popLA Manual (PDF) - Materials Science and Engineering

esponse to some procedure you have asked for; others (such as ROTATE by 90°) do not: you have to edit the
file afterwards.
The simplest system would be XYZ=123=ABN=RTC. This could work, for example, for rolling – if you
mounted your sample correctly on the goniometer, called the rolling plane normal 3, the rolling direction 1,
plotted the RD to the right, and used Roe (or Matthies or Kocks) conventions for the Euler angles. It would also
work if you mounted your sample differently, called the rolling direction 2, plotted it upwards, and used Bunge
angles. (Kallend uses the Roe convention, but likes the RD up: that's why some popLA programs default to
IPER=( 2 1 3).
Clearly, such procedures are not general, and no convention exists for tests other than rolling. The general
procedure we use and recommend is as follows.
1) The most important step is to mark your sample before you initiate a texture measurement. (If you
should later want to change those marks, you can simply edit IPER in the resulting files.) Unless the sample has
at least orthotropic symmetry, make sure the marks have a sign. (If you have a clockwise goniometer, it would
be best to choose the marks in a left-handed system so that, after spin inversion, it is right-handed.) It is best to
enter IPER in the sequence ABN, so that when the RAW and EPF pole figures are plotted (RTC=ABN), they
can be related directly to the specimen (perhaps with inverted spin).
2) For the analysis, first decide on what type of OD you want to use; in other words, in which sequence the
numbers should appear in the SOD file (and the subsequent COD, etc.). (If you want to use LApp, or a weights
file for any other purpose, you are stuck with Kocks; but for the present discussion, Roe and Matthies would be
equivalent.) Then manipulate the EPF until the first row proceeds from a sample azimuth (Ψ or α or ϕ1) of zero
to increasing values. Use this EPF for input to the harmonic and/or WIMV analysis programs. If you prefer, for
visualization, a pole figure that is rotated from the so-obtained EPF, make it separately (for example, in
ROTATE, or from within POD). You should now re-edit IPER so that the labels on the OD sections and/or the
pole figures relate correctly to the specimen.
3) The above procedure assumed that Z=N=C (but not necessarily =3). If you want to analyze your data
with a Z axis that is convenient (e.g., because it has higher symmetry), but is not easy to measure (Z=C*N), the
best procedure is to first complete the measured EPF, go right through to a WPF in the "wrong" system, then
TILT this by 90° about the horizontal axis (you may have to EXPAND and/or ROTATE first), and use the
resulting (full) pole figure as input for a second WIMV analysis, now in the preferred coordinate system.
(Again, re-editing IPER is advised.)
APPENDICES 46