On a partially debonded rigid line inclusion penetrating a circular inhomogeneity

We derive closed-form solutions to the mixed boundary value problem of a partially debonded rigid line inclusion penetrating a circular elastic inhomogeneity under antiplane shear deformation. The two tips of the rigid line inclusion are just mutual mirror images with respect to the inhomogeneity/matrix interface, and the upper part of the rigid line inclusion is debonded from the surrounding materials. By using conformal mapping and the method of image, closed-form solutions are derived for three loading cases: (i) the matrix is subjected to remote uniform stresses; (ii) the matrix is subjected to a line force and a screw dislocation; and (iii) the inhomogeneity is subjected to a line force and a screw dislocation. In the mapped ξ-plane, the solutions for all the three loading cases are interpreted in terms of image singularities. For the remote loading case, explicit full-field expressions of all the field variables such as displacement, stress function and stresses are obtained. Also derived is the near tip asymptotic elastic field governed by two generalized stress intensity factors. The generalized stress intensity factors for all the three loading cases are derived.     

Elastic field of a deforming circular inclusion in an infinite strip

Present investigation analyzes the problem of an infinite elastic strip having a symmetrically situated circular inclusion which tends to undergo a spontaneous physical change. In the case when the straight edges of the strip are assumed traction free, the consequent elastic fields both in the inclusion and the strip are determined with the aid of complex variable technique. Expressions for complex potentials and stress components are derived in the form of infinite integrals. Numerical values of stress are computed in some cases of interest.

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Zusammenfassung In dieser Arbeit wird das Problem eines unendlichen elastischen Streifens untersucht, mit einer symmetrisch angeordneten kreisförmigen Einlage, an der plötzlich eine physikalische Änderung aufgeprägt wird. Für den Fall, daß die geraden Begrenzungen des Streifens spannungsfrei sind, werden die elastischen Felder sowohl in der Einlage als auch im Streifen berechnet. Ausdrücke für das komplexe Potential und für die Spannungskomponenten werden in Form von unendlichen Integralen angegeben. Numerische Werte von Spannungen werden für einige Fälle berechnet.

     

Elastic state of a plate with a circular plug and a rectilinear thin elastic inclusion

There is considered the problem of the state of stress of an infinite elastic plane with a bonded circular plug and an arbitrarily located thin elastic inclusion under biaxial tension. Conditions of ideal mechanical contact are satisfied on the line separating the materials. By using the complex Kolosov — Muskhelishvili potentials, the problem is reduced to a system of integro-differential equations which is solved numerically by utilization of a mechanical quadrature method. A numerical analysis is given for the solution of the problem of the elastic equilibrium of a plane with a circular hole and an arbitrarily located thin inclusion.     

Symmetric deformation of a circular cylindrical shell of variable wall thickness

Zusammenfassung Es werden für die Differentialgleichung der Biegung einer zylindrischen Schale mit kreisförmigem Querschnitt und veränderlicher Wandstärke Lösungen in Form bekannter Funktionen angegeben.

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Supported by the Office of Naval Research under contract with the Massachusetts Institute of Technology.     

Block diagonal dominance of matrix and spectral inclusion regions

Suppose that comlex matrix A or order n is partitioned as where the diagonal submatrices A_(ⅱ) are square of order n_i(1≤i≤N) .If each A_(ⅱ)is nonsingular and satisfies sum from (j=1 j≠i) to N(‖A_(ij)~(-1)A_(ij)‖≤1),1≤i≤N. thon A is called quasi-block diagonally domfnant. Specially, if strictly inequality in(2) is valid for all 1≤i≤N then A is called quasi-block strictly diagonally dominant. If strict inequality in (2) is valid for at least one i (1≤i≤N) and     

Radial deformation of a nonhomogeneous spherically isotropic elastic sphere with a concentric spherical inclusion

The elasticity of a spherically isotropic medium bounded by two concentric spherical surfaces subjected to normal pressures is discussed. The material of the structure is spherically isotropic and, in addition, is continuously inhomogeneous with mechanical properties varying exponentially as the square of the radius. An exact solution of the problem in terms of Whittaker functions is presented. The St. Venant’s solution in the case of homogeneous material and Lamé’s solution in the case of homogeneous isotropic material are derived from the general solution. The problem of a solid sphere of the same medium under the external pressure is also solved as a particular case of the above problem. Finally, the displacements and stresses of a composite sphere consisting of a solid spherical body made of homogeneous material and a nonhomogeneous concentric spherical shell covering the inclusion, both of them being spherically isotropic, are obtained when the sphere is under uniform compression.     

Steady-state motions of a massif with a circular cavity under an antiplane deformation

We give a solution of the problem of antiplane deformation of an isotropic massif with a cavity of circular cross-section, reinforced by a multilayer cylinder under steady-state motions. We give the results of numerical studies that characterize the influence of reinforcement on the stress distribution in a neighborhood of the cavity. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 23, 1992, pp. 78–81.     

Dynamic contact between a spherical inclusion and a matrix upon incidence of an elastic wave

Using the boundary element method, we have studied the dynamic displacements and stresses in an infinite elastic matrix with a spherical elastic inclusion, caused by the propagation of an elastic wave. The original problem has been reduced to a system of boundary integral equations for the contact displacements and tractions on the interface between the inclusion and matrix. Based on the numerical solution of these equations, we have analyzed the influence of the direction of wave propagation and frequency on the important physical parameters, depending on the elastic characteristics of composite constituents.     

Stability loss in an infinite plate with a circular inclusion under uniaxial tension

Loss of stability under uniaxial tension in an infinite plate with a circular inclusion made of another material is analyzed. The influence exerted by the elastic modulus of the inclusion on the critical load is examined. The minimum eigenvalue corresponding to the first critical load is found by applying the variational principle. The computations are performed in Maple and are compared with results obtained with the finite element method in ANSYS 13.1. The computations show that the instability modes are different when the inclusion is softer than the plate and when the inclusion is stiffer than the plate. As the Young’s modulus of the inclusion approaches that of the plate, the critical load increases substantially. When these moduli coincide, stability loss is not possible.     

Preservers of eigenvalue inclusion sets of matrix products

For a square matrix A, let S(A) be an eigenvalue inclusion set such as the Gershgorin region, the union of Cassini ovals, and the Ostrowski’s set. Characterization is obtained for maps Φ on n×n matrices satisfying S(Φ(A)Φ(B))=S(AB) for all matrices A and B.     

On circuit inclusion sets for the singular values of a square matrix

The paper considers different circuit inclusion sets for the singular values of a square matrix. It is shown that in both the general and the structurally symmetric cases, the circuit inclusion sets are of theoretical interest only, because they coincide with the much simpler Ostrowski–Brauer type inclusion sets, which should be used in practice. Bibliography: 10 titles. Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 359, 2008, pp. 78–93.     

The finite deformation of a pressurized circular tube for a class of compressible materials

This investigation is concerned with the problem of a hollow circular cylinder subjected to uniform internal and external pressure within the equilibrium theory of finite elasticity. The tube is composed of homogeneous, isotropic,compressible materials of special type, namely harmonic materials. Explicit closed-form solutions for the deformation and stress fields are obtained. The true stress distribution, expressed as a function of the undeformed coordinates, is shown to be essentially independent of material properties. The two cases of internal pressure only, and external pressure only, are examined in detail. In the former case, there is a critical value of the applied pressure at which the maximum hoop stress in the tube, occurring at the inner surface, becomes unbounded. Results appropriate for thin shells are also obtained. For the case of external pressure only, a critical value of the applied pressure exists for which closing of the cavity is predicted. For nearly solid cylinders, or equivalently, for a cavity in an unbounded medium, explicit results are provided for the corresponding stress concentration factor.Furthermore the stability of the preceding equilibrium states is investigated by employing a standard linearized perturbation scheme. It is found that an internally pressurized tube is always stable in the range of interest whereas an externally pressurized tube buckles prior to cavity closure.

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Zusammenfassung Die Untersuchung befaßt sich im Rahmen der Gleichgewichtstheorie fmiter Elastizität mit dem Problem eines Hohlzylinders, der einem gleichförmigen inneren und äußeren Druck ausgesetzt ist. Das Rohr besteht aus homogenen, isotropen,kompressiblen Materialien eines speziellen Typs, nämlich harmonischen Materialien. Explizite Lösungen in geschlossener Form werden für Verformung und Spannungsfelder erhalten. Es wird gezeigt, daß die Verteilung der wahren Spannung in Abhängigkeit von den unverformten Koordinaten im wesentlichen unabhängig von den Materialeigenschaften ist. Die beiden Fälle, nur innerer Druck und nur äußerer Druck, werden detailliert behandelt. Im ersten Fall gibt es einen kritischen Druck, bei dem die maximale Tangentialspannung im Rohr, und zwar an der inneren Oberfläche, über alle Grenzen wächst. Es werden außerdem Ergebnisse erhalten, die für dünne Schalen zutreffen. Im Fall eines ausschließlich äußeren Drucks existiert ein kritischer Druckwert, bei dem ein Schließen des Hohlraums vorhergesagt wird. Für annähernd massive Zylinder, oder damit gleichbedeutend, für einen Hohlraum in einem unendlichen Medium, werden explizite Ergebnisse für den entsprechenden Spannungskonzentrationsfaktor vorgelegt.Darüberhinaus wird die Stabilität vorausgehender Gleichgewichtszustände durch Anwendung eines üblichen linearisierten Störungsschemas untersucht. Es wird gefunden, daß das Rohr unter Innendruck im interessierenden Bereich immer stabil ist, während ein Rohr unter Außendruck einknickt, bevor sich der Hohlraum schließt.

     

Axisymmetric deformation of a thick circular glass-reinforced plastic cylinder with stiffening ribs

The state of stress of a circular glass-reinforced cylinder strengthened with equally spaced stiffening ribs has been investigated for uniform axisymmetric and longitudinal loads of intensity p. A system of equilibrium equations is obtained for the shell on the assumption that Hooke's law is valid and that the angles of rotation and shear are commensurable for deformation of an element of the structure. A solution of this system is given for boundary conditions that take into account the compatibility of strains of shell and ribs. As a result of an analysis of the solution the limits of applicability of the theory of thin shells to this type of structure are determined, the effect of anisotropy of the material is estimated, and recommendations are made regarding the choice of optimal reinforcing schemes for cylindrical shells.Mekhanika Polimerov, Vol. 2, No. 1, pp. 108–115, 1966     

Unsteady deformation of elastic solids in the shape of a circular cylindrical segment

The unsteady deformation of cylindrical solids is investigated using the dynamic theory of elasticity. Special cases of the general solution are pointed out. Numerical results are presented which reflect the specific feature of the stressed state of an infinitely long thick-walled cylinder, which is subjected to plane nonaxi-symmetrical loading. The method of investigating unsteady wave processes in cylindrical solids is similar to that described previously [1–3].     

Closed-form solutions for a mode III radial matrix crack penetrating a circular inhomogeneity

In this research we address in detail a mode III radial matrix crack penetrating a circular inhomogeneity. One tip of the radial crack lies in the matrix, while the other tip of the radial crack lies in the circular inhomogeneity. In addition the two tips of the crack are mutually image points (or inverse points) with respect to the circular inhomogeneity-matrix interface. First we conformally map the crack onto a unit circle C_a in the new ζ-plane. Meanwhile the inhomogeneity-matrix interface is mapped onto C_b, a part of another circle in the ζ-plane. In addition C_a and C_b intersect at a vertex angle π/2. By using the method of image in the ζ-plane, closed-form solutions in terms of elementary functions are derived for three loading cases: (1) remote uniform antiplane shearing; (2) a screw dislocation located in the unbounded matrix; and (3) a radial Zener–Stroh crack.     

Criterion for the stability of the partial indices of a circular matrix function

Translated from Matematicheskie Zametki, Vol. 44, No. 4, pp. 536–545, October, 1988.     

A model of the elastodynamic interaction of a thin-walled inclusion with a matrix under antiplanar shear

Using the example of antiplanar shear we give a generalized scheme for constructing models of elastodynamic interaction of an elastic matrix with a thin-walled elastic curvilinear inclusion lying in the matrix under conditions of ideal contact subject to steady vibrations, by introducing suitable conditions on the middle line of the inhomogeneity. The procedure for the study is based on the application of the methods of the theory of singular perturbations. We describe the behavior of the stress-strain state of the body near the edges of the inhomogeneity, where boundary-layer phenomena appear. Translated fromMatematychni Metody ta Fizyko-Mekhanichni Polya, Vol. 41, No. 1, 1998, pp. 54–61.