共查询到20条相似文献,搜索用时 31 毫秒
1.
L. F. Fatullaeva 《Mechanics of Composite Materials》2007,43(6):513-520
The limiting state of a multilayer eccentric ring made of a nonlinearly elastic material and subjected to a uniform external
pressure is investigated. The topicality and importance of the problem are connected with the search for reserves of savings
in materials, with a simultaneous in crease in the load-carrying capacity of structures. Since rings often must have walls
of varying thickness, their critical buckling force is determined as a function of a parameter considering this fact. In solving
the problem, the geometric nonlinearity is also taken into account.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 761–770, November–December, 2007. 相似文献
2.
The buckling in stability of a long multilayer linearly viscoelastic shell, composed of different materials and loaded with
a uniformly distributed external pressure of given intensity, is investigated. By neglecting the influence of fastening of
its end faces, the initial problem is reduced to an analysis of the loss of load-carrying capacity of a ring of unit width
separated from the shell. The new problem is solved by using a mixed-type variational method, allowing for the geometric nonlinearity,
together with the Rayleigh-Ritz method. The creep kernels are taken exponential with equal indices of creep. As an example,
a three-layer ring with a structure symmetric about its midsurface is considered, and the effect of its physicomechanical
and geometrical parameters, as well as of wave formation, on the critical time of buckling in stability of the ring is determined.
It is found that, by selecting appropriate materials, more efficient multilayer shell-type structural members can be created.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 617–628, September–October, 2007. 相似文献
3.
R. Yu. Amenzadeh E. T. Kiyasbeyli L. F. Fatullaeva 《Mechanics of Composite Materials》2006,42(3):243-252
The loss of the load-carrying capacity of a nonlinearly elastic multilayer rod is investigated. The rod, whose layers have
various thickness and are made of different materials, is rigidly fixed at both its ends. Rigid contact conditions between
the layers are assumed. The problem posed is solved by using the variational method of mixed type in combination with the
Rayleigh-Ritz method. The initial analysis is reduced to the solution of the Cauchy problem for a nonlinear ordinary differential
equation solved for the first derivative. As the initial condition, the maximum initial eccentricity of the rod is assumed.
In the case of zero eccentricity, the Shanley critical force for an axially compressed rod is determined. For a three-layer
rod whose outer layers have equal thickness and are made of the same material, numerically, for various degrees of nonlinearity,
the effect of physicomechanical and geometric parameters on the critical load of buckling instability is determined. It is
found that, by matching the heterogeneity of the rod, it is possible to raise its load-carrying capacity.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 347–360, May–June, 2006. 相似文献
4.
The problem on the elastoplastic deformation of reinforced shells of variable thickness under thermal and force loadings is
formulated. A qualitative analysis of the problem is carried out and its linearization is indicated. Calculations of isotropic
and metal composite cylindrical shells have shown that the load-carrying capacity of shell structures under elastoplastic
deformations is several times (sometimes by an order of magnitude) higher than under purely elastic ones; the heating of shells
with certain patterns of reinforcement sharply reduces their resistance to elastic deformations, but only slightly affects
their resistance to elastoplastic ones; not always does the reinforcement in the directions of principal stresses and strains
provide the greatest load-carrying capacity of a shell; there are reinforcement schemes that ensure practically the same resistance
of shells at different types of their fastening.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 707–728, November–December, 2006. 相似文献
5.
The external confinement by CFRP wrappings is a very efficient method to increase the load-carrying capacity of round concrete
columns. Nevertheless, the serviceability of such columns under loads exceeding the strength of unconfined concrete is limited
by different factors. One of them is the reduced stability of the columns due to the significantly reduced tangent elastic
modulus inactive loading. To increase the critical load of buckling instability of concrete columns, an additional longitudinal
composite reinforcement can be used. In this paper, the stability and strength of concrete columns confined by circumferential
wrappings and strengthened with a longitudinal external CFRP reinforcement are studied. Plain and confined columns of length
300 and 1500 mm were tested. Theoretical predictions show that the additional longitudinal reinforcement is efficient in improving
the stability of confined columns in the region of moderate slenderness. The prediction for the ultimate strength and stability
of the columns coincides rather well with experimental results.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 295–308, May–June, 2005. 相似文献
6.
Zhi-Min Li 《Mechanics of Composite Materials》2007,43(6):535-560
A postbuckling analysis is presented for a shear-deformable anisotropic laminated cylindrical shell of finite length subjected
to external pressure in thermal environments. The material properties are expressed as linear functions of temperature. The
governing equations are based on Reddy’s higher-order shear-deformation shell theory with the von Karman-Donnell-type kinematic
nonlinearity. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into
account. The boundary-layer theory of shell buckling, which includes the effects of nonlinear prebuckling deformations, large
deflections in the postbuckling region, and the initial geometric imperfections of the shell, is extended to the case of shear-deformable
anisotropic laminated cylindrical shells under lateral or hydrostatic pressure in thermal environments. The singular perturbation
technique is employed to determine the interactive buckling loads and postbuckling equilibrium paths. The results obtained
show that the variation in temperature, layer setting, and the geometric parameters of such shells have a significant influence
on their buckling load and postbuckling behavior.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 789–822, November–December, 2007. 相似文献
7.
Jones G. W.; Chapman S. J.; Allwright D. J. 《The Quarterly Journal of Mechanics and Applied Mathematics》2008,61(4):475-495
The problem of a thin spherical linearly elastic shell perfectlybonded to an infinite linearly elastic medium is considered.A constant axisymmetric stress field is applied at infinityin the matrix, and the displacement and stress fields in theshell and matrix are evaluated by means of harmonic potentialfunctions. In order to examine the stability of this solution,the buckling problem of a shell which experiences this deformationis considered. Using Koiter's nonlinear shallow shell theory,restricting buckling patterns to those which are axisymmetricand using the Rayleigh–Ritz method by expanding the bucklingpatterns in an infinite series of Legendre functions, an eigenvalueproblem for the coefficients in the infinite series is determined.This system is truncated and solved numerically in order toanalyse the behaviour of the shell as it undergoes bucklingand to identify the critical buckling stress in two cases, namely,where the shell is hollow and the stress at infinity is eitheruniaxial or radial. 相似文献
8.
A method for calculating the buckling stability of layered cylindrical shells made of composite materials with one plane of
symmetry of mechanical characteristics is worked out. As a special case, shells made of fibrous materials by winding in directions
not coinciding with coordinate axes are considered. An analysis of stability of shells under an axial compression, external
pressure, and torsion is carried out. It is shown that, at a great number of layers and appropriate reinforcing angles, the
shells can be considered orthotropic. The solution to the problem of the initial postbuckling behavior of shells made of composites
with one plane of symmetry is also obtained. It is found that shells of this type can be less sensitive to geometrical imperfections.
This fact is important from the practical point of view.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 2, pp. 213–236, March–April, 2007. 相似文献
9.
Summary The problem considered here is that of a thin-walled circular cylindrical shell whose external surface is submitted to uniform fluid pressure. The condition under which bifurcation will occur in the shell beyond the elastic limit is examined and the true tangent modulus formula for the plastic buckling is established. Numerical results are presented for the critical pressure, covering both elastic and plastic ranges of buckling.
Zusammenfassung Einige Betrachtungen über das Verzweigungsproblem einer dünnen Kreiszylinderschale mit homogen verteiltem Aussendruck führen zu einem exakten Ausdruck für die kritische Last im elastisch-plastischen Bereich. Verschiedene numerische Resultate für die kritische Last im elastischen sowie im plastischen Bereich werden angegeben.相似文献
10.
The equations for integral instantaneous characteristics of composite materials consisting of elastoplastic fibers and matrix are derived based on the known hypotheses of uniform strain or stress fields. The constitutive relations for a layered shell are obtained. The numerical algorithm elaborated is used to solve the stability problem for conical boron-aluminum shells under external pressure and axial compression. It is shown that the shells of medium thickness lose their stability under loads whose magnitude depends on the plasticity of the binder. The plasticity has a decisive influence on the choice of the optimum directions of reinforcement. If the parameters of a shell are such that the buckling occurs beyond the elastic limit, the shell must be reinforced in the direction of precritical stresses. However, this is possible only upon separate action of loads. 相似文献
11.
E. A. Aliyev 《Mechanics of Composite Materials》2007,43(6):521-534
Within the framework of a piecewise homogenous body model and with the use of a three-dimensional linearized theory of stability
(TLTS), the local near-surface buckling of a material system consisting of a viscoelastic (elastic) half-plane, an elastic
(viscoelastic) bond layer, and a viscoelastic (elastic) covering layer is investigated. A plane-strain state is considered,
and it is assumed that the near-surface buckling instability is caused by the evolution of a local initial curving (imperfection)
of the elastic layer with time or with an external compressive force at fixed instants of time. The equations of TLTS are
obtained from the three-dimensional geometrically nonlinear equations of the theory of viscoelasticity by using the boundary-form
perturbation technique. A method for solving the problems considered by employing the Laplace and Fourier transformations
is developed. It is supposed that the aforementioned elastic layer has an insignificant initial local imperfection, and the
stability is lost if this imperfection starts to grow infinitely. Numerical results on the critical compressive force and
the critical time are presented. The influence of rheological parameters of the viscoelastic materials on the critical time
is investigated. The viscoelasticity of the materials is described by the Rabotnov fractional-exponential operator.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 771–788, November–December, 2007. 相似文献
12.
R. M. Martynyak B. S. Slobodyan V. M. Zelenyak 《Journal of Mathematical Sciences》2009,160(4):470-477
A model of contact between an elastic half space and a rigid base with a shallow surface rectangular hole is proposed. The
hole contains an incompressible liquid and gas. The liquid occupies the middle part of the hole and forms a capillary bridge
between the opposite surfaces. The remaining volume of the hole is filled with gas under a constant pressure. The liquid completely
wets the surfaces of the bodies. The pressure drop at the liquid–gas interface caused by the surface tension is defined by
the Laplace formula. The corresponding plane contact problem for the elastic half space is essentially nonlinear because the
pressure of the liquid and the length of the capillary in the contact-boundary conditions are not known in advance and depend
on the external load. The problem is reduced to a system of three equations (a singular integral equation for the function
of height of the hole and two transcendental equations for the length of the capillary and the height of the meniscus). An
analytic-numerical procedure for the solution of these equations is proposed. Dependences of the length of the capillary and
the pressure drop at the liquid–gas interface on the external load, volume of liquid, and its surface tension are analyzed.
Translated from Matematychni Metody ta Fizyko-Mekhanichni Polya, Vol. 51, No. 1, pp. 150–156, January–March, 2008. 相似文献
13.
V. N. Paimushin 《Russian Mathematics (Iz VUZ)》2016,60(4):37-46
We investigate the possibilities for simplification of previously proposed refined linearized equations of perturbedmotion to identify, by dynamic method, the buckling mode shapes of isotropic spherical shells undergoing external hydrodynamic pressure. In the analysis of classical flexural buckling shapes of spherical shells, it is shown that preserving of nonconservative parametric terms in governing equations of formulated problem, which are related with loading of the shell with follower pressure practically does not affect the value of critical load and the resulting bucklingmode shapes in shell. 相似文献
14.
The problem of the buckling of elastic, isotropic, thin-walled cylindrical shells with small initial shape defects that are under the action of an external pressure is solved in a geometrically non-linear formulation. Equations that are identical to Marguerre's equations for a shallow cylindrical shell are used in formulating the problem. The solution is constructed by the Rayleigh–Ritz method with the points of the middle surface of the shell approximated by double functional sums over trigonometric and beam functions. The system of non-linear equations obtained is solved by arc-length methods. Cases of the clamped and supported shells when loading with a lateral and uniform hydrostatic pressure are considered. Its deflections from the limit points of the postbuckling branches of its loading trajectory are used as the initial imperfections. An inspection of the different forms of the initial imperfections when they have maximum values of up to 30% of the shell thickness made it possible to obtain practically the whole range of experimentally found critical pressures. 相似文献
15.
The nonlinear buckling behavior of a 3D-braided composite cylindrical shell of finite length subjected to internal pressure
in thermal environments is considered. According to a new micromacromechanical model, a 3D-braided composite may be treated
as a cell system where the geometry of each cell strongly depends on its position in the cross section of the cylindrical
shell. The material properties of the epoxy matrix are expressed as linear functions of temperature. The governing equations
are based on Reddy’s higher-order shear deformation theory of shells with a von Karman–Donnell-type kinematic nonlinearity
and include thermal effects. The singular perturbation technique is employed to determine the buckling pressure and the postbuckling
equilibrium paths of the shell. 相似文献
16.
17.
We discuss the results of the determination of the stress and displacement fields in nonaxisymmetrically loaded nonlinear-elastic
shells of revolution. The original nonlinear system of equations is linearized in accordance with the method of variation
of elastic parameters. The two-dimensional linear boundary-value problem is reduced to a sequence of one-dimensional problems,
which are solved using a numerical method. We carry out an analysis of the stress-strain state of a conical shell made of
a composite material of granular structure.
Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, No. 37, 1994, pp. 80–83. 相似文献
18.
We develop a mathematical model of the boundary value problem describing magnetic field shielding by a cylindrical thin-walled shell (screen) made of materials whose permeability depends nonlinearly on the magnetic field intensity. Integral boundary conditions on the shell surface are used. A numerical method is suggested for solving a nonlinear boundary value problem of magnetostatics with integral boundary conditions. The shielding efficiency coefficient characterizing the external magnetic field attenuation when passing into the interior of the cylindrical screen is studied numerically. 相似文献
19.
20.
We present a method for rational application of the deformation properties of a shell system with an elastic filler: design
of a shell with variable thickness while preserving the load-bearing ability of the system as a whole. For the equi-strength
shell thereby obtained we state and solve the mixed contact problem taking account of dry friction with nonmonotone loading,
making it possible to estimate the structural hysteresis in the system.
Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, No. 37, 1994, pp. 86–91. 相似文献