Static lateral stiffness of wire rope isolators

This paper presents an analytical model for the static lateral stiffness of Wire Rope Isolators (WRI). The wire rope isolator, which is a passive isolation device, has been widely adopted as a shock and vibration isolation for many types of equipment and lightweight structures. The major advantage of the WRI is its ability to provide isolation in all three planes and in any orientation. The WRI in the lateral roll mode, is required to possess the required lateral stiffness to support and isolate the equipment effectively. The static lateral stiffness of WRI depends mainly on the geometrical characteristics and wire rope properties. The model developed in this paper is validated experimentally using a series of monotonic loading tests. The flexural rigidity of the wire ropes, which is required in the model, was determined from the transverse bending test on several wire rope cables. It was observed that the lateral stiffness is significantly influenced by the wire rope diameter and height of the isolator. The proposed analytical model can be used for the evaluation of lateral stiffness and in the preliminary design of the WRI.     

The sputtering temperature of a cooling cylindrical rod with an insulated core

By a standard application of Jones's method associated with the Wiener-Hopf technique an explicit solution is obtained for the temperature distribution inside a cylindrical rod with an insulated inner core when the rod is allowed to enter into a fluid of large extent with a uniform speed, and a simple integral expression is derived for the value of the sputtering temperature of the rod at the points of entry. Numerical results under certain special circumstances are also obtained and presented in the form of a table.     

Buckling of a sandwich symmetrical circular plate with varying mechanical properties of the core

This paper is devoted to analytical and numerical studies of global buckling of a sandwich circular plate. The mechanical properties of the plate core vary along its thickness, remaining constant in the facings. The middle surface of the plate is its symmetrical plane. The mathematical model of the plate is presented. The field of displacements is formulated using the proposed nonlinear hypothesis that generalizes the classical hypotheses. The equations of equilibrium are formulated based on the principle of stationary total potential energy. The proposed mathematical model of the displacements considers the shear effect. The numerical model of the plate is also formulated with a view to verify the analytical one. Numerical calculations are carried out for the chosen family of plates. The values of the critical load obtained by the analytical and numerical methods are compared. The effects of the material properties of the core and the change of the plate radius on the critical load intensity are presented.     

The influence of a space environment on the mechanical behavior of metals

The effect of low pressures on the fatigue, tensile and creep behavior is discussed. The data are interpreted in terms of the accumulation of dislocations in the surface region. It is suggested that the mechanical behavior is influenced by the rate of escape of dislocations through the surface. Initially, the oxide layer plays an important role; however, as the strain increases, the dislocation layer exerts a large influence.     

Stratification of a gas by an incandescent wire

The propagation of a shock wave in a gas in which there is a wire rendered incandescent by a pulsed electrical discharge enables one to discover the stratified structure in space acquired by the gas as a result of nonuniform heating.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 175–176, July–August, 1984.     

The influence of a magnetic field on the mechanical behavior of a fluid interface

This work focuses on a theoretical investigation of the shape and equilibrium height of a magnetic liquid–liquid interface formed between two vertical flat plates in response to vertical magnetic fields. The formulation is based on an extension of the so called Young–Laplace equation for an incompressible magnetic fluid forming a two-dimensional free interface. A first order dependence of the fluid susceptibility with respect to the magnetic field is considered. The formulation results in a hydrodynamic-magnetic coupled problem governed by a nonlinear second order differential equation that describes the liquid–liquid meniscus shape. According to this formulation, five relevant physical parameters are revealed in this fluid static problem. The standard gravitational Bond number, the contact angle and three new parameters related to magnetic effects in the present study: the magnetic Bond number, the magnetic susceptibility and its derivative with respect to the field. The nonlinear governing equation is integrated numerically using a fourth order Runge-Kutta method with a Newton–Raphson scheme, in order to accelerate the convergence of the solution. The influence of the relevant parameters on the rise and shape of the liquid–liquid interface is examined. The interface shape response in the presence of a magnetic field varying with characteristic wavenumbers is also explored. The numerical results are compared with asymptotic predictions also derived here for small values of the magnetic Bond number and constant susceptibility. A very good agreement is observed. In addition, all the parameters are varied in order to understand how the scales influence the meniscus shape. Finally, we discuss how to control the shape of the meniscus by applying a magnetic field.     

Stokes flow past a porous sphere with an impermeable core

Stokes flow of a viscous, incompressible fluid past a porous sphere with an impermeable core using Darcy law for the flow in the porous region is discussed. The formulae for drag and torque are found by deriving the corresponding Faxen's laws. It is found that torque is always less than that on a solid sphere and it does not depend on the radius of the impermeable core. Some illustrative examples are discussed.     

Response of a wire rope strand to axial and torsional loads: Asymptotic modeling of the effect of interwire contact deformations

The refined discrete mathematical model of a simple helical wire rope strand is developed. The effect of the transverse contraction of the wire strand through Poisson’s ratio and also through local contact deformations (wire flattening) has been studied in detail. In order to express the interwire contact deformation in terms of the parameters describing the strand deformation, we formulate a two-dimensional model interwire contact problem. The interwire contact interaction is treated as a frictionless unilateral plain strain problem. The nonlinear model interwire contact problem has been solved by the method of matched asymptotic expansions. The constitutive equations for a helical wire rope strand, which take into account both the Poisson’s ratio effect and the effect of contact deformation, are obtained in a closed form.     

Chaotic behavior of a parametrically excited nonlinear mechanical system

The chaotic dynamics of a single-degree-of-freedom nonlinear mechanical system under periodic parametric excitation is investigated. Besides the well known type-I and type-III intermittent transitions to chaos we give numerical evidence that the system can follow an alternative route to chaos via intermittency from an equilibrium state to a chaotic one, which was not found in the previous simulations of the dynamics of the system.     

Non-linear behavior of delaminated unidirectional sandwich panels with partial contact and a transversely flexible core

The paper presents the results of an investigation of the non-linear behavior of delaminated sandwich panels with a compressible core. The delaminated zone, at one of the face-core interfaces, consists of through-the-width crack, which is free of shear stresses but is capable of accommodating partial contact with compressive stresses only within the debonded zone. The governing non-linear equations along with the appropriate boundary conditions and the continuity conditions are derived through variational principles. The governing equations include moderate deformations type of kinematic relations, and include the high-order effects due to the transverse flexibility of the core. The governing equations along with the stress and displacements fields for the core and the appropriate continuity conditions are presented. The effects of the non-linear response and the partial contact are described through some numerical cases of three points bending typical sandwich panels with inner delaminations in the vicinity of a concentrated load, in the vicinity of a stiffened core and, finally, far from the load. Numerical results in the form of displacements, bending moments, shear stresses in the core and vertical interfacial normal stresses at the upper and lower face-core interfaces along the panel length and at the delamination crack tips are presented. Buckling curves of load versus various extreme structural parameters are included. The analyses show that a full contact type of delamination transforms into a partial contact area with buckling of the compressed face sheet, as the load is increased and it is associated with extreme large displacements and stresses.     

High-order nonlinear contact effects in the dynamic behavior of delaminated sandwich panels with a flexible core

The nonlinear dynamic behavior of delaminated sandwich panels with a flexible core is studied. A general analytical model that accounts for the real contact characteristics of the delaminated interface is developed. The analysis characterizes the influence of the contact phenomenon on the dynamic behavior of the sandwich structure and compares them to simplified models in which the contact conditions at the delaminated interface are assumed a priori. The dynamic model uses the high-order sandwich panel theory (HSAPT) that takes into account the flexibility of the core and considers the geometrically nonlinear effects of the face-sheets as well as the nonlinearity associated with the real contact characteristics of the delaminated surfaces. The dynamic governing equations, boundary conditions, and continuity requirements are derived through the Hamilton principle. The formulation yields a set of coupled nonlinear partial differential equations. The solution in time is based on the Newmark method of integration, and the solution in space uses the Multiple Shooting method combined with a Newton–Raphson iterative scheme. Numerical results that reveal the influence of the contact characteristics on the dynamic response of a sandwich panel are presented. In addition, the results are compared with finite element analysis, and with the simplified models. The study reveals the influence of the real contact phenomenon on the linear and nonlinear response and highlights its role in the dynamic response of the sandwich panel.     

The mechanical behavior of nanoscale metallic multilayers: A survey

The mechanical behavior of nanoscale metallic multilayers(NMMs) has attracted much attention from both scientific and practical views. Compared with their monolithic counterparts, the large number of interfaces existing in the NMMs dictates the unique behavior of this special class of structural composite materials. While there have been a number of reviews on the mechanical mechanism of microlaminates, the rapid development of nanotechnology brought a pressing need for an overview focusing exclusively on a property-based definition of the NMMs, especially their sizedependent microstructure and mechanical performance. This article attempts to provide a comprehensive and up-to-date review on the microstructure, mechanical property and plastic deformation physics of NMMs. We hope this review could accomplish two purposes:(1) introducing the basic concepts of scaling and dimensional analysis to scientists and engineers working on NMM systems, and(2) providing a better understanding of interface behavior and the exceptional qualities the interfaces in NMMs display at atomic scale.     

多晶体变形、应力的不均匀性及宏观响应

从单晶滑移变形分析的角度探讨多晶体塑性变形和应力的不均匀性及宏观力学响应：建议了 一种当前构形下以应力为基本变量的单晶黏塑性增量迭代计算方法；用Voronoi晶粒集合体 模型研究多晶体由于晶粒几何及取向的随机性造成的变形和应力的不均匀性, 进行了多晶集 合体的宏观响应和晶粒位向演化数值分析. 结果表明：(1)多晶体内等效塑性应变和应力分量在统计上呈现高斯分布，在应变硬化过程中, 随着塑性变形增加多晶体微观应力的统计变异系数会越来越大；(2)用Voronoi模型计算可得到沿最大剪应力方向的滑移变形带；(3)多晶体内最高三轴拉应力一般出现在晶界特别是三晶交界处；(4)Voronoi模型能用于织构分析.     

国外力学核心期刊的研究及其意义

详细介绍综合测定国外力学核心期刊的研究方法,扼要阐述了它对力学学科文献资源建设及学术交流的作用,并对所测定出的国外力学核心期刊结论做了比较客观的评价．