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--- software:mtex [2020/07/31 11:03]
matthias [Importing ODF data from MAUD into MTeX]
+++ software:mtex [2020/10/06 15:14] (current)
matthias
@@ Line 225: / Line 225: @@
 Now you have an ODF in MTeX, which should be almost identical to the one from MAUD.
+===== Component analysis =====
+A component analysis provides you with the components, which "make" your textures.
+Example: Figure a) shows the inverse pole figure (IPF) of a textured material with tetragonal symmetry. Although the raw data consists of dozens of individual crystals, there are only two distinct "types" of orientations visible: at [001] and close to [-110]. A component analysis provides you the exact contribution of each of these two components.
+{{:software:qz2mgc2_st_43gr_ipf_hw10.jpg?330|Textured material with two components}}
+{{ :software:qz2mgc2_st_43gr_ipf_hw15.jpg?330|Textured material with two components}}
+//Left: Figure a): HW = 10; right: Figure b): HW = 15//
+==== Procedure in MTeX ====
+//See https://mtex-toolbox.github.io/ODFComponents.html for more info on this chapter.//
+Have an odf ready in the workspace. Then, use the command
+  [ori, vol] = calcComponents(odf)
+(works only in MTeX 5.4.0 or later). Then, call 'ori' and 'vol' individually to see their actual values. You will get something similar to this:
+<code>
+ori = orientation (show methods, plot)
+  size: 7 x 1
+  crystal symmetry : Sample (4/mmm)
+  specimen symmetry: mmm
+  Bunge Euler angles in degree
+     phi1     Phi    phi2    Inv.
+.667 154.883 358.816       0
+.8 136.584 197.771       0
+.344 72.8023 126.642       0
+.004  100.88 314.985       0
+.9998      90 89.9845       0
+.529 75.4564 352.913       0
+.0032 90.0012 224.993       0
+vol =
+.325581
+.209302
+.186047
+.162791
+.069767
+.023256
+.023256
+</code>
+You can see that MTeX calculated - very surprisingly - even seven components. To visualize these components, you can implement them in your pre-made figure, like so (see Figure c):
+  annotate(ori,'MarkerFaceColor','red')
+{{:software:qz2mgc2_st_43gr_ipf_hw10_comp.jpg?330|Textured material with two components}}
+{{ :software:qz2mgc2_st_43gr_ipf_hw15_comp.jpg?330|Textured material with two components}}
+//Left: Figure c): HW = 10; right: Figure d): HW = 15//
+These components are obviously not correct. Apparently, the texture is sharper in certain areas than it looks like in the figure. That´s why MTeX finds more components than there are actually there. To solve this issue, one has to smoothen the odf. This is done by increasing the halfwidth of the kernel (HW) when calculating the odf at the very beginning. The IPF above was created by using a HW of 10. This is how it looks like after increasing it to 15 (fig b). You can see that the IPF slightly changed. However, the data is still the same. When we calculate the components again, it looks a little bit better:
+<code>
+  Bunge Euler angles in degree
+     phi1     Phi    phi2    Inv.
+.944 24.0138 179.783       0
+.975 98.2499 315.004       0
+.0001 89.9999  90.006       0
+.9998 90.0166 224.972       0
+vol =
+.558140
+.348837
+.069767
+.023256
+</code>
+The number of components decreased to four. Their location in the IPF seems also much more reasonable (see Figure d). Now, you can decide either to increase the HW even more to hopefully get only the two components, which you expected, or you continue.
+==== Interpreting the results ====
+You now have to find out, which component belongs to which point in the IPF. For this step, it is helpful to plot the Euler sections:
+  figure
+    plotSection(odf,'sections',18)
+Note that for the cases of compression and tension experiments you have to change the specimen symmetry to 'mmm' before. For torsion and shear experiments, it should be '2'. If you don´t, the Euler space will be too large. In the Euler section plot, you can ''annotate'' again to see where your components are.
+Now, try to assign your components to the location in the plot with the help of the given Euler angles. Some of them might be easy to find, other angles don´t seem to match the location in the plot at all. This is because some are represented differently. Try to subtract 90°, 180° or 360° from the angles. If this is not enough to assign the angles, try to subtract the angle from 90°.
+<code>
+Example: phi2 = 250°
+This could mean one of the following opitions:
+a) phi2 = 250° (not for crystal symmetry = tetragonal)
+b) phi2 = 250° - 180° = 70°
+c) phi2 = 90° - (250° - 180°) = 20°
+</code>
+If the values still don´t make sense you should consider modifying the HW to make sure that you can always follow what is going on.
+The parameter ''vol'' gives you the volume proportion of each of the components (they are listed in the same order as the angles). If you realize that two of the components are basically the same, you can also add their proportion.
+By performing this analysis on different samples (by using the same HW), you can not only see how certain textures evolve over time but also support this observation with numbers.

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