**crack_2d#

Description#

This command is used to insert a crack in a 2D mesh.

A duplicate of this command, named crack_2d_quarter_nodes, will also modify the nodal positions on edges surrounding the crack tip to \(1/4\) node positions. The elements with modified node positions embody \(\dfrac{1}{\sqrt{r}}\) of singularity, thus providing a stress field which agrees with the theoretical stress singularity of linear fracture mechanics [U1].

../../_images/barsoum.png

Syntax#

The command has the following syntax:

**crack_2d_quarter_nodes \(~\,\) *liset liset-name \(~\,\) [ *node node-id ] \(~\,\) [ *crack_nset nset-name ] \(~\,\) [ *half ] \(~\,\) [ *shrink_factor s_factor ]

The options for this command are described below:

*liset

give the liset name which describes the crack plane. This liset will be kept after the meshing operation.

*node

Give node ids or nset names indicating nodes which are crack tips. These nodes terminate the crack surface creation.

*crack_nset

enter a name for a new nset to be created, which makes up the opposing surface from the crack definition liset. This lets one do contact, or other manipulations on the newly created surface.

*half

Only make a closed crack tip at the first end of the given liset. That is for an edge-crack, make the line set originating where the crack tip is to be and leading out to the free surface.

*shrink_factor

It applies a displacement of crack nodes (By default s_factor = 0, i.e. no displacement is applied). It is useful to do so to visualize the crack.

Example#

An example use is shown below taken from the test case Jint_test/INP/ccp_2.inp which is shown in the figure below.

../../_images/ccp_2.png

This case includes 2 cracks, one of which is open ended (the first) and one which automatically detects the crack tip nodes.

****mesher
 ***shell
   rm -f ccp_2.geof
   Zrun -B ccp_2.mast
 ***mesh ccp_2
  **open ccp_2.geof
  **crack_2d_quarter_nodes
   *liset crack
   *half
  **crack_2d_quarter_nodes
   *liset crk
****return

**crack_3d_quarter_nodes#

Description#

This command is used to set \(1/4\) node positions for adjacent faces of a 3d crack, as defined by a line set. It does not yet provide crack insertion via splitting face sets.

Syntax#

The command has the following syntax:

**crack_3d_quarter_nodes \(~\,\) *liset liset-name

liset-name

is the name of a valid line set defining the crack tip line.