Tensile Test Example Tutorial Using Gmsh

Introduction

Tensile test simulations provide a valuable means of verification and validation of material models before proceeding to more complex component level or system level simulations

An example is provided here for the creation of a Tensile Test model for OpenRadioss using /MAT/LAW36 (PLAS_TAB) and /FAIL/BIQUAD using the open source meshing tool Gmsh [1] to create the mesh from step file format geometry

The Finite Element Model is predefined in terms of material properties, Loading and boundary conditions , the gmsh_tensile_LAW36_BIQUAD_0000.rad file provided calls the mesh as an include file tensile_test_coupon.inc

Sample Results

Model Files

The model files include the OpenRadioss Starter and Engine files (_0000.rad and _0001.rad), step geometry for the coupon, and a premeshed example coupon if you want to skip the mesh creation

Model Files (22KB)

Step 1: Meshing (Optional)

The files for this example include an example Gmsh tensile test coupon mesh .inc file, so you may skip this part of the process if you are not interested in meshing and simply submit the provided files in Step 2

If you want to try and create your own mesh in Gmsh, then you may follow the steps below

1.1: Download the ‘4.11.1’ release of Gmsh binary and extract

1.2: Open gmsh.exe (windows) or run gmsh executable in Linux

1.3: From File Menu, open the tensile_test_coupon.step file

Coupon Geometry in gmsh

1.4: From Tools → Options → Mesh Menu, choose General tab options,

The example mesh shown here uses options below, but you can experiment with different mesh sizes/types, the ‘wrapper’ model calling the mesh include uses /BOX/RECTA to define the end /RBODY so the node ids of the mesh do not matter so long as the mesh is in the correct location (per the step file).

2D algorithm: Quasi-Structured Quads

Element size factor: 0.5

Mesh Options in Gmsh

then create your mesh

1.5: expand the Mesh option in the menu, then click ‘2D’

These options should result in a mesh similar to below:

Gmsh Quasi-Structured Quad Mesh size factor 0.5

The mesh can now be exported,

1.6: go to File → Export, save as type ‘RADIOSS BLOCK’ into the folder where your model files are saved and use the filename tensile_test_coupon.inc overwriting the supplied example file (this is what the Model file is pre-defined to look for)

When Prompted for further options, these can be left as default (they have no effect in the Radioss export template)

Step 2: Running Model in OpenRadioss

The model file gmsh_tensile_LAW36_BIQUAD_0000.rad can be run in OpenRadioss and will automatically call the include file tensile_test_coupon.inc (either the version previously meshed in Gmsh included in the example model files zip or your new mesh created in Gmsh in the previous step)

Viewing Results

The engine file _0001.rad as contained in the zip requests animation files (Annn) and Time History File (Txx) these are convertable to vtk and csv respectively for reading in ParaView. Check the Pre and Post Processing for OpenRadioss page for information.

In the bottom of the _0001.rad there are requests commented out for .h3d output format, if these lines are uncommented, then the resulting .h3d will be playable in HyperView Player, but will show only the model motion, no results (Stress etc.) will be able to be shown.

References

1: Gmsh (C. Geuzaine and J.-F. Remacle. Gmsh: a three-dimensional finite element mesh generator with built-in pre- and post-processing facilities. International Journal for Numerical Methods in Engineering 79(11), pp. 1309-1331, 2009)

2: Steel Material Data from SSAB: SSAB – a stronger, lighter, and more sustainable world