.. _ucLaserLayerPowder:
Laser Hatched Layer with Powder Layer
=====================================

Goal
----

A powder bed over a plate of SS316L is taken as an initial geometry.
The Gaussian laser pulse with normal incidence melts the metal, and hatches a layer.

Powder generation is possible in KiSSAM, but it takes simulation time. 
When powder is set on a flat substrate, the same powder can be reused in different simulations. 
In this sample simulation, we use powder layer that was generated before. 
It should be in a vdb format, with mesh size that corresponds to the simulation setting. 

Run
---

Copy the :download:`JSON file provided with the usercase <../jsonfiles/Laser_layer_powder.json>` into the simulation folder, and the :download:`powder layer file <../jsonfiles/init_spheres.vdb>`, into the simulation folder.

.. code:: bash

  > cp <path>/Laser_layer_powder.json .
  > cp <path>/init_spheres.vdb .

Run the code from terminal with the provided JSON file. You may need to edit the information on the license file in it. 

.. code:: bash

  > INPUT_JSON_FILE=Laser_layer_powder.json /opt/KiSSAM/start_calc.sh

Make sure that simulation is started by making sure there are no fatal errors in the :file:`.log` file that has appeared. 
It might be necessary to insert the correct license filepath.

Input Configuration
-------------------

The simulation parameters can be adjusted by editing the JSON file.

.. literalinclude:: ../jsonfiles/Laser_layer_powder.json
   :language: json
   :linenos:


The parameters that are not specified here are taken from the :file:`/opt/KiSSAM/default.json` file. 

Simulation Results
------------------

The simulation runs for ~18 hours. 
The default name for the simulation output directory is `output`. 

3D view
^^^^^^^

The track geometry is stored in the openVDB format :file:`output/geometry.vdb`.
It is updated during the simulation process and stores the latest state.
View it with Blender or VDB view.

.. figure:: ucdata/LLpowder/blender-view.png
   
   openVDB file loaded and rendered in Blender


Images and animation output
^^^^^^^^^^^^^^^^^^^^^^^^^^^

The meltpool states are rendered as images and stored in :file:`output/rendered3D`.
The images of cross-sections are found in :file:`output/cross-sections`.


.. figure:: ucdata/LLpowder/rendered-pic494000.png
  
   Example of the combined image :file:`combinedIMG/pic-250000.png`


Surface analysis
^^^^^^^^^^^^^^^^

In the simulation folder, run the script generating file geometry data in text format:

.. code:: bash

  > /opt/KiSSAM/scripts/surfaceAnalyzer.x output/geometry.vdb > heights.dat

The output is the text file :file:`heights.dat`. 

.. code::

  #units: millimeters
  #Xcoord Ycoord SurfaceHeight MeltpoolDepthPosition
  0 0 4.56 4.56
  0.003 0 4.56 4.56
  0.006 0 4.56 4.56
  0.009 0 4.56 4.56
  0.012 0 4.56 4.56
  0.015 0 4.56 4.56
  0.018 0 4.56 4.56
  0.021 0 4.56 4.56

  ...

Here we plot the third and the fourths columns as a colormap

.. figure:: ucdata/LLpowder/heights.png

   Surface information plotted in the xy plane
   

Cross Section Image
^^^^^^^^^^^^^^^^^^^

Let us run this script to extract cross-section at :math:`x=1.5` mm from the track start `startPosX` (:math:`1` mm):

.. code:: bash

  > /opt/KiSSAM/scripts/drawCrossSection.x output/geometry.vdb trackXcrossSection.png --box 2.5,1.91,4.4867 2.5,2.09,4.6 --background E8F0F200 --substrate 295569FF --remelted CD86F2FF

One pixel of the image is one mesh step: `NumericalParams.dr` (3 μm) in the input file. 

.. figure:: ucdata/LTplate/trackXcrossSection.*

  Cross section in simulation