Sharif Digital Repository

The material presented in thesis uses concepts of finite element and doublet panel method to develop a structural aerodynamic coupled mathematical model for the analysis of morphing wing tip composed of smart materials. Much research is currently being performed within many facets of engineering on the use of smart of intelligent material. Examples of the beneficial characteristics of smart materials might include altering a structure's mechanical properties, controlling its dynamic response and sensing flaw that might progressively become detrimental to the structure. This thesis describes a bio inspired adaptive structure that will be used in morphing an aircraft's wing tip. The actuation... 

In this study, HSS and double angle braces subjected to cyclic loading in order to study the buckling and post buckling behavior have been investigated by Finite Element method. The results of FE analysis are fairly in good agreement with experiments. Analysis demonstrate that when local buckling occurs in middle span, subsequently, strain rises severely. Accordingly, this strain jumping causes early fracture in braces. Therefore, local buckling can be one of the primary reasons of fracture in braces. As a result, local buckling must be considered one of the primary limit state of Performance-Based design of steel braces. In addition, finding a way to predict local buckling can help us to... 

In recent years, growth of industries has led to consistent increase in energy consumption around the globe. On the other hand, non-renewable energy sources are the most consumed ones in the world. Therefore, governments and companies have tried to introduce budgets to facilitate the use of renewable energy sources and make their use cheaper. One of the renewable energy sources is geothermal energy which one economical way to havest it is thermal energy exchange between the building foundation and the ground. Therfore, thermal piles , by the use of a heat exchanger fluid, transfer the heat on the surface to the ground in warmer seasons and in cold seasons, they transfer the heat from the... 

Considering the role of fluid storage tanks within or after an earthquake and the irreparable damages from their destruction that arise from the nature of the fluids of flammable or toxic nature stored in those tanks, it is very important to ensure stability and durability of the tanks when an earthquake is occurring. One of the most important damages to storage tanks within the past earthquakes has been lack of stability of their walls taking place in the form of elephant buckling. A certain storage tank was subject to a case study in this research and the tank's body, foundation, anchorages, the tread between the fluid and tank's body and between the bottom sheet and foundation were... 

Today using cold-formed steel elements as members of light-weight structures is more common especially in low-rise residential and industrial buildings. Due to Thin-walled plates used to make these sections, members of the frame are prone to premature local buckling and they don’t show good ductility under seismic loadings. Beacause of these reasons, using cold-formed steel elements in moment frames has become a big challenge for scientists. Lots of numerical and experimental models have been presented.
In this study, we investigated the behavior of a beam-column moment connection, consists of two back to back channel sections with curved flanges, using a plate passing through the... 

The exploitation of oil and gas were changed dramatically with the advent of hydraulic fracturing. By using enhanced oil recovery methods in unconventional reservoirs, USA could raise the rate of production in comparison with the rate of consumption. Hydraulic fracturing is one of the enhanced oil recovery methods.The purpose of this research is the study of the effects of geomechanical parameters in the characteristics of the cracks induced by hydraulic fracturing in unconventional oil reservoirs. The minimum in-situ stress and tensile stress of rock can be overcome by injecting fluid and thus the rock will be cracked. Changes in geomechanical parameters such as modulus of elasticity,... 

Studying the failure mechanics of FGM materials is inevitable due to the increasing use of these materials in various industries. Stress intensity factor and integral-J are important parameters in fracture mechanics. Due to the fragile nature of ceramic components in FGM During the processing of these types of composite materials, cracks are encouraged. Therefore, crack analysis is inevitable in optimizing the design, reliability and durability of FGM materials and structures in innovative engineering applications. In this research, transverse crack growth in beams made of FGM materials has been investigated. First, a MATLAB code was prepared to extract the mechanical properties of these... 

During the last two decades usage of unstructured grids was very common in the oil reservoir simulators; which is due to free formulation’s structure and independence of the grids to any special boundary lines or surfaces. The use of these types of grids in Computational Fluid Dynamics texts is widely seen in form of Control Volume discretization techniques; and on the other side, Weighted Integral methods known as Galerkin Finite Elements are one of popular methods to approximate displacement differentials quantities. In this study we tried to review application of a new numerical calculation method – which is a combination of Finite Elements and Control Volume methods – in simulation of... 

The present article studies the isothermal and non-isothermal water injection into naturally fractured oil reservoirs by numerical simulation. The fractures in naturally fractured reservoirs can possess different characteristics. In addition. a remarkable number of naturally fractured reservoirs contain relatively heavy oils that could not be extracted economically; hence. the thermal recovery methods are extensively used for these reservoirs. Hot water injection is one of the thermal recovery methods that has not been explored enough compared to its alternatives. In this study. the effectiveness of the hot water injection over the cold (isothermal) water injection in oil production is... 

As the crowded cities require public transportation and because of lack of space on the ground, Subway and boring underground tunnels encountered. In this thesis the interaction of boring the line 7 of Tehran metro with the existing station of line 1 of Tehran metro (Molavi station) is studied. By changing the soil specification, The surface settlement is significant so the soil specification is one of the important parameters of the interaction. For comparinf the effect of these parameters, the soil settlement and bending moments is investigated in different parts of station while the lower tunnel is passing beneath it. The 3D Abaqus software is used for modeling this interaction. In... 

This study investigates the reliability analysis of mechanically stabilized earth (MSE) wall and takes into account the uncertainty associated in the mechanical properties of soil and geogrid, the magnetude of surcharge load and the soil-geosynthetic interface friction angle. In addition, the effect of number, length and place of the geogrid layers on the performance of this wall has been evaluated. The failure modes related to external stability, internal stability and horizontal displacement of the wall were considerd. In order to determine the probabilistic characteristics and the probability distribution function of soil and soil-geosynthetic interface friction angle, direct shear test... 

Nowadays, the use of advanced composite materialsin different structureshas been increased and many industriesextend application of these high-tech materials because of their very high ratio of strength to weight and variation in ply configurationsuch asdifferent fiber angles which can control the response of these planes due to design requirements.One the most recent applications of such materials inreinforcing various structures are preventing crack propagation in aircraft structures and strengthening buildings against earthquakes which have been developed considerably. But, a lot of intact topics in this criterion are available which should be studied carefully. So, according to what was... 

In the recent years, neural networks have been used to solve many problems in different fields, specifically in engineering problems. Neural networks have different applications in material science and structures including modeling stress-strain relationship of composite materials and static and dynamic analysis of structures. Recently, a new method called neuro-finite element has been developed for nonlinear static analysis of structures manufactured by one-dimensional elements. In this method, by investigating the load-deflection diagram of each element, it is possible to analyze and produce a load-deflection diagram for the whole structure using neural networks. This experimental study... 

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... 

In this study, Interfacial crack is modeled by the extended finite element method (XFRM) in order to evaluate the stress intensity factors for interface crack problems. These problems have crack edge discontinuity, material interfaces and singularity at the crack tip, which is inappropriate to finite element (FEM) mesh. Furthermore, around crack tips and interface edge, extremely fine discretization is required to achieve reasonable accuracy. All these factors increase the time and cost of the FEM solution. Recently the extended finite element method is developed and applied to interface fracture problems. In the XFEM, special enrichment functions are added to the finite element displacement... 

The aim of the work presented in this thesis is deal with some of the aspects in the FEM analysis of sandwich panels containing holes which comprised with foam core. It is a new topic in this field; so the activities that have been done about this case are poor with respect to its performances in engineering. The main emphasis is placed on the treatment of the foam core since the core often is the weakest part of the sandwich and therefore in many ways governs the capacity and lifetime of the whole sandwich structure. Because of increasing application including construction, aircraft and transportation, marine and etc., different load conditions are considered for the analysis and... 

In current study, we investigate crack propagation is saturated porous media by using the extended finite element method. The porous media is simulated by using well-known u-p formulation. In this regard the equilibrium equation of the bulk is employed together with momentum and mass balance equations of the fluid phase. The XFEM, known as one of the best methods in crack simulations, will be employed for numerical modelings. According to the method, crack propagation does not involve any changes in meshing, yet by using the concept of enrichment the elements are enabled to possess crack interfaces inside themselves. Thus by crack growth, only discritization alters and new DOFs are inserted... 

Twophase medias are one of the most complicated medias in engineering and because of its importance, its been considered by a lot of researchers ever since. Varaioty of the problems in these medias, has ended in lots of methods for studing them. The primariative efforts in modeling deformable pouros medias was done by Terzaghi and others have improved the primary consepts and have suggested different methods. One of the most common and applicable methods in these medias is u-p formulation. This form is applicable in low frequencies (such as earthquakes) with great accuracy. In this thises, this form is used as primery formulation. Because deformation in multiphase problems can be large, in... 

Hydraulic fracture propagation occures in fractured saturated porous media due to fluid leakage from the crack faces and the consequent fluid pressure. In many cases, hydraulic fracturing may be considered as a detrimental phenomenon which endangers stability of human made structures like rock-fill dames. However, in recent decades the hydraulic fracturing has been an appealing method for increasing the production rate of low-permeability oil and gas reservoirs in petroleum industries.
In order to efficiently assess the behavior of saturated madia one needs to consider the coupling between the solid and fluid phases of the medium. To do so, the coupled formulation refered to as u-p...