Boundary integral equations of unique solutions in elasticity

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Singular integral inequalities with several nonlinearities and integral equations with singular kernels

We deal with an integral inequality with a power nonlinearity on its left-hand side, n nonlinearities on its right-hand side, and weakly singular kernels. The obtained result is an extension of the Bihari, Henry, Pachpatte, and Pinto inequalities and results obtained by the author. Using these results, we prove sufficient conditions for the existence of global solutions of some nonlinear Volterra integral equations with singular kernels and n nonlinearities. Published in Neliniini Kolyvannya, Vol. 11, No. 1, pp. 71–80, January–March, 2007.     

Boundary integral equations for inverse problems in the elasticity theory

The paper is concerned with the application of the boundary integral equation method for the holomorphic vector to nonclassical problems in the static theory of elasticity. Problems are considered for the case when on part of a body conditions are overvalued, i.e. the vectors of displacements and loads are prescribed, and on the other part of the body conditions are unknown (so-called (u, p) problem). It is shown that the method proposed is efficient and can be applied to the problems of computer defectoscopy in stationary potential fields.     

Singular integral equations in Hilbert space applied to crack problems

Crack problems are solved by application of a system of singular integral equations in Hilbert space. The method consists of replacing the singular integral equation by a system of linear algebraic equations for the values of the unknown function at specially chosen points within the range of integration. Obtained is a solution for a nonsymmetric cross-shaped crack in an infinite and isotropic solid subjected to a constant pressure, the symmetric configuration being a special case.     

Numerical analysis of singular solutions of two-dimensional problems of asymmetric elasticity

An algorithm for the numerical analysis of singular solutions of two-dimensional problems of asymmetric elasticity is considered. The algorithm is based on separation of a power-law dependence from the finite-element solution in a neighborhood of singular points in the domain under study, where singular solutions are possible. The obtained power-law dependencies allow one to conclude whether the stresses have singularities and what the character of these singularities is. The algorithm was tested for problems of classical elasticity by comparing the stress singularity exponents obtained by the proposed method and from known analytic solutions. Problems with various cases of singular points, namely, body surface points at which either the smoothness of the surface is violated, or the type of boundary conditions is changed, or distinct materials are in contact, are considered as applications. The stress singularity exponents obtained by using the models of classical and asymmetric elasticity are compared. It is shown that, in the case of cracks, the stress singularity exponents are the same for the elasticity models under study, but for other cases of singular points, the stress singularity exponents obtained on the basis of asymmetric elasticity have insignificant quantitative distinctions from the solutions of the classical elasticity.     

Numerical solution of integro-differential and singular integral equations for plate bending problems

Two integral equation formulations for the determination of the vertical displacement and the bending moment around holes in an elastic plate are presented. Each formulation consists of two equations, the first one an integral equation and an integro-differential equation and the second one two singular integral equations. The equations are solved using B-splines as approximations to the unknowns and the method is applied to the case of one elliptic hole in a twisted plate.

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Zusammenfassung Zwei verschiedene Integralgleichungssysteme für die Bestimmung von die Durchbiegung und die Biegemoment in einer gelochten elastischen Platte werden entwickelt. Die eine Systeme besteht von einer Integralgleichung und einer Integro-Differentialgleichung und die andere von zwei singulären Integralgleichungen von Cauchy'schen Typus. Bei der Auflösung der Systeme werden die unbekannten mit Hilfe B-splines ausgedrückt. Beide Systeme werden benutzt in dem Fall von einer elliptischen Loch in einer uendlichen, tordierten Platte.

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An abbreviated version of this paper was included in a paper Integral equation solutions to mechanical problems. A review and an application to plate theory which will appear in the Proceedings from second national congress of theoretical and applied mechanics, Druzba, Bulgaria, 1973.     

On some singular integral equations appearing in contact problems for the elastic cylinder

It is shown that the coupled singular integral equations with trigonometric kernels appearing in the problem of adhesive contact between an elastic circular cylinder and two identical rigid compressive rollers may be reduced to a problem of Muskhelishvili type and may be explicitly solved. The solution is applied to the cases when the rollers are either flat or circular, and the results are compared with those found by Hill and Tordesillas [2].     

平面弹性外问题的等价的直接变量边界积分方程

用变分法证明平面弹性力学外边值问题的正确提法。在此基础之上，确立外问题的等价的直接变量边界积分方程。对传统的惯用的直接变量边界积分方程进行了深入的讨论，表明它与原边值问题不等价。     

Singular integral equations in elastic dielectrics

Galerkin representations for the displacement vector, polarization vector and the potential field are obtained by elementary matrix inversions of the equations of equilibrium. Matrices of fundamental solutions of an infinite elastic dielectric continuum subjected to a concentrated body force, an electric force, and a charge density, are constructed. Theorems are proved on the discontinuity of double layer potentials and R, M, M operators of single layer potentials. By means of these theorems, the solution of the two basic boundary value problems has been reduced to the solution of a system of seven singular integral equations.     

EQUIVALENT BOUNDARY INTEGRAL EQUATIONS WITH INDIRECT VARIABLES FOR PLANE ELASTICITY PROBLEMS

IntroductionIthasbeenratheralonghistorythattheBoundaryElementMethod (BEM )isappliedtosolvetheplaneelasticityproblems[1～2 ].However,theEBIE ,whichisequivalenttotheoriginalboundaryvalueproblem ,hasnotbeenfullyappreciatedandsolvedinBEMcommunity .TheconventionalboundaryintegralequationswithindirectvariablesarediscussedthoroughlyanditisshownthatthepreviousresultsarenotEBIE ,i.e .,sometimes,thereexistsnosolutionormorethanonesolutiontothem .Themainkeyliesintheexactformoftheexteriorproblems.I…     

Singular integral equations in asymmetric thermoelasticity

Integral representations for the displacement vector, rotation vector and the temperature have been constructed by making use of the three basic singular solutions in asymmetric thermoelasticity. The potentials of a single and double layer have been constructed. The solution of the basic boundary value problems has been reduced to the solution of a system of seven singular integral equations by utilizing the theorems proved on the discontinuities of the double layer potentials and P (stress), M (couple-stress) and /n operators of the single layer potentials.

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Zusammenfassung Unter Benutzung der drei Fundamentallösungen der asymmetrischen Thermoelastizitätstheorie werden Integraldarstellungen für den Verschiebungsvektor, den Rotationsvektor und das Temperaturfeld konstruiert. Es werden die Potentiale der Einfach-und Doppelbelegung angegeben. Die Lösung der Randwertprobleme wird zurückgeführt auf die Lösung eines Systems von sieben singulären Integralgleichungen. Dabei werden Theoreme benutzt, die für die Unstetigkeiten der Doppelbelegungspotentiale sowie die P (Spannungs-), M (Momenten-pannungs-) und /n-Operatoren der Einfachbelegungspotentiale nachgewiesen werden.

     

Numerical solution of singular integral equations in stress concentration problems under longitudinal shear loading

Summary The paper deals with numerical solutions of singular integral equations in stress concentration problems for longitudinal shear loading. The body force method is used to formulate the problem as a system of singular integral equations with Cauchy-type singularities, where unknown functions are densities of body forces distributed in the longitudinal direction of an infinite body. First, four kinds of fundamental density functions are introduced to satisfy completely the boundary conditions for an elliptical boundary in the range 0≤φ _k ≤2π. To explain the idea of the fundamental densities, four kinds of equivalent auxiliary body force densities are defined in the range 0≤φ _k ≤π/2, and necessary conditions that the densities must satisfy are described. Then, four kinds of fundamental density functions are explained as sample functions to satisfy the necessary conditions. Next, the unknown functions of the body force densities are approximated by a linear combination of the fundamental density functions and weight functions, which are unknown. Calculations are carried out for several arrangements of elliptical holes. It is found that the present method yields rapidly converging numerical results. The body force densities and stress distributions along the boundaries are shown in figures to demonstrate the accuracy of the present solutions. Received 26 May 1998; accepted for publication 27 November 1998     

On a new integration rule with the Gegenbauer polynomials for singular integral equations used in the theory of elasticity

Summary A new technique is proposed for the numerical solution of the Cauchy-type singular integral equations, by using the well known Gegenbauer polynomials. A large class of problems of mathematical physics, and especially several plane and antiplane elasticity problems, not possessing closed-form solutions, can be reduced to the solution of certain systems of such a type of singular integral equations. Also by using a certain method the new formula which is used for the numerical solution of the Cauchy-type integral equations can be extended for the general type of the finite-part singular integrals, too.

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über eine neue, in der Elastizitätstheorie anwendbare Integrationsregel mit Benutzung der Gegenbauer-Polynome zur Lösung singulärer Integralgleichungen

übersicht Es wird eine neue Technik zur numerischen Lösung von Cauchyschen singulÄren Integralgleichungen unter Benutzung der bekannten Gegenbauer-Polynome vorgeschlagen. Eine gro\e Klasse von Problemen der mathematischen Physik und besonders verschiedene ebene und antiplanare Probleme der ElastizitÄtstheorie, welche keine geschlossenen Lösungen besitzen, können zur Lösung auf solche singulÄren Integralgleichungen zurückgeführt werden. Die für die numerische Lösung von Cauchyschen Integralgleichungen hergeleitete Methode kann für den allgemeinen Fall singulÄrer Integrale mit endlichem Anteil erweitert werden.

     

Stress tensor symmetry and singular solutions in the theory of elasticity

In the plane problem of the theory of elasticity about a cantilever strip bending, we study the stress state near its fixed end. It is found that the solution singularity at the corner points does not have any physical nature and is generated by specific characteristics of the statement of the problem in which it is assumed that the stress tensor symmetry is violated at these points.     

Matrix inversions and singular solutions in the linear theories of elasticity

Elementary matrix multiplications and inversions lead to Galerkin type representations for the steady-state vibration equations of linear classical elasticity, thermoclasticity, Mindlin's couple stress and Eringen's micropolar theories of elasticity. The use of representations and the equations satisfied by potentials is further illustrated by obtaining singular solutions. Some of the results agree with known solutions.     

Numerical solutions of singular integral equations for planar rectangular interfacial crack in three dimensional bimaterials

Stress intensity factors for a three dimensional rectangular interfacial crack were considered using the body force method. In the numerical calculations, unknown body force densities were approximated by the products of the fundamental densities and power series; here the fundamental densities are chosen to express singular stress fields due to an interface crack exactly. The calculation shows that the numerical results are satisfied. The stress intensity factors for a rectangular interface crack were indicated accurately with the varying aspect ratio, and bimaterial parameter.     

Singular solutions and Green's method in micropolar theory of elasticity

The matrices of fundamental solutions are constructed for a concentrated force as well as a concentrated couple varying harmonically in time and acting in an unbounded micropolar elastic continuum. These solutions are then used to obtain solutions for some other loading singularities. Integral representations, for the displacement and the rotation vectors are obtained by making use of the basic singular solutions. The formal solutions to two fundamental boundary value problems are expressed in terms of integrals which include given surface and body data and Green's functions.     

Solution of statistical problems in elasticity theory in the singular approximation

A method of calculating elastic fields and effective moduli of microheterogeneous solids is developed in the random field theory. The solution is obtained in the form of an operator series, each term of which is constructed on the basis of the regular component of the second derivative tensor of the equilibrium Green function. The zeroth approximation of such a series consists of the local part of the interaction between inhomogeneity grains. The possibilities of the method are illustrated on the example of an isotropic mixture of two isotropic components.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 98–102, January–February, 1972.