Sharif Digital Repository

Laminated composite beams are being widely used in engineering applications, including aerospace and automobile where the structures are highly subjected to non-deterministic random loadings, requiring a reliable technique to ensure the stability of structure during operation. A Novel N-layer model of layerwise theory (LWT) for laminated composite beams incorporated with magnetorheological fluid (MR-laminated beams) is developed. In addition, a finite element model of tapered laminated composite beams incorporated with magnetorheological fluid (MR-tapered beam) based on layerwise theory is developed. The dynamic response of the present model for uniform and tapered beams have been compared... 

Magnetorheological (MR) materials show variations in their rheological properties when subjected to varying magnetic fields. They have quick time response, in the order of milliseconds, and thus are potentially applicable to structures and devices when a tunable system response is required. When integrated with a structural system, they can produce higher variations in the dynamic response of the structure. In this thesis, vibration behavior of laminated-composite beam with MR Fluid is investigated.In most studies, shear strain across the thickness of MR layer has been considered as a constant value which does not precisely describe the actual shear strain field. Shear modulus of MR layer in... 

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... 

During the past two decades, laminated composite structures have been used for many engineering applications, including aerospace, automotive, sport equipment and pressure vessels.
In spite of the excellent properties of strength to weight ratio, composite structures are vulnerable to failure when subjected to impact and vibration. It is well known that impact damage may severely degrade the strength and stability of laminated composite structures. For this reason the effect of impact on composites has been a subject of extensive research.
There are several ways of decreasing the vibration energy of structures, such as diminishing the source energy, designing structures... 

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... 

In this thesis, we investigate the theoretical and experimental vibrations of a cylindrical shell with an electrorheological core. Magnetorheological and electrorheological fluids are the most suitable materials used in smart structures and have various applications in the automotive, aerospace, civil engineering, medical engineering and robotics industries. We use starch particles and silicone oil to make electrorheological fluid. Then we make a sandwich beam with an ER core and extract the modal parameters of the structure using the modal test. Using the ASTM standard, we estimate the shear modulus of the fabricated ER fluid. In the following, based on the equations developed for the... 

This study is a comprehensive analysis on the nonlinear vibration of a sandwich plate containing magnetorheological (MR) fluid as the core layer. The nonlinear aeroelastic analysis of the structure is also discussed to determine the flutter boundaries. In this study, the numerical Generalized Differential Quadrature (GDQ) method is applied to investigate the free vibration analysis of a sandwich plate with a MR fluid core. The classical thin plate theory (CPT) and the First-order Shear Deformation Theory (FSDT) are assumed for face layers and core layer, respectively. These theories along with Von-Karman kinematic formulations are incorporated to extract governing equations. The equations of... 

The present study investigates the effect of MR materials on the vibrations of three-layer pretwisted rotating beams. For this purpose, by considering MR material as the core of the rotating beam and using Hamilton's principle, the equations governing the three-layer rotating beam are extracted. After solving the desired equation, we optimize the dynamic behavior of the three-layer beam at different rotational speeds. Using the Genetic Algorithm optimization tool, the desired beam weight will be minimized and maximum damping will be applied to the desired system. The goal is to find the optimum magnetic field strength for maximum damping in the system at any rotational speed, in addition to... 

Various public transportation types, e.g., Trains, Buses, and Airplanes, are susceptible to damages made by the impacts of the external objects, which are typically classified as low to medium velocity impacts. This problem reveals the significance of investigating the effects of impact on thin-walled structures, which are the main components of these vehicles' bodies. Owing to the controllable rheological properties of the Magnetorheological fluid with respect to the magnetic field, it can be utilized to control the structure exposed to impact adaptively and minimize the damages. Due to this purpose, sandwich structures such as sandwich beams and plates, thanks to their extended response... 

This study considers the flutter analysis rotating blade of a turbo machinery made of magneto rheological elastomer core. The Smith theory is used for modeling the compressible subsonic flow. The classical Hamilton’s principle along with the assume mode method is used to set up the equations of motion. The validity of the derived formulation is confirmed through comparison with those obtained from the finite element software and the available results in the literature. Various parametric studies including the effects of applied magnetic field, core layer thicknesses, rotating speed, setting angle are examined for considered configuration of the rotating blade. The results show that the first... 

Magnetorheological fluids are suspensions of magnetic solid particles suspended in a nonmagnetic matrix fluid. By imposing an external magnetic field, particles are arranged in microstructures aligned with the external field and hence, dramatically affect the fluid flow. Since the strength of the magnetic field determines the resistance of these microstructures against flow, the rheology of the suspension is a function of the intensity of the external magnetic field. The goal of the present work is to study the role of non-gap-spanning magnetic clusters on the rheology of a magnetorheological fluid. Here, first a robust tool for direct numerical simulation of magnetic suspensions is... 

Regaining biomechanical function, comfort and quality of every-day life is a prime consideration when designing prosthetic devices for amputees. The magnetorheological (MR) prosthetic knee, which is the subject of this study, is an example of such a device. The study presents a comprehensive and a combined MR device design and MR fluid design approach, aiming to advance the MR prosthetic knee. First, this study focuses on developing a new configuration on magnetorheological (MR) brake damper as prosthetic knee. The new configuration is a rotary damper using MR fluid with a single rotary disc will act as a brake while MR fluid is activated by magnetic field in different walking gait. The main... 

This work is related to the research in the fields of particulate flow with the presence of external magnetic field and simulating movements of particles till making chain of particles. Using direct numerical simulation method for a two-way coupling of fluid and magnetic governing equations makes a more roboust and precise method. Also, using some assumptions simplified general maxwell equations to set of magnetostatic equations. these eqautions are solved by the boundary element method and the integral equations. Using analytic integrals and calculation of magnetic intensity are some techniques suggested for improving the preciesion of the presented work. the magnetic force and torques can... 

The Quadriceps Muscle as one of the major muscles of the human body plays a key role in knee function. Strengthening of this muscle is recommanded to prevent knee pain and even cure some diseases. Many believe that by strengthening the medial part with respect to the lateral part of the quadriceps muscles, patellofemoral pain syndrome can be prevented or treated. In this regard, a muscle strengthening system, based on magneticorheological brake is designed which provides isometric, isotonic and isokinetic exercise of knee joint and also enables the selective muscle strengthening. Beforehand a musculoskeletal model of lower extremity is developed in OpenSim software, capable to estimate force...