Design and Analysis of SMA-Based Tendon for Marine Structures

A tension-leg platform (TLP), as an offshore structure, is a vertically moored floating structure, connecting to tendon groups, fixed to subsea by foundations, to eliminate its vertical movements. TLPs are subjected to various non-deterministic loadings, including winds, currents, and ground motions, keeping the tendons under ongoing cyclic tensions. The powerful loads can affect the characteristics of tendons and cause permanent deformation. As a result of exceeding the strain beyond the elastic phase of the tendons, it makes unbalancing on the floated TLPs. Shape memory alloy (SMA)-based tendons due to their superelasticity properties may potentially resolve such problem in TLP structures. In the present work, performance and functionality of SMA wire, as the main component of SMA-based tendon under cyclic loading, have been experimentally investigated. It shows a significant enhancement in recovering large deformation and reduces the amount of permanent deformation

The Recent Advances in Magnetorheological Fluids-Based Applications

The magnetorheological fluids (MRF) are a generation of smart fluids with the ability to alter their variable viscosity. Moreover, the state of the MRF can be switched from the semisolid to the fluid phase and vice versa upon applying or removing the magnetic field. The fast response and the controllability are the main features of the MRF-based systems, which make them suitable for applications with high sensitivity and controllability requirements. Nowadays, MRF-based systems are rapidly growing and widely being used in many industries such as civil, aerospace, and automotive. This study presents a comprehensive review to investigate the fundamentals of MRF and manufacturing and applications of MRF-based systems. According to the existing works and current and future demands for MRF-based systems, the trend for future research in this field is recommended

Vibration and buckling analyses of tapered composite beams using conventional and advanced finite element formulations

Tapered composite beams are being used in various engineering applications such as helicopter yoke, robot arms and turbine blade in which the structure needs to be stiff at one location and flexible at another locations. Laminated tapered beams can be manufactured by terminating some plies at discrete locations. Different types of ply drop-off can be achieved depending on the application. Due to the variety of tapered composite beams and complexity of the analysis, no analytical solution is available at present and therefore finite element method has been used for the calculation of response. In the present thesis, the free vibration response and buckling of different types of tapered composite beams are analyzed first using conventional finite element formulation. Conventional finite element formulation requires a large number of elements to obtain acceptable results. In addition, continuity of curvature at element interfaces can not be guaranteed with the use of conventional formulation. As a result, stress distribution across the thickness is not continuous at element interfaces. In order to overcome these limitations, an advanced finite element formulation is developed in the present thesis for vibration and buckling analysis of tapered composite beams based on classical laminate theory and first-order shear deformation theory. The developed formulation is applied to the analysis of various types of tapered composite beams. The efficiency and accuracy of the developed formulation are established in comparison with available solutions, where applicable, as well as with the results obtained using conventional formulation. A detailed parametric study has been conducted on various types of tapered composite beams, all made of NCT/301 graphite-epoxy, in order to investigate the effects of boundary conditions, laminate configuration, taper angle, the ratio of the length of the thick section to the length of the thin section and the ratio of the height of the thick section, to the height of thin section

Impact Analysis of MR-Laminated Composite Structures

Laminated composite structures are being used in many applications, including aerospace, automobiles, and civil engineering applications, due to their high stiffness to weight ratio. However, composite structures suffer from low ductility and sufficient flexibility to resist against dynamic, particularly impact loadings. Recently, a new generation of laminated composite structures has been developed in which some layers have been filled fully or partially with magnetorheological (MR) fluids; hereafter we call them MR-laminated structures. The present article investigates the effects of MR fluid layers on vibration characteristics and specifically on impact loadings of the laminated composite beams. Experimental works have been conducted to study the dynamic performance of the MR-laminated beams

Hysteresis Behavior of Pre-Strained Shape Memory Alloy Wires Subject to Cyclic Loadings: An Experimental Investigation

Shape memory alloys (SMAs) are a class of smart materials with the ability to recover their initial shape after releasing the applied load and experiencing a relatively large amount of strain. However, sequential loading and unloading which is an unavoidable issue in many applications significantly reduces the strain recovery of SMA wires. In the present work, experimental tests have been performed to study the pre-strain effect of SMA wires on hysteresis behavior of SMA under cyclic loadings. The effects of cyclic loading on austenite and martensite properties have been investigated. SMA wires with diameter of 1.5 mm and length of 560 mm subjected to about 1000 cycles show about 3 mm residual deformation, which is approximately equal to 0.5% residual strain. It is observed that applying 1.7% pre-strain on the SMA wire fully eliminates the residual strain due to cyclic loading

Analysis, design optimization and vibration suppression of smart laminated beams

A general frame work is developed for the sensitivity analysis and design optimization of smart laminated composite beams with capability to suppress the vibration under random excitations. The smart structure consists of a host laminated composite beam with embedded/surface bonded piezoelectric sensors/actuators. A layerwise displacement model including the electro-mechanical coupling is utilized to account for the strong inhomogeneities through the thickness and to develop the finite element model. To perform the sensitivity analysis of the smart structure for different design parameters, analytical gradients based on developed layerwise finite element model for both static and dynamic problems are proposed. The developed sensitivity gradients provide an efficient way to predict the behavior of responses of smart structure without re-analysis. A design optimization algorithm based on developed analytical gradients and layerwise finite element model is then developed to determine the optimal design of the smart laminated beams for a variety of objective and constraints functions, including interlaminar stresses, weight and natural frequencies. The smart laminated beam design based on the developed optimization algorithm is used in the dynamic analysis and vibration control. An optimal control strategy, Linear Quadratic Regulator (LQR) is used to design the feedback control gain and to control the vibration response of system under deterministic loads. Effects of laminate configuration and sensor/actuator location are investigated in controlled response. An in-house experimental set-up is designed to demonstrate the performance and functionality of the proof-of-concept of smart composite beam. In many practical applications, including aerospace and automotive industries, smart laminated structures are exposed to random loading, considering this, an optimal control algorithm is developed to suppress the vibration response of the smart beam under random excitations. Different types of random loadings, including Gaussian white-noise, band limited and narrow-band excitations are investigated

Optimal Design of Adaptive Laminated Beam Using Layerwise Finite Element

First, an efficient and accurate finite element model for smart composite beams is presented. The developed model is based on layerwise theory and includes the electromechanical coupling effects. Then, an efficient design optimization algorithm is developed which combines the layerwise finite element analysis model for the smart laminated beam, sensitivity analysis based on analytical gradients and sequential quadratic programming (SQP). Optimal size/location of sensors/actuators is determined for dynamic displacement measurement purposes and for vibration control applications. For static and eigenvalue problems, the objective is to minimize the mass of the beam under various constraints including interlaminar stresses, displacements, and frequencies. For transient vibration problems, the objective is the minimization of the actuation control effort to suppress the vibration in a controlled manner. Illustrative examples are provided to validate the formulation and to demonstrate the capabilities of the present methodology