A quasi-static Signorini contact problem for a thermoviscoelastic beam

This paper is concerned with the existence, uniqueness and numerical solution of a system of equations modelling the evolution of a quasi-static thermoviscoelastic beam that may be in contact with two rigid obstacles. A finite element approximation is proposed and analysed and some numerical results are given. Work partially supported by the Brazilian institution CNPq.     

Existence of a solution for a Signorini contact problem for Maxwell-Norton materials

The aim of this article is to study the quasistatic evolutionof a Maxwell–Norton three-dimensional viscoelastic solidwith contact constraints. After introducing the appropiate functionalframework, we will discretize the problem in time using an implicitscheme whose resultant variational inequality is well posed.By using monotonicity arguments together with compensated compactnesstechniques, we will prove that the corresponding discrete solutionconverges to a solution of the continuous problem.     

An asymptotic solution of the Dirichlet problem for the Poisson equation on a nonperiodic frame

In this paper, the Dirichlet problem for the Poisson equation is considered in a nonperiodic framelike domain that consists of thin short strips or cylinders. We construct a complete asymptotic expansion for the solution. We obtain an estimate for the difference between the exact solution and the asymptotic one. Bibliography: 9 titles. Dedicated to Olga Arsenievna Oleinik Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 19, pp. 000-000, 0000.     

An asymptotic solution of the Cauchy problem for the Davey-Stewartson-I equation

We construct and asymptotic solution of the Cauchy problem for the Davey-Stewartson-I equation as t→∞. The solution, which is of order t⁻¹, is rapidly oscillating. The envelope of the oscillations can be defined by an integral equation. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 114, No. 1, pp. 104–114, January, 1998.     

An asymptotic approach to the problem of the free oscillations of a beam

Equations describing the free small longitudinal and transverse oscillations of a straight elastic beam of rectangular cross section are obtained using the plane linear theory of elasticity and the method of integrodifferential relations. The initial system of partial differential equations is reduced to a system of ordinary linear differential equations with constant coefficients. The effect of the geometrical and elastic characteristics of the beam on the frequency and form of the natural oscillations is investigated. For longitudinal motions it is shown that different types of natural displacements and internal stresses of the beam exist. For transverse oscillations, it is found that there are frequency zones corresponding to different forms of the solutions of the characteristic equation obtained using the proposed model.     

An asymptotic solution to the cycle decomposition problem for complete graphs

Let m₁,m₂,…,mt be a list of integers. It is shown that there exists an integer N such that for all n?N, the complete graph of order n can be decomposed into edge-disjoint cycles of lengths m₁,m₂,…,mt if and only if n is odd, 3?mi?n for i=1,2,…,t, and . In 1981, Alspach conjectured that this result holds for all n, and that a corresponding result also holds for decompositions of complete graphs of even order into cycles and a perfect matching.     

An algorithm for the asymptotic solution of a singularly perturbed linear time-optimal control problem

An algorithm for the approximate solution (in the asymptotic sense) of a singularly perturbed linear time-optimal control problem is proposed. A computational procedure is outlined, which permits the use of the resulting asymptotic approximation for. the exact solution of the problem with a prescribed value of the small parameter.     

The problem of the bending of a beam lying on an elastic base

The plane contact problem of the transmission of a normal force of specified strength onto an elastic anisotropic, wedge-shaped plate by an elastic beam of variable flexural stiffness is considered. The beam is coupled to one of the edges of the plate and its other edge is stress-free. The solution of the problem is obtained in closed form by reducing it to a Karleman boundary-value problem with shear for a strip. A conclusion is reached concerning the nature of the discontinuity of the normal contact stress at the vertex of the wedge.     

Optimal regularity for the Signorini problem

We prove under general assumptions that solutions of the thin obstacle or Signorini problem in any space dimension achieve the optimal regularity C ^1,1/2. This improves the known optimal regularity results by allowing the thin obstacle to be defined in an arbitrary C ^1,β hypersurface, β > 1/2, additionally, our proof covers any linear elliptic operator in divergence form with smooth coefficients. The main ingredients of the proof are a version of Almgren’s monotonicity formula and the optimal regularity of global solutions.     

Regularity for the nonlinear Signorini problem

We study the regularity of the solution to a fully nonlinear version of the thin obstacle problem. In particular we prove that the solution is C1,α for some small α>0. This extends a result of Luis Caffarelli of 1979. Our proof relies on new estimates up to the boundary for fully nonlinear equations with Neumann boundary data, developed recently by the authors.     

Semi-smooth Newton methods for the Signorini problem

Semi-smooth Newton methods are analyzed for the Signorini problem. A proper regularization is introduced which guarantees that the semi-smooth Newton method is superlinearly convergent for each regularized problem. Utilizing a shift motivated by an augmented Lagrangian framework, to the regularization term, the solution to each regularized problem is feasible. Convergence of the regularized problems is shown and a report on numerical experiments is given.     

一个渐近非线性Dirichlet问题的对径解的存在性

利用锥上的不动点定理获得了一个渐近非线性Dirirchlet问题的对径解的存在定理。     

Analysis of a Signorini problem with friction

This paper deals with the study of a nonlinear problem of frictionalcontact between an elastic body and a rigid foundation. Theelastic constitutive law is assumed to be nonlinear and thecontact is modelled with Signorini's conditions and a versionof Coulomb's law of dry friction. We present two weak formulationsof the problem and establish existence and uniqueness results,using arguments of elliptic variational inequalities and a fixed-pintproperty. Moreover, we prove some equivalence results and studythe behaviour of the solution when the coefficient of frictiontends to zero.     

Asymptotic solution to the Signorini problem with small parts of the free boundary

Translated fromSibirskiî Matematicheskiî Zhurnal, Vol. 35, No. 2, pp. 258–277, March–April, 1994.     

Closed-form solution for the free axial-bending vibration problem of structures composed of rigid bodies and elastic beam segments

In this paper, the coupled axial-bending vibration of planar serial frame structures composed of rigid bodies and Euler-Bernoulli beam segments is considered. The corresponding mode orthogonality conditions for this kind of structures are derived. It is assumed that the mass centers of rigid bodies have both the transverse and the axial eccentricity with respect to beam neutral axes and that the mass centers are located in the plane in which the rigid bodies perform planar motion. The system responses to initial excitation in the case of distinct as well as repeated natural frequencies are considered. Theoretical considerations are accompanied by four numerical examples.     

Hybrid finite element methods for the Signorini problem

We study three mixed linear finite element methods for the numerical simulation of the two-dimensional Signorini problem. Applying Falk's Lemma and saddle point theory to the resulting discrete mixed variational inequality allows us to state the convergence rate of each of them. Two of these finite elements provide optimal results under reasonable regularity assumptions on the Signorini solution, and the numerical investigation shows that the third method also provides optimal accuracy.