Sharif Digital Repository

Large-size buried pipelines are an efficient way of transporting of water, waste water, sewage, gas, and oil resources in across the world. Since the buried pipe lines are exposed to many unexpected conditions, such as landslides, corrosion, fatigue, unexpected loading, earthquakes, material flaws or even intentional damaging, so the inspection requirements lead to adoption of new method of maintenance, protection and conserving of pipelines. This proposed project aims to improve the trustworthiness, reliable, yet economical technologies for monitoring of behavior of buried pipe lines during operation and assessing the risk of pipe lines failure. Piezoelectric sensor is bonded on the surface... 

Marine offshore structures are huge structures constructed in very harsh environments, like oceans and seas. These structures are highly exposed vibration due to ocean’s waves, wind, helicopter landing, etc. Preventing the damage to these structures due unpredicted vibration using a semi active vibration control is being considered. Magnetrorehological (MR) dampers have been used as active element to control the vibration and to provide the structural integrity of the structure. Providing high dynamic range, lower power requirements, large force capacity, robustness, and safe manner operation in case of fail made the MR dampers attractive devices to passive, semi-active and active control... 

Minimally Invasive Surgery (MIS) is a modern surgical technique in which the operation is performed through small incisions in the body. Therefore, the surgeon looses his/her sense of touch which is of high importance in any medical operation. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum applied by surgeon and to measure the transmitted force/momentum to the tissue/organ. First, an accurate electro-mechanical model of the smart grasper is developed and the relations... 

Structures that change shapes are often called morphing structures. Smart morphing composites refer to the morphing structures that can detect the change in conditions and, through a control mechanism, command the actuators to maintain the stability and/or perform a new task. The present report provides a framework on the eld of smart morphing composite structures. The emphasis on this work is on, particularly, multi-stable composite structures with capability to detect the new conditions and adapt themselves to properly respond to them. Due to cycling nature of applied load on morphing, these structures are vulnerable to failure due to fatigue. A failure control mechanism utilizing a... 

Vibration is one of the major problems in gas and oil pipelines. Vibrations can cause damage to the pipes, supports, valves and other equipment installed in the system. These vibrations can be caused by equipment installed on pipelines like compressors and pumps or by fluid flow in pipes and fixed equipment like connections and valves. This research investigates the dynamic behavior of fluid flow in pipelines in Karanj and Parsi oil fields located in the southern part of Iran. The pipeline is responsible for injecting gas into the field. Excessive vibrations in the system cause repeatable damage which in turn increases the operating and maintenance cost. First, the vibration of pipelines has... 

Structural Health Monitoring (SHM) of pipelines is an important task for economic/safety reasons which depends on the method of study of the integrity profile of the pipeline structure. Process pipes, particularly, pipelines in thermal power plants are susceptible to stress corrosion cracking (SCC). Failure of these pipes may result in catastrophic damages, thus, require systematic regular inspections. The damage assessment may demand embedding of appropriate sensors and specific data analysis techniques. According to what is reported from the respective experiments, data analysis of a single sensor may not be adequate to provide a reasonable damage assessment, and in turn to making a... 

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... 

Magnetorheological (MR) materials indicate variations in their rheological properties when subjected to different magnetic fields. They have quick time response, in the order of milliseconds, and therefore are potentially applicable to structures and devices when a tunable system response is required. This study presents vibration analysis of laminated composite plate using MR fluid lumps under Random Excitation. A structural dynamic modeling approach is discussed and vibration characteristics of MR adaptive structures are predicted for different magnetic field levels. Linear Quadratic Regulator (LQR) controller is designed to achieve the vibration suppression of the laminated plate. The... 

This project is intended to introduce a semi-active control for suspension systems of passenger cars wherein, in addition to usual dampers, the damper using Magnetorheological (MR) fluid instead of ordinary oil is used. In order to model the suspension system, a mass-spring model with eight degree-of-freedoms without considering the effect of car velocity is developed. A semi-active vibration control is presented to reduce the amplitude of automotive vibration caused by the alteration of road profile. In order to design a suitable control mechanism, first, an optimal control algorithm, Linear Quadratic Regulator (LQR) and Linear Quadratic Gaussian (LQG), are used to control the system;... 

A Reaction Wheel (RW) is a torque actuator which is used for attitude control of a satellite. Reaction Wheels usually consist of a brushless DC motor which rotates a flywheel. When the flywheel is accelerated by the motor, the reaction torque of the motor applies to the base of the RW and therefore the satellite can rotate along the RW spin axis. Due to frictionless surrounding of a satellite in space, a very small disturbance in a reaction wheel structure during its function may lead to instability of satellite and decrease the satellite precision and performance. There are some important sources of disturbance in an RW. Some of them are: 1- Unbalances in wheel (offset of center of gravity... 

Over the last decades the attention of the most modern countries about usage of wind has grown due to the recent crisis of energy. This renewable energy source offers a cost effective solution for electricity production. Wind energy is the best candidate among other sources due to wind turbines technology reliability. In order to gain maximum power from wind turbines, their size becomes relatively large, which creates more complexity in their repair and maintenance, furthermore Wind turbine downtime is outside the expectations, which is more costly than corrective maintenance, therefore in order to minimize sudden downtimes and related huge maintenance, a reliable monitoring technique must... 

Long bone reduction is one the conventional but hard and time consuming process in orthopedic surgery. This difficulty becomes harder when it comes to lower limbs which are under large tensile forces by strong muscles surrounding. With considerable progress in technology development robotic surgery in recent years, using robotic systems for simplification, accuracy improvement and quality of long bone fracture surgery is considered. In this study a six degrees of freedom parallel mechanism is considered for femoral reduction. The purpose of this project is designing a master robot for moving the mentioned mechanism with considering hardware limitation of this mechanism. This limitations... 

Nowadays a major part of energy, fresh water and sewer water in over the world are transmitted by buried pipe, and always these lines are under the loads and different stresses such as corrosion, earth quick and etc.
In many countries the age of these lines are more than 30 years which causes corrosion of the pipe wall and the necessity of health investigating of transmission lines has a special importance for the governments and leak detection can also keep the natural environment healthyand the costs will come down significantly, scientists and researchers have always tried different ways to check the health of the pipes.
In the field of leak detection and the problems of age... 

Non-uniform composite structures are widely being utilized in many modern industries including aerospace and automobile and wind turbine machines. Excessive vibration in these structures leads to dynamic instability and structural failure. In the present work, the vibration control of non-uniform composite structure particularly trapezoidal plates has been investigated using magnetorheological materials. The application of various smart materials including magnetorheological (MR) elastomer and magnetorheological fluids has been reviewed for vibration control. A trapezoidal composite plate with holes filled by MR elastomer has been considered for numerical simulations. The effect of location... 

Rotary equipment are being used in many industries over a wide range of applications, such as gas turbine. Due to the nature of the operating conditions, gas turbines are subjected to variety of damages especially crack propagation of a blade. The Cracks propagation may lead to catastrophic failure during operation. Therefore, detection of the crack presence and its propagation is very important and may reduce possible significant cost of the whole system failure. The thesis aims to investigate the cracks presence and their propagation effects on vibration of a turbine blade which is located at the National Iranian South Oilfields. First, theoretical study is calculated to validate an... 

Rotary machines including gas turbines have been widely used in many industries like gas reducing pressure stations and power plants. Blades are important components of gas turbines which are subjected to failure due to different kind of damages like crack occurrence. There are various reasons for crack occurrence and its propagation in blades. Presence of crack in the blades may lead to major failure, which in turn, result in emergency shutdown of the system. Therefore condition monitoring is employed to check the possibility of failures. In recent years, condition monitoring techniques have been developed to prevent unnecessary shutdown of the systems. The present thesis aims to... 

Concerns like fuel cost, pollution and global warming has made it necessary to look for new energy solutions. Renewable and alternative energies have proven themselves to be helpful in this matter. Renewable energy(RE) is the energy that comes from natural resources such as sunlight, wind, rain, tides, waves and geothermal heat, which are naturally replenished at a constant rate. Renewable energies are environmentally friendly, not cheap at the beginning but naturally available in a constant rate and wide spread, unlike fossil fuels that are localized in the limited places. In this thesis in order to generate environmental friendly power we consider two renewable energy resources: wind and... 

Corrosion study of the reinforced concrete is one of the most commonly investigation for the construction in civil engineering. The corrosion of embedded steel for the structures in the marine area like the Persian Gulf Sea Water needed considerable attentions. Presence of chlorides and decrease of pH in pores reinforcement depth of concrete is a serious problem. Research the corrosion rate in reinforced concrete system using fibers with a rebar is investigated. Cellulose and Carbon fiber materials are used as inhibitors. The addition of small quantities of these materials into the concrete mixture, will change the concrete permeability and the corrosion resistance rate. Tests demonstrate... 

Pipeline systems are one of the cheapest ways for distribution and transportation of petroleum and natural gas. The testing of pipes used in the petroleum industry is necessary to avoid unplanned process interruptions, environmental pollution and provide good safety. One of the methods which is used for pipeline inspection is the ultrasonic non-destructive testing (NDT) technique. The use of conventional NDT techniques such as ultrasonic thickness gauging is a slow inspection process, which becomes very expensive when full inspection is needed. Ultrasonic guided waves provide an appropriate fast screening technique. These waves stress the whole pipe wall and propagate along the length of the... 

The aerial vehicle capable of vertical takeoff and landing (VTOL), have created an interest in the community of researchers and admirers of Unmanned Aerial Vehicles. Among the existing UAV's, those with the capability of vertical takeoff and landing are prominent due to their higher maneuverability and hover capability. Quadrotors mostly have been considered as a flying robot for save and rescue operations in dangerous and unreachable places in addition to its military application. In cross shape of Quadrotor platform on each edge is appointed an electric motor with light rotors that usually are controled by considering motor rates as their only inputs. This thesis aims, to simulate and...