Ring Load Research Articles

Snap-through Buckling of Shallow Spherical Shells under Ring Loads

Snap-through buckling behaviour of rigid vinyl polyethylene shallow spherical shells, undergoing large displacements, subjected to static ring loads is investigated by using finite difference and the Newton-Raphson Method. The load-deflection diagrams corresponding to various values of thickness, depth and ring diameter of the shell with simply supported and clamped edges are sketched and compared. The accuracy of the used algorithm and the prepared computer program are tested by comparing some of the numerical results obtained in this study with those obtained by an experimental study, available in the relevant literature. Further steps on the concerning subject are achieved.

A fast computational model for near- and far-field noise prediction due to offshore pile driving.

This paper presents a computationally efficient modeling approach for predicting underwater noise radiation from offshore pile driving. The complete noise prediction model comprises two modules. First, a sound generation module is adopted to capture the interaction between the pile, the fluid, and the seabed, aiming at modeling the sound generation and propagation in the vicinity of the pile. Second, a sound propagation module is developed to propagate the sound field at larger distances from the pile. To couple the input wavefield obtained from the sound generation module, the boundary integral equations (BIEs) are formulated based on the acousto-elastodynamic reciprocity theorem. To advance the mathematical formulation of the BIEs, the Green's tensor for an axisymmetric ring load is derived using the complex wavenumber integration technique. The model advances the computational efficiency and flexibility of the noise prediction in both near- and far-fields from the pile. Finally, model predictions are benchmarked against a theoretical scenario and validated using measurement data from a recent offshore pile-installation campaign.

Calculation of a radially nonhomogeneous ring loaded with normal and tangential loads

In a two-dimensional plane problem of the theory of elasticity in polar coordinates for a nonhomogeneous body, it is possible to obtain analytical or numerical-analytical solutions only for a one-dimensional nonuniformity [1 - 3]. As a rule, this is possible when all unknown functions depend on the radius. These tasks correspond to the majority of ring and cylindrical structures exposed to the axisymmetric effects of temperature, radiation, humidity, etc. The article considers the problem when radial and ring loads are unevenly distributed along the outer surface of the ring. The problem is solved by two methods: analytical and numerical-analytical, the methods comparison is presented.

An Improved Tunnel‐Track Model in Saturated Poroelastic Soils to a Moving Point Load

To predict the mechanical response of a circular cavity/tunnel buried in saturated poroelastic soils to a moving point load, a semianalytical model is provided in this work. The soils are governed by Biot’s theory that describes the wave propagations for saturated poroelastic materials. The displacement and stress vectors for the solid skeleton and pore‐water fluid are represented by scalar and vectorial potentials. The governing equations for the tunnel and surrounding soils are solved in the frequency domain with the aid of separation of variables and Fourier transformations. To check the feasibility of the present analytical model, the solution is compared with other available results calculated for the ring load case. The good agreement shows the correctness of the present model. Numerical results suggest that the mechanical response from a moving point load in a tunnel for two‐phase poroelastic materials is quite different from that in single‐phase elastic materials. The critical velocity of the tunnel‐soil system is around the shear wave speed of soils while the second one introduced into the track‐tunnel‐soil system with very high value is around the critical velocity of the track structure itself.

Stress-stain state in elastic spherical shells under the action some asymmetrical of circular loads

The paper presents the basic differential equations for calculating shells of rotation. It is considered that the material of the shell works beyond the elastic limit. The conclusion of the resolving system of differential equations is based on the linear shell theory and the Kirchhoff-Love hypothesis. The physical correlations are based on the small elastic-plastic deformation theory. With the construction of the solution of the load function, also unknown resolving functions expand to the Fourier series along the circumferential coordinate. In the present work, the action of the asymmetrical distribution along the parallel loads is considered. The solution is approached by the elastic decisions method. The study of stress-stain state in the isotropic spherical shells is presented in the work. The results of the calculation are presented in the example of a spherical shell. The work of the material beyond the elastic limit is taken into account using assuming linear hardening of the material. The shell is loaded with ring distributed loads, and they are applied on a certain segment in a parallel circle. The diagrams of bending moments and areas of the appearance of plastic deformations along the thickness of the shell are presented. The areas of plastic deformations for ring loads distributed along the parallel relative to the zero meridian in the range of 45, 90,135 degrees are shown.

Computation of the influence of the surcharge on the state of stress of the round plate on a bumping foundation

The problem of calculating a round plate located on the surface of a combined foundation is being considered in the paper. An analytical solution is deduced for a plate of finite stiffness and a stiff plate (round stamp) under the influence of an axisymmetric bending. The influence of an axially symmetric ring load applied to the surface of the base outside the slab is analyzed.

Numerical Investigation of Innovative Support Frame of Openings in the Segmental Tunnel Lining

Introduction: To supply safety in the tunnels, it is necessary to construct escape routes and emergency exits that are performed by locating cross passages. Methods: These passages connect two tunnels transversely and apply escape routes. Using temporary steel structures to supply the ring stability in practice and reinforced concrete frame to stabilize the ring permanently can be appropriate to form a solid frame that transfers the opened ring's load to the opening surroundings. In this paper, a 3D finite element simulation was performed to analyze the influence of opening construction in the segmental concrete lining and a temporary support system. Using the simulation, stress and deformation distribution of the steel frame, bolts, and segmental lining were obtained. Results: The results show that by increasing the number of bolts from 18 to 30, the induced stress in the steel frame and bolts decreased to 76 and 59 percent, respectively. In addition, the maximum displacement in the segmental lining and the maximum opening value of the joints decline to 62.7 and 75 percent, respectively. Conclusion: Finally, it can be concluded that the steel frame can be used as a temporary support system.

The floating plate–load system: a new stability problem

The interesting problem of a flat elastic plate and a weight which would sink individually but may float as a system is presented. Using beam and plate theories, the two-dimensional strip and the circular disc are solved exactly for the minimum width for which the system would float. Three types of loading are considered: a centered point load, two symmetric point loads or a ring load, and a continuous uniform load. These problems represent a new class of stability problems which illustrate the interaction of load, elasticity, and hydrostatics.

Do Fully Threaded Transiliac–Transsacral Screws Improve Mechanical Stability of Vertically Unstable Pelvic Fractures? A Cadaveric Biomechanical Analysis

To determine whether fully threaded transiliac-transsacral (TI-TS) fixation is biomechanically superior to partially threaded TI-TS fixation of vertically unstable transforaminal sacral fractures. Vertically unstable zone 2 sacral fractures were created in 20 human cadaveric pelves with a unilateral osteotomy and resection of 1 cm of bone through the foramen of the sacrum to represent comminution. Ten specimens received either 2 7.3-mm fully threaded or 2 7.3-mm partially threaded TI-TS screw fixation at the S1 and S2 body, and every specimen received standard 3.5-mm 8-hole parasymphyseal plating anteriorly. Each pelvis was loaded to 250 N at 3 Hz for 100,000 cycles and then loaded to failure. The primary outcome was fracture displacement at the S1 foramen, which was measured at 25,000, 50,000, 75,000, and 100,000 cycles. Secondary outcomes were simulated clinical failure of ≥1 cm displacement at the S1 foramen to determine occurrence probability of failure, and load at failure was defined as 2.5 cm of the linear loading system displacement. Specimens in the fully threaded and partially threaded cohorts were otherwise respectively comparable in regards to age, gender, and bone density. Five of the 10 TI-TS partially threaded specimens experienced simulated clinical failure with >1 cm displacement at the S1 foramen compared with 0 of the 10 TI-TS fully threaded cohort (50% vs. 0%, P = 0.03). The mean maximal displacement at the S1 foramen was greater in the partially threaded cohort (9.3 mm) compared with the fully threaded cohort (3.6 mm; P = 0.004). Fully threaded specimens also demonstrated greater mean force to failure than the partially threaded specimens (461 N vs. 288 N; P = 0.0001). Fully threaded TI-TS screw fixation seems to be mechanically superior to partially threaded fixation in a cadaveric vertically unstable transforaminal sacral fracture model with significantly less displacement of the posterior pelvic ring and greater load to failure.

Online algorithms for the mixed ring loading problem with two nodes

In this paper, we introduce the mixed ring loading problem, where the ring contains undirected and bidirected links. When the ring consists of two nodes, we consider the online mixed ring loading problem under three different scenarios including splittable, integer splittable and unsplittable. When the demands are (integer) splittable, we present an (asymptotically) optimal online algorithm. When the demands are unsplittable, we present an online algorithm which generalizes the previous result.

Experimentally and Numerical Investigation on Behavior of Annular RC Slabs under Ring Loading

This research presents the experimentally measured displacement and strain at specified locations of the concrete of tested annular reinforced concrete slabs subjected to lateral load with three different ratios of inner to outer radii and simply supported at the outer circumference. Performed 3D model of annular RC slabs under the axisymmetric ring load applied, as close as at the inner edge, and investigated their stress-strain state in the elastic stage. This study contains different approaches based on classical thin-plate (CTP) theory and performed a 3D finite-element (FE) model to predict the fields of radial and circumferential stresses and deflection of the slab. Experimentally investigated the crack widths and crack pattern of the two groups of slabs-group A- radially reinforced and group M–orthogonally reinforced. added a correction factor to the CTP equations, which used to determine both radial and circumferential stresses. Also, investigated the appearance of the first cracks, deflection, failure mode, and the maximum value of the failure load for both cases of the reinforcement.

Vertical vibration of a rigid circular disc embedded in a transversely isotropic and layered poroelastic half-space

Fundamental solution for the time-harmonic vertical vibration of a rigid circular disc embedded in a transversely isotropic and layered poroelastic half-space is developed using a semi-analytical method. First, based on the Green's function of the time-harmonic vertical circular load embedded in the layered half-space, function of the corresponding annular ring load is determined via the method of superposition. Then the disc-medium contact area is discretized into annular ring elements with unknown densities which are determined via an integral least-square approach. Finally, the dynamic vertical compliance is derived by virtue of the equilibrium between the applied load on the disc and the resultant contact stress. Based on the derived fundamental solution, selected numerical examples on the dynamic vertical compliance are presented to investigate the influence of the surface hydraulic condition, fluid saturation, embedment depth of the disc, material anisotropy, material layering, and input frequency.

Indentation of a nanolayer on a substrate by a rigid cylinder in adhesive contact

Nanoindentation is employed to characterize the mechanical properties at the nanoscale. This paper considers the mechanical response of a nanoscale elastic layer on an elastic substrate that is indented by an adhesively bonded flat-ended rigid cylindrical punch. The complete Gurtin–Murdoch continuum model is employed to capture the size effects. The contact problem is analyzed by relating displacements of the contact region to contact stresses by a flexibility equation system, which is developed by discretizing the contact region into annular elements. The flexibility equation involves displacement influence functions corresponding to axisymmetric normal and radial surface ring loads applied on the layer-substrate system. The displacement influence functions are derived by using the Hankel integral transforms. Convergence and accuracy of the proposed solution scheme are verified by comparing with limiting cases such as the classical elasticity solution. Selected numerical results indicate that the substrate becomes stiffer and the elastic field is size-dependent due to the surface energy effects.

Influence Investigation of Rolling Bearing Test Conditions on the Informativity Assessment of their Technical Condition

Establishing patterns of the relationship of informative diagnostic parameters signals’s and test modes and operation of rolling bearings is an urgent task of technical diagnostics. The determining factor in the use of certain methods for assessing the condition and bearings faults, as well as the use of certain informative diagnostic parameters, is their sensitivity to changes in the condition of the bearing or to the size and degree of the defect development. The paper presents the results of the dependence study of the rolling bearings vibration parameters on the test and operation conditions: the rotation frequency of the inner ring, axial and radial loads. Numerical values of the listed factors are obtained that are optimal for testing bearings at the input control according to the sensitivity criterion. The study was conducted in accordance with the provisions of the experiment planning theory. It has been established that the magnitude of the vibration parameters and the level of components at the frequencies of bearing defects depend on the speed of rotation in direct proportion and increase with the deterioration of the technical condition of the bearings. It was experimentally confirmed that axial and radial loads significantly affect the values of the controlled vibration parameters only when defects appear in the tested bearings.

Exact bending solutions of circular sandwich plates with functionally graded material-undercoated layer subjected to axisymmetric distributed loads

In this study, the closed-form bending solutions of simply supported circular sandwich plates subjected to linearly or power-law, or partial uniform distributed loads are derived. The circular sandwich plate contains two homogeneous substrates and a functionally graded material-undercoated layer added between two homogeneous substrates. The Poisson’s ratio of the circular sandwich plates is assumed to be uniform. The Young’s moduli in the undercoated functionally graded material layer vary continuously throughout the thickness according to the volume fraction of constituents based on power-law, sigmoid, or exponential function. To solve the problem, first, the in-plane and bending problems of circular sandwich plate are uncoupled by properly choosing the origin of the z-axis such that the parameter [Formula: see text]. Then the fundamental bending solution of a simply supported circular sandwich plate under axisymmetric ring load is found based on the classical plate theory. Finally, by superposing the fundamental solutions, the closed-form bending solutions of circular sandwich plates under arbitrarily axisymmetric transverse loads are determined. Results reveal that the closed-form solutions agree very well with the finite element calculation and, when degenerated, coincide with the available solutions for isotropic homogenous plates in the literature. Moreover, the exact solutions of the circular sandwich plates subjected to axisymmetric transverse loads exhibit the relation of [Formula: see text] for the stresses [Formula: see text] and bending moments [Formula: see text]. The effects of the material gradient, the material distribution, and the thickness of the undercoated-functionally graded material layer on the mechanical behaviors of the circular sandwich plates are under investigation in detail.

Building a model for calculating stress under dynamic loading of metal rings by the magnetic pulse method

Many recent studies have focused on specifics of behavior of materials under dynamic loading as it is considerably different from cases with quasi-static loading. This paper considers the method of magnetic pulse deformation of metal rings, which is a continuation of the authors’ research. [1]. The methods used in the experiment, which are described in this paper, allow to carry out laboratory studies into material deformation at a speed reaching the values of around 107c−1. This paper is dedicated to building a mathematical model for determining the stress in the test samples under dynamic loading of materials by the magnetic pulse method.

Dynamic effect of a moving ring load on a cylindrical structure embedded in poroelastic space based on nonlocal Biot theory

The dynamic response of a cylindrical structure embedded in a saturated poroelastic medium, which is subjected to a moving ring load, is theoretically investigated based on nonlocal Biot theory. General solutions regarding the displacement, stress, and pore pressure in the terms of frequency and wavenumber domains are derived through Fourier transform. The solutions for the displacement, stress, and pore pressure in the time and space domains are obtained by using a double inverse Fourier transform. The effects of nonlocal parameter and load speed on the displacement fields are analyzed in detail. The effects of nonlocal parameter on the displacement are enhanced as the load speed increases. Self-vibration frequency of the applied moving load also has significant influence on the displacement and pore pressure. Results show that high self-vibration frequency can reduce the amplitude of the displacement and pore pressure. Furthermore, increasing the self-vibration frequency results in considerable effects of nonlocal parameter on the displacement and pore pressure.

Wave propagation in a transversely isotropic porous ocean bottom

The equations of wave motion are considered in this article for three-layered medium which consists of liquid and porous layers with finite depth and solid half-space such as ocean bed. By virtue of scalar potential functions for each layer, complicated differential equations of layers are reduced to ordinary differential equations. An analytical method is applied to determine the Green’s functions of media based on an arbitrary shaped time-harmonic excitation at the interface of liquid and porous layers. A Mathcad code is provided to compute the complex integrals. Displacement and stress fields of three layers are discussed. Comparing with special cases, existing answers represent the validity of the proposed method. Numerical results are carried out for circular patch, ring and point loads, and the effects of various parameters on the behavior of the system are plotted. Finally, the achieved results were under discussion.

Piston-ring performance: limitations from cavitation and friction

PurposeCavitation in piston-ring lubrication is studied as part of the performance of piston-ring assemblies. Cavitation degrades performance in engineering applications and its effect is that it alters the oil film pressure, generated at the converging-diverging wedge of the interface. Studies tried to shed light to the phenomenon of cavitation and compare it with cavities that have been identified in bearings. The paper aims to discuss this issue.Design/methodology/approachLubricant formulations were used for parametric study of oil film thickness (OFT) and friction providing the OFT throughout the stroke and LIF for OFT point measurements. Lubricant formulation affects cavitation appearance and behaviour when fully developed.FindingsCavitation affects the ring load carrying capacity. Different forms of cavitation were identified and their shape and size (length and width) is dictated from reciprocating speed and viscosity of the lubricant. A clear picture is given from both techniques and friction results give quantifiable data in terms of the effect in wear and cavitation, depending on the lubricant properties.Research limitations/implicationsEngine results are limited due to manufacturing difficulties of visualisation windows and oil starvation. Therefore, full stroke length sized windows were not an option and motoring tests were implemented due to materials limitations (adhesive and quartz windows). Lubricant manufacturer has to give data regarding the chemistry of the lubricants.Originality/valueThe contribution of cavitation in piston-ring lubrication OFT, friction measurements and lubricant parameters that try to shed light to the different forms of cavitation. A link between viscosity, cavitation, shear thinning properties, OFT and friction is given.

Soil-pile interaction in inhomogeneous transversely isotropic media

Through a rigorous mathematical formulation, this paper considers the axisymmetric interaction analysis of a thin-walled cylindrical pile with finite length embedded in an exponentially graded transversely isotropic half-space under axial loads at the top of pile. The action of pile to the embedding medium is represented with axial and radial ring loads and the relevant set of Green's functions for the pile and semi-infinite soil medium has been developed. By satisfying the compatibility conditions between the two interacting media, the interaction analysis is shown to be reducible to a pair of Fredholm integral equations. Due to the complex nature of mathematical formulations and the intrinsic singularity of stress transfer, the analytical solution of obtained boundary integral equations is not possible and a suitable numerical scheme has been developed. By means of adaptive gradient shape functions which are capable of smoothly capturing regular and singular solutions, the given Fredholm integral equations are discretized in the common boundary of interacting media and solved numerically for the interfacial stress components. The numerical procedure is verified through comparisons with previous studies and the effect of inhomogeneity of soil layer on different responses of the interaction process is discussed by presenting several numerical results.