> For the complete documentation index, see [llms.txt](https://tlcfem.gitbook.io/suanpan-manual/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://tlcfem.gitbook.io/suanpan-manual/example/structural/statics/double-edge-notched-specimen.md).

# double-edge notched specimen

The double edge notched specimen was investigated by [Nooru-Mohamed (1992)](http://resolver.tudelft.nl/uuid:a6a773f1-dacd-4598-aa6a-960dddf71117).

This example is taken from the [thesis](https://doi.org/10.5281/zenodo.3731921). The details of the model can be seen in Section 6.3.

The model can be downloaded [here](https://github.com/TLCFEM/suanPan-manual/tree/dev/docs/Example/Structural/Statics/double-edge-notched-specimen.zip).

## Model Setup

The definitions of nodes and elements can be seen in `element_f.supan` and `node_f.supan`.

To ease the work of defining boundary conditions and load, some node groups can be defined first.

In total four edges will be used, here the `generatebypoint` command is used to find all relevant nodes.

```
# find all nodes on the line segment defined by (0,0) and (200,0)
generatebypoint nodegroup 1 0. 0. 200. 0.

# find all nodes on the line segment defined by (200,0) and (200,100)
generatebypoint nodegroup 2 200. 0. 200. 100.

# find all nodes on the line segment defined by (0,200) and (200,200)
generatebypoint nodegroup 3 0. 200. 200. 200.

# find all nodes on the line segment defined by (0,100) and (0,200)
generatebypoint nodegroup 4 0. 100. 0. 200.
```

The boundary conditions are explicitly assigned to the corresponding node groups.

```
# for all four edges, the drilling DoFs are constrained
grouppenaltybc 1 ur3 1 2 3 4

# constrain horizontal movement of edge 2
grouppenaltybc 2 1 2
# constrain vertical movement of edge 1
grouppenaltybc 3 2 1
```

Two displacement loads are applied. Two files `h` and `v` are used to define the amplitudes.

```
# horizontal displacement to generate a 5kN total horizontal tension force
amplitude Tabular 1 h
groupdisplacement 1 1 -16.5E-3 1 4

amplitude Tabular 2 v
groupdisplacement 2 2 .1 2 3
```

If **VTK** is enabled, it is possible to record the distribution of tension damage at each converged substep.

```
hdf5recorder 1 Visualisation DT width 3 scale 0
```

Since we are not interested in the displacement, `scale` is simply set to zero. The output file are automatically numbered with a total width of four. It is changed to three in this example. The generated visualisation files can be loaded into **ParaView** as a group to generate animations.

The analysis has a duration of two seconds. In the first second, the horizontal tension is applied, then the vertical load is applied.

```
step static 1 2
set fixed_step_size 1
set ini_step_size 5E-3

converger RelIncreDisp 1 1E-4 20 1
```

## Results

Results are shown as follows, which agree with experimental results.

![tension damage distribution](https://1124082496-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FEquxr3H9WpPg4iPvT2mB%2Fuploads%2Fgit-blob-7fdcdd7b1d76bb4a79faac3a1457b1b39f8f041b%2Fdouble-edge-notched-specimen-a.png?alt=media)

![the first principal stress distribution](https://1124082496-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FEquxr3H9WpPg4iPvT2mB%2Fuploads%2Fgit-blob-9b782c18156f57196f856e04cde509223fbec0d5%2Fdouble-edge-notched-specimen-b.png?alt=media)

## Element Deletion

It is possible to further define a criterion so that for elements that exceed a certain value of $$d\_t$$, they are removed from the model. This is an approach adopted widely to simulate crack propagation.

```
criterion MaxHistory 1 DT .9
```

The animation of crack development is shown as follows.

![crack development](https://1124082496-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FEquxr3H9WpPg4iPvT2mB%2Fuploads%2Fgit-blob-cb4b6a903e80a8ef9fa91d25abe2c5782a67df3e%2Fdouble-edge-notched-specimen.gif?alt=media)

## Performance

See a typical [profiling](https://github.com/TLCFEM/suanPan-manual/tree/dev/docs/Example/Structural/Statics/double-edge-notched-specimen.html).


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