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*PRE-TENSION SECTION

Keyword type: model definition

This option is used to define a pre-tension in a bolt or similar structure. There are two required parameters: SURFACE and NODE. With the parameter SURACE an element face surface is to be defined on which the pre-tension acts. This is usually a cross section of the bolt. The parameter NODE is used to define a reference node. This node should not be used elsewhere in the model. In particular, it should not belong to any element. The coordinates of this node are immaterial. The first degree of freedom of this node is used to define a pretension force with *CLOAD or a differential displacement with *BOUNDARY. The force and the displacements are applied in the direction of the normal on the surface. The user must specify the normal underneath the *PRE-TENSION SECTION keyword. So if the normal is specified away from the elements to which the surface belongs, a positive force or positive displacements correspond to tension in the underlying structure. Notice that the surface must be defined by element faces, it cannot be defined by nodes.

Internally, the nodes belonging to the element face surface are copied and a linear multiple point constraint is generated between the nodes expressing that the mean force is the force specified by the user (or similarly, the mean differential displacement is the one specified by the user). Therefore, if the user visualizes the results with CalculiX GraphiX, a gap will be noticed at the location of the pre-tension section.

Right now, *PRE-TENSION SECTION only works for three-dimensional elements. It does not work yet for 1-d or 2-d elements such as axisymmetric elements or plane stress elements.

First line:

- *PRE-TENSION SECTION
- Enter the SURFACE and NODE parameter and their values

Following line:

- First component in global coordinates of the normal on the surface
- Second component in global coordinates of the normal on the surface
- Third component in global coordinates of the normal on the surface

    Example:

    *PRE-TENSION SECTION,SURFACE=SURF1,NODE=234
    1.,0.,0.

defines a pre-tension section consisting of the surface with the name SURF1 and reference node 234. The normal on the surface is defined as the positive global x-direction.

Example files: pret.

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