Annular Disk Research Articles

Creep stress analysis of functionally graded transversely isotropic piezoelectric disc with variable thickness under rotation

Materials exhibiting different piezoelectric properties throughout their volume are referred to as functionally graded piezoelectric materials (FGPM). Due to their graded composition, the characteristics of these materials can be customized to fit particular needs in a variety of applications. Functionally graded piezoelectric materials are beneficial in many technical applications because of their versatility that enables increased performance, efficiency, and adaptability in a variety of disciplines. The objective of the current study is to analyse creep stresses in an annular disc composed of transversely isotropic, functionally graded piezoelectric material with varying thickness parameters. Creep stresses are evaluated analytically using the approach of Seth's transition theory. By using the stress-strain relations, the equations for mechanical stresses and electrical displacement are determined. Substituting these relations into the equilibrium equation a nonlinear differential equation is obtained. The findings are presented both numerically and graphically, demonstrating how the thickness parameter affects the circumferential stresses in the intermediate surface of the rotating disc. The disc made of transversely isotropic piezoelectric material PZT-4 exhibits higher creep stresses than other materials under consideration according to all of the numerical discussions and calculations. This work may provide an effective methodology for the analysis of functionally graded piezoelectric rotating discs and contribute to theoretical research and engineering applications.

Piezo-viscous micropolar fluid flow between two parallel annular disks

A theoretical analysis of the piezo-viscous dependence of micropolar fluid flow between parallel annular disks has been conducted. It is assumed that viscosity changes exponentially with pressure. Pressure is analytically approximated using a small perturbation method with the viscosity coefficient as the perturbation parameter. Squeeze film time, pressure, and load carrying capacity are calculated and graphically demonstrated across various viscosity–pressure characteristics. The study examines how an increase in cross-viscosity correlates with notable growth in pressure, response time, and bearing load. According to the results, micropolar fluid offers an increase in the load-bearing capacity and therefore lengthens the response time to prevent the contact of parallel annular disks. These observations are useful for bearings, seals, and lubrication systems, where controlling viscosity and pressure is crucial for smooth operation and productivity. As the limiting case of micro-polar fluid when the coupling number tends to zero or the couple stress parameter approaches infinity, without the annular ring, the present derivation agrees well with the Newtonian viscous case of parallel planar squeezing disks described by Bird et al. [Transport Phenomena (John Wiley & Sons, 2006)].

Magneto-Aeroelastic Dynamic Buckling and Flutter of rotating conductive annular disks under air-film loading

Magneto-Aeroelastic Dynamic Buckling and Flutter of rotating conductive annular disks under air-film loading

Memory-based thermoelastic modelling of an annular disc under heating and cooling processes

Memory-based thermoelastic modelling of an annular disc under heating and cooling processes

Effect of void geometry and magnetic anisotropy in controlling the vortex in sub-micron annular Permalloy disc

Ferromagnetic rings, particularly asymmetric Permalloy (Py) rings are recognized as promising configurations for spintronic devices, offering additional degrees of freedom for manipulating magnetic states, especially in vortex configurations. Through micromagnetic simulations, our study explores the impact on magnetization states and spin configuration concerning ring symmetry, aligning with the interest in controlling vortex states for information storage. We initially obtained zero-field spin configurations by varying ring thickness (t), observing a 360° domain wall in rings with t < 12 nm and bi-vortex wall in rings with t ∼36 nm during magnetization reversal. Notably, an extended stability of the global-vortex state was observed in rings with t > 36 nm, indicating the dominance of global-vortex nucleation in thick asymmetric rings during domain wall movement. We investigate the hysteresis loops and spin configurations by varying the in-plane and out-of-plane anisotropy values. Our findings reveal the presence of multiple vortex cores with different polarities and sense of rotations in the ring for the in-plane anisotropy ∼30 to ∼40 kJ m−3. Additionally, a global-vortex with two vortex cores was formed due to demagnetization energy. We analysed the energy profile of stable magnetization states for various t and anisotropy values. Interestingly, the shape of the hysteresis loop changes significantly for the disc containing different shapes of void. Circular and square-shaped geometries suggest that the bi-vortex state is a stable configuration during magnetization reversal in both cases. The study also indicates the stability of the vortex with a square-shaped void geometry up to a sufficiently large field. For the case of triangular-shaped voids, the global-vortex state was favored with even the small fields. The estimated spin canting angles are found to be correlated with the presence of vortex spin configurations. Overall, these results are important for the development of magnetization vortex-based spintronics devices.

Frictional Slippage of Annular Elastomeric Disks Compressed Between Rigid Platens

Abstract Compression of compressible, linearly elastic, annular disks by flat rigid platens is analyzed. Coulomb (Amonton) friction is assumed to act at the interfaces between the disk and the platens. Slip may occur in an outer annular region while the inner annular (bonded, stick) region of the disk does not slip. The critical radius (slip boundary) is of major interest. The governing equilibrium equations in terms of the deflections are satisfied exactly. Approximations are made in some of the boundary conditions and the transition (matching) conditions at the critical radius. Numerical results are presented for nearly incompressible disks. The effects of the radius ratio, aspect ratio, and Poisson's ratio of the disk, and of the coefficient of friction at the platens, on the critical radius, effective compression modulus, stresses, and radial deflection are investigated. Applications include structural (especially bridge) bearings, seismic-isolation devices, mounting blocks and bushings, gaskets, and sealing components.

Thermal stresses associated with a thermosensitive multilayered disc analysed due to point heating

In this paper, analytical solutions are presented for temperature and thermal behavior of a thermosensitive multilayered annular disc due to point heat source. Convective heating is applied to both the innermost and outermost layers. The nonlinearity of the thermal diffusivity equation is dealt using Kirchhoff’s transformation technique. A finite integral transform in the form of Bessel’s function is used to deal with the radial variable r. Fourier transform and angular eigen functions are also used to solve the thermal diffusivity equation. Deflection, resultant forces, shearing forces, resultant moments and thermal stresses are obtained. A mathematical representation is formulated for a 3-layered disc, with the inner, middle and outer layers composed of copper, zinc and aluminum respectively. The results are depicted graphically.

Thermoelastic response of a finite thick annular disc with radiation-type conditions via time fractional-order effects

The study investigates thermal interactions in a two-dimensional time fractional-order thermoelastic problem in a homogeneous, isotropic, and perfectly conducting thick annular disc subjected to a point impulsive sectional heat source. We utilize unconventional integral transformation techniques to study the thermoelastic response of a disc, in which an internal heat source is generated according to the linear function of the temperature and radiation-type boundary conditions. The time fractional-order thermoelastic theory is used to determine temperature, displacement, and stresses through a series of Bessel functions. Numerical calculations analyze fractional-order parameters on aluminum discs, incorporating time-based fractional derivatives into field equations for practical engineering scenarios, enhancing thermal properties analysis.

Nymphanthus namkadingensis, a new species of Phyllanthaceae from Laos

A new species of Nymphanthus (Phyllanthaceae), N. namkadingensis from Bolikhamxai Province, central Laos, is described and illustrated, along with its vernacular name and preliminary conservation status. The new species is similar to N. rubescens, but distinguished by having larger stipules, longer pedicels, and connate annular disc glands (vs. free disc glands) of pistillate flowers.

Uniplanar printed four‐port MIMO antenna with self‐coupling‐self‐decoupling mechanism

SummaryThe proposed research is primarily investigated with a new methodology of utilizing parasitic constrictors (PCs) as self‐coupling‐self‐decoupling (SCSD) mechanism which has been strategically implemented in multiple‐input multiple‐output (MIMO) antenna design. The design asserts an uniplanar printed four‐port MIMO antenna configuration in a confined footprint of 0.6 0.6 0.015 ( = lowest operating wavelength at 2.9 GHz), where the radiator and reflector act as an effective SCSD invoking spatial diversity. The orthogonally oriented radiators are composed of 4 circular disc with a 45° tilt and cutaway for reducing near‐field condensed currents and improve 10‐dB impedance matching. The antennas are assisted with a uniquely designed coplanar wave guides as SCSD, with rotationally symmetric PC. The PC has coplanar slots and a thin metallic strip that connects to a center‐fed annular disc as intrinsic current neturalizer. A pair of inverted L‐shaped symmetric strips is introduced in the coplanar slots to effectively couple the near‐field currents for self‐induced resonance mechanism as well as self‐decoupled for isolation improvement. To validate the rational counterparts, a prototype antenna has been simulated, fabricated, and experimented to operate from (2.9–5.45) GHz. The potential outcomes show good convergence in simulated and experimental results, with effective 10‐dB IBW, isolation, and diversity parameters, and demonstrate its prospective in C‐band (5G) applications.

Instability and trajectories of buoyancy-driven annular disks: A numerical study

Instability and trajectories of buoyancy-driven annular disks: A numerical study

Design of the Monopulse Feeding Network for a Slotted Waveguide Array on an Annular Disk

Design of a monopulse feeding network including a compact power distribution network and a monopulse comparator for a dual polarization slotted waveguide array fabricated on an annular disk is presented in this paper. As the slotted waveguide array is arranged on an annular disk, the feeding network is more complicated than that of a regular array such as a rectangular array. The design details of some key waveguide components, such as the compact assembly of H-plane T-junctions and E-plane elbows used to connect power distribution networks and radiation waveguides, are provided. Quasiplanar magic tees are designed and used to construct the compact sum and difference comparator. The antenna system contains two comparators, which are used to generate sum and difference beams for horizontal polarization and vertical polarization, respectively. Finally, the monopulse slotted waveguide array antenna is divided into two modules, a comparator module and an antenna module (including power distribution network), and fabricated with the layered processing and bonding process. The comparator module is measured using a network analyzer to verify its amplitude-frequency characteristics and phase-frequency characteristics. Screwing the comparator module and the antenna module together, a monopulse slotted waveguide array antenna is obtained, and the sum beam and difference beam characteristics of the antenna are measured in a microwave chamber and presented.

Analytical approach on stress analysis in a functionally graded piezoelectric annular disk with varying compressibility and varying density under internal pressure

When a crystal is subjected to mechanical stress, it exhibits piezoelectricity, also known as the piezoelectric effect, which is the emergence of an electrical potential across the crystal's sides. A few examples of piezoelectric materials include quartz, Rochelle salt, lead zirconate titanate (PZT4) and zinc oxide (ZnO). Piezoelectricity has many applications in regards to electrical transducers and signal devices. In this paper, the analytical solution is obtained for elastic-plastic stresses in a thin rotating disc formed of functionally graded piezoelectric material with varying compressibility and varying density for distinct angular velocity with internal pressure using Seth's transition theory. The distribution of the mechanical and electrical components can be precisely controlled by applying functionally graded piezoelectric materials (FGPMs). Transition theory assumes that a mid-zone (transition state) exists between elastic state and plastic state. A nonlinear Governing equation of the problem is formulated using equilibrium equation by substituting the values of stresses. For evaluation of transitional stresses, transition function R is assumed in terms of radial stresses and equations are solved analytically by considering the transition (critical points) of the differential equation. The investigation focuses on how the rotational velocity and internal pressure affects the radial and circumferential distribution of stresses. With the help of graphs and mathematical calculations, it is observed that both variable density and variable compressibility have significant effect on the performance of a functionally graded piezoelectric materials. Therefore, it can be concluded that an annular disc made up of functionally graded piezoelectric materials is safer than that of homogeneous piezoelectric materials for engineering design purposes.

Electrostatic potential of a uniformly charged annulus

The calculation of the electrostatic potential and/or electrostatic field due to a continuous distribution of charge is a well-covered topic in all calculus-based undergraduate physics courses. The most common approach is to consider bodies with uniform charge distribution and obtain the quantity of interest by integrating over the contributions from all the differential charges. The examples of a uniformly charged disk and ring are prominent in many physics textbooks since they illustrate well this technique at least for special points or directions of symmetry where the calculations are relatively simple. Surprisingly, the case of a uniformly charged annulus, namely, an annular disk, is largely absent from the literature. One might speculate that a uniformly charged annulus is not extremely interesting since after all, it is a uniformly charged disk with a central circular hole. However, we show in this work that the electrostatic potential created by a uniformly charged annulus has features that are much more interesting than one might have expected. A uniformly charged annulus interpolates between a uniformly charged disk and ring. However, the results of this work suggest that a uniformly charged annulus has such electrostatic features that may be essentially viewed as ring-like. The ring-like characteristics of the electrostatic potential of a uniformly charged annulus are evident as soon as a hole is present no matter how small the hole might be. The solution of this problem allows us to draw attention to the pedagogical aspects of this overlooked, but very interesting case study in electrostatics. In our opinion, the problem of a uniformly charged annulus and its electrostatic properties deserves to be treated at more depth in all calculus-based undergraduate physics courses covering electricity and magnetism.

Wave scattering in cylindrical waveguides: Analyzing flexible shells and liner conditions

The scattering of fluid-structure-coupled waves is investigated in a cylindrical waveguide consisting of flexible shells and an expansion chamber connected via annular rigid discs. The scattering performance of the waveguide is studied in the presence of acoustic liners along the walls of the expansion chamber and the geometric variations along interfaces. A mode-matching method is applied to solve the corresponding mathematical problem. The study focuses on fluid- and structure-borne modes propagating in the flexible shells. The eigenfunctions in this case are non-orthogonal and obey generalized orthogonal properties, involving auxiliary parameters related to the ring conditions at the edges of the flexible shells. Although we considered clamped connections, the analysis can be extended to other ring conditions with appropriate changes. Through continuity conditions at the interfaces, orthogonal modes are used to project solutions in liner regions, resulting in linear algebraic systems. The performance of the waveguide is examined in terms of scattering powers and transmission loss as functions of frequency, chamber length, liner length, and porous screen impedance. It is observed that the variations in these parameters have a major influence on acoustic attenuation in the waveguide. These results are relevant for designing acoustic enclosures for different frequency bands.

Experimental and numerical study of high-intensity sound in the cavity between rotator and stator of high- pressure compressor

An experiment is conducted in a multistage high-pressure compressor to investigate noise and rotor blade vibration. When vibration with high amplitude occurs in the rotor blade, high-intensity sound occurs within the compressor. The amplitude of noise inside the compressor varies with the amplitude of blade vibration, and the variation laws are consistent. Therefore, an annular disk cavity model, the simplified cavity between the rotator and stator of a high-pressure compressor, is built to study the high-intensity sound in the compressor by numerical simulation. The motion processes of the vortex structure inside the cavity are captured. The acoustic mode of the annular disk cavity model is excited at Ma 0.2, at the same time the sound pressure in the cavity is characterized with obvious a form of circumferential second order. The internal sound pressure gradually increases along the radial direction. Meanwhile, an annular disk cavity structure is established for experimental study. The characteristics of the acoustic mode of the annular disk cavity structure obtained in the simulation and experiment are consistent.

A proof-of-concept Bitter-like HTS electromagnet fabricated from a silver-infiltrated (RE)BCO ceramic bulk

A novel concept for a compact high-field magnet coil is introduced. This is based on stacking slit annular discs cut from bulk rare-earth barium cuprate ((RE)BCO) ceramic in a Bitter-like architecture. Finite-element modelling shows that a small 20 turn stack (with a total coil volume of < 20 cm3) is capable of generating a central bore magnetic field of > 2 T at 77 K and > 20 T at 30 K. Unlike resistive Bitter magnets, the high-temperature superconducting (HTS) Bitter stack exhibits significant non-linear field behaviour during current ramping, caused by current filling proceeding from the inner radius outwards in each HTS layer. Practical proof-of-concept for this architecture was then demonstrated through fabricating an uninsulated four-turn prototype coil stack and operating this at 77 K. A maximum central field of 0.382 T was measured at 1.2 kA, with an accompanying 6.1 W of internal heat dissipation within the coil. Strong magnetic hysteresis behaviour was observed within the prototype coil, with ≈30% of the maximum central field still remaining trapped 45 min after the current had been removed. The coil was thermally stable during a 15 min hold at 1 kA, and survived thermal cycling to room temperature without noticeable deterioration in performance. A final test-to-destruction of the coil showed that the limiting weak point in the stack was growth-sector boundaries present in the original (RE)BCO bulk.

In-plane vibration of circular annular disk for application to water pipe diagnosis

In-plane vibration of circular annular disk for application to water pipe diagnosis

Semi-analytical approach-based studies of the squeeze film lubrication between rough porous annular discs: Rabinowitsch fluid model

In recent years, there has been much interest in the effects of porosity and surface roughness (SR) or geometric irregularities between two moving plates under hydrodynamic lubrication. Porous bearings are used extensively in wide range of equipment, including computers, office equipment, home appliances, electric motors, and vehicles. In light of the importance of the aforementioned applications, we explored how SR and porous materials affect annular discs under the condition of a squeeze film. A five-point Gauss quadrature integral formula has been used to examine the characteristics of annular discs and a small perturbation method has been used to discretise the governing Rabinowitsch fluid flow (RFF) equations. The impact of nonlinear parameters on the behaviour of porosity and SR have been visualised in terms of film pressure (FP), load carrying capacity (LCC), and squeeze response time (SRT) of annular discs. Under the conditions of pseudoplastic and dilatant fluids, the effects of SR and porous materials between annular discs have been estimated in the form of the film pressure, LCC, and SRT and are presented in this manuscript as tables and graphs. According to the findings, the performance of an annular disc is significantly affected by porous material and radial roughness patterns. In addition, when RFF is carried through a rough surface and porous media, the performance is found to improve for dilatant fluids but suffer for pseudoplastic fluids.

Stresses occurring on a cylinder with annular B4C, Tİ and AL (2024) materials

In this study, the calculated thermal stresses on a layered annular circular disk were analyzed analytically. At the end of the analysis, it was observed that the thermal tensile strength of the boron carburetor (B4C) with a high modulus of elasticity is higher than titanium, and titanium is more than aluminum. The results obtained are shared with the literature and presented with graphs.