Sharif Digital Repository

Given that the mean of the cost of drilling operation related to the required martials and preparation of the drilling fluids, therefore, the design and construction drilling fluid which omit has to be a proper rheology is essential in drilling operations and oil industry. A desirable property of the drilling fluid is the minimum fluid loss volume which can be achieved by formation of a low permeability filter cake on the wellbore. Drilling fluid filtrating invasion into the formation can cause formation damage and reduction in the productivity of the well. In drilling fluids, a series of natural synthetic and polymers may be used as fluid (filtration) loss control additives. However, high... 

Development of composite materials is one of the boldest technological advances of the last half of the twentieth century. This is due to their specific characteristics mostly considerably high strength-to-weight ratio, compared to metals and their highly customizing properties for different applications which make them a suitable material to be used in variety of domain from aerospace and automobiles to medical and sport equipments. Multi-stable asymmetrical laminates and non-uniform thickness laminated composite beams are being used as structural elements in a wide range of advanced engineering applications. Multi-stable asymmetrical laminates can be snapped between two or more geometries... 

With the progress of engineering science, the development of underground spaces and buried tunnels has witnessed remarkable expansion. Considering the frequency of hazardous events such as earthquakes and unforeseen consequences arising from underground activities and geology in underground engineering, the determination of the Dynamic Stress Concentration Factor (DSCF) has been widely recognized as a crucial factor in the study and design of tunnels and underground structures. It is also extensively considered in evaluating their damage. The investigation of wave dispersion and determination of the stress concentration factor was first proposed by Sezawa (1927). In this study, the... 

In this study the axisymmetric and asymmetric problem of interaction between a transversely isotropic half-space and various rst order shear deformation plate theories including Mindlin, Reissner and Vasil'ev are addressed. In order to improve the accuracy of solution, the surface boundary conditions of the half-space are modied.Moreover, the results compared with the exact solution and the most appropriate result is identied. The displacement Green's functions are obtained for both cases, modied and unmodied boundary conditions which can be expressed in a closed form and a numerically evaluated part. The latter is calculated exploiting Built-in numerical interrelation function of... 

In this thesis the performance of anew energy dissipative device, slit steel damper (SSD) is investigated. The slit steel damper is manufactured with I-shaped, wide flange H-shaped profiles with a number of slits cut from the web. The device is installed between beam and chevron brace and fastened by four bolts on each side, which enables the replacement of the device due to strong earthquake.A numerical study is conducted to studythe nonlinear behavior of the SSD systems by using a nonlinear FE program. It is found that the numerical modeling results have a good agreement with the existing test results.In the next step a parametric study is performed to study the effects of the number of... 

There are different technologies for supplying water from alternative sources that meet different needs. In relation to thermal technologies such as multi-effect distillation, the highest water quality is obtained, there is no limit on the concentration of the incoming water, and there is the least need for maintenance. On the other hand, thermal technologies consume higher energy than membrane technologies. In this process, the better the heat transfer, the number of steps can be increased, and this means the production of more distilled water for the same amount of thermal energy. The distilled water layer on the surface of the heat exchanger has a high thermal resistance compared to the... 

In this thesis the dynamic behavior of the thick-walled shell with variable thickness is investigated. Such structures are used in a variety of industries including aerospace, oil, gas and petro-chemistry. In this study, the dynamic behavior of a rotating truncated conical thick-shell with various geometries is investigated. For this purpose, modal analysis is performed using the refined finite element method. Then,the natural frequencies and corresponding mode shapes are calculated for several different geometries. Also, the relationship between geometrical variables such as thickness, the ratio of length to radius, ratio of cross-sectional radius and so on, with the natural frequency of... 

Spray-wall impingement is one of the phenomenon that associated in different subject such as spray cooling, combustion chamber and gas turbine. With the impingement of spray to the wall, liquid film begins to form. Wall film characteristics is still an important subject to study. Due to the various stages of liquid film formation from injection of spray till spray-wall impingement, the investigation of this phenomenon is far more complicated. This paper is meant to provide detailed data on spray-wall impingement and wall film formation physics with the help of computational analysis of OpenFOAM . A Lagrangian-Eulerian method based on discrete phase model (DPM) was employed to model... 

Numerical simulation of flow fields inside and outside of a pressure-swirl injector is considered in the present study. Injector characteristics such as the injected liquid sheet thickness, liquid sheet breakup length, and spray angle can be accurately captured via numerical simulations and used for the design optimization of an injector. The flow fields inside of a pressure-swirl injector leading to the primary atomization process outside the injector have been simulated assuming laminar flow with periodic boundary conditions using a coupled volume of fluid (VOF) and a level set model for the two phase fluid. The ANSYS Fluent commercial program is used for simulations. The computational... 

A semi-analytical solution for rotating axisymmetric disks made of functionally graded materials was previously proposed by Hosseini Kordkheili and Naghdabadi [10]. In the present work the solution is employed to study thermoelastic creep behavior of the functionally graded rotating disks with variable thickness in to the time domain. The rate type governing differential equations for the considered structure are derived and analytically solved in terms of rate of stress and strain as a reduced to a set of linear algebraic equations. The advantage of this method is to avoid simplifications and restrictions which are normally associated with other creep solution techniques in the literature.... 

Considering the undeniable role of technology in modern era, we investigate both the concept of technology as well as its relation as a tool with human beings. Modern technologies have had both positive and negative impact on human individual and social lives. In particular, the labor problems, environmental problems, distortion of the classic human perception of the world, and many other problems provide a very disparate perspective compare with the notion of techno-utopianism. Therefore, many contemporary philosophers such as Andrew Feinberg have made serious criticisms of technology and its consequences. Feinberg states that there is a possibility in reforming the currently derailed role... 

Stress Absorbing Membrane Interlayer (SAMI) is a slightly thin layer made of bitumen and aggregate placed between a pavement with limited cracking and overlay in order to avoid reflective cracking in overlay. SAMI’s performance depends on many factors such as pavement layer’s materials and thickness and existing pavement’s condition. Numerical simulations are powerful tools to evaluate SAMI’s performance. Previous studies showed that construction of SAMI does not necessarily reduce reflective cracking. This research investigated the effect of different parameters on SAMI’s performance using numerical simulations. The focus of this study was on the performance of SAMIs used between asphalt... 

Steel Concentrically Braced Frames are common lateral load resisting frames. Poor design of this system can lead it to premature failure of braces. This failure may be due to non-elastic buckling of brace members or their connections. Design Codes divide Concentrically Braced frames into two groups: Ordinary Concentrically Braced Frames and Special Concentrically Braced Frames and for each, specific limitations have been determined for width to thickness ration and slenderness. Many of these limitation have been obtained on the basis of experimental tests. In this thesis steel braces behavior under cyclic loading is studied. For parametric investigation, Finite Element Method is used. Abaqus... 

The need to build underground structures like tunnels, oil reservoirs are increasing and it requires a good knowledge of behavior of mass rock, exact data and parameters for safe and economic design. Filling materials which usually transfer with water into the joints reduce shear strength of joints significantly and change the behavior of the joints. To evaluate shear behavior of filled joints, 24 tests were conducted with large scale direct shear test apparatus on model rock joints with a regular “saw tooth” surface profile with the dimensions of 15cmx15cmx18cm. Filled material had specified specifications like particles size and strength parameters.
Infill thickness, moisture content... 

Dynamic impedance functions method is most recent approach in the analysis of soil-foundation dynamic interaction, and presented for massless rigid foundations. Impedance functions are frequency dependent functions, and used to obtain dynamic response of foundation with arbitrary mass subjected to dynamic loading of any frequency and magnitude. The important assumptions for appropriate useof mentioned method are rigidity of foundation and visco-elastic behavior of the soil beneath the foundation. In this study, experimental vertical impedance functions of square and circular foundations have been investigated,using physical modeling tests. A granular soil layer with finite thickness... 

Today, titanium and its alloys are the most widely used metals in manufacturing of biomedical implants. But unfortunately, most of bulk (nonporous) titanium alloys implants are facing problems such as stress shielding. If titanium is produced in such a way that has sufficient amount of porosity on the surface and inside of the sample, it provides sufficient space for connection and proliferation of new bone tissues and transmission of body fluids. However, machining of porous titanium causes pore closing. Due to the importance of recognizing the machining mechanism of materials such as porous titanium for manufacturing of implants, in this study micromachining of porous titanium with the... 

Vertical milling machine is one of the most common machine tools for precision parts production. The static deflection of the machine tool and thus the displacement of the tool, is due to the high machining forces is the most important factor in reducing the dimensional Precision of the work piece. Also, the overlap of the frequency range of operation with the natural frequencies causes an undesirable resonance phenomenon. Reducing the strain energy of the column and thus the reducing the displacement of the tool, and increasing the first natural frequency of the milling machine, given that the frequency range of operating is below the first frequency, is a desirable change that can be... 

Mode І critical strain energy release rate at crack initiation, Jci, of SAC305 solder joints between two copper substrates was measured using double cantilever beam (DCB) specimens at a strain rate of 0.03 s-1 as a function of bond-line width (i.e. joint size in the out-of-plane dimension), solder thickness, copper adherends thickness and suface roughness. Fracture force per unit width and Jci were relatively insensitive to width of the joint ranging from 8 to 21 mm. Variations in solder thickness (i.e. 150 µm, 250 µm and 450 µm) also had an insignificant influence on the fracture energy of solder joints. This behavior was explained in terms of stress distribution, plastic zone area and... 

One of the most useful methods in metal forming is Sheet Metal Forming. Use of Forming limit diagrams (FLD) in designing is a conventional method. Therefore many experimental and theoretical efforts have been carried out in order to investigate the FLDs. Many ways to obtain this FLDs and their effective parameters have been studied. But the stress state at these studies is planar which lead to an untrue model for several metal forming process such as incremental sheet forming. With this technique, the forming limit curve (FLC) appears in a different pattern, revealing an enhanced formability, compared to conventional forming techniques. Therefore, in this study, the effect of through... 

Acoustic noise from turbulent jet flow discharged to the einvironment is called turbulent jet noise which is a problem for turbojets, turbofans, missiles, rockets and everywhere the discharge of a jet at high speed exists. In order to achieve the jet noise reduction methods, understanding this phenomenon with modeling on a detailed theory for the future developments in this field is required. In this study the noise generation from coherent large scale structures for a subsonic jet with acoustic Mach number of 0.5 is studied using linear stability analysis. To get the base flow used in instability analysis, the jet flow is modeled using different two equation k-ε models and after...