Build Cross-section in Abaqus and Export to VABS
================================================

Brief Instruction
--------------------------

Overall, the process is similar to creating a meshed beam cross-section part in Abaqus.

* Part:

  * Modeling space: 2D planar
  * Type: Deformable
  * Base feature: Shell

* Property:

  * Material: Any
  * Section: Composite layup (Solid, Homogeneous)

* Mesh: Any

Write the Abaqus model to an INP file.

Convert the INP file to a VABS input file using the command:

..  code-block:: bash

    python -m sgio convert <filename>.inp <filename>.sg -ff abaqus -tf vabs


Detailed Instruction
--------------------------

Part module
^^^^^^^^^^^

As a cross-section of a slender structure, it is natural to create a "Deformable" "Shell" part in the "2D Planar" modeling space.

.. (See Figure :ref:`fig-abaqus-cs-part`)

..  figure:: /images/abaqus_cs_create_part.png
    :name: fig-abaqus-cs-part
    :align: center
    :width: 200

Composite structures can have different materials in different regions.
A useful tip is to create a base shape, such as a circle, large enough to cover the entire cross-section.
Then, use the "Partition Face" tool to divide the base shape into regions.

..  figure:: /images/abaqus_cs_partition_face.png
    :align: center
    :width: 500


Property
^^^^^^^^

Any type of material can be used for the cross-section, such as isotropic, engineering constants, or orthotropic.
VABS requires local orientation data and allows additional in-plane rotations (fiber angle) for each layer.
Hence, it is required to use the "Composite Layup" section type.
Here are instructions for setting up a "Composite Layup" section:

* Each section contains only one ply.
* Layer orientation is defined by assigning the local :math:`y` axis, while the local :math:`x` axis is always normal to the cross-sectional plane.
  For a composite layer, the local :math:`y` axis is usually set to be tangent to a base line.
* To set the fiber angle for each layer, use the column "Rotation Angle".

..  figure:: /images/abaqus_cs_comp_section.png
    :align: center
    :width: 800

It is okay to use the "Composite Layup" section for all materials.
However, if a material is isotropic and no local orientation and fiber angle are needed, then it is also acceptable to use the "Solid" section.

..  figure:: /images/abaqus_cs_solid_section.png
    :align: center
    :width: 500


Mesh
^^^^

There is no restriction on meshing.

..  figure:: /images/abaqus_cs_mesh.png
    :align: center
    :width: 700



File export
^^^^^^^^^^^

Create a job and write the model to an INP file.
Then use the command below to convert the INP file to a VABS input file:

..  code-block:: bash

    python -m sgio convert <filename>.inp <filename>.sg -ff abaqus -tf vabs

By default, the Timoshenko beam model will be used.
To use the Euler-Bernoulli beam model, add the option ``-m bm1``:

..  code-block:: bash

    python -m sgio convert <filename>.inp <filename>.sg -ff abaqus -tf vabs -m bm1

To see help messages, use the command:

..  code-block:: bash

    python -m sgio convert -h