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    Hydraulic Crack Propagation in Heterogeneous Reservoir Based on Extended Multi-Scale Finite Element Method

    , Ph.D. Dissertation Sharif University of Technology Hajiabadi, Mohammad Reza (Author) ; Khoei, Amir Reza (Supervisor)
    Many natural and engineering materials have a heterogeneous structure at a certain level of observation. These materials are often referred to as composite materials or multi-phase materials or heterogeneous materials. It has been widely recognized that many macroscopic phenomena originate from the mechanics of the microstructural constituents, such as inclusions, cracks, voids, etc. The size, shape, spatial distribution, volume fraction and properties of the microstructural constituents have a significant impact on the behavior of the material observed at the macroscale. The nature of hydrocarbon reservoirs as multi-phase porous media are known for heterogeneous media at various multiple... 

    A Novel Moving Magnetic Levitation Device for 3D Manipulation of Small Objects

    , M.Sc. Thesis Sharif University of Technology Molavian Jazi, Mehdi (Author) ; Vossoughi, Gholamreza (Supervisor)
    Magnetic levitation is an appropriate solution for noncontact 3D manipulation. Workspace of the previously proposed maglev systems is confined to a relatively small cube, which severely limits the application of this technology. In addition, most of the previously given mechanisms require the design and application of a subsystem in order to unify their magnetic field. In this paper, a moving magnet is proposed which results in a horizontally extendable workspace; moreover, the field unifying section is not needed since one electromagnet only is used. Further, details of the mechanism and finite element based design procedure of the magnet are presented. Dynamic equations of the system... 

    Thermal Local Buckling of Metal Truncated Conical Shells with Composite Rainforced Layers by Finite Element Method

    , M.Sc. Thesis Sharif University of Technology Merati, Ali (Author) ; Hosseini Kordkheili, Ali (Supervisor)
    In this study, the thermal buckling behavior of thin metal liner reinforced by composite shell in present of the initial imperfection is investigated. For this purpose, the Ryzener – Myndlyn shear-deformation theory & the virtual work method are used to extract equilibrium equations. In this work, the conical shell with c-c, s-s, c-f boundary conditions has been studied. The outer layer of reinforced composite is exposed to constant ambient temperature and iner layer is exposed to heat. Metal liner and reinforced composite shell are merged with together. In other words, the degrees of freedom at each node for both shells are assumed to be equal. Solution method is finite element method using... 

    XFEM Analysis of Non-Linear Thermomechanical Problems

    , M.Sc. Thesis Sharif University of Technology Alipour, Kamran (Author) ; Kouchakzadeh, Mohammad Ali (Supervisor)
    In this thesis a nonlinear thermomechanical model based on Lagrangian-extended finite element method is proposed to simulate discontinuities under thermal and mechanical loads. At first, a geometrically nonlinear model is presented for large deformation problems and then the model is completed by considering thermomechanical aspects. In extended finite element method, different enrichment functions are stated and also using analytical methods, a new set of functions are introduced to enrich the temperature filed around biomaterial crack tips. For numerical simulations, an object oriented code is created in C++. The results of numerical simulations are verified by the use of ABAQUS  

    Application of Isogeometric Analysis in Determining Stress Distribution at the Tip of a Crack

    , M.Sc. Thesis Sharif University of Technology Zandinia, Meysam (Author) ; Jahanshahi, Mohsen (Supervisor)
    Isogeometric Analysis is one of the new methods for solving partial differential Equations which has special advantages compared to conventional methods such as the finite Element method. Some of these benefits can be used to approximate the geometry and solving the Equations governing the behavior of materials. Calculating the stress intensity factor at the tip of the Crack using classical method such as finite element method is done as well as IGA and gives Acceptable Results in linear range. Studying how to calculate these coefficients in combination with Isogeometric analysis method and comparing results with FEM due to novelty of the approach can have considerable importance for... 

    Polygonal Finite Element Modeling of Fracture Mechanism and Crack Propagation

    , M.Sc. Thesis Sharif University of Technology Yasbolaghi, Reza (Author) ; Khoei, Amir Reza (Supervisor)
    Fracture is one of the most important engineering problems, and the lack of knowledge about this phenomenon will result in loss of life and property. Before the computer age, fracture mechanics has been studied by many analytical mechanics researchers; and after that, lots of attempts have been done to accurately model this phenomenon.
    Finite element method, one of the best methods in Computational Mechanics, is common in computational fracture mechanics. Polygonal finite element is a new concept which has been recently applied in finite element analysis. This research utilized this concept in com-putational fracture mechanics. In another word, the crack discontinuity and crack tip... 

    Chatter Phenomena Prediction in Two-dimensional Milling Process from Chip Formation by Using Finite Element Method

    , M.Sc. Thesis Sharif University of Technology Tavassoli, Meysam (Author) ; Movahhedy, Mohammad Reza (Supervisor)
    Chattering in cutting process is one of the destructive phenomena in machining, which results in ripple of workpiece surfaces. In this phenomenon, the displacement of the tool tip moves towards instability and the tool vibration continues. Eventually, the tool jumps or breaks out with relatively large shear forces, which leads to a reduction in the rate of production and machining. Since machining processes are very widespread, phenomenological studies of chatter have progressed in the field of modeling and empirical experiments. Research in the field of modeling is mainly intended to examine the dynamics of the tool in two ways: analytic and finite element. In these methods, there are... 

    Prediction and Compensation of Intraoperative Brain Shift Using Biomechanical Modeling

    , M.Sc. Thesis Sharif University of Technology Pasandideh Pour, Javad (Author) ; Farahmand, Farzam (Supervisor)
    The human brain is the most sensitive and important human organ and surgery must be done with high precision and without risk. During surgery, brain tissue deform continuously due to gravity, out of the cerebrospinal fluid and the changing pressure of the cerebrospinal fluid and the surgical maneuvers. Because the surgeon has no direct view on brain internal, the ways to solve this problem is to pay attention. This method makes it possible to the surgeon see in the brain and the brain tissue deformation. This thesis method is based on biomechanical modeling. After forming finite element model from the pre-operative MRI, brain surface and volume datasets during surgery as a load, apply to the... 

    Prediction of Cooling Rate and Thermal Stresses during Cooling on Run-Out Table in Hot Sheet Rolling Process

    , M.Sc. Thesis Sharif University of Technology Hasannasab, Malihe (Author) ; Serajzadeh, Siamak (Supervisor)
    Control of the product manufacturing and evaluating its behavior during deformation is one of the most important issues in hot deformation, especially hot rolling. One of the factors affecting on quality of hot rolled steel strips is the flatness after run-out table cooling.Distortion in a steel strip results from non-uniform temperature profile as the strip cools to room temperature. Increase in the rolling velocity and subsequently the cooling rate affect thermal stresses. In this study a mathematical model for prediction of austenite- ferrite phase transition kinetics and thermo-mechanical stresses on the run-out table after hot rolling was developed for low carbon ferrite steels.... 

    Prediction of Temperature Distribution and Flow Behavior in Hot Extrusion of AA6061-%5 SiCp Composite

    , M.Sc. Thesis Sharif University of Technology Mahdiakhgar, Jafar (Author) ; Serajzadeh, Siamak (Supervisor)
    In this study, hot extrusion of AA6061-%5 SiCp composite has been predicted and flow behavior of material during deformation process has been investigated. At the first step, hot compression tests have been carried out to obtain the flow behavior of the material at different temperatures and strain rates. In the next step, an FE-based temperature-displacement coupled model by employing ABAQUS software has been proposed in order to solve the energy and heat transfer equations and to determine the required energy and force for the extrusion process. Experimental investigations have also been performed to verify the proposed model. Comparison between the results from the model and the... 

    Prediction of Temperature and Velocity Fields in Friction Stir Welding of 7xxx AA

    , M.Sc. Thesis Sharif University of Technology Rezaei Farkoosh, Amir (Author) ; Serajzadeh, Siamak (Supervisor)
    In this work a mathematical model has been developed to predict large deformation of work piece in friction stir welding process. Commercially finite element package; ABAQUS is used to solve the governing equations while an elasto-viscoplastic materials behavior is utilized in the model. The model is capable of considering the effects of process parameters such as welding speed and tool geometry on various aspects of the process including temperature and stress distribution within the work piece as well as tool, and velocity and strain fields with in the work piece. Experimental works have been carried out to assess the accuracy of the model and also to determine the effects of various... 

    Prediction of Deformation Field And Temperature Distribution in Extrusion of Composite AA6061-10%SiC(p)

    , M.Sc. Thesis Sharif University of Technology Goodarzi Hosseinabadi, Hossein (Author) ; Serajzadeh, Siamak (Supervisor)
    In this research, the extrusion of composite AA6061-SiC has been investigated and the temperature distribution field and energy required for the process has been predicted. In this regard, to predict the flow behavior of material, hot extrusion tests conformed at various ranges of temperatures and strain rates. Afterward, the finite element method coupled with the upper bound technique to calculate the temperature distribution and energy required during hot extrusion. This model has also used for wire drawing and cold extrusion processes. The present model is capable of considering various process parameters such as speed of extrusion, reduction and the initial billet/die temperature on the... 

    Prediction of Machining Chatter Based on 2 Dimensional FE Dynamic Modeling of Chip Formation

    , M.Sc. Thesis Sharif University of Technology Haj Mohammadi, Mohammad Saleh (Author) ; Movahhedi, Mohammad Reza (Supervisor)
    In machining processes, chip formation is one of the most important methods to obtain the final shape of a work-piece. Improving the machining processes leads to the increase in the material removal rate (MRR) and reduction of high economical costs. Vibration is an undesirable phenomenon in machining processes because it results in reduction of material removal rate (MRR), poor surface finish and increased tool wear. Among various types of vibration, self-excited vibration or chatter is the most important one. It is obvious from previous investigations that for prediction of machine tools vibration, many simplifications were assumed while the linear and non-linear effects are not considered... 

    Prediction of Sand Production in Extraction Wells Using Numerical Simulation Based on Finite Element Method

    , M.Sc. Thesis Sharif University of Technology Fetrati, Majid (Author) ; Pak, Ali (Supervisor)
    Sand production is a phenomenon of producing solid particles together with the reservoir fluid. Material degradation is a key process leading to sanding. Drilling operation, cyclic effects of shut-in and start-up, operational conditions and reservoir pressure depletion may gradually lead to sandstone degradation around perforations and boreholes. Sand production is a major issue and has an adverse impact on production cost that gas and petroleum industry have faced for decades. Corrosion of the pipelines and surface facilities, sand-oil separation cost, repeated shut-in and clean-up of the wellbore are some of the examples. On the other hand, a controlled sanding could be beneficial in... 

    Prediction of Stable Fatigue Crack Growth in Laser Peened 316L SS with Variable Beam Diameter and Pre-crack Length Using Artificial Neural Network

    , M.Sc. Thesis Sharif University of Technology Ariyanfar, Alireza (Author) ; Farrahi, Gholamhossein (Supervisor)
    Processing an alloy can enhance its mechanical properties. Based on repeated radiation of high-power pulsed laser beam, laser shock peening (LSP) is one way to impart favorable residual stress in an alloy and to enhance its damage tolerance property. Study of overlapping LSP is possible through the simulation of limited laser shots. Still, its computational cost is higher than that of a single shot. This research, primarily, is aimed at improving a methodology for reduction of computations in the study of an overlapping LSP and its impacts on fatigue crack growth. Addressing research gaps by utilizing the methodology is the secondary goal. The methodology consists of plastic strain... 

    Prediction of Strain, Stress, and Microstructure in Sever Plastic Deformation of Equal Channel Angular Extrusion

    , Ph.D. Dissertation Sharif University of Technology Narooei, Keivan (Author) ; Karimi Taheri, Ali (Supervisor)
    Sever plastic deformation can be used for decreasing the grain size and increasing the mechanical properties. In this method a square or circular cross section specimen is passed from two intersecting channel with equal cross section. Thereby, a large plastic strain without change of cross section is produced in the specimen. This large strain is the main reason for the interest of researchers in many fields. In the experimental research fields, researchers can study the response of material in the large plastic strain range, investigation of stage III of hardening and after it, change of microstructure to submicron and Nano, and increase of strength simultaneously with preserving of... 

    Parallel Computing of Black Oil Model in Porous Media in 2-D Unstructured Grid Using Control Volume Finite Element Based

    , M.Sc. Thesis Sharif University of Technology Riazat, Mahdi (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)

    Prediction of Strain Field in Strip and Work-Roll During Cold Rolling of a Low Carbon Steel

    , M.Sc. Thesis Sharif University of Technology Koohbor, Behrad (Author) ; Serajzadeh, Siamak (Supervisor)
    In this research, distribution of stress, strain and temperature fields in the strip and workroll were determined during steady state cold rolling process. To do this, first an initial guess based on the approach proposed by Hill for the velocity field was taken and accordingly, the real velocity distribution and then the strain rate and stress fields in the strip were calculated. Then, using the obtained stress and strain rate fields, the deformation power was determined and used as a boundary condition for solving the thermal behavior of the strip. By considering the Streamline Upwind Petrov-Galerkin method and solving the finite element relations, the temperature distribution within the... 

    Health Monitoring and Damage Detection of Marine Structure

    , M.Sc. Thesis Sharif University of Technology Tahmasebi Boldaji, Ebrahim (Author) ; Seif, Mohammad Saeed (Supervisor) ; Behzad, Mehdi (Supervisor)
    Structural health monitoring is a process that aims to provide accurate and immediate information about the condition and performance of the structure. Processed is a very important eld in the eld of civil, aerospace and marine engineering, because the use of structural health monitoring allows us to increase human and environmental safety while reducing economic damage. e main component of the health monitoring process is the real-time reconstruction of displacement and three-dimensional stress in the structure using a network of strain gauges and other sensors. e inverse nite element method is a relatively new method and stress measurement that has been shown to be fast and accurate for... 

    Structural Health Monitoring of Elbows, Tee Junctions, Composite to Composite and Composite to Metal Joints for Pressurized Tubular Structures Using Strain and MPCA Algorithm

    , M.Sc. Thesis Sharif University of Technology Robatjazi, Hassan (Author) ; Abedian, Ali (Supervisor)
    In this thesis, due to the importance of pressurized structures, method or methods that can be used to monitor the health of important structures, such as pressurized pipes (gas transmission and distribution lines or hydraulic lines), are considered. A key point in monitoring such structures is to ensure the function of pipes, elbows, Tee junctions, composite to composite and composite to metal joints. The topic that will be discussed more than anything else here is to monitor the health of the structure in the presence of cracks in some layers of composite pieces. In fact, it must be recognized before cracking occurs in all layers of composite pieces and causing overall damage to the...