Basics about Stats generator

[Method Engineer]

Hi developers,

I am working on single crystal nickel superalloy.

I wanted to know how to calculate these basic things in stats generator. as in user manual there is less information available. So i request please help me out with my some basic doubts.

1. what is mean feature ESD , means what is meant by equivalent sphere dia actually ? and from where to get it ?

2. What does Bin step size , Mu and sigma defines ?

3. Is there any experimental procedure to extract these parameters ?

Or these should be assumed randomly ?

Thanks & regards

Rushikesh

[Method Engineer]

Hello,

I have already gone through some previous replies. But still have some doubts.

1. Like I want to generate a microstructure for single crystal - does that mean I have to generate only one bin ?

2. If I am selecting 32*32*32 dimensions and 5*5*5 resolution  in Initialize synthetic volume filter , then what will be the size of the cube ?

Does 1 resolution means 1 micron ?

3. Suppose I wanted to make a cube of 1mm side size. then as I am working for single crystal , the size of grain size also would be 1 mm. so what should I use bin step size, mu, sigma values in stats generator ? and I need atleast 32*32*32 voxels for my simulation.  So what should be the resolution ?

Thank you

[Michael Jackson]

Hello Rushikesh,

    If you are truly working with a single crystal where every voxel of the microstructure represents the same exact crystal orientation then you can just manually create the Image Geometry with the necessary cell and ensemble level data. I have attached a pipeline that shows how to do that.

DREAM3D is basically unit-less. We do not specifically assign units to the geometries or voxels. What ever length you select, just stay consistent in other filters if those filters are asking for a “length” in a value other than voxel units. So if you want to create a 1mm ^3 cube where each voxel represents 1 micron^3 then you would need 1000 x 1000 x 1000. If you want each voxel to be 100 microns on a side then you would need an Image Geometry that is 10 x 10 x 10. You take the number of voxels and multiple by the “resolution” value to get the true length of that side of the virtual microstructure.

There are enough filters that you could process experimental data to calculate the necessary input data to generate a synthetic microstructure. There is an example pipeline that does this. But in your case I’m not convinced that you need to do this, again, assuming that you wanting a truly “single” crystal.

—

Mike Jackson

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[Method Engineer]

Hello Mike,

Thank you for the quick reply and clarified answer.

Actually it's not a truly single crystal. I am using EBSD euler angle file in ODF tab of stats generator. so actually wanted to use stats generator and initialize synthetic volume filter.

So to get single crystal of roughly in 1mm^3 volume of the cube. what should be the values of number of bins, Mu, sigma in stats generator.

and values in Dimensions in x,y,z and resolution also ?

To get single crystal, does that mean "Estimated Primary Features" generated should be "One" only ?

Thank you

[Michael Jackson]

Dear Rushikesh,

  Let's start with the average grain size which is expressed in StatsGenerator as the ESD value. This allows you to adjust the grain size. Remember that StatsGenerator is unitless so be consistent. If you want a 20 micron average grain size then adjust mu and sigma values to have a peak around 20. The sigma values will control how wide the distribution is. The Min and Max cut off will remove the front and back tails of the distribution. I would adjust the Bin Size to get about 10 bins which is typically enough for 99% of the synthetics that are generated.

Once you have that figured out, then you will need to start to calculate just how many voxels you will need to represent the number of grains that you need. The recommended number of voxels across the diameter of a feature is 10. Some rough calculation would be then with a diameter of 20 microns you want 10 voxels, so 2 microns per voxel. Now If you want 1000 microns (1mm) on a side then you will need about 500 voxels in each direction for the synthetic volume. 

The Estimate Primary Features is just a user-feedback part that we added into the UI to allow the user a greater understanding of just how many features (grains) they are going to end up creating.

With this method you are going to end up creating a bunch of grains. If you select from an extremely narrow orientation bin range the features will all have very close Euler Angles which will effectively make it a single crystal (from what I remember about single crystal products)

Hopefully that helps clear up some confusion.

—

Mike Jackson

Principal DREAM.3D Developer

BlueQuartz Software

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