Crack

Add a node to indicate that certain boundaries represent a crack. A crack can either be infinitely thin, and represented by a single boundary, or being represented by disjoint surfaces in the geometry.

A crack can have any number of branches and corresponding crack fronts.

The node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/). It is available for 3D, 2D, and 2D axisymmetry.

This section is only shown if is set to in the Crack Definition section. In this case, it is not possible to deduce the number of crack fronts uniquely from geometric analysis, so you must explicitly select the crack front or crack fronts.

	For 3D components, select a boundary or set of edges representing the crack fronts.

	For 2D and 2D axisymmetry, select points located at the crack fronts.

This section is only shown if is set to in the Crack Definition section. In this case, the main selection will contain both sides of the crack. In this section, select one of the crack faces, so that it is possible to discriminate between the two faces of the crack.

The coordinate system selection is only used when a user defined crack orientation is selected in the Crack Orientation section.

In this section, you select how the crack is represented in the geometry.

Select a — , , or .

•

When the crack is represented as an internal boundary, select . This will cause the displacements of the two sides of the boundary to be decoupled from each other so that a crack is formed.

•

If only half of a symmetric structure is modeled, so that the crack is an external boundary, select . In 2D axisymmetry, this is only meaningful for cracks that are perpendicular to the axis of rotation. There are two cases:

The crack is infinitely thin and located in the symmetry plane. Other boundary conditions like or will be overridden on the crack surface, so that the crack can be opened.

The direction of the crack growth is important if you are going to compute a J-Integral.

Select a — or . In most cases the crack growth direction can be automatically deduced from the geometry of the crack. If this is not the case, select and then enter a vector for the . The vector is represented in the coordinate system selected in the Coordinate System Selection section.