Sharif Digital Repository

This study presents an image processing technique for automatic strain and stress measurement in sheet metals. In order to measure the strain automatically, the sheet blank is electrochemically etched to create circular and rectangular grids. After press forming of the sheet, circular grids are deformed into elliptical grids and rectangular grids are deformed into quadrilateral grids. Different photos are captured for using in image processing technique. These photos are taken in different positions. Finally strain can be measured by processing these photos and the stress is obtained by using Levy-Mises flow rule. In this study, three methods of image processing technique are simultaneously... 

Chemical dispersants applied to the surface of Persian Gulf during the oil spill in 2010 were more than one million gallons. Following the addition of dispersants, oil mixes below the seawater surface and can be degraded or dissolved into the water column. The aforementioned condition is a perfect opportunity for degradation of organic pollutants using Ultraviolet light emitting diodes Advanced Oxidation Processes (AOPs). These methods are based on activation of oxidants such as persulfate and hydrogen peroxide to generate extremely reactive radicals. Dispersants would increase the degradation rate by providing more active area (homogenous solution) for these radicals. AOPs have shown to... 

Sheet metals are widely used in different industries such as ship building and pressure vessels. In these industries, One important problem is Line Heating Forming. This method needs simple initial equipment and is economically advantageous.In this research heat transfer between gas torch and plate, cooling effects and edge effects are studied more precise. Impingement jet model is used to simulate effect of heat source (flame) and cooling air on plate. The temperature distribution in sheet metal due to the rates of cooling air and heated gas (flame) are calculated by using commercial engineering software, Fluent. Then, the computed temperature field by FLUENT is fed into the ANSYS FEM... 

Nowadays, climate change is one of most important environmental challenges in all over the world. In addition to climate change, population growth, increase in water demand, which surpasses available resources so that the water system cannot meet the demands, and the subsequent growth in the development of water resources plans make watershed management become a challenging issue . In the last decade, due to significant reduction of precipitation, continuous increase in water development plans and utilization of too much water for agricultural and other uses, water inflow to the lake Urmia has reduced. Furthermore, Urmia lake have a strategic location which flows in three provinces of East... 

Lakes, marshes, and wetlands shrinkage and drying up due to natural and human driving forces is today one of the most important concerns in the world. Mahaarloo Salt Lake in southern part of Iran is (18 km far from south eastern of Shiraz ) drying-up and is faced with ecologic and environmental degradation. It recharges from western north by upstream basin of Shiraz and 3 rivers named Khoshk, Chenaarrahdaar, Soltaanabad and also from eastern south by Nazarabad river located in Sarvestan basin (Regional water org. of Fars 1382). In recent years, the shrinkage of Mahaarloo has been exacerbated by mismanagement of water resources, inappropriate land use, ignoring allocation of environmental... 

Eyesight is one of the most important tools for humans to communicate with environment and consequently, blindness or poor eyesight results in unsatisfactory effect on life quality. Owing to the importance of the sense and to assist to the patients, this thesis aims to design and assemble cybernetic glasses using ultrasound waves. To this end, firstly, the notion of waves focusing on ultrasound waves is described and reactions of human hearing system to the waves are studied. Then, the transducers as a key device are introduced. Afterward, bat sense system to communicate with environment which is based ultrasound waves is described. Next, attenuation effects on ultrasound wave pressures are... 

One of the oldest and most used methods in shaping metals is the formation of metal sheets. In designing the process of printing, it's important to know how much the strain on the sheet prior to slipping is. In order to predict the permissible strains in the two-axis stretch of the sheet, they introduced an empirical diagram called the shape-forming diagram. There are various methods for analyzing the formation of metallic sheets, which can be referred to by M-K method, GTN method, continuous damage mechanics method (CDM). In this research, we have tried to obtain the shape of a metal sheet in various strain paths by studying the method of CDM and modeling the mechanical behavior of the... 

Little research has been conducted on the topic of water resources management in case of deep uncertainty. It is vital for the management method to be upgraded in order to accompany future changes. The purpose of this study is to inspect some viable scenarios and deriving proper reservoir management solutions in case of deep uncertainty. This is important due to the fact that future changes are often not considered when water resources structured are being designed. In the past, some researches in this field of study were done; For instance, the effects of climate change on reservoirs have been assessed. Also methods for coming up with scenarios have been proposed, most of which are based on... 

The Droughts in various parts of the world cause a lot of economic and social damage every year. In fact, droughts are due to climate fluctuations that are inherent in the natural processes of meteorological and hydrological processes and reduce water resources; population growth; Of course population growth, exacerbates its consequences. Research as well as observations have shown that climate change also exacerbates extreme phenomena such as drought and flood. The population of Kabul city, the capital of Afghanistan, is increasing due to migration from other cities, and on the other hand, the flow of the river in the summer is minimized, which for some years leads to drought. In these... 

In this dissertation, using experimental and numerical methods, the effects of grain morphology on the formability of sheet metals are investigated. In this regard, in the first stage, by conducting heat treatment on two different sheet metals with bcc and fcc crystal structures, different grain sizes are produced. Using metallographic observations, these grain structures are examined and the grain sizes are measured. Tensile test and Nakazima formability test have been implemented on these specimen. The grains are also shaped in the rolling process and different grain morphologies are created. In the second stage, a software has been developed to generate various grain structures and... 

Cyclic Contraction Expansion Extrusion (CCEE) is a new Severe Plastic Deformation (SPD) method used to refine the microstructure and improve mechanical properties of Magnesium AZ91 alloy. In this study, different CCEE process zones are investigated via optical microscopy to understand this process better. The average grain size in the contraction zone decreased to 8.5 microns from an initial value of 106 microns. In the expansion zone, the average grain size was equal to 4.8 microns. Microhardness tests were conducted to study the improvements in mechanical properties. Microhardness of the sample increased from the initial value of 66 HV to 74.4 HV in the contraction zone and 88 HV in... 

One of the common methods of removing blood clots is angioplasty with stents. Due to the fact that the mechanical properties of the stent are directly related to the microtube it is made of. Therefore, investigating the mechanical properties of microtubes is very important. One of the ways used to evaluate the plasticity of microtubes; Drawing a graph is the limit of shaping. The purpose of this research is to extract the forming limit diagram of magnesium microtube by simulating the hydroforming process in Abaqus software. First, in order to confirm the modeling, the hydroforming process for aluminum has been simulated and compared with the existing experimental results. The comparison... 

Properties of stents are significantly dependent on the mechanical properties of the microtubes used in their construction. Therefore, investigating the influence of various factors on the mechanical behavior of magnesium microtubes employed in the fabrication of biodegradable stents can play an indispensable role in the development of the emerging industry of biodegradable stent manufacturing. In this dissertation, the effects of different parameters on the mechanical behavior of magnesium microtubes used in the construction of biodegradable stents have been examined. To achieve this, the objectives of this dissertation have been divided into three main sections. In the first section, a... 

The purpose of this work is to introduce an inverse finite element tool for prediction of the blank geometry and forming severity in stamping of 3D sheet metal parts. To achieve this goal total deformation theory of plasticity has been employed. In this method the final 3D part is unfolded on the flat surface in one step and on predefined surface in multistage analysis. The problem for one step analysis is reduced to two dimensional computations. The effect of curvature of initial blank and the number of stages in forming process are also considered. To investigate the capability of this work, predictions of the blank shape and strain distribution and forming severity have been performed on... 

In this thesis, type and importance of corporate social responsibility (CSR) based on Carroll’s framework was investigated among companies of Tehran Stock Exchange. Beside, the types of companies’ motivation to engage in CSR base on model of Garriga & Mele (2004) were studied. In addition, hypothesis 1) instrument motivation for companies of Tehran Bourse is more attractive than the other type of motivations 2) companies that have higher income, have higher costs in CSR was tested. Using questionnaire tool and help of descriptive and inferential statistical analysis, questions and assumptions was studied and results illustrated that legal and ethical dimensions is most-widely used definition... 

In this study, the forming limit stress and strain diagrams have been determined based on the strain gradient plasticity theory. Forming limit stress diagram (FLSD) has been reported as being much less path-dependent and much more favorable than the forming limit diagram (FLD) in representing forming limits in the numerical simulation of sheet metal forming processes. Therefore, the purpose of this study is to develop a methodology for prediction of the forming limits both in strain and stress spaces. All simulations are based on strain gradient theory of plasticity in conjunction with the so-called Marciniak-Kuczynski (M-K) approach. This method introduces an internal length scale into... 

Recently, the number of multi business companies in Iran has increased. Nevertheless, they are challenged with several management and control issues, due to an unstable business and political environment in Iran as well as a lack of comprehensive knowledge in related fields. Thus conducting studies to address these issues in Iran’s special context would have a suitable impact on the successful management of these multi business companies. The main objective of this study is to determine suitable management mechanisms for regulating subsidiary-parent relationship. These mechanisms should be selected in a way to be aligned with subsidiary’s business context, which would lead to create benefit... 

It is the goal of this thesis to develop an analytical model for the hydro-mechanical deep drawing (HDD) process of an axisymmetric sheet metal with the fixed gap method to evaluate the effects of some assumptions such as: proportional loading, plane stress, and constant thickness conditions. The effect of parameters on the HDD process is also studied. The main model is developed with considering the normal stress and part thickness change, non-proportional loading, bending and unbending effects at the top of the cup wall. The interrelationships between geometrical and mechanical variables are obtained in the finite difference form based on the incremental strain theory, thereby being solved... 

The inverse Finite Element method (IFEM) has been used for estimation of the initial length of tube, axial feeding and fluid pressure in tube hydroforming. The already developed IFEM algorithm, which has been used in this work, is based on the total deformation theory of plasticity. Although the nature of tube hydroforming is three-dimensional deformation, a technique has been used to perform the computations in two-dimensional space. Therefore, compared with conventional forward finite element methods, the present computations are quite fast with no try and error process. The solution provides all the components of strain. Using the forming limit diagram (FLD), the components of strain can...