A review of vibration control methods for marine offshore structures

Aeroelastic characteristics of magneto-rheological fluid sandwich beams in supersonic airflow

Vibration and damping of composite sandwich box column with viscoelastic/electrorheological fluid core and performance comparison

In this paper, active flutter suppression of a simply supported circular sandwich cylindrical shell with a tunable electrorheological fluid (ERF) core, under axial supersonic gas flow, is studied. The structural analysis is based on the classical thin shell theory, the ERF core is modeled as a first-order Kelvin–Voigt material, and the Krumhaar's modified supersonic piston theory is utilized to model the aerodynamic loading. Hamilton's principle is used to formulate the dynamic equations of motion together with the relevant boundary conditions. The generalized Fourier expansions in the circumferential and axial directions in conjunction with the classical Galerkin method are employed to set up the governing equations in the state-space domain. The critical free stream static pressures at which unstable oscillations arise are calculated for selected applied electric field strengths and cylinder length ratios. The Runge–Kutta time integration algorithm is used to determine the open-loop aeroelastic response of the system in two basic loading configurations, namely, a concentrated impulse point load and a sonic boom line load. Subsequently, a sliding mode control (SMC) strategy is adopted to actively suppress the closed loop system dynamic response in supersonic flight condition. Simulation results demonstrate performance and effectiveness of the adopted ERF-based SMC scheme. Limiting cases are considered and good agreements with the data available in the literature are obtained.

Supersonic flutter control of an electrorheological fluid-based smart circular cylindrical shell

This paper investigates the active control of the supersonic flutter motion of an elastically supported rectangular sandwich plate, which has a tunable electrorheological (ER) fluid core and rests on a Winkler–Pasternak elastic foundation, subjected to an arbitrary flow of various yaw angles. The classical thin plate theory is adopted. The ER fluid core is modeled as a first order Kelvin–Voigt material, and the quasi-steady first order supersonic piston theory is employed for the aerodynamic loading. The generalized Fourier expansions in conjunction with Galerkin method are employed to formulate the governing equations in the state-space domain. The critical dynamic pressures at which unstable panel oscillations occur are obtained for a square sandwich plate, with or without an interacting soft/stiff elastic foundation, for selected applied electric field strengths and flow yaw angles. The Runge–Kutta method is then used to calculate the open-loop aeroelastic response of the system in various basic loading configurations. Subsequently, a sliding mode control (SMC) synthesis is set up to actively suppress the closed loop system response in yawed supersonic flight conditions with imposed excitations. The results demonstrate the performance, effectiveness, and insensitivity with respect to the spillover of the proposed SMC-based control system.

Flutter suppression of an elastically supported plate with electro-rheological fluid core under yawed supersonic flows

In this paper, the vibration and damping of a hollow sandwich box column containing a viscoelastic layer (VEL) or an electrorheological (ER) or magnetorheological (MR) fluid core with a constraining layer are analyzed and a comparison of performance is made. The hollow sandwich box column comprises two skin plates and a VEL/ER/MR fluid core layer. The finite element method is used to study the vibration and damping behaviors of the column. The natural frequencies and modal loss factors are obtained by solving the complex eigenvalue problem. The modal dampings and natural frequencies of the column are calculated for various electric as well as magnetic fields and their performance is compared with that of the viscoelastic core layer for the clamped-free boundary condition. Effects of core thickness, electric voltage and magnetic field on the vibration behavior of the sandwich box column are investigated.

Vibration and damping studies on a hollow sandwich box column with a viscoelastic/electrorheological/magnetorheological fluid core layer by the finite element method

Gout is a form of metabolic arthritis originated on grounds of increased accumulation of monosodium urate (MSU) crystals in joints. Current study focuses on anti-arthritic activities of β -carotene on MSU crystal-induced gouty arthritis rats in comparison with the non-steroidal anti-inflammatory drug, indomethacin. The evaluation was done by taking into account paw oedema, lysosomal enzymes, anti-oxidant enzymes, lipid peroxidation, serum biochemical parameters (uric acid, creatinine), serum cytokines (TNF- α , IL-1 β ) and histopathological studies. After the induction of MSU crystals, the lysosomal enzymes were increased, antioxidant enzymes were reduced, lipid peroxidation increased and paw volume increased. β -carotene treated at a dose of 10 mg/kg of body weight stabilizes lysosomal enzymes, increases anti-oxidant enzymes, regulates lipid peroxidation and decreased paw volume. The drug β -carotene potentially influences anti-inflammatory effects in arthritic group which is evident from the reduction in the elevated levels of inflammatory cytokines, TNF- α and IL-1 β . Current study is an evidence of anti-inflammatory and anti-oxidant effects of β -carotene against MSU-crystal induced gouty arthritis rats.

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K. Ram Kumar

Papers

Vibration and damping studies on a hollow sandwich box column with a viscoelastic/electrorheological/magnetorheological fluid core layer by the finite element method

Supplementation with β-carotene aids minimize inflammation in monosodium urate crystal- induced gouty arthritis in Wistar albino rats