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Marc Levenston
01-11-1994, 06:14 AM
The following announcement appeared in the December 1993 issue of the
ASB newsletter. It briefly describes some software for calculating
areal and torsional properties of cross sections.

Marc Levenston

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To facilitate more accurate interpretation of whole bone torsion
tests, we have developed a FORTRAN package (VA-TWIST) to calculate
areal and torsional properties of an arbitrary bone cross section.
VA-TWIST solves for the actual torsional properties of the bone
section, eliminating the need for "equivalent" circular or elliptical
approximations of the cross section (which can result in errors in
excess of 40 % for maximum shear stresses). VA-TWIST computes the
centroidal location (X, Y), area (A), moments and product of inertia
(Ix, Iy, Ixy, J), principal moments of inertia (I1, I2), torsion
constant (K) and the distribution of shear stresses throughout the
cross section.

VA-TWIST accepts digitized descriptions of the outer (periosteal) and
inner (endosteal) contours of a cross section, automatically generates
a finite element mesh, and solves a finite element problem for the
torsional properties. Alternatively, the user can provide a
pre-defined mesh for more complicated geometries (e.g., a section with
several holes). VA-TWIST will run on most workstations, PC
compatibles or Macintosh computers which have a FORTRAN compiler.

A copy of the source code and documentation can be obtained by sending
an electronic mail message to:

levenston@roses.stanford.edu

Alternatively, a Macintosh formatted diskette should be sent to:

Marc E. Levenston
Rehabilitation Research and Development Center (153)
Palo Alto VA Medical Center
3801 Miranda Avenue
Palo Alto, CA 94304-1200