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elasticity
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Investigation of Local Buckling in Marine Pipelines under External Pressure
, M.Sc. Thesis Sharif University of Technology ; Fallah Rajabzadeh, Famida (Supervisor) ; Seef, Mohammad Saeed (Co-Advisor)
Abstract
To keep up with the growing demands for energy, the oil and gas industry ventures into deeper waters. This increases complexity of offshore projects. Part of this complexity is due to the resistance of a pipeline against local buckling collapse due to external pressure that is more significant in higher pipe laying depth and consequently higher external pressure. Pipeline response to external pressure is an important factor in design of marine pipeline.Local buckling of a pipeline is the buckling behaviour within the pipeline cross section. Other types of buckling behaviour such as upheaval and lateralbuckling are not in the scope of this thesis.In this thesis, the installing pipeline is...
Experimental and Analytical Investigation of Elastic-Plastic Behavior of Glass Fiber Reinforced Polymer Composites
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Asghari, Mohsen (Supervisor)
Abstract
In this thesis, we aim to study the elastic-plastic behavior of short fiber reinforced composites experimentally and analytically. The experimental investigation is applied to glass fiber-polypropylene composites (PP/GF). The samples are produced by injection process with maximum temperature of 190C. Fibers are randomly oriented in this procedure of fabrication. The samples are tested in tension, and the mechanical strength is measured by changes in fiber content. The Young's modulus is also investigated in these experiments.Also in this thesis, an analytical model for calculation of Young’s modulus of fiber reinforced composite materials is proposed. In this analysis a displacement field is...
DNA Molecule in Confined Geometries
, Ph.D. Dissertation Sharif University of Technology ; Ejtehadi, Mohammad Reza (Supervisor)
Abstract
DNA molecule is one of the most important macromolecules in cell, which carries genetic information for life. DNA is often in confined geometries, such as, packaging in cell and DNA-protein interactions. While DNA is nearly a stiff polymer, its elastic behaviour plays a crucial role on its functionalities.Therefore, investigating the elastic and mechanical properties of DNA is really important.The elastic behaviour of a long and free DNA can be predicted very accurately by ”worm-like chain“ (WLC) model. In WLC model, DNA is assumed as a elastic rod with harmonic potential of local bending and twist.Many structural properties of DNA have been ignored in this model. But in recent years, by...
Equilibrium States of Nano scaled DNA-loops in Different Elastic Models
, M.Sc. Thesis Sharif University of Technology ; Ejtehadi, Mohammad Reza (Supervisor)
Abstract
DNA cyclization mechanism, has an important role in many biological processes such as gene regulation, DNA replication and recombination. In addition there are DNA-loops in Bacteria an around the Histones in Chromosomes in scale of 5-100 nm. We need to a appropriate model to study about bending and loop formationin in this important molecule which is able to describe elasticity properties of DNA.One of the most successful models, to describe the physical behaviour of a long DNA molecule, is the elastic rod model. In this model, DNA is considered as a ixable rod that its bending energy is isotropic. Asymmetric elastic rod model is another model to describe elasticity properties of DNA....
Production of Porous Ti and Ti-26Nb-1Si Via Powder Metallurgy Method andInvestigation Some of Their Physical and Mechanical Properties
, M.Sc. Thesis Sharif University of Technology ; Abachi, Parvin (Supervisor) ; Ziaei Moayyed, Ali Akbar (Supervisor)
Abstract
Porous titanium and titanium alloys products are proper to use as implants which because of good properties such as high corrosion resistance, good biocompatibility, high strength to weight ratio and low elastic modulus. Porosity induces a decrease in elastic modulus and an increase of bioactivity. In present work, porous specimens of pure titanium and Ti-26Nb-1Si alloy were produced via conventional powder metallurgy route by applying low pressure. The influence of TiH2 Powder addition on some physical and mechanical properties of samples was investigated. The amount of TiH2 powder was used in the range of 0-40 weight percent. The powders were firstly mixed for 3 hours and then compacted...
Active Control of beams/Plates on Elastic Foundation under the Effect of Random Loadings
, Ph.D. Dissertation Sharif University of Technology ; Khalu, Alireza (Supervisor)
Abstract
The dynamic behavior of beams and rectangular plates on elastic foundation under the effect of deterministic and random excitations is investigated in the cases of controlled and uncontrolled systems. The equations of motion are developed in each case in both deterministic and stochastic states. In all cases, the eigenfunction expansion method is used to solve the obtained equations.Moreover, the classical linear optimal control algorithm with displacement-velocity is considered to achieve the required control efforts. The applied dynamic excitations are supposed as moving loads, moving masses accompanied with random lateral excitations of supports and the uniform distributed linear loading...
Estimating Demand Function for Antihypertensives in Iran
, M.Sc. Thesis Sharif University of Technology ; Fatemi Ardestati, Farshad (Supervisor)
Abstract
The essential need for allocation of appropriate resources to the wellbeing and medication plans in a society can be understood from the fundamental impact of health on the performance of the labor force of the society, which can lead to significant increase in the economic growth rate. The high costs associated with research and development make pharmaceutical industry owners to be very vigilant about their investment on new drugs and expected sales. The purpose of this study is to evaluate current Iranian market for a part of Antihypertensive drugs and to estimate the demand for this group of drugs. The method used to obtain the estimation involved multi-stage budgeting, which benefits...
Estimation of the Price Elasticity of Gasoline Smuggling Demand in Iran
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
This study investigates the price elasticity of gasoline smuggling demand in Iran. For this purpose, a panel data of monthly gasoline consumption has been used that contains data for 160 regions of distribution for Iran's Oil Production Company between 2005 and 2014. The results of estimating the monthly elasticity of gasoline smuggling demand in each region show a significant impact of the gasoline price differential between Iran and its neighboring countries, as well as the distance of each region with the neighboring countries on the demand. The results of this study show that whenever gasoline prices increase inside the country, the inclination to smuggling has been decreased due to a...
Effect of Soil-Structure Interaction on Practical Design of Ordinary Buildings Based on Iranian Seismic Code
, M.Sc. Thesis Sharif University of Technology ; Ghannad, Mohammad Ali (Supervisor)
Abstract
In the last few decades Seismic Regulations attitude’s has been undergone significant changes from various aspects. One of these aspects is entering new topics based on the latest scientific achievements. Soil-Structure Interaction terms was from such issues which had found their ways into Seismic codes as an optional effective factor. In recent years, Based on this new attitude and Scientific achievements, Soil-Structure Interaction terms entrance into Iranian seismic code (2800 Standard), is also has been studied. Naturally, applying these criteria will impact on the design and performance of structures, because of reducing effect of soil structure interaction on decreasing base shear...
Assessment of Soil-Structure Interaction Regulations in ASCE/SEI 7-10 Standard
, M.Sc. Thesis Sharif University of Technology ; Ghannad, Mohammad Ali (Supervisor)
Abstract
Usually the structures are designed based on the fixed-base assumption; however this assumption is not always correct and the bed flexibility should be considered. This effect which is called soil-structure interaction, change the response of structure on both elastic and inelastic behavior. In the regulations for the design of structures on flexible base, generallysoil-structure system is replaced with an equivalent fixed base structure; in the way that the design force of soil-structure system with reasonable accuracy can be estimated by equivalent fixed-base structure. In some regulations, dynamic characteristics of equivalent structure have been determined on elastic state and the...
Influence of Polystyrene on Behavior of Light-Weight Concrete
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor) ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Normal aggregates are replaced by polystyrene beads (EPS) due to their low unit weight. EPS concrete is known for its low density and environmentally friendly properties apart from having various pros such as better heat and sound isolation, affordability, and ease of construction. EPS grain size can also affect the compressive strength, and the tensile strength of EPS concrete compression is also inversely related to EPS grain diameter. The EPS concrete has four different percentages of EPS; 0%, 25%, 50%, and 75%. Each EPS percentage has six different unit weights; 15,20,25,30,35 and 40 kg/m3. In the present study 19 different types of mixing designs were used, the one with no EPS beads has...
Determination of Electro-elastic Fields in General Anisotropic Piezoelectric Mediums Due to Periodic and Non-periodic Distribution of Self-Assembled Quantum Wires and Quantum Dots
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shoja, Hossein (Supervisor)
Abstract
Studying the behavior of piezoelectric materials containing self-assembled quantum wires and quantum dots is of great interest. This work is devoted to analytical and exact determination of the electro-elastic fields associated to quantum wires and quantum dots in piezoelectric mediums. The present work accounts for: (1) different shapes and orientations of quantum wires and quantum dots, (2) different types of anisotropy, and (3) high concentrations of quantum wires and quantum dots, that is, the corresponding interaction is considered properly. The presented solution is valid for general anisotropy and different shapes of quantum wires and quantum dots. In this work, periodic and...
Innovative Theories of Micro and Nano Ellipsoidal Inclusion and Inhomogeneity in Magneto-electro-elastic Media with General Anisotropy
, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
In the current work, the two- and three-dimensional electro-elastic fields of periodically as well as arbitrarily distributed interacting quantum wires (QWRs) and interacting quantum dots (QDs) of arbitrary shapes within a piezoelectric matrix are studied analytically. The lattice mismatch between the QWR/QD and the barrier is accounted through prescribing an initial misfit strain field within the QWR/QD. The distinction between the electro-mechanical properties of the QWR/QD and those of the barrier is treated by introducing a novel electro-mechanical equivalent inclusion method in Fourier space (FEMEIM). Moreover, the theory can readily treat cases where the QWRs/QDs are multi-phase or...
Numerical Analysis of Channel Flow over an Elastic Bump, Using Lattice Boltzmann Method- A Biological Application
, M.Sc. Thesis Sharif University of Technology ; Taeibi Rahni, Mohammad (Supervisor)
Abstract
In recent years, lattice Boltzmann method (LBM) has been developed to be used as an alternative and promising computational technique to simulate various flows. It originates from classical statistical physics. The ability to simply solve complex flows, simulating of multiphase and multi-component without need to follow the boundaries of different phases, and the inherent ability of parallel processing are notable features of this approach. On the other hand, finite element method (FEM) is widely used in many practical engineering fields, especially in solid mechanics. In this study, in addition to simulating flow over a rigid body, flow over an elastic body is also simulated with a...
Estimating Price Elasticity of Gasoline Demand Using Transaction-Level Data
, M.Sc. Thesis Sharif University of Technology ; Vesal, Mohammad (Supervisor) ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
One of the most widely discussed parameters in energy economics is the price elasticity of gasoline demand due to its substantial implications for taxation, energy efficiency, and environmental policies. This paper aims to estimate the price elasticity of gasoline demand using a novel source of data. The data is from Iran, in the early months of 2014. Vehicles get a quota of 60 liters per month as subsidized gasoline at a lower price. The quota is transferable to the next months if it has not been consumed. All of the information about each pumping transaction is gathered in a centralized database, assigning a unique fuel card to each vehicle. Consequently, the structure of the market provides...
Numerical Modeling of Two Interacting Circular Holes Using a Gradient Elasticity Based Meshless Method
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shoja, Hossain (Supervisor)
Abstract
A theory of gradient elasticity is used and numerically implemented by a meshless method that is called reproducing kernel particle method (RKPM) to model size effects. Some of the problems are modeled under the consideration of gradient elasticity for the first time and all of them are also modeled with classical elasticity to compare with gradient elasticity. First of all, the RKPM formulation and computing the amount of shape functions and requisite derivatives will be explained with details and a mathematical innovation that will decrease the computational cost seriously proposed for the first time. Several 1D and 2D shape functions with first and second derivatives that are resulted...
Stability Analysis of Hybrid Nanotubes Based on the Nonlocal Continuum Theories
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
Strong van der Waals (vdW) potential fields of carbon nanotubes (CNTs) makes them capable to encapsulate some nanostructures inside their hollow space, which leads to the construction of new hybrid nanostructures under specific conditions. Carbon nano-peapods, carbon nanowires and the hybrid of DNA and CNT are the main categories of hybrid nanostructures of CNT. Characteristics of hybrid nanotubes are unique and different from those of CNT. In nanostructures, the lattice spacing between individual atoms is considerable with respect to the structural dimensions. Also, the range of internal characteristic length is relatively close to external ones. So that utilizing the classical continuum...
Developing a Model for Simulation of Dynamic Behavior of Nano-beams
, M.Sc. Thesis Sharif University of Technology ; Nejat, Hossein (Supervisor)
Abstract
The utility of nano-beams in MEMs and NEMs has progressed a lot in recent years. Such systems have found wide spread use in sensors and actuators due to small size, low weight, high accuracy and low energy consumption. By a decrease in size of nano-beams, surface effect increases which makes the classical theories unable to modeling such beams. Therefore new models are required for evaluating the dynamic behavior of nano-beams. In this thesis we have attempted to develop a suitable Coarse-Grain model for analysis of such beams. At first a suitable Coarse-Grain mapping with determined Sutton-Chen potential parameters is introduced for FCC metals. In the next step, EAM is considered as...
Control of a Link on Elastic Torsional Support and Experimental Verification
, M.Sc. Thesis Sharif University of Technology ; Mohammad Navazi, Hossein (Supervisor)
Abstract
A simple control system contains at least an actuator, a controlled link, and a foundation. These structures are not ideally rigid, this flexibility can appear willingly or unwillingly in any parts of the system or the connections between them. As a consequence of this flexibility, the movement of the controlled part will fluctuate unintentionally. In this thesis, a control system with rigid controller and flexible torsional base is investigated and controllers are designed and compared to reduce these unwanted vibrations. Finally, by implementing the controllers on the constructed system, the experimental results are obtained and compared with the analytical results.To fabricate the...
Kinematic and Constitutive Modeling of Elastic and Thermoelastic Continua with Finite Deformation using Multiplicative Decomposition of Deformation Gradient
, Ph.D. Dissertation Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Kargarnovin, Mohammad Hassan (Supervisor)
Abstract
In this thesis, a deformation measure is introduced which leads to a class of strain measures in the Lagrangian and Eulerian descriptions. In order to develop a constitutive equation, a second-order constitutive relation based on these strain measures is considered for modeling the mechanical behavior of solids at finite deformation. For this purpose and performance evaluation of the proposed strains, a Hookean-type constitutive equation is considered and the uniaxial loading as well as simple shear and pure shear tests are examined and the results are compared with the test data. Also, in order to characterize the mechanical behavior of elastic continua, constitutive equations through a...