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*TIE

Keyword type: model definition

This option is used to tie two surfaces. It can only be used with 3-dimensional elements (no plane stress, plane strain, axisymmetric, beam or shell elements).Optional parameters are POSITION TOLERANCE, NAME, CYCLIC SYMMETRY and MULTISTAGE. The dependent surface is called the slave surface, the independent surface is the master surface. The user can freely decide which surface he takes as slave and which as master. The surfaces are defined using *SURFACE. Nodes belonging to the dependent surface cannot be used as dependent nodes in other SPC's or MPC's. Only nodes on an axis of cyclic symmetry can belong to both the slave as well as to the master surface.

Default (i.e. in the absense of the CYCLIC SYMMETRY and the MULTISTAGE parameter) is a tie of two adjacent surfaces. This is also called tied contact. In that case MPC's are generated connecting the slave nodes with the master faces, provided the distance between the nodes and the adjacent face does not exceed the POSITION TOLERANCE. If no tolerance is specified, or the tolerance is smaller than , a default tolerance is calculated equal to of the typical element size. For tied contact the slave surface can be a nodal or element face surface, whereas the master surface has to consist of element faces.

The parameter CYCLIC SYMMETRY is used to tie two surfaces bounding one and the same datum sector in circumferential direction. Both the slave and the master surface have to be nodal surfaces. For each slave node, a master node is determined which matches the slave node within a tolerance specified by the parameter POSITION TOLERANCE after rotation about the cyclic symmetry axis . Subsequently, a cyclic symmetry constraint is generated. If no tolerance is specified, or the tolerance is smaller than , a default tolerance is calculated equal to of the mean of the distance of the master nodes to their closest neighbor. If no master node is found within the tolerance, the face on the master surface is identified to which the rotated slave node belongs, and a more elaborate multiple point constraint is generated. If none is found, the closest face is taken. If this face does not lie within of its length from the slave node, an error is issued and the program stops.

The parameter MULTISTAGE is used to tie two coincident nodal surfaces each of which belongs to a different datum sector. In that way two axially neighboring datum sectors can be tied. In this case, the order in which the user specifies the surfaces is not relevant: the surface belonging to the smallest datum sector is taken as master surface. The larger datum sector should not extend the smaller datum sector by more than once the smaller datum sector, no matter in what circumferential direction (clockwise or counterclockwise).

The parameter NAME is needed if more than one *TIE constraint is defined. It allows the user to distinguish the tie constraints when referring to them in other keyword cards (e.g. *CYCLIC SYMMETRY MODEL).

First line:

- *TIE
- enter the required parameter CYCLIC SYMMETRY and any of the optional parameters, if needed.

Following line:

- Name of the slave surface.
- Name of the master surface.

    Example:

    *TIE,POSITION TOLERANCE=0.01
    left,right

defines a datum sector with slave surface left and master surface right, and defines a position tolerance of 0.01 length units.

Example files: segment, fullseg.

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