Sharif Digital Repository

The axisymmetric contact problem of a rigid inclusion embedded in the piezoelectric biomaterial frictionless interface subjected to simultaneous far-field compression and electric displacement is addressed. With the aid of a robust technique, the coupled governing integral equations of this mixed boundary-value problem are reduced to decoupled Fredholm integral equations with a constraint equation. A useful limiting case for the contact problem of transversely isotropic bimaterials is addressed. The present solution is analytically in agreement with the existing solution for an isotropic bimaterial. Selected numerical results of interest to engineering applications including the radius of... 

Electrical connectors that used in high speed systems interrupt the connection at the effect of Inertia. Also connectors should be able to work in high vibration conditions without any problems. Vibration of the connector pins can reduce the contact area or even remove it at very short time intervals, which lead to increase connector resistance or disconnection of instantaneous current. These current fluctuations will result in unpredictable performance disturbanceof the electrical system in very sensitive systems and therefore it should be avoided. In this Project, impacts of shock and vibration loads on the connectors is modeled by using FEM and with consideration of this model, connection... 

Investigation stability of chatter vibration is of great importance in machining processes. Finding frequency response function (FRF) at the tool tip is an effective method to predict stable machining regions. Commonly, the tool tip FRF is obtained using experimental modal analysis but this approach is often time consuming and requires expertise. In addition, changing tool or holder requires modal test which is a disadvantage, consequently modeling methods are of interest for researchers. Moreover, optimum design of machine tool is another benefit of modeling method. Also, in machining with flexible or micro tools in which experimental tests can not be performed, modeling methods would be... 

In this thesis contact problem between wheel and rail has been studied. Also rolling contact fatige (RCF) has been studied in detail. Unlike previous studies that have focused on FEM solution, in this study the problem has been formulated based on analytical methods. Evaluating the loads in wheel-rail contact zone is necessary to find the defects. This thesis presents the evaluation of the stress field inside elastic rolling bodies with an elliptic area of contact. This kind of model can be applied to wheel-rail contact mechanics. The problem has been solved for two main models: with friction and without friction. The results have shown that shear stress reaches the maximum magnitude... 

In recent decades, micro-electromechanical systems – MEMS – havefound extensive applications in applied science and engineering. One of the most popular MEMS actuatorsis micro Scratch Drive Actuator (SDA), which can be used in various applications, for instance: precision positioning, micro-chip displacement and rotating micromotors. Their outstanding capabilities such as: high controllability, precise step displacement, vast transportation domain and large force relative to their small size, have made them popular among researchers. Recently, a new generation of SDA is introduced, known as Bounce-back Scratch Drive Actuator or BSDA, which is fundamentally different in motion generation from... 

Delay Tolerant Networks are types of mobile Ad-hoc networks, in where because of the high node mobility, low node density and node diversity, there is not full connection between nodes in the whole network; therefore, the probability of existence of end-to-end path between source and destination is low. Due to these properties, message routing in delay tolerant networks has turned to be a challenge, this type of networks work based on the concept of store, carry, forward; for instance, a node may store a message in the buffer for a long time and carry it along until meeting an appropriate contact opportunity. Delay tolerant networks are capable of providing communication services in... 

Concrete has long been considered by engineers as one of the most used constructional materials. Therefore, recognition of mechanical behavior of concrete materials is of particular importance. So, extensive studies have been undertaken to understand and analyze its behavior under different loading conditions. Based on these studies, many models for describing the behavior of concrete are presented. Of these, many models are based on the combination of plastic theory and damage mechanics, and by using them, significant success has been achieved in the correct modeling of concrete materials. On the other hand, one of the important loading conditions encountered by concrete structures is in... 

Most of the current application and potential FGM included in the areas related to contact mechanic .These issues essentially are related to the transfer of force between two objects, that in general is with friction, so in this study the contact under the loading of horizontal and vertical with its different aspect such as the effect of contact region, the effect of round and also the effect of getting harden and soften of FGM.
The used method is a numerical method ¬(finite element method) that will resulted in contact equation discretisce by use of Penalty method. In this thesis is also presented the needed algorithms for solving the problem and the finite element code for solving the... 

One of the most important issues in modeling natural phenomena that always takes into consideration is the problem of contact and collision between objects. Finite element method is known as the most basic and commonly used in numerical modeling techniques to simulate the above phenomenon.This method has specific problems such as dependency of this approach to the domain mesh especially near the contact region. Due to the dynamic and complex nature of impact problems in which drastic changes occur in short duration that often deals with large deformations, one of the perennial concerns, is the weaknesses of methods applied to enforce contact constrains, and so it is essential to use an... 

Fretting fatigue is one of the main factors leading to failure in structures that have components temporarily connected to each other. The occurrence of fretting at the connection region of a structure under cyclic loading is inevitable, and only various methods can delay its occurrence or minimize the damage resulting from it. Fretting is dependent on various factors, and this has made previous studies unable to lead to a unified approach for predicting the fretting fatigue crack initiation life. In this thesis, after reviewing previous studies, a proving ring is designed for fretting fatigue testing. In the next step, fretting fatigue tests using the bridge-type method are performed on...