Search for: hyperelastic
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    A hyperelastic constitutive model for fiber-reinforced rubber-like materials

    , Article International Journal of Engineering Science ; Volume 71 , 2013 , Pages 36-44 ; 00207225 (ISSN) Fereidoonnezhad, B ; Naghdabadi, R ; Arghavani, J ; Sharif University of Technology
    In this paper, a Strain Energy Function (SEF) is proposed to characterize the hyperelastic behavior of transversely isotropic incompressible fiber-reinforced rubbers. The kinematics of the deformation is based on a strain measure consistent with the physics of the deformation. The SEF consists of an isotropic part and an anisotropic one where a simple form of SEF is used for both parts. In order to investigate the capabilities of the proposed model, two fiber-reinforced rubbers under homogeneous deformations are examined. The predictions of the model show a good agreement with the experimental data for both tensile and shear deformations. Also, torsion of a fiber-reinforced rubbery circular... 

    A hyperelastic constitutive model for rubber-like materials

    , Article European Journal of Mechanics, A/Solids ; Volume 38 , 2013 , Pages 144-151 ; 09977538 (ISSN) Khajehsaeid, H ; Arghavani, J ; Naghdabadi, R ; Sharif University of Technology
    Hyperelastic behavior of isotropic incompressible rubbers is studied to develop a strain energy function which satisfies all the necessary characteristic properties of an efficient hyperelastic model. The proposed strain energy function includes only three material parameters which are somehow related to the physical quantities of the material molecular network. Moreover, the model benefits from mathematical simplicity, well suitting in all ranges of stretch and possessing the property of deformation-mode-independency. This reduces the required number of experimental tests for parameter calibration of the model. Results of the proposed model are compared with results of some available models... 

    Simulating the Insertion of Intrastromal Corneal Ring Segments in Keratoconic Corneas

    , M.Sc. Thesis Sharif University of Technology Dashti, Azadeh (Author) ; Zohoor, Hassan (Supervisor) ; Ahmadian, Mohammad Taghi ($item.subfieldsMap.e)
    Keratoconus is a progressive corneal illness that appears due to reduced thickness of cornea in some area. Normal cornea has semi sphere shape with uniform thickness from center of cornea to the limbus. However, keratoconic cornea’s shape becomes conic. One of the treatments in moderate state of keratoconus is implantation of IntraStromal Corneal Ring Segments( ICRS). Ring Segments are made of PMMA and inserted in 0/7- 0/8 of depth of cornea.In this study, before surgery data from 3 patient’s cornea images were prepared in order to 3D modeling of cornea, for importing to FEM software( ABAQUS). Material properties of cornea is considered hyperelastic second-order Ogden Model; elastic... 

    Hyperelastic materials behavior modeling using consistent strain energy density functions

    , Article Acta Mechanica ; Volume 213, Issue 3-4 , 2010 , Pages 235-254 ; 00015970 (ISSN) Darijani, H ; Naghdabadi, R ; Sharif University of Technology
    Springer-Verlag Wien  2010
    Hyperelastic materials have high deformability and nonlinearity in load-deformation behavior. Based on a phenomenological approach, these materials are treated as a continuum, and a strain energy density is considered to describe their hyperelastic behavior. In this paper, the mechanical behavior characterization of these materials is studied from the continuum viewpoint. For this purpose, the strain energy density is expressed as sum of independent functions of the mutual multiple of principal stretches. These functions are determined by applying the governing postulates on the form of the strain energy density. It is observed that a consistent strain energy density is expressible in terms... 

    Modeling of damage in soft biological tissues

    , Article Biomechanics of Living Organs: Hyperelastic Constitutive Laws for Finite Element Modeling ; 2017 , Pages 101-123 ; 9780128040607 (ISBN); 9780128040096 (ISBN) Holzapfel, G. A ; Fereidoonnezhad, B ; Sharif University of Technology
    Elsevier Inc  2017
    The mechanical responses of biological tissues are well characterized by hyperelastic or viscoelastic models within the physiological loading range. However, during supra-physiological mechanical loading, as occurs during interventional procedures such as balloon angioplasty and arterial clamping, damage may occur in the tissue. The continuum and computational treatments of damage in soft biological tissues have attracted considerable attention over the recent years. In this chapter, we review the state of the art of this challenging area. We summarize and critically discuss various damage models, which are based on continuum damage mechanics, the theory of pseudo-elasticity, and the... 

    Application of hyperelastic models in mechanical properties prediction of mouse oocyte and embryo cells at large deformations

    , Article Scientia Iranica ; Volume 25, Issue 2B , March , 2018 , Pages 700-710 ; 10263098 (ISSN) Abbasi, A. A ; Ahmadian, M. T ; Alizadeh, A ; Tarighi, S ; Sharif University of Technology
    Sharif University of Technology  2018
    Biological cell studies have many applications in biology, cell manipulation, and diagnosis of diseases such as cancer and malaria. In this study, Inverse Finite Element Method (IFEM) combined with Levenberg-Marquardt optimization algorithm has been used to extract and characterize material properties of mouse oocyte and embryo cells at large deformations. Then, the simulation results have been validated using data from experimental works. In this study, it is assumed that cell material is hyperelastic, isotropic, homogenous, and axisymmetric. For inverse analysis, FEM model of cell injection experiment implemented in Abaqus software has been coupled with Levenberg-Marquardt optimization... 

    Mechanical Simulation of Corneal Ring Implant Surgery for Keratoconus Treatment

    , M.Sc. Thesis Sharif University of Technology Bagheri Tadi, Hamid Reza (Author) ; Asghari, Mohsen (Supervisor)
    Keratoconus is a progressive disease in which the cornea becomes thin and due to the presence of internal pressure in the eye and its application to the cornea, the cornea becomes bulging and conical. In recent years, due to the relatively large number of patients with keratoconus and also the ability of this disease to progress over time, the need to study and research on the treatment of this disease is noticeable. Early and non-surgical methods for the treatment of keratocous are use glass and contact lenses, but since the disease is progressive and usually appears more severely over time, ophthalmologists use the method of corneal ring implant for treatment.In this study, 9 types of... 

    Consistent Strain Energy Functions for Transversely Isotropic and Orthotropic Hyperelastic Materials

    , M.Sc. Thesis Sharif University of Technology Fereidoonnezhad, Behrouz (Author) ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor) ; Arghavani, Jamal (Co-Advisor)
    Process Variation is seen as statistical variations in leakage current and delay of transistors in nano-scale technologies. The amount of process variations increase as the size of transistors decrease by technology scaling such that those effects can be seen in frequency of MPSoC (Multi-Processor System-on-Chip) cores and their leakage power deviation. These variations cause the tasks duration and power consumption fluctuate in different processors in an MPSoC instance. Consequently, some chip instances of the same MPSoC may consume more time and power than their considered limitations. Hence considering the process variation is necessary and required for MPSoC optimization at different... 

    , M.Sc. Thesis Sharif University of Technology Emami Talaremi, Ali Asghar (Author) ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
    Increasing the application of elastomeric structures in industries has caused an interest in the researchers for nonlinear elasticity and viscoelasticity of solids. Such materials which show large deformation and rate dependent behavior are treated by visco-hyperelastic constitutive equations. Based on visco-hyperelastic constitutive equations, total stress is divided into two parts: quasi-static and viscous stress. The method for determining the visco-hyperelastic constitutive equation is strictly dependent on the chosen rheological model. In this project, a new visco-hyperelasic constitutive equation in the integral form was introduced based on the Zener model. Also, based on the internal... 

    Numerical Investigation of Geometrical and Material Parameters Effect on Inflation and Deflation of oil well Inflatable Packers

    , M.Sc. Thesis Sharif University of Technology Eftekhari, Ahmad (Author) ; Arghavani Hadi, Jamal (Supervisor)
    Inflatable packers have a great value in downhole operations due to their unique ability to expand to several times their initial diameter. These type of packers have a sealing element. This element is constructed of thin overlapped sheet metal ribs which are surrounding an inner tube. These overlapped ribs protect inner tube against the extrusion. The outer surface of this element covered by a layer of rubber. The outer elastomeric cover seals the annulus of the casing and isolates the zones in the well. In this study, some of the geometrical and material parameters effects on inflation and deflation of inflatable packers are investigated by numerical method. At first, for this purpose, the... 

    A strain energy function for rubber-like materials

    , Article Constitutive Models for Rubber VIII - Proceedings of the 8th European Conference on Constitutive Models for Rubbers, ECCMR 2013 ; 2013 , Pages 205-210 ; 9781138000728 (ISBN) Khajehsaeid, H ; Naghdabadi, R ; Arghavani, J ; Sharif University of Technology
    Hyperelastic behavior of isotropic incompressible rubbers are studied to develop a strain energy function. The proposed function includes only three material parameters which are related to physical properties of the material molecular network. Furthermore, the model benefits from well suitting in all ranges of stretch as well as possessing the property of deformation mode independency. This reduces the required number of experimental tests for parameter calibration. Results of the model are compared with results of Mooney-Rivlin, Arruda-Boyce, Gent and Gao models as well as the experimental data  

    An investigation on the validity of Cauchy-Born hypothesis using Sutton-Chen many-body potential

    , Article Computational Materials Science ; Volume 44, Issue 3 , January , 2009 , Pages 999-1006 ; 09270256 (ISSN) Khoei, A. R ; Abdolhosseini Qomi, M. J ; Kazemi, M. T ; Aghaei, A ; Sharif University of Technology
    The Cauchy-Born hypothesis has been used to concurrently bridge atomistic information to continuum model. It has been a prevalent assumption in computational nano-mechanics during the past decade. This kinematic assumption relates the deformation of the continuum to the deformation of its underlying crystalline structure. The main objective of this paper is to investigate the validity of this hypothesis by means of direct atomistic simulations and the continuum mechanic calculations. In fact, we intend to determine under which strain or stress state the crystalline structure undergoes inhomogeneous deformation due to a small perturbation of the homogeneously deformed system. Two failure... 

    Investigation of the Recovery Time and Hyper-Viscoelastic Properties of the Brain Tissue

    , M.Sc. Thesis Sharif University of Technology Mohajery, Mohammad (Author) ; Ahmadian, Mohammad Taghi (Supervisor)
    FE simulations have been widely used to investigate the response of the brain tissue in various circumstances. The accuracy of the material models critically affects the results of the numerical simulation. However, despite the numerous studies aiming for the material modeling of the brain, there is still divergence between the results reported in the literature. A part of this discrepancy is due to the inherent difference between samples. Nonetheless, another part of it is resulted from the differences between testing protocols used by researchers. In some protocols multiple mechanical tests are performed on each sample. Enough recovery time should be considered between consecutive test... 

    Hyperelastic Modeling of Atomistic Continuum in the Presence of Inhomogeneity

    , M.Sc. Thesis Sharif University of Technology Asadollahzadeh, Niloofar (Author) ; Khoei, Amir Reza (Supervisor) ; Jahanshahi, Mohsen (Supervisor)
    In this study, a pioneer multiscale hierarchical molecular dynamics (MD) – finite element (FE) coupling method is proposed to illustrate the influence of large deformation on mechanical properties of heterogeneous nano-crystalline structures. The embedded-atom method (EAM) of many-body interatomic potential is applied to evaluate pairwise interactions between atoms in the metallic alloys with face-centered-cubic (FCC) lattice structure at room temperature. In addition, the Nose-Hoover thermostat is used to control the instability of temperature. A weight average between the lattice parameters of atomic structures is utilized in order to calculate the equivalent lattice parameter. The... 

    Investigation of the Effect of High Accelerations on Human Cardiac Function

    , M.Sc. Thesis Sharif University of Technology Jamshidi, Masoud (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Meghdari, Ali (Co-Advisor)
    When the human body is subjected to high accelerations, cardiac function and blood supply to the body can be changed. Due to the complex geometrical and mechanical properties of heart, finite element method is useful way for analysis of response of this structure under different load types. Modeling heart using finite element method requires mechanical and geometrical properties of heart. Soft tissues modeling, such as heart muscle using finite element method is one of the most challenging issues in field of biomechanics. In this thesis, the mechanical properties of heart are obtained by performing experimental compression tests on samples of fresh bovine heart. Using obtained experimental... 

    Modeling of Incompressible Materials Using the Extended Finite Element Method (XFEM)

    , M.Sc. Thesis Sharif University of Technology Mirkhosravi, Poorya (Author) ; Khoei, Amir Reza (Supervisor)
    In the limit case of incompressibility, the displacement-based finite element methods are not capable of finding the solutions with adequate accuracy. Moreover, discontinuities in displacement field or strain field which exist in the interior of the elements should be dealt with appropriately. The u/p mixed formulation provides a suitable context for modeling the incompressible problems. It is capable of solving general problems in which there exist geometrical or material nonlinearities. In the case of employing the eXtended Finite Element Method (XFEM), uniform meshes can be used for problems with discontinuities and in fact the discontinuities can be decoupled from the mesh. In this... 

    Multisclae Modeling Of Regular Collagenous Soft Tissues

    , Ph.D. Dissertation Sharif University of Technology Fallah, Ali (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firozbakhsh, Keikhosro (Supervisor) ; Mohammadi Aghdam, Mohammad (Co-Supervisor)
    In this study, mechanical behavior of soft tissue is investigated considering its hierarchical structure. The elastic and viscoelastic behavior of tissue is investigated using multisclae methods. To this end, the tissue is considered as nonlinear composite material consists of non fibrillar matrix reinforced by the collagen fibers. A physically motivated constitutive model is proposed to predict the tisues constitutents behavior. The numerical homogenization is preforemd with the aid of the ABAQUS software and the UMAT subroutine. The results of the presented study is validated with the available experimental results in the literature. Results show that the increasing the loading rate can... 

    Mechanical Analysis of the Influence of Surgical Glues on the State of the Aorta after Cardiovascular Surgery

    , M.Sc. Thesis Sharif University of Technology Nejadsadeghi, Nima (Author) ;
    With the emergence of a variety of surgical glues in the market and utilizing them in recent years, nowadays, based on the post-surgery studies, it has become transparent that there are additional factors, such as the long-term effect of surgical glues on tissue, to consider beyond the sealants ability to act as a mechanical barrier or a means to buttress friable tissue so that it can hold sutures. Mechanical properties of the surgical glues have especially a significant role in the applications that the tissue undergoes cyclic loading (such as arteries’ tissues). A mismatch between the mechanical properties of the tissue and the sealant can result in the remodeling of the artery that may... 

    A visco-hyperelastic constitutive model for rubber-like materials: A rate-dependent relaxation time scheme

    , Article International Journal of Engineering Science ; Volume 79, June , 2014 , Pages 44-58 ; ISSN: 00207225 Khajehsaeid, H ; Arghavani, J ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
    A three-dimensional visco-hyperelastic constitutive model is developed to describe the rate-dependent behavior of rubber-like materials at large deformations. The model encompasses a hyperelastic part which uses the "Exp-Ln" strain energy function to characterize the equilibrium response and a viscous part capturing the rate sensitivity using a hereditary integral form which links the overstress to the history of stored strain energy. A physically consistent rate-dependent relaxation time scheme is introduced which reduces the number of required material parameters and also facilitates the calibration process. The proposed model is verified using various uniaxial experimental data in... 

    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) Khajehsaeid, H ; Baghani, M ; Naghdabadi, R ; Sharif University of Technology
    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...