University of Technology Zandi, Mohammad (Author) ; Saeedi, Mohammad Hassan (Supervisor)
    The lab-on-a-chip (LOC) devices utilizing electroosmosis for flow actuation are usually encountered with non-Newtonian behavior of working fluids. Hence, studying the flow of non-Newtonian fluids under an electroosmotic body force is of high importance for accurate design and active control of these devices. In this thesis, mixed electroosmotically and pressure driven flow of salivathrough a rectangular microchannel is examined utilizing two viscoelastic constitutive equations, namely PTT and FENE-P models. Since the hydrodynamic entry length is usually negligible for microflows, a hydrodynamically developed flow is considered in the analysis. The governing equations in dimensionless form... 

    The Effect of Thyroid Hormones on The Viscoelastic Behavior of Red Blood Cells

    , M.Sc. Thesis Sharif University of Technology Laktarash, Shaghayegh (Author) ; Seyed Reihani, Nader (Supervisor)
    Blood is one of the most important fluids in the human body, consisting of three parts: red blood cells, white blood cells and platelets. The mechanical properties of red blood cells are important in many diseases. The study of viscosity and other mechanical properties of red blood cells in recent years has attracted the attention of scientists in this field. The mechanical properties of red blood cells are related to the outer membrane and its cytoskeleton, and the study of these components can predict the behavior of red blood cells in diseases. The thyroid gland is located in front of the neck and secretes hormones that control many chemical processes in different parts of the body.... 

    Effects of viscoelastic polymer solutions on the oil extraction from dead ends

    , Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1912-1920 ; 2345-3605 (e-ISSN) Kamyabi, A ; Ramazani, A. S. A ; Kamyabi, M. M ; Sharif University of Technology
    Sharif University of Technology  2013
    This research deals with the numerical simulation of two viscoelastic uids ow in an open capillary of a reservoir. Oldroyd-B and Leonov models have been used to describe the rheological behavior of polymer solutions. The finite volume method on a structured and collocated grid has been used for discretization of the governing equations. The discrete elastic viscous stress splitting technique has also been used. The steady state, isothermal and incompressible uids past through a two dimensional micropore have been considered. The numerical method has been validated through the comparison of numerical results by the analytical solutions of Oldroyd-B uid ow through a planar channel. The effects... 

    Evaluation of interfacial layer properties in the polystyrene/silica nanocomposite

    , Article Journal of Applied Polymer Science ; Volume 119, Issue 4 , August , 2011 , Pages 2039-2047 ; 00218995 (ISSN) Mortezaei, M ; Farzi, G ; Kalaee, M. R ; Zabihpoor, M ; Sharif University of Technology
    Processing conditions and final mechanical properties of polymer nanocomposites are affected by their interfacial layers behavior. However, it is impossible to determine directly the properties of these layers by dynamic rheometry tests. In this work, the interfacial layers properties are evaluated for polystyrene containing silica nanoparticles by the concept of glass-transition temperature shift. The samples were prepared via solution-mixing method and dynamic rheometry was used to determine the viscoelastic behavior of filled polymers in the melt state. This initial step showed that addition of silica particles increased the glass-transition temperature. By preference, decrease in the... 

    Application of radial basis functions and sinc method for solving the forced vibration of fractional viscoelastic beam

    , Article Journal of Mechanical Science and Technology ; Volume 30, Issue 7 , 2016 , Pages 3001-3008 ; 1738494X (ISSN) Permoon, M. R ; Rashidinia, J ; Parsa, A ; Haddadpour, H ; Salehi, R ; Sharif University of Technology
    Korean Society of Mechanical Engineers  2016
    In this paper, the forced vibrations of the fractional viscoelastic beam with the Kelvin-Voigt fractional order constitutive relationship is studied. The equation of motion is derived from Newton’s second law and the Galerkin method is used to discretize the equation of motion in to a set of linear ordinary differential equations. For solving the discretized equations, the radial basis functions and Sinc quadrature rule are used. In order to show the effectiveness and accuracy of this method, some test problem are considered, and it is shown that the obtained results are in very good agreement with exact solution. In the following, the proposed numerical solution is applied to exploring the... 

    Reduction of production rate in y-shaped microreactors in the presence of viscoelasticity

    , Article Analytica Chimica Acta ; Volume 990 , 2017 , Pages 121-134 ; 00032670 (ISSN) Helisaz, H ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
    The viscoelasticity effects on the reaction-diffusion rates in a Y-shaped microreactor are studied utilizing the PTT rheological model. The flow is assumed to be fully developed and considered to be created under a combined action of electroosmotic and pressure forces. In general, finite-volume-based numerical simulations are conducted to handle the problem; however, analytical solutions based on the depthwise averaging approach are also obtained for the case for which there is no reaction between the inlet components. The analytical solutions are found to predict accurate results when the width to height ratio is at least 10 and acceptable results for lower aspect ratios. An investigation... 

    Stability analysis of a fractional viscoelastic plate strip in supersonic flow under axial loading

    , Article Meccanica ; Volume 52, Issue 7 , 2017 , Pages 1495-1502 ; 00256455 (ISSN) Asgari, M ; Permoon, M. R ; Haddadpour, H ; Sharif University of Technology
    Springer Netherlands  2017
    The stability of a viscoelastic plate strip, subjected to an axial load with the Kelvin–Voigt fractional order constitutive relationship is studied. Based on the classical plate theory, the structural formulation of the plate is obtained by using the Newton’s second law and the aerodynamic force due to the fluid flow is evaluated by piston theory. The Galerkin method is employed to discretize the equation of motion into a set of ordinary differential equations. To determine the stability margin of plate the obtained set of ordinary differential equations are solved using the Laplace transform method. The effects of variation of the governing parameters such as axial force, retardation time,... 

    On the geometrically nonlinear analysis of sandwich shells with viscoelastic core: a layerwise dynamic finite element formulation

    , Article Composite Structures ; Volume 230 , 2019 ; 02638223 (ISSN) Hosseini Kordkheili, A ; Khorasani, R ; Sharif University of Technology
    Elsevier Ltd  2019
    The objective of this work is to present a finite element formulation for dynamic analysis of sandwich shells with viscoelastic core under large deformation. The present study is based on an incremental updated Lagrangian approach together with the Newmark integration scheme. The viscoelastic constitutive model which is used to define the behavior of the core, comes from the Riesz theorem and the corresponding creep functions are estimated using Dirichlet-Prony series. Also, the viscoelastic deferred strain is derived in an appropriate incremental form using the state variables. The employed layerwise shell element which is based on zig-zag theory has eight nodes on its mid layer. What's... 

    Vibration analysis of pipes conveying fluid resting on a fractional Kelvin-Voigt viscoelastic foundation with general boundary conditions

    , Article International Journal of Mechanical Sciences ; Volume 179 , 2020 Askarian, A. R ; Permoon, M. R ; Shakouri, M ; Sharif University of Technology
    Elsevier Ltd  2020
    In this paper, the stability of pipes conveying fluid with viscoelastic fractional foundation is investigated. The pipe is fixed at the beginning while the pipe end is constrained with two lateral and rotational springs. The fluid flow effect is modeled as a lateral distributed force, containing the fluid inertia, Coriolis and centrifugal forces. The pipe is modeled using the Euler-Bernoulli beam theory and a fractional Kelvin-Voigt model is employed to describe the viscoelastic foundation. The equation of motion is derived using the extended Hamilton's principle. Presenting the derived equation in Laplace domain and applying the Galerkin method, a set of algebraic equations is extracted.... 

    Optical flow-based motion estimation of ultrasonic images for force estimation in percutaneous procedures: Theory and experimental validation

    , Article IECON Proceedings (Industrial Electronics Conference), 25 October 2012 through 28 October 2012 ; October , 2012 , Pages 1557-1560 ; 9781467324212 (ISBN) Maghsoudi, A ; Jahed, M ; Sharif University of Technology
    In recent years, there hass been a pronounced emphasis on percutaneous needle steering with the aid of advanced soft tissue modeling techniques. In this work an optical flow based motion estimation method is used to estimate the force applied to the needle by the soft tissue during percutaneous applications. The study considers Finite Element Model (FEM) of the tissue evaluated by the deformation data acquired through the optical flow method. To represent the soft tissue behavior, dynamic FEM with Rayleigh damping and viscoelastic models are used. The method is validated experimentally through offline evaluation of the ultrasonic images of the chicken breast punctured by a needle. The force... 

    Pure axial flow of viscoelastic fluids in rectangular microchannels under combined effects of electro-osmosis and hydrodynamics

    , Article Theoretical and Computational Fluid Dynamics ; Volume 32, Issue 1 , 2018 ; 09354964 (ISSN) Reshadi, M ; Saidi, M. H ; Ebrahimi, A ; Sharif University of Technology
    Springer New York LLC  2018
    This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien–Tanner (PTT) model with the Gordon–Schowalter convected derivative which covers the upper convected Maxwell, Johnson–Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson–Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid... 

    Three Dimensional Dynamic Model of Human Patellofemoral Joint

    , M.Sc. Thesis Sharif University of Technology Akbar, Mohammad (Author) ; Farahmand, Farzam (Supervisor) ; Saadat Foumani, Mahmoud (Supervisor)
    Patellofemoral joint has an important role in knee extension. Because of this joint importance and complicated mechanical behavior, a lot of mathematical models have been used, to obtain a better understand of this joint, considering this joint as a part of knee joint or as a separate joint. Although these works have comprehensively studied the patellofemoral joint but they don’t emphasis on dynamic aspects. Also there is no work to compare the experimental and theoretical results calculated from one specified subject knee.In this study, the kinematic and dynamic of patellofemoral joint has been studied, constructing a three dimensional dynamic model of patellofemoral joint and experimental... 

    Rheological Evaluation of Ageing Properties of Modified Bitumens

    , M.Sc. Thesis Sharif University of Technology Naderi, Koorosh (Author) ; Tabatabaee, Nader (Supervisor)
    Bitumen ageing is one of the principal factors causing the deterioration of asphalt pavements. Ageing is a complex process that is affected by different parameters.With the rapid growth of modified binders in road paving applications over the past twodecades, it is important to study the ageing properties of these binders. A number of laboratory methods are used tosimulatethe bitumenageing at various stages of the production and service of hot mix asphalt.Recent studies have shown that Superpave testing protocol does not fully address the ageing of modified binders. To study the ageing properties of modified binders, three different types of binder modifiers, plastomer, elastomer, and ground... 

    Developing the MIDA Method for Structures Equipped with Dampers and Exerting this Method on a Structure with SCVDs Damper

    , M.Sc. Thesis Sharif University of Technology Zafarkhah, Elyar (Author) ; Mofid, Masood (Supervisor)
    Determining nonlinear dynamic behavior of structures is always one of the main goals of structure and earthquake engineers. The Modal Incremental Dynamic Analysis (MIDA) is one of the newest methods for analyzing the seismic behavior of structures. Indeed, this method has superseded the exact IDA method which is too complicated and prolix. Although, this method represents approximate results, high accuracy, fastness and low cost procedure made it an efficient and useful technique. Many researchers have used this method and investigated the accuracy of that and achieved proper results. Up to now no one has applied this method on structures which are equipped with dampers. In the procedure of... 

    Optimization of Die Profile in Screw Extrusion Process for an Arbitrary Profile by Considering Viscoelastic Effects of the Material

    , M.Sc. Thesis Sharif University of Technology Fadaei Naeini, Vahid (Author) ; Asghari, Mohsen (Supervisor)
    In this thesis, equations related to large deformation of a polymer were derived by considering viscoelastic effects. To express type of material behavior which includes elastoplastic and viscoelastic property at the same time, two-layer viscoplastic model was used. An axisymmetric model was used for modeling problem in finite element software. By derivation of parameters related to two layer model and entering them in finite element software and also entering other properties required to model the forming process, modeling was performed by special profile connecting input and output sections. Due to favorable properties of spline functions, profiles used in die geometry, were selected from... 

    Numerical and Analytical Study of Mixing in Y-shaped Micromixers: Electroosmotic and Poiseuille Flow of PTT Fluids

    , M.Sc. Thesis Sharif University of Technology Reshadi, Milad (Author) ; Saeedi, Mohammad Hassan (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
    Dissemination of an analyte under the laminar flows plays a major role in measuring and assessment of biological fluids such as sample preparation in the context of microfluidic systems. Due to the development of manufacturing technology in the Lab-on-a-chip devices, the production of rectangular microchannels with finite aspect ratios and micron and submicron sizes has been provided by which the effect of electrokinetic phenomena on concentration distribution will be magnified in these systems. On the other hand, these biofluids are viscoelastic and show extraordinary flow behaviors, not existing in Newtonian fluids and adopting appropriate constitutive equations these exotic flow behaviors... 

    Analysis and Simulation of Three-Dimensional Torsional Viscous Dampers

    , M.Sc. Thesis Sharif University of Technology Matbou, Farshad (Author) ; Behzad, Mehdi (Supervisor)
    Torsional vibrations of internal combustion engines and reciprocating compressors, is one of the challenges in the design process. It can reduce power of productivity, equipment operating lifetime and increase noise of the system. Torsional viscous damper is a method to reduce torsional vibrations in rotating equipment. In this study, three-dimensional simulations of torsional viscous damper is performed as a matter of FSI, with consider harmonic excitation on the external walls and calculation of damping response inertia ring in CFX software. The viscoelastic non-Newtonian model properties of damping fluid is calculated in MATLAB software with respect to viscoelastic parameters. For... 

    The Study on Relationship between Viscoelastic Properties and Drug Release of Wound Dress Polyvinyl Alcohol Hydrogel

    , M.Sc. Thesis Sharif University of Technology Rezvan, Gelareh (Author) ; Bagheri, Reza (Supervisor) ; Pircheraghi, Gholamreza (Supervisor)
    Wound is a defect or failure in the skin texture which occurs as a result of physical or heat injuries or physiological conditions. The wound dress as a temporary cover can improve wound healing process and due to the unique properties, hydrogels have become appropriate choice for this application. Hydrogel’s structure allows drug to be loaded in the wound dress. Hydrogel wound dress should have adequate fluidity to cover wound’s bed and make full contact with the skin. Sufficient cohesion and strength is also necessary to allow the wound dress to remove from wound completely. Therefore, the study on the viscoelastic properties of hydrogel is important. In this study, polyvinyl alcohol...