Sharif Digital Repository

Rapid growth in generating power from wind turbines led to application of long laminated composite blades. However, as the length of blades increases, the risk of failure due to excessive vibration increases. Therefore, a reliable wind power generator requires an efficient and accurate, yet economical structural health monitoring system to detect vibration and apply a reliable control to prevent from unpredicted failure. This paper presents an optimal, low cost and continuous vibration monitoring system for laminated composite blades using Fiber Bragg Grating (FBG). Utilizing a layerwise displacement theory, the Finite Element (FEM) model has been developed for the wind turbine blade. The... 

Vibration characteristics of laminated composite beams with magnetorheological (MR) layer are investigated using layerwise theory. In most studies, shear strain across the thickness of MR layer has been considered as a constant value, which does not precisely describe the shear strain. In this study, layerwise theory is employed to develop a finite element formulation to investigate MR-laminated beams. Experimental tests under different magnetic fields are carried out to verify the numerical results. Layerwise numerical results are compared with the experimental results and other theories. An empirical expression for complex shear modulus is presented. The effects of MR layer thickness on... 

Vibration behavior of adaptive laminated composite beams integrated with magnetorheological (MR) fluid layer has been investigated using layerwise displacement theory. In most of the existing studies on the adaptive laminated beams with MR fluids, shear strain across the thickness of magnetorheological (MR) layer has been assumed a constant value, resulting in a constant shear stress in MR layer. However, due to the high shear deformation pattern inside MR layer, this assumption is not adequate to accurately describe the shear strain and stress in MR fluid layer. In this work a modified layerwise theory is employed to develop a Finite Element Model (FEM) formulation to simulate the laminated... 

Vibration behavior of adaptive laminated composite beams integrated with magnetorheological (MR) fluid layer has been investigated using layerwise displacement theory. In most of the existing studies on the adaptive laminated beams with MR fluids, shear strain across the thickness of magnetorheological (MR) layer has been assumed a constant value, resulting in a constant shear stress in MR layer. However, due to the high shear deformation pattern inside MR layer, this assumption is not adequate to accurately describe the shear strain and stress in MR fluid layer. In this work a modified layerwise theory is employed to develop a Finite Element Model (FEM) formulation to simulate the laminated... 

Laminated composite beams with non-uniform thickness are being used as primary structural elements in a wide range of advanced engineering applications. Tapered composite structures, formed by terminating some of the plies, create geometry and material discontinuities that act as sources for delamination initiation and propagation. Any small damage or delamination in these structures can progress rapidly without any visible external signs. Due to this reason early detection of damage in these systems during their service life is receiving increasing attention. The presence of a crack in a component or structure leads to changes in its global dynamic characteristics results in decreases in... 

Buried pipe lines are an efficient way of transporting of water, sewage, oil, and gas resources in all over the world. Since the buried pipe lines are exposed to many unexpected conditions, such as landslides, corrosion, fatigue, earthquakes, material flaws or even intentional damaging, so the inspection requirements lead to adoption of new method of maintenance, protection and conserving. This report aims to improve the trustworthiness, reliability, yet economical technologies for monitoring of behavior and manner of buried pipe lines during operation and assessing the risk of pipe lines failure. Distributed sensors (piezoelectric) are surface designed and embedded to investigate the... 

Structural integrity and ensuring the stability of steel frame structures, including marine and coastal structures, are the main challenges for designers in civil infrastructures, particularly in oil platforms, subjected to tough periodic and non-periodic environmental loading conditions. Variable loadings with different amplitudes and frequencies may lead to the stability of steel structures loss. In order to keep the stability of the steel structures and prevent possible damages, reliable yet efficient structural control systems are in demand. Conventional structural control systems need significant activation energy and/or in-depth users knowledge to be effective. Most recently, smart... 

A novel semi-active control system for suspension systems of passenger car using Magnetorheological (MR) damper is introduced. The suspension system is considered as a mass-spring model with an eight-degrees-of-freedom, a passive damper and an active damper. The semi-active vibration control is designed to reduce the amplitude of automotive vibration caused by the alteration of road profile. The control mechanism is designed based on the optimal control algorithm, Linear Quadratic Regulator (LQR). In this system, the damping coefficient of the shock absorber changes actively trough inducing magnetic field. It is observed that utilizing the present control algorithm may significantly reduce... 

The developing of technology has discovered new materials which have been applied to improve the performance of structures. The researchers have recently increased the attention in controllable fluids and its applications. Magnetorheological (MR) dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, robustness and safe manner operation in case of fail have made them attractive devices to passive, semi-active and active control in mechatronic, civil, aerospace and automotive applications. The characteristics of the MR damper change when the rheological fluid is... 

This paper deals with vibrational behaviors of blades with cracks which are key components in rotating machines. However, since modelling and analysis of real blade is a complex problem, a simplified cantilever beam with both chordwise (in X-Y plane) and flapwise (in X-Z plane) motion are modeled instead. Finite Element Method (FEM) is used to model beam and to investigate its natural frequencies with a crack. Finally a limit function using modal data is developed and reliability analysis of beam model is performed. © 2017 IEEE  

Shape Memory Alloys (SMAs) are a new generation of smart materials with the capability of recovering their predefined shape after experiencing a large strain. This is mainly due to the shape memory effects and the superelasticity of SMA. These properties make SMA an excellent alternative to be used in passive, semi-active, and active control systems in civil engineering applications. This paper presents a comprehensive review of the recent developments in the applications of SMA in civil infrastructures, including, steel, concrete, and timber structures. This review reveals the significance of SMA in civil infrastructures particularly, the enhancement of structural behavior and energy... 

The vibration suppression of semi-actively controlled jacket-type offshore platforms using Magnetorheological (MR) dampers is studied. The main goal of using MR damper system is to reduce vibration caused by wave hydrodynamic forces. A fixed jacket-type offshore platform affected by wave-induced hydrodynamic forces and controlled by MR dampers is modelled as a semi-active controlled system with 30 DOFs. In comparison with earlier studies, an improvement in problem modelling is made. Based on the wave theory and Morison equation, an exosystem is designed to simulate regular wave forces. The necessary input voltage to MR dampers to generate desired damping force is derived by clipped optimal... 

Magnetorheological (MR) damper is a prominent semi-active control device to vibrate mitigation of structures. Due to the inherent non-linear nature of MR damper, an intelligent non-linear neuro-fuzzy control strategy is designed to control wave-induced vibration of an offshore steel jacket platform equipped with MR dampers. In the proposed control system, a dynamic-feedback neural network is adapted to model non-linear dynamic system, and the fuzzy logic controller is used to determine the control forces of MR dampers. By use of two feedforward neural networks required voltages and actual MR damper forces are obtained, in which the first neural network and the second one acts as the inverse... 

In the present work, a multi sensing grasper has been developed for minimally invasive surgery with embedded ZnO piezoelectric and Fiber Bragg Grating sensors. In this model, a sensing patch equipped with three FBG sensors to sense the temperature in rage of 800 n.m and two separated FBG in range of 1550 m.m to detect the displacement in x and y directions. ZnO piezoelectric is highly sensitive to time and provides a good resistance to temperature. Therefore, this sensor is used for measuring the rate of strain and creep coefficient. A finite element approach based on the viscous material theory and plane displacement theory of anisotropic materials has been utilized to obtain the compliance... 

Pipelines are one of the most important and efficient ways for transporting energy like water, gas, oil and etc. between different places all across the world. As these pipelines are located in different conditions and situations, they are all sensitive to a wide variety of damages like vibration, so monitoring their structural behavior is an essential task. Monitoring pipeline vibration caused by cavitation through an orifice by a piezoelectric sensor is presented in this paper  

Titanium matrix composites (TMCs) have wide application prospects in the field of aerospace, automobile and other industries because of their good properties, such as high specific strength, good ductility, and excellent fatigue properties. However, in order to improve their fatigue strength and life, crack initiation and growth at the surface layers must be suppressed using surface treatments. Shot peening (SP) is an effective surface mechanical treatment method widely used in industry which can improve the mechanical properties of a surface. However, artificial neural networks (ANNs) have been used as an efficient approach to predict and optimize the science and engineering problems. In... 

In Minimally Invasive Surgery (MIS) the operation is performed through introducing surgery instruments, graspers, scissor into the body. 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 by surgeon and to measure the transmitted response to the tissue/organ. © 2009 IEEE  

In recent years, structures integrated with magnetorheological (MR) fluid have been considered for their tunable dynamic characteristics. Shear modulus of MR layer in composite structure is dramatically lower than the elastic layers, leading to high shear deformation inside the MR layer, thus classical theories are not accurate enough to predict the dynamic behavior of such structures. In present study a layerwise displacement theory has been utilized to predict a more accurate deformation for MR-composite beam and equation of motions derived using finite element model (FEM). ASTM E756-98 was employed to evaluate the complex shear modulus of MR fluid. By experimental test a practical... 

Considerable attention has been devoted recently to vibration control using intelligent materials as sensor/actuator. An intelligent control technique using a neural network is proposed for vibration control of micro-cantilever beam with bonded piezoelectric sensor and actuator. Structure modal characteristic analysis is done to determine the optimal configuration of piezoelectric sensor and actuator. With the piezoelectric elements are surface-bonded near the same position to the fixed end of micro-cantilever beam, an optimal controller, linear quadratic Gaussian (LQG), and an intelligent strategy based on neural network are investigated. Finally, the simulation results are given to... 

A novel intelligent semi-active control system for an eleven degrees of freedom passenger car's suspension system using magnetorheological (MR) damper with neuro-fuzzy (NF) control strategy to enhance desired suspension performance is proposed. In comparison with earlier studies, an improvement in problem modeling is made. The proposed method consists of two parts: a fuzzy control strategy to establish an efficient controller to improve ride comfort and road handling (RCH) and an inverse mapping model to estimate the force needed for a semi-active damper. The fuzzy logic rules are extracted based on Sugeno inference engine. The inverse mapping model is based on an artificial neural network...