What exactly means the magnitude in the scalebars for pole and inverse pole figures?

[Italo Persechino]

Hi group, maybe is a silly question but I don't understand and I haven't found anything about the meaning of the magnitude in the scale bars that you get when you plot pole figures and inverse pole figures.

I am not sure if it is a normalized number of grain oriented in a specified direction or it depends on the number of grains. I am running a VPSC simulation and I have a good agreement with experiments for the inverse pole figures but the magnitude is smaller. I know probably the question is not related to MTEX but I trust your experience in texture microstructure. If you have some good resource where I can find and study about this arguments I would appreciate because is not my field of study. Thank you.

[Ralf Hielscher]

Hi Italo,

If you plot smooth plots the scale is usually mrd, i.e., multiples of random distribution. If you take your ODF from VPSC simulations, i.e., from individual orientations, be aware that the choice of the kernel halfwidth has a big impact to the intensities. You may want to play around a bit with the halfwidth. 

I hope this helps,

Ralf.

PS: If you have further questions. you should include the MTEX code you use.

[David Mainprice]

Just for discussion ... 

I think it is more correct to call it a mud  i.e., multiples of UNIFORM distribution as random is rather hard to define exactly ? MUD with a value of 1 is exactly UNIFORM.

all the best David

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[Italo Persechino]

I am using the 4.0.20 version of MTEX. One thing that I don't get is this one

I have plotted the inverse pole figure IPF from individual orientations, importing as EBSD the texture from the VPSC simulation and I have obtained this:

and then I have imported the texture as ODF, with kernel deLaValeePoussinKernel and halfwidth of 13. And I have this:

so, I don't get why in the IPDF from ODF the density is higher in 111 while from the IPF from the EBSD the 101 seems to be preferred direction. And I played a bit with the halfwidth but the 101 in the IPF from ODF is always with lower density.

[Ralf Hielscher]

Hi Italo,

you can also plot a contour plot of you ebsd data by

plotIPDF(ori,zvector,'contourf')

and compare it to the ODF result. Maybe you can attach you script and your data such that we can have a look at it.

Ralf.

[Italo Persechino]

Thanks for the quick reply Ralf.
Here there is the code:

%% Import Script for ODF Data

%

% This script was automatically created by the import wizard. You should

% run the whoole script or parts of it in order to import your data. There

% is no problem in making any changes to this script.

%% Specify Crystal and Specimen Symmetries

% crystal symmetry

CS = crystalSymmetry('m-3m', [3.615 3.615 3.615], 'mineral', 'Copper', 'color', 'light blue');

% specimen symmetry

SS = specimenSymmetry('1');

% plotting convention

setMTEXpref('xAxisDirection','east');

setMTEXpref('zAxisDirection','outOfPlane');

%% Specify File Names

% path to files

%pname = 'C:\Users\ItaloP\Documents\AADottorato\Lavoro-Andrew\VPSCsimulations\Verifica_texture_independence_with_hardening_parameters\tensile_test\param_1';

% which files to be imported

fname = ['TEX_PH1.OUT'];

%% Import the Data

% % specify kernel

% psi = deLaValeePoussinKernel('halfwidth',13*degree);

% 

% % create an EBSD variable containing the data

% odf = loadODF(fname,CS,SS,'density','kernel',psi,'resolution',5*degree,...

%   'interface','VPSC');

ebsd = loadEBSD_generic(fname,'ColumnNames',{'Euler1','Euler2','Euler3'},'HEADER',4);

 %% plot inverse pole figures 

 

%Specify Miller Indice

m1 = Miller(0,0,1,CS);

m2 = Miller(1,0,1,CS);

m3 = Miller(1,1,1,CS);

%Specify vector

v1 = vector3d(1,0,0);

v2 = vector3d(0,1,0);

v3 = vector3d(0,0,1);

%% plot IPF from EBSD discrete

figure(01)

plotIPDF(ebsd.orientations,v1)

annotate([Miller(m1),Miller(m2),Miller(m3)],'all','labeled')

saveas(figure(01),'IPF from EBSD discrete.jpeg')

%% plot IPF from EBSD contour

figure(02)

plotIPDF(ebsd.orientations,v1,'contourf')

colorbar

annotate([Miller(m1),Miller(m2),Miller(m3)],'all','labeled')

saveas(figure(02),'IPF from EBSD contour.jpeg')

%% Import the Data

% specify kernel

psi = deLaValeePoussinKernel('halfwidth',13*degree);

% create an EBSD variable containing the data

odf = loadODF(fname,CS,SS,'density','kernel',psi,'resolution',5*degree,...

  'interface','VPSC');

%% plot inverse pole figures from ODF

figure(03)

plotIPDF(odf, v3,'contour','antipodal','resolution',5*degree) %'contour',0:0.2:3.2, 'minmax', 'off')

annotate([Miller(m1),Miller(m2),Miller(m3)],'all','labeled')

colorbar

saveas(figure(03),'IPF from ODF.jpeg')

just run it. Ihave also attached the file of the texture I have obtained from VPSC simulations.

I tried plotting the IPF from EBSD as contour plot (and added the script to mine) but it's still different from the IPF from ODF.

Many thanks

[Kunze Karsten]

Hi,

carefully check your reference direction for IPDF:
In your script it is v1 for figure 1 and 2, but v3 for figure 3.

 

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Von: mtex...@googlegroups.com [mtex...@googlegroups.com]" im Auftrag von "Italo Persechino [italo.pe...@gmail.com]
Gesendet: Mittwoch, 20. Mai 2015 10:27
An: mtex...@googlegroups.com
Cc: italo.pe...@gmail.com
Betreff: {MTEX} Re: What exactly means the magnitude in the scalebars for pole and inverse pole figures?

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[Italo Persechino]

I was getting crazy for this stupid mistake. I am really sorry to have wasted your time.

One last question if I can, now the qualitative results are the same for both the IPF from the EBSD and ODF. The problem still remain for the quantitative results, which are different. Is it a good method, in your opinion, to play with the halfwidth and make the value of density for the IPF from ODF equal to the one of the IPF from EBSD?

[Ralf Hielscher]

 Is it a good method, in your opinion, to play with the halfwidth and make the value of density for the IPF from ODF equal to the one of the IPF from EBSD?

At least it gives you a feeling how large is the ambiguity of the reconstruction. Keep in mind both method have the halfwidth  as the main parameter that effects the results. Try

plotIPDF(ori,zvector,'contourf','halfwidth',10*degree)

Keep in mind that the one halfwidth is in orientation space while the other is in directional space and can not directly be compared. 

Further, there is no general concept what is the "correct" halfwidth. Choose what you think is reasonable and report this in your paper.

Ralf.