Sharif Digital Repository

In many structures, crack creation is one of the most significant fracture mechanisms. To predict these fracture mechanisms accurate numerical modeling is necssary. Finite Element Method (FEM) is one of the substantial methods in analysis of numerical fracture problems in recent past decades. But, this method has difficulties in remeshing of elements in each step of calculation in fracture mechanics or large deformation analysis. Therefore, the theory was defined that, without using elements, just with setting of characteristics nodes in geometry of problem, the differential equations can be solved. These methods are called Meshfree or Meshless methods. RKPM is a new meshfree method for... 

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... 

Recent studies show that irregular structures have been damaged more than regular ones during earthquakes. This proves importance of seismic response determination of this type of structures. Today, Codes define irregularity in structures and restrict seismic analysis and design of these types of structures. The Endurance Time (ET) method is a time-history based dynamic pushover procedure for seismic analysis and design of structures that has been recently proposed in Sharif University. This thesis illustrates ET capability in analysis and design of vertically irregular frames. Irregular frames with three, seven and twelve story high were designed with two types of mass and stiffness... 

In this work, we want to gain and analyze the dynamic equations of an open four bar mechanism with two flexible links and three flexible hinges. In continue, one of the applications of a 3-RRR mechanism has been mentioned and dynamic equations and angles behavior have been analyzed. The effect of hinge stiffnesses and their sequence has been investigated by using Hamilton principle. In addition, The behavior of the mechanism with flexible links has compared to the mechanism with non-flexible. At last, the results have been validated by ADAMS software.

 

Excellent mechanical properties and high aspect ratio of carbon nanotubes have been the reason for extensive research on nanocomposites reinforced by this nanostructure, and recently metal matrix type of these nanocomposites, due to their advantages, have received great attention. Moreover, nanoporous materials are another type of nanostructured materials which due to their very high porosity have special applications in hydrogen storage, separating molecules, purification and energy absorption. Because of completely neglecting the details of nanoscale structure and not paying attention to the length scale, classical continuum mechanics methods are not precise enough for evaluating different... 

Classical theory of elasticity, which is founded upon results of mechanical experiments on the large scale materials, has reasonable results in predicting mechanical properties. The basic idea in this theory is that stress at a point of the material is only a function of the local strain and it is independent of the nonlocal strains. Therefore, the size of the material does not play any role in analyzing mechanical behavior of materials using this theory. However, results from experiments and atomic simulations have shown that in nano scale materials, such as carbon nanotubes (CNTs) and their composites, mechanical properties are strongly dependent on the size parameters of these materials.... 

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... 

In recent years, carbon nanotubes have been the focus of considerable researches. Numerous investigators have reported remarkable physical and mechanical properties for this new form of carbon. In particular, the exceptional mechanical properties of carbon nanotubes, combined with their low density, offer scope for the development of nanotube reinforced composite materials. The potential for nanocomposites reinforced with carbon tubes having extraordinary specific stiffness and strength represent tremendous opportunity for application in this century and recently metal matrix type of these nanocomposites, due to their advantages, have received great attention. Classical theories of... 

Modeling of contact is a important problem in word science, so a lot of method presented by researchers .
In practical industry, if members of contact have complex shape or large deformation, analytical method can not solve the problem and use numerical method.
This method by using ansys , first analyze one-area contact and compare between numerical result and analitical result, then analyze two-area contact between two body with vertical force, and compare result with considering effect of slip and target surface.
Finaly to analyze a practical multiple contact problem, use modeling of tyre and road surface partial slip, and compare between ansys result with experimental result ,... 

Breast cancer is considered as the most common type of cancer in women worldwide and mammography is currently utilized as the principal method for screening the breast cancer. Breast Magnetic resonance imaging (MRI) can be used as a complementary imaging technique besides mammography. MRI technique involves scanning a patient before and repeatedly after the injection of the contrast agent (DCE-BMRI). This examination often takes 7-10 minutes and any movement of the patient’s breasts due to breath, heartbeat or deliberate movement, made in this relatively long acquisition period, leads to a distortion in images called motion artifact. This problem makes the quantitative analysis of the images... 

Nowadays, the use of finite element Software applications in enigineering departments has become Inevitable and commonplace. Acceptance of the necessity of using such software applications for reducing the cost of research and development does not require any evidences of financial instruments to be presented. Reducing design and manufacture time together with pseudo-empirical approach has cuased the finite element science to become a conventional designing tools.
Since contact is the main method to apply a load on a ductile object,and stress concentration caused thereby is often a major cause of failure in mechanical parts, the issue of contact is a fundamental topic in mechanics of... 

In this thesis the impact of inflation on urban household saving is investigated. For calculating sensitivity of saving respect to price changing of different groups of commodities, firstly we divided household cost to two separated groups of durable and nondurable and then by defining total income as summation of monetary and nonmonetary income of households, We consider saving as total income minuses nondurable consumption. Finally we estimated the “Extended Linear Expenditure System” model base on the prepared data. Since inflation is result of unequal changes in prices of goods and services, the approach of expenditure system allows us to assess unequal changes in prices for eight... 

In this thesis, the goal is movement recording by observer and learning it to Fuzzy Elastic Matching Machine (FEMM). For this purpose, first using the camera (Microsoft LifeCam HD-3000), the information specified on the man, taken during the move. After preprocessing performed on the data, Data on each node of the FEMM the classified and is given to special FEMM for that movement and the FEMM to be trained by adaptive neuro fuzzy inference system. During each iteration of training, Sensitivity of FEMM for training new movement information is reduced because the FEMM updated correctly. In test part, one movement among all movements that training in all FEMMs is selected and is done by... 

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... 

Nowadays, robots are become more common in many important applications, such as academic and industrial issues. One of the most important robots are Multi-Arm manipulators which are used in many application such as moving objects, coloring, automatic welding and etc. Working with this kind of robots needs some vital attentions like planning their moving path. It is Because of the large number of obstacles that they face with in the path. Therefore, not only robots are not allowed to collision with themselves, but also they must not touch the obstacles. In the other words, they need Path planning. Generally, the equations of these robots are nonlinear. Therefore, computers and numerical... 

Characterization and simulation of carbon nanotube-reinforced composites at large scale have been a concern of researchers in the past decade. This is due to the computational complication of considering many embedded carbon nanotubes (CNTs). However a simple meshing of organized CNT distribution in the matrix can ease this obstacle. In this study, a finite element approach is employed to investigate the elastodynamic behavior of a wavy CNT-reinforced composite structure. A three dimensional structure with up to 6400 uniformly distributed wavy CNTs is embedded in a polymer matrix. Each wavy nanotube is represented by a set of beam elements. The effect of nanotube waviness and volume fraction... 

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... 

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... 

According to the principle No. 44 of the Constitution of the Islamic Republic of Iran, Roads are in the public domain and are at the discretion of the Government. The result of this rule is that there is always a free route on the side of the freeway and motorists have the right to choose between a freeway and its successor road. This is a perfect laboratory condition which gives the opportunity that can be used with discrete choice models to estimate the demand of freeway versus its successor. In this paper we estimate the determinant parameters of the freeway demand versus the successor road and price elasticity of demand that can be calculated separately for each path. The results show...