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This article aims to study the active control of free and forced vibration of a rotating functionally graded (FG) cylindrical shell using FG piezoelectric patches. Accordingly, this study uses sensors and actuators embedded in the shell's inner and outer surfaces. Considering classical theory and Love relations, ordinary differential equations of the system are extracted through the energy method and Lagrange equation. The validation part of the study involves comparing the results of this study with previous studies of rotating and nonrotating cylindrical shells. In addition, the convergence of vibration responses of the rotating cylindrical shell is investigated. Using the LQR method and considering the appropriate value for the weighting matrices, the system's vibration is attenuated, and the required voltage of the actuators is also obtained. Lastly, the effects of parameters such as position and performance index of piezoelectric on the closed-loop response are studied. The results show that changing piezoelectric properties in the form of a power law lead to a quicker decrease in vibration amplitude. [ABSTRACT FROM AUTHOR]

Coaxial magnetic gear is a cutting-edge technology introduced a few years ago. Its middle rotor is a rotating steel cylindrical shell with a variable array of holes that are filled by brass screws, hence it is such a complicated structure due to these holes. At first glance, it seems impossible to apply shear deformation theories to this unusual geometry, but for the first time, this article has introduced a novel mathematical methodology that creatively makes this possible. Consequently, an analytical formulation is presented for free vibration of this complicated structure, with no need to finite element software. The final aim is to extract natural frequencies and critical speeds in terms of different parameters. The formulation begins with the first-order shear deformation theory as the displacement field and continues with the Hamilton approach to gain governing equations of motion. Additionally, the effect of an external radial magnetic field is modeled by Maxwell's relation. In the end, the Galerkin scheme is followed for discretization of the governing equations. This scheme is compared to an older article to guarantee its accuracy. Subsequently, the natural frequencies are estimated in terms of physical parameters of the rotor such as angle and number of holes, hole-thickness to total-thickness ratio, magnetic field and some other parameters. The mode shapes are also depicted for better interoperation of rotor's behavior. The findings show that unlike geometric parameters (e.g., angle and number of holes), the radial magnetic field does not significantly affect the natural frequency. [ABSTRACT FROM AUTHOR]

The present study investigates vibrational behavior of a porous conical hollow rotor. Inner and outer rotor surface, sensor, and actuator strips made of piezoceramic are modeled and positioned, which are symmetrically distributed in the circumferential direction. Kinetic and potential energies were computed considering the effects of Coriolis and centrifugal force. Modeling of the system has been carried out assuming classical theory and using Lagrange approach for simple-supported boundary conditions. Also, the relations of piezoceramic and three types of porosity attend in equilibrium equations. The discretization of kinetic and potential energies using displacement field which is defined as double mixed series based on independent mode shape and time function leads to obtaining the equations in form of ordinary differential. To calculate the natural frequencies, the equations were converted to a special form of state space model. The correctness of the study is examined by comparing it with similar study results. The most consequential parameters affecting the forward and backward natural frequency, such as type and porosity coefficient, size, number, and thickness of piezoceramic, and the rotor angular velocity, are researched. The results demonstrate that the effect of porosity coefficient in various longitudinal modes on natural frequency is different. [ABSTRACT FROM AUTHOR]

This article studies free vibration of a functionally graded porous cylindrical small-scale shell made from porous metal and ceramic based on power law distribution. It is bonded with an adjustable array of strip-like piezoelectric elements. The behavior of integrated structure is modified by change of quantity and location of the elements. Motion equations are achieved through first-order shear deformation theory and principle of virtual work. Stress-strain relations are developed via nonlocal theory. Two comparative studies are presented for validation of formulation. A parametric study is reported to investigate effects of input parameters. [ABSTRACT FROM AUTHOR]

AbstractVortex-bladeless wind power generators are revolutionary concepts that use wind vortex-induced vibration to generate electricity through oscillation and vibration. This unique approach allows for a simpler design, environmental friendliness, on-site production, and lower initial costs than traditional wind turbines. This article presents a vibration analysis on the rod of a vortex bladeless wind power generator for a sandwich Timoshenko beam with various face sheets, including carbon nanotube (CNT), graphene platelets (GPL), and carbon nanorods (CNR), and cores, including positive and negative Poisson’s ratios in honeycomb structure, porous material, and metal foam. The governing equations of motion are derived using Hamilton’s principle and solved using trigonometric functions for different boundary conditions. The results of this research are compared with previous studies, and the maximum error is 3.05%. This study examined the effects of various parameters on the dimensionless natural frequencies. To obtain the highest peak amplitude for maximum energy harvesting, to choose the best rod for the bladeless wind power generator among the four types of cores and three types of factsheet layers, the honeycomb core with a positive Poisson’s ratio and the GPL-reinforced composite with the SNUPD distribution are selected because they have the most deflection. Some researchers have worked in the field of sandwich beams. Still, in this study, the main goal is to investigate the Timoshenko sandwich beam by examining all types of cores and reinforcements to increase efficiency and optimize bladeless wind generators to achieve maximum power. [ABSTRACT FROM AUTHOR]