Hollow Cylinder Research Articles

3D‐structure coupled monopole designs with lower frequency resonance

AbstractIn this study, we investigated three‐dimensional configurations involving a monopole‐coupled wired ring, a hollow metallic cylinder, and wired helix spring to achieve resonance lower than quarter‐wave resonance. The resonance frequency of a quarter‐wave monopole, originally 2.05 GHz, was significantly lowered by 54.53% through effective coupling with a wired ring, and a quarter‐wave monopole properly coupled with a hollow metallic cylinder experienced a large decrease of 64.34%. The primary incentive for connecting a wired ring to a hollow metallic cylinder is to significantly reduce resonance frequency. Efforts were also made to lower resonance frequency in a wired helix spring with a length close to that of the wired ring, resulting in a substantial 78.83% reduction in resonance frequency. The −10 dB bandwidth was 14.63% for the quarter‐wave monopole, 27.21% for the monopole‐coupled wired ring, 33.71% for the monopole‐coupled hollow metallic cylinder, and 4.69% for the monopole‐coupled helix spring. The ka values for the monopole‐coupled wired ring, hollow metallic cylinder, and helix spring were 0.35, 0.27, and 0.16, respectively. Hence, these antennas can be classified as electrically small antennas. The achieved resonant frequencies have applications in various wireless communication scenarios. The experimental results from the fabricated prototype agree well with the simulation results.

A comparison of Finite difference schemes to Finite volume scheme for axially symmetric 2D heat equation

In this work, we compare finite difference schemes to finite volume scheme for axially symmetric 2D heat equation with Dirichlet and Neumann boundary conditions. Using cylindrical coordinate geometry, we describe a mathematical model of axially symmetric heat conduction for a stationary, homogeneous isotrophic solid with uniform thermal conductivity in a hollow cylinder with an exact solution in a particular case. We obtain the numerical solution of the PDE adapting finite difference and finite volume discretization techniques. Compared to the exact solution, we explore that the numerical schemes are the sufficient tools for the solution of linear or nonlinear PDE with prescribed boundary conditions. Furthermore, the numerical solution discrepancies in the results obtained from Explicit, Implicit and Crank-Nicolson schemes in Finite Difference Method (FDM) are extremely close to the exact solution in the case of Dirichlet boundary condition. The solution from the Explicit scheme is slightly far from the exactsolution and the solutions from Implicit and Crank-Nicolson schemes are extremely close to the exact solution in the case of Neumann boundary condition. Likewise, the numerical solutions obtained in the Finite volume method (FVM) are extremely close to the exact solution in the case of the Dirichlet boundary condition and slightly away from the exact solution in the case of the Neumann boundary condition.

Corrosion-Induced Cracking Model of Concrete Considering a Transverse Constraint.

The performance of corrosion-induced cracking of reinforced concrete members under transverse constraints was studied. Based on the theory of elastic-plastic mechanics and the hypothesis of uniform corrosion of a steel bar, a three-layer hollow cylinder model was established to predict the critical corrosion of the steel bar at the time of the cracking of the concrete cover. Taking the constraint of stirrups on surrounding concrete into consideration, it can be used to predict the corrosion rate of members with stirrups at the time of the cracking of the concrete cover, which further expands the application range of the corrosion-induced cracking models of concrete. On this basis, the critical corrosion rate of concrete under different stirrup ratios at the time of cracking was measured. The calculated results of the model are in accordance with experimental data. For corner steel bars, when the stirrup spacing is less than 100 mm, the existence of stirrups can effectively delay the occurrence of rust expansion cracks and enhance the durability of the structure. On the basis of this study, the problem of corrosion expansion and cracking of the concrete cover caused by non-uniform corrosion of steel bars along longitudinal and radial directions needs to be further studied in the future.

Parabolic Boundary-Value Problems of Mathematical Physics in a Piecewise Homogeneous Wedge-Shaped Hollow Cylinder

Parabolic Boundary-Value Problems of Mathematical Physics in a Piecewise Homogeneous Wedge-Shaped Hollow Cylinder

Numerical Analysis of the Stress State of Near-Circular Hollow Cylinders Made of Functionally Graded Materials

Numerical Analysis of the Stress State of Near-Circular Hollow Cylinders Made of Functionally Graded Materials

Задача нелинейной теории упругости о растяжении и кручении составного цилиндра с предварительно напряжённым включением, содержащим винтовую дислокацию

The problem of large torsional and tension-compression deformations of a composite circular cylinder of incompressible Bartenev-Khazanovich material is considered. The cylinder contains a central circular cylindrical inclusion in which a concentrated screw dislocation is formed. It is pre-twisted and stretched (or compressed) along the axis and bonded to an unstressed external hollow cylinder. A single reference configuration is used when solving a problem for a composite body. This configuration is natural (unstressed) for the outer hollow cylinder and prestressed for the inner solid cylinder. The large deformation superposition theory is used to write the determining ratios of the material of the inner cylinder. The nonlinear theory of torsion of elastic cylinders containing a screw dislocation is used to solve the problem of the prestressed state of the internal inclusion. This theory is physically correct not for any models of isotropic elastic materials, but only for those for which the screw dislocation in the cylinder has a finite linear energy and creates a longitudinal force of finite value. The Bartenev-Khazanovich model belongs to this class. The problem for a composite cylinder is solved by a semi-inverse method. Using this method, it is reduced to nonlinear ordinary differential equations. The assumption of isotropy and incompressibility of the material makes it possible to find an exact solution to the problem.

An analytical solution for hollow cylinders under temporary torsional strain that includes several fractures and an orthotropic coating

In this study, an analytical solution is used to strengthen a hollow cylinder bar with an orthotropic coating and is subjected to short-term torsional loading. First, the Fourier transform is used to find the stress field of a hollow circular bar with an orthotropic coating and a Volterra-type screw dislocation. Next, using the distributed dislocation approach, the issue is reduced to a set of integral equations with a Cauchy singularity in the domain. By analyzing the integral equations, the elements influencing stress intensity at the solitary fracture points and torsional rigidity are found. Lastly, a number of examples are provided to show how the orthotropic coating affects the domain under consideration's torsional rigidity and dynamic stress intensity characteristics.

Semi-Analytical Solution for a Single-Phase Thermal Conduction Problem of a Hollow Cylinder with a Growing or Receding Inner Radius

Abstract A semi-analytical solution for the thermal conduction of a single phase, homogeneous, circular, hollow-cylinder with a growing or receding inner radius at a constant rate under unit-loading was derived using conformal mapping, Laplace transformation, and a Zakian series representation of the inverse Laplace transform. All solutions allow for convection on the fixed outer radius. Predictions were compared to finite-element simulations with excellent agreement observed. Given the changing thickness, thermal transients could not reach true steady-state equilibrium, especially for faster growth or recession rates. Indeed, the temperature states become somewhat linear with respect to time, reflecting the constant velocity of growth or recession. In practice, the resulting solutions can be used to determine temperatures during machining, wear, erosion, corrosion, and/or additive manufacturing, especially for lower temperature solid-state methods such as cold-spray.

Modelling the mechanics of 32 T REBCO superconductor magnet using numerical simulation

High-temperature REBCO superconducting tapes are very promising for high-field magnets. With high magnetic field applications there are high electromechanical forces, and thus a concern for mechanical damage. Due to the presence of large screening currents and the composite structure of the tape, the mechanical design of these magnets is not straightforward. In addition, many contemporary designs use insulated winding. In this work, we develop a novel two-dimensional axi-symmetric finite element tool programmed in MATLAB that assumes the displacement field to be within a linear elastic range. The stack of pancakes and the large number of REBCO tape turns are approximated as an anisotropic bulk hollow cylinder. Our results agree with uni-axial stress experiments in the literature, validating the bulk approximation. Here, we study the following configuration. The current is first ramped up to below the critical current and we calculate the screening currents and the forces that they cause using the minimum electromagnetic entropy production method (MEMEP) model. This electromagnetic model can now take insulated magnets into account. As a case study, a 32 T REBCO superconductor magnet is simulated numerically. We perform a complete mechanical analysis of the magnet by including the axial and shear mechanical quantities for each pancake, unlike in previous work where only radial and circumferential quantities were focused on. The effect on mechanical quantities without the screening current is also calculated and compared. It is shown that including the screening current-induced field strongly affects the mechanical quantities, especially the shear stress. The latter may be a critical quantity for certain magnet configurations. Additionally, in order to overcome high stresses, a stiff overbanding of different materials is considered and numerically modelled, which significantly reduces the mechanical stresses. The finite element-based model developed is efficient in calculating the mechanical behaviour of any general superconductor magnet and its devices.

Analytical solutions and material tailoring for combined radial expansion and twisting of functionally graded orthotropic hollow cylinders

Assuming that material properties are described by the same function of the radius, we first analytically find the displacement field in a functionally graded, orthotropic and linearly elastic hollow cylinder undergoing combined radial expansion and twisting. Subsequently, either for a desired axisymmetric displacement field or a stress distribution, we determine the required variations of the material properties to produce them in an inhomogeneous orthotropic cylinder. Numerical results presented for four example problems reveal the possibility of suitably varying material properties in the radial direction to simultaneously minimize the structural mass and the maximum circumferential stress on the inner surface of a hollow cylinder. It is found that out of the three heterogeneous cylinders of the same geometric and material parameters, the one having the least mass also has the smallest value of the maximum circumferential stress on the cylinder's inner surface. It occurs when the material moduli essentially vary affinely through the cylinder thickness. The analytical solutions presented here can serve as benchmarks for others to verify their numerical algorithms.

Shear modulus of sand-rubber mixtures: element testing and constitutive modeling

In this study, a series of resonant column tests was conducted to measure the shear modulus of sand-rubber mixtures at small strain amplitudes (i.e. between 10−4% and 10−2%), considering different rubber percentages and confining stress levels. The results were then combined with data obtained by dynamic hollow cylinder tests to investigate shear modulus degradation of the mixtures over a wider shear strain range. Based on the test results, a new expression was proposed to improve the prediction of maximum shear modulus of sand-rubber mixtures using the modified equivalent void ratio concept. A new constitutive model was also developed for estimation of strain-dependent shear modulus of the mixtures based on the modified hyperbolic framework. The shear modulus of the mixtures was found to be a function of rubber percentage, confining stress, the modified equivalent void ratio and the relative shear stiffness of rubber and sand. The experimental data and the developed models showed that the shear modulus decreased with rubber percentage and increased with confining stress. Moreover, the reference shear strain of the modified hyperbolic model increased with both rubber percentage and confining stress while its curvature coefficient increased more considerably with rubber percentage compared to the confining stress.

Research on Longitudinal Thermoelastic Waves in an Orthotropic Anisotropic Hollow Cylinder Based on the Thermoelastic Theory of Green–Naghdi

Research on Longitudinal Thermoelastic Waves in an Orthotropic Anisotropic Hollow Cylinder Based on the Thermoelastic Theory of Green–Naghdi

IMPACT OF DIFFERENT TPMS TESSELATION APPROACHES ON MECHANICAL PROPERTIES OF PARTS

In the paper influence of several factors on shape accuracy and compressive strength of parts is analysed. First simulation software is used for prediction. Parts are cylindrical with 20 mm diameter, manufactured via SLA additive manufacturing technology. 1mm thick Gyroid TPMS structure is generated in cylinders with different volume % (30,40,50 %). Thanks to drainage holes it was possible to create parts that are hollowed, but have solid shell around and TPMS inside. Different tesselation approaches are tried (cylindrical and rectangural). Different radius of roundness is also tried on the surfaces joining tpms and shell of cylinder (0, 0.5, 1mm) Compression tests are then conducted and results are analysed in the form of graphs and colour map of deviations. Results are also compared with solid and fully hollow cylinders. Study finds that the maximum strength of the bodies is influenced by tessellation method, infill percentage, and blend radius. Higher infill percentages generally result in increased strength due to greater material volume transmitting loading force. While tessellation affects samples without shells, its impact is negligible on samples with shells.

Interaction Assessment of Stress Intensity Factors of Surface Cracks on Thick Cylinders under Tension Force and Bending Moment

From an engineering perspective, hollow cylinders have various applications in the industry due to their strength, versatility, and geometric properties, making them vital for various applications in diverse industries. Therefore, it could be seen in many aspects such as fluid conveyance, manufacturing and fabrication, rotating machinery, structural components, storage, and pressure vessels. As it is well-known fracture is the most dominant type of failure in cylinders that is caused by defects or flaws. With time, these cracks (flaws) may extend and lead to a tragic failure, posing significant risks to both the nearby environment and humans. Moreover, crack cooperation which is known as (crack interaction) represents a chief apprehension, where cooperation or interaction may accelerate the crack growth and cause unpredictable failure. In this work, a wide variety of crack configurations were examined to quantify the interaction of double-interacting surface cracks located on a thick cylinder numerically via ANSYS software. The Stress Intensity Factor (SIFs) has been utilized as a driving force to describe the crack interaction. The results found that crack interaction influenced both cracks by the same rate, and SIFs distributed along the crack front by the same style as that of a single crack. Also, an inversely proportional relationship has been found between the crack interaction and the separation distance between the cracks. It is possible to conclude that the crack interaction of double interacting cracks exhibited a shielding effect, where SIFs for the case of double cracks were less than those of single crack.

Electrochemical hydrogen permeation measurement during cyclic stress testing of a ferritic chromium steel

AbstractIn the present work, the hydrogen diffusion during cyclic stress testing in the ferritic chromium steel 1.4521 (X2CrMoTi18‐2) is investigated. Therefore, electrochemical hydrogen permeation measurements are carried out on a hollow cylinder geometry. Simultaneously an alternating stress is applied using a stress ratio of R=‐1. At low stress amplitudes, no influence on the diffusion behaviour of hydrogen is found. At a higher stress amplitude, close to the macroscopic yield strength, a delayed hydrogen permeation by a factor of two is observed. It is postulated that this observation is a result of the nucleation of new hydrogen traps during the measurement. Hydrogen content measurements using carrier gas hot extraction support this hypothesis.

Nonintrusive thermal contact conductance estimation in double-layered pipelines: A reciprocity functional method perspective

Thermal contact conductance (TCC) is a critical factor in various engineering applications involving heat transfer between solid surfaces. Accurate knowledge of TCC enables a more precise thermal system analysis, leading to improved efficiency, reduced energy consumption, and prevention of thermal damages. Moreover, TCC estimation can help to identify material discontinuities or failures. A recent tool for TCC estimation is the Reciprocity Functional Method (RFM) coupled with the Classical Integral Transform Technique (CITT). This method allows the solution of inverse boundary value problems without the need of iterative methods or intrusive measurements, making it valuable for nondestructive testing of interfacial flaws between solid materials. Furthermore, it enables the computation of TCCs using analytical expressions, resulting in a computationally fast procedure. The technique involves the solution of two auxiliary problems: one for the temperature discontinuity estimation, and the other for the interfacial heat flux estimation, both at the inaccessible interface between the two contacting materials. In this study, we applied the RFM and the CITT to estimate different types of TCCs, using a three-dimensional double-layer hollow cylinder geometry as a representative model, like double-layer pipelines used in the oil industry. Temperature measurements for solving the inverse problem were considered available on the outer surface of the pipe which, in the case of a real experiment, could be obtained via an infrared camera. The results demonstrated a good estimate for various analyzed test-cases, even when the measurements were contaminated with Gaussian noises.

Magneto–thermoelastic behavior of an orthotropic hollow cylinder based on Lord–Shulman and Green–Lindsay theories

Magneto–thermoelastic behavior of an orthotropic hollow cylinder based on Lord–Shulman and Green–Lindsay theories

A simple method for mechanical analysis of pressurized functionally graded material thick-walled cylinder

The complex function method is employed to establish a mechanical model for pressurized thick-wall cylinders made of functionally graded materials (FGM). This model is applicable to all radial varying modes of material properties, including both continuous and discontinuous variations in Young’s modulus and Poisson’s ratio. The main concept behind this mechanical model involves dividing the thick-walled cylinder into concentric thin cylinders, each equipped with a pair of analytical functions representing stress functions. By imposing continuity conditions between adjacent thin cylinders and considering the stress boundary conditions of the entire structure, all unknown forms of analytical functions can be determined. Subsequently, by establishing the correspondence relationship between these analytical functions and stress or displacement, it becomes possible to solve for the stress or displacement at any radial position within the thick-walled cylinder. Through comparison and verification against the numerical simulation results, it can demonstrate that as long as the differential scale is sufficiently small, high accuracy can be achieved in the final result. In other words, solutions obtained for multi-layered hollow cylinder converge toward those obtained for continuously graded thick-walled cylinder. Notably, by starting from the level of stress function and avoiding complex differential and integral equations, a linear equation system can provide information on stress and displacement distributions along the radial direction. Therefore, compared to other solving methods available, this proposed approach offers simplicity and applicability.

Analysis of a hollow cylinder with variable thermal conductivity and diffusivity by fractional thermoelastic diffusion theory

Based on fractional thermoelastic diffusion theory, an infinite hollow cylinder with variable thermal conductivity and diffusivity is studied. The inner surface of the hollow cylinder is free and subjected to thermal and chemical shocks, while the outer surface is fixed and adiabatic. The closed forms of dimensionless displacement, temperature, chemical potential, stress, and concentration in the Laplace transform domain are given by eigenvalue method. These physical quantities are then numerically obtained through the inverse Laplace transformation. The effects of fractional order parameters, variable thermal conductivity and diffusivity on these quantities are discussed. The present model may be helpful for better understanding the thermoelastic diffusion problems in actual engineering.

Water entry of hollow cylinders with fronts of different fillet radii: A visualization study

In the present study, we investigate the water entry of three hollow cylinders with fronts of different fillet radii of 0, 5, and 10 mm. Particular attention is given to the effect of fillet radius of front on cavity dynamics. To interpret the mechanism of cavity evolution, a high-speed photography system is employed to capture instantaneous impact phenomena and behaviors of the hollow cylinders. Unique characteristics of the internal jet and ring-rupture pinch-off of the cavity are described and discussed. The results show that both dynamic patterns and characteristic parameters of the cavities differ with the fillet radius of the front. For the flat-front hollow cylinder, a fully developed streamlined gas cavity is formed, and the expansion rate and size of the cavity are substantially greater than those associated with slanted fronts. The cavity trajectory remains nearly vertical, and the internal jet is the most extended. With increasing fillet radius of the front, underdeveloped cavities with relatively small size are produced and the collapse time of the cavity is shortened. Furthermore, the cavity trajectory is characterized by lateral deflections, and the maximum attainable height of the internal jet is reduced.