Search for: large-deformation
0.009 seconds
Total 110 records

    Elastic-plastic modeling of kinematic hardening materials based on F = FeFp decomposition and the logarithmic strain tensor

    , Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 1 , 2004 , Pages 337-342 ; 0791841731 (ISBN); 9780791841730 (ISBN) Ghavam, K ; Naghdabadi, R ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    In this paper, based on the multiplicative decomposition of the deformation gradient tensor an elastic-plastic modeling of kinematic hardening materials is introduced. In this model, the elastic constitutive equation as well as the flow rule and hardening equation are expressed in terms of the corotational rate of the elastic and plastic logarithmic strains. As an application, the simple shear problem is solved and the stress components are plotted versus shear displacement for a kinematic hardening material  

    Modeling of hot isostatic pressing of metal powder with temperature–dependent cap plasticity model

    , Article International Journal of Material Forming ; Volume 6, Issue 3 , September , 2013 , PP. 363-376 Khoei, A. R. (Amir Reza) ; Molaeinia, Z ; Keshavarz, Sh ; Sharif University of Technology
    In this paper, the coupled thermo–mechanical simulation of hot isostatic pressing (HIPing) is presented for metal powders during densification process. The densification of powder is assumed to occur due to plastic hardening of metal particles. The constitutive model developed is used to describe the nonlinear behavior of metal powder. The numerical modeling of hot powder compaction simulation is performed based on the large deformation formulation, powder plasticity behavior, and frictional contact algorithm. A Lagrangian finite element formulation is employed for the large powder deformations. A modified cap plasticity model considering temperature effects is used in numerical simulation... 

    An efficient thermo-mechanical contact algorithm for modeling contact-impact problems

    , Article Asian Journal of Civil Engineering ; Volume 16, Issue 5 , 2015 , Pages 681-708 ; 15630854 (ISSN) Khoei, A. R ; Saffar, H ; Eghbalian, M ; Sharif University of Technology
    Building and Housing Research Center (BHRC)  2015
    In this paper, the thermo-dynamic analysis of contact-impact problem is presented in the large deformation of hyperelastic material based on the Taylor-Galerkin method. The technique is applied for the time domain discretization of thermo-dynamic governing equations in the advection-diffusion problems. The impenetrability condition and frictional contact constraints are fulfilled by imposing the augmented-Lagrange technique for nonmatching contact surfaces. The Taylor-Galerkin method is employed to describe the advection-diffusion effect in the numerical solution of parabolic equation of unsteady heat transfer condition. The effect of temperature is taken into account in the stress field by... 

    A large plasticity deformation of unsaturated soil for 3d dynamic analysis of lower San-Fernando dam

    , Article Asian Journal of Civil Engineering ; Volume 12, Issue 1 , 2010 , Pages 1-25 ; 15630854 (ISSN) Khoei, A. R ; Anahid, M ; Zarinfar, M ; Ashouri, M ; Pak, A ; Sharif University of Technology
    In this paper, a large plasticity deformation finite element modeling is presented for three-dimensional dynamic analysis of unsaturated soils with special reference to the failure of lower San Fernando dam under the 1971 earthquake. The finite element method is applied to the governing equations for the spatial discretization, followed by a generalized Newmark scheme used for the time domain discretization. Time stepping scheme is used in the fully implicit coupled method and a direct solution procedure is used for the coupled equation system. The framework of generalized plasticity is presented and the numerical results of unsaturated soils are demonstrated based on the Pastor-Zienkiewicz... 

    An arbitrary lagrangian-eulerian finite element method for cone-cap plasticity; application to powder compaction simulation

    , Article European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS 2004, Jyvaskyla, 24 July 2004 through 28 July 2004 ; 2004 Khoei, A. R ; Anahid, M ; Azami, A. R ; Azizi, S ; Sharif University of Technology
    The compaction forming of metal powder is a process involving large deformations, large strain, non-linear material behavior and friction. Consequently, the numerical analysis of such a highly non-linear process is a formidable computational problem. In this paper, an ALE technique is presented based on a generalized cap plasticity model in simulation of powder forming processes. In ALE formulation, the reference configuration is used for describing the motion, instead of material configuration in Lagrangian, and spatial configuration in Eulerian formulation. This formulation introduces some convective terms in the finite element equations and consists of two phases. Each time step is... 

    A new computational algorithm for contact friction modeling of large plastic deformation in powder compaction processes

    , Article International Journal of Solids and Structures ; Volume 46, Issue 2 , 2009 , Pages 287-310 ; 00207683 (ISSN) Khoei, A. R ; Biabanaki, S. O. R ; Vafa, A. R ; Yadegaran, I ; Keshavarz, Sh ; Sharif University of Technology
    In this paper, the large deformation frictional contact of powder forming process is modeled based on a new computational algorithm by imposing the contact constraints and modifying the contact properties of frictional slip. A simple and efficient numerical algorithm is presented for imposing the contact constraints and frictional contact properties based on the node-to-surface contact technique to simulate the large deformation contact problem in the compaction process of powder. The Coulomb friction law is used to simulate the friction between the rigid punch and the workpiece by the use of penalty approach. A double-surface cap plasticity model is employed together with the nonlinear... 

    A thermodynamically consistent electro-chemo-mechanical theory for modeling axonal swelling

    , Article Journal of the Mechanics and Physics of Solids ; Volume 145 , 2020 Dehghany, M ; Naghdabadi, R ; Sohrabpour, S ; Li, Y ; Hu, Y ; Sharif University of Technology
    Elsevier Ltd  2020
    In the present study, for the first time, a thermodynamically consistent large deformation theory is developed to model the multi physics problem of axonal swelling which is the hallmark of most of the brain diseases. To this end, the relevant axonal compartments are first explained and the corresponding model parts are introduced. Next, the problem is formulated as an open thermodynamic system and the corresponding constitutive and evolution equations are extracted utilizing the balance laws. Here, a multiplicative decomposition of the deformation gradient is used to capture the active behavior of the axonal actin cortex. Specific free energy functions are given for the model parts to... 

    Extended Finite Element Modeling of Large Deformation with Approprate Blending Elements

    , M.Sc. Thesis Sharif University of Technology Ehsaniardestani, Hedieh (Author) ; Khoei, Amir Reza (Supervisor)
    In a classical finite element approach, interfaces are tracked and meshed. This mesh strategy introduces mesh distortions and difficulties to mesh the possibly complex interface shape. The Partition of Unity Method (PUM) alleviates these difficulties by allowing the discontinuities to be mesh-independent. This thesis concentrates on the blending elements in the eXtended Finite Element Method (XFEM).
    The XFEM method enables local enrichments of approximation spaces. The standard finite elements are used in the major part of the domain and enriched elements are employed where special solution properties such as discontinuities and singularities shall be captured. In the extended finite... 

    Elastic-plastic modeling of the hardening materials based on an Eulerian strain tensor and a proper corotational rate

    , Article 2005 ASME Pressure Vessels and Piping Conference, PVP2005, Denver, CO, 17 July 2005 through 21 July 2005 ; Volume 2 , 2005 , Pages 201-206 ; 0277027X (ISSN) Naghdabadi, R ; Ghavam, K ; Sharif University of Technology
    In this paper a model for analyzing elastic-plastic kinematic hardening materials is introduced, based on the additive decomposition of the corotational rate of an Eulerian strain tensor In this model, the elastic constitutive equation as well as the flow rule and the hardening equation is expressed in terms of the elastic and plastic parts of the corotational rate of the mentioned Eulerian strain tensor and its conjugate stress tensor. In the flow rule, the plastic part of the corotational rate of the Eulerian strain tensor is related to the difference of the deviatoric part of the conjugate stress and the back stress tensors. A proportionality factor is used in this flow rule which must be... 

    Periodicity in the response of nonlinear plate, under moving mass

    , Article Thin-Walled Structures ; Volume 40, Issue 3 , 2002 , Pages 283-295 ; 02638231 (ISSN) Shadnam, M. R ; Rahimzadeh Rofooei, F ; Mofid, M ; Mehri, B ; Sharif University of Technology
    The dynamics of nonlinear thin plates under influence of relatively heavy moving masses is considered. By expansion of the solution as a series of mode functions, the governing equations of motion are reduced to an ordinary differential equation for time development of vibration amplitude, which is Duffing's oscillator with time varying coefficients. Through the application of Banach's fixed-point theorem, the periodic solutions are predicted. The method presented in this paper is general so that the response of plate to moving force systems can also be considered. © 2002 Published by Elsevier Science Ltd  

    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... 

    Constitutive Modeling for Transient Swelling Behavior of Polymeric Hydrogel with Large Deformations

    , Ph.D. Dissertation Sharif University of Technology Mazaheri, Hashem (Author) ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor) ; Baghani, Mostafa (Co-Advisor)
    In this work, the mechanical behavior of smart hydrogels is studied for temperature sensitive and, pH and temperature sensitive ones. First, an equilibrium model is presented for the temperature sensitive hydrogles which is continuous and numerically stable especially in the vicinity of the phase transition temperature. The model results are validated through comparing them with the experimental data available in the literature. The model results are in good agreement with those of experiments especially for hydrogels with high cross-linking density. Then, the model is implemented in a finite element framework by which some homogeneous and inhomogeneous problems are numerically solved.... 

    Hierarchical Multiscale Modeling in Large and Plastic Deformations

    , M.Sc. Thesis Sharif University of Technology Sarkari Khorrami, Mohammad (Author) ; Khoei, Amir Reza (Supervisor)
    In this study, the hierarchical multiscale method is presented to model macro-scale materials with considering large and plastic deformations. Since the classic methods such as continuum mechanics were unable to model defects such as dislocations, voids, and etc. at nano scale. Also, the molecular dynamics methods have high computational costs; hence, recearchers try to develop multiscale methods in order to utilize them. Multiscale modeling in which two scales are considered and some information be transferred from fine scale to coarse scale. In this work, the coarse scale is modeled by finite element method (FEM) and the fine scale is analysed by molecular dynamics (MD). In fact, two... 

    Modeling and Control a Flexible Large Deformation Beam Actuated by Some SMA Actuators

    , Ph.D. Dissertation Sharif University of Technology Zakerzadeh, Mohammad Reza (Author) ; Sayyaadi, Hassan (Supervisor) ; Vossoughi, Gholamreza (Co-Advisor)
    Smart structures are the combination of structure, smart material, electronics and control technologies. Changing the shape of the structures by smart actuators is one of the most important applications of Shape Memory Alloy (SMA) in these structures. Having used these actuators, we can effortlessly and continuously deform and reshape the structures. Nevertheless, working with SMA actuated smart structures has one obvious drawback that is their hysteretic and nonlinear behavior, making modeling and control of these structures complex. Another difficulty in the control of smart structures is their great sensitivity to the actuating force that reduces the controllability of these structures.... 

    Numerical Simulation of Large Deformations in Impact to Composite Concrete-Steel Structures Using Coupled Damage-plasticity Model

    , Ph.D. Dissertation Sharif University of Technology Eslahi, Reza (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Concrete has long been considered by engineers as one of the most used constructional materials. Therefore, recognition of mechanical behavior of concrete materials is of particular importance. So, extensive studies have been undertaken to understand and analyze its behavior under different loading conditions. Based on these studies, many models for describing the behavior of concrete are presented. Of these, many models are based on the combination of plastic theory and damage mechanics, and by using them, significant success has been achieved in the correct modeling of concrete materials. On the other hand, one of the important loading conditions encountered by concrete structures is in... 

    Constitutive Modeling and Numerical Investigation of Damage and Healing Phenomena in Self-healing Polymers at Finite Deformation

    , Ph.D. Dissertation Sharif University of Technology Shahsavari, Hamid (Author) ; Naghdababdi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
    In this thesis, employing the definition of an effective configuration in the Continuum Damage-Healing Mechanics (CDHM), mechanical responses of elf-healing materials are investigated. Firstly, a constitutive model is proposed to investigate damage and healing phenomena in concrete materials. In order to consider the different behavior of concretes in tension and compression, a spectral decomposition of the stress is utilized. In addition, employing the Clausius-Duhem inequality and considering the irreversible thermodynamics, conjugate forces of the damage and healing are expressed. The Gibbs potential energy is decomposed into three parts; elastic, damage and healing. In the next section,... 

    Development of consistent Thermomechanical ALE Formulation with Application to Simulation of Machining

    , Ph.D. Dissertation Sharif University of Technology Tadi Beni, Yaghob (Author) ; Movahhedy, Mohammd Reza (Supervisor) ; Farrahi, Hossein (Supervisor)
    Accurate description of kinematics of continuum mechanics is essential in simulation of large deformation problems in solid mechanics. From the numerical viewpoint, two main approaches have been used for such description; the Lagrangian approach and the Eulerian approach. However, each of these approaches suffer from shortcomings which hinders their application in large deformation problems. A more general approach called the Arbitrary Lagrangian-Eulerian method (ALE) provides an opportunity to exploit the advantages of both Lagrangian and Eulerian approach, while avoiding their shortcoming. In an ALE analysis, the FE mesh is neither attached to the material nor fixed in space, necessarily.... 

    Contact Friction Modeling Using a new Node-to-Surface Algorithm

    , M.Sc. Thesis Sharif University of Technology Vafa, Alireza (Author) ; Khoei, Amir Reza (Supervisor)
    The present research illustrate the finite element modeling of contact between solid bodies, with a special emphasis on the imposing the contact constraints and modification of contact properties on surface in the case of frictional slip. A new approach for both two-dimensional and three-dimensional formulation of contact constraint that allows for a simple and unified treatment of all potential contact scenarios in the presence of large deformations in static case, is presented. The most important outstanding issue in this approach is symmetrical contact stiffness matrix which reduces computational efforts. Based on the observation of numerical results and comparison by experimental models,... 

    Real Time Simulation of Grasping Procedure of Large Internal Organs during Laparoscopic Surgery

    , M.Sc. Thesis Sharif University of Technology Dehghani Ashkezari, Hossein (Author) ; Farahmand, Farzam (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
    Surgical simulation systems facilitate a safe and efficient training process by providing a virtual environment in which the trainee can repeat the surgical procedure unlimitedly at different situations. The present study attempted to provide a real time simulation for the grasping procedure of a large internal organ during laparoscopic surgery. A mass-spring-damper model was employed to simulate the nonlinear viscoelastic large deformations of spleen tissue interacting with a triple-jaw large organ grasper. A novel collision detection algorithm was designed and implemented to determine the contact points between the tissue and the grasper jaws. The boundary conditions imposed at the contact... 

    Multiscale Multiphysics Analysis of Deformable Microwave Metasurfaces Under Large Deformations and Prototype Fabrication

    , Ph.D. Dissertation Sharif University of Technology Karimi Mahabadi, Rayehe (Author) ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor) ; Goudarzi, Taha (Co-Supervisor)
    Electromagnetic metamaterials are designed artificial materials with sub-wavelength resonant inclusions. They can exhibit extraordinary properties such as negative permittivity, negative permeability, and anomalous reflection/refraction. Metasurfaces are 2D counterparts of metamaterials. Here, we proposed a framework for the multiscale multiphysics analysis of deformable metasurfaces. Nonlinear mechanical analysis (Geometry and material behavior), periodic boundary conditions, homogenization, multiscale analysis, and electromagnetic analysis are implemented in this framework. Benefiting from the framework, we proposed a multifunctional hyperelastic structured surface that can generate...