# Nonlocal barrier records

Nonlocal material models of integral type are based on replacement of certain suitable local quantity in local constitutive law by their nonlocal counterparts, that are obtained as weighted average over some characteristic volume. The weighted average is computed as a sum of a remote value multiplied by weight function value. The weight function typically depend on a distance between remote and receiver points and decreases with increasing distance. In some cases, it is necessary to disregard mutual interaction between some points (for example if they are on the opposite sides of a thin notch, which prevents the nonlocal interactions to take place). The barriers are the way how to introduce these constrains. The barrier represent a curve (in 2D) or surface (in 3D). When the line connecting receiver and remote point intersects a barrier, the barriers is activated and the corresponding interaction is not taken into account.

Currently, the supported barrier types are following:

• Polyline barrier

 polylinebarrier (num#)(in) vertexnodes #(ia) [xcoordindx #(in)] [ycoordindx #(in)]

This represents a polyline barrier for 2D problems. Barrier is a polyline, defined as a sequence of nodes representing vertices. The vertices are specified using parameter vertexnodes array, which contains the node numbers. The optional parameters xcoordindx and ycoordindx allow to select the plane (xy, yz, or xz), where the barrier is defined. The xcoordindx is the first coordinate index, ycoordindx is the second. The default values are 1 for xcoordindx and 2 for ycoordindx, representing barrier in xy plane.

• Symmetry barrier

 symmetrybarrier (num#)(in) origin #(ra) normals #(ra) activemask #(ia)

Implementation of symmetry barier, that allows to specify up to three planes (orthogonal ones) of symmetry. This barrier allows to model the symmetry of the averaged field on the boundary without the need of modeling the other part of structure across the plane of symmetry. It is based on modifying the integration weights of source points to take into account the symmetry. The potential symmetry planes are determined by specifying orthogonal right-handed coordinate system, where axes represent the normals of corresponding symmetry planes. Parameter origin determines the origin of the coordinate system, the normals array contains three components of x-axis direction vector, followed by three components of y-axis direction vector (expressed in global coordinate system). The z-axis is determined from the orthogonality conditions. Parameter activemask allows to specify active symmetry planes; i-th nonzero value activates the symmetry barrier for plane with normal determined by corresponding coordinate axis (x=1, y=2, z=3).

Borek Patzak
2018-01-02