Smooth boundary

Let a solid body occupy the domain fl C with the smooth boundary T. The solid particle coincides with the point x = xi,X2,xs) G fl. An elastic solid is described by the following functions ... 

Let a solid body occupy a domain fl c with the smooth boundary L. The deformation of the solid inside fl is described by equilibrium, constitutive and geometrical equations discussed in Sections 1.1.1-1.1.5. To formulate the boundary value problem we need boundary conditions at T. The principal types of boundary conditions are considered in this subsection. 

Let a solid occupy a bounded domain fl c with the smooth boundary r (see Fig.1.1). Let fl contain a smooth unclosed surface Fc, probably intersecting F. We assume that Fc is an oriented surface such that there exists a mapping... 

Now we intend to derive nonpenetration conditions for plates and shells with cracks. Let a domain Q, d B with the smooth boundary T coincide with a mid-surface of a shallow shell. Let L, be an unclosed curve in fl perhaps intersecting L (see Fig.1.2). We assume that F, is described by a smooth function X2 = i ixi). Denoting = fl T we obtain the description of the shell (or the plate) with the crack. This means that the crack surface is a cylindrical surface in R, i.e. it can be described as X2 = i ixi), —h < z < h, where xi,X2,z) is the orthogonal coordinate system, and 2h is the thickness of the shell. Let us choose the unit normal vector V = 1, 2) at F,, ... 

Let C i be a bounded domain with a smooth boundary L, and n = (ni,n2,n3) be a unit outward normal vector to L. Introduce the stress and strain tensors of linear elasticity (see Section 1.1.1),... 

Now we consider a two-dimensional solid occupying a bounded domain fl C with a smooth boundary T. Let the bilinear form B be introduced by the formula... 

Let C be a bounded domain with smooth boundary T, <3 = x (0, T). Our object is to study a contact problem for a plate under creep conditions (see Khludneva, 1990b). The formulation of the problem is as follows. In the domain Q, it is required to find functions w, Mij, i,j = 1,2, satisfying the relations... 

Let Q C he a bounded domain with a smooth boundary j. An external normal to 7 is denoted by n = (ni,ri2). Introduce the following operators defined at 7 by... 

Let a plate occupy a bounded domain fl c with smooth boundary F. Inside fl there is a graph Fc of a sufficiently smooth function. The graph Fc corresponds to the crack in the plate (see Section 1.1.7). A unit vector n = being normal to Fc defines the surfaces of the crack. 

Let (9 C be a bounded domain with smooth boundary 7 and outward normal n = (ni,ri2). We introduce the following notation for the bending moment and transverse forces on 7 ... 

A thin isotropic homogeneous plate is assumed to occupy a bounded domain C with the smooth boundary T. The crack Tc inside 0 is described by a sufficiently smooth function. The chosen direction of the normal n = to Tc defines positive T+ and negative T crack faces. 

To estimate the third-order derivatives of the function w with respect to y, we make use of the following fact (see Duvaut, Lions, 1972). Let O d E be a bounded domain with smooth boundary and let u be a distribution on O such that u, Du G Then u G L 0) and there is a constant c,... 

Let the mid-surface of the Kirchhoff-Love plate occupy a domain flc = fl Tc, where C is a bounded domain with the smooth boundary T, and Tc is the smooth curve without self-intersections recumbent in fl (see Fig.3.4). The mid-surface of the plate is in the plane z = 0. Coordinate system (xi,X2,z) is assumed to be Descartes and orthogonal, x = xi,X2)-... 

Let C be a bounded domain with the smooth boundary L, which has an inside smooth curve Lc without self-intersections. We denote flc = fl Tc. Let n = (ni,ri2) be a unit normal vector at L, and n = ( 1,1 2) be a unit normal vector at Lc, which defines a positive and a negative surface of the crack. We assume that there exists a closed continuation S of Lc dividing fl into two domains the domain fl with the outside normal n at S, and the domain 12+ with the outside normal —n at S (see Section 1.4). By doing so, for a smooth function w in flc, we define the traces of w at boundaries 912+ and, in particular, the traces w+ and the jump [w] = w+ — w at Lc. Let us consider the bilinear form... 

To conclude the section we write the formula (4.159) in the form which does not contain the function 9. To this end, consider a neighbourhood Sl of the set L with a smooth boundary T l assuming that 9 = 1 on Sl- Denote by vi,V2,i 3) the unit external normal vector to T. Integrating by parts in (4.159) we obtain... 

We prove the existence of solutions for the three-dimensional elastoplastic problem with Hencky s law and Neumann boundary conditions by elliptic regularization and the penalty method, both for the case of a smooth boundary and of an interior two-dimensional crack (see Brokate, Khludnev, 1998). It is shown in particular that the variational solution satisfies all boundary conditions. 

Let C i be an open, bounded and connected set with smooth boundary r. We define the Banach space... 

Let fl C he an open, bounded and connected set with a smooth boundary T, and Tc C R be a smooth orientable two-dimensional surface. We assume that this surface can be extended up to the outer boundary T in such a way that fl is divided into two subdomains Ri, fl2 with Lipschitz boundaries. We assume that this inner surface Tc is described parametrically by the equations... 

In this section the existence of a solution to the three-dimensional elastoplastic problem with the Prandtl-Reuss constitutive law and the Neumann boundary conditions is obtained. The proof is based on a suitable combination of the parabolic regularization of equations and the penalty method for the elastoplastic yield condition. The method is applied in the case of the domain with a smooth boundary as well as in the case of an interior two-dimensional crack. It is shown that the weak solutions to the elastoplastic problem satisfying the variational inequality meet all boundary conditions. The results of this section can be found in (Khludnev, Sokolowski, 1998a). 

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