orthotest.txt

orthotest(1)                                                      orthotest(1)



NNAAMMEE
       orthotest  -  see  if  a  set  of  anisotropic  elastic  constants  are
       orthorhombic

SSYYNNOOPPSSIISS
       oorrtthhootteesstt << eellaassttiicc__ccoonnssttaannttss

       oorrtthhootteesstt expects to read from standard input  an  anisotropic  elastic
       stiffness  matrix in the form of 6 numbers on each of 6 lines of input.
       It finds the best-fitting orthorhombic medium to this, and outputs:
       0) the input anisotropic stiffness constants,
       1) the elastic constants rotated so that the best-fitting  orthorhombic
       matrix has the X, Y, and Z axes as principal axes,
       2) the orthorhombic approximation to the rotated matrix,
       3) the orthorhombic approximation in the original coordinate system,
       4)  the  percent  difference between the input stiffness matrix and the
       best-fitting orthorhombic approximation  in  the  original  coordinates
       (normalized by dividing each difference by the norm of the input stiff-
       ness matrix),
       5) the percent difference of the  anisotropic  elastic  constants  from
       orthorhombic, and
       6)  the  coordinates of the 3 principle axes in the original coordinate
       system, in both cartesian and spherical notation.

       Theoretically, it is arbitrary how the three principal axes  should  be
       assigned  to  X, Y, and Z.  This program tries each axis in turn to see
       how close it is to being an axis of transversely isotropic (TI)  symme-
       try.   The axes are then reordered so that the Z axis is the closest to
       being a TI axis of symmetry, then Y  next  closest,  then  X  furthest.
       Thus, if the input medium is TI the Z axis will always be chosen as the
       axis of symmetry.  (Note  that  if  the  input  medium  is  arbitrarily
       anisotropic, there is no reason to expect that the Z axis found by this
       program should precisely coincide with the best-fitting TI  axis  found
       by the program titest.)

       Spherical coordinates are specified using phi and theta:
       phi=0 is the +Z axis
       phi=90 theta=0 is the +X axis
       phi=90 theta=90 is the +Y axis

       For  more  about what "best-fitting" means for elastic stiffness matri-
       ces, see the article by Arts,  Helbig,  and  Rasolofosaon  in  the  SEG
       extended  abstracts  for  1991, page 1534: "General Anisotropic Elastic
       Tensor in Rocks: Approximation, Invariants, and Particular Directions".

       See the ttiitteesstt man page for example input.

OOPPTTIIOONNSS
       Currently there are no options or arguments.

AAUUTTHHOORR
       This program was written by Joe Dellinger at the Amoco Tulsa Technology
       Center during February 1997.

SSEEEE AALLSSOO
       ttiitteesstt(l)



                                  18 Feb 1997                     orthotest(1)