Structural mechanics: orientation of principal stresses

Hi,

I am interested in computing principal stress orientation. I am aware that there is a function to compute the magnitude (eigenvalues) of the principal stresse called princse, but is there a function to compute the directions or orientations (eigenvectors)?

Thanks in advance

Mikel

You could use the principal stress function template below to modify the call to eig(...) and return the eigenvectors too.

function [ se_p ] = princse( se_x, se_y, se_z, se_xy, se_yz, se_xz, icomp )
% PRINCSE Compute principal stresses and strains.
%
%   [ SE_P ] = PRINCSE( SE_X, SE_Y, SE_Z, SE_XY, SE_YZ, SE_XZ, ICOMP ) Computes
%   principal stresses and strains (for the ICOMP component, default 1). In two
%   dimensions only inputs SE_X, SE_Y, SE_Z, SE_XY, and ICOMP are required.

n  = length( se_x );
eg = zeros( 3, 3, n );
eg(1,1,:) = se_x;
eg(2,2,:) = se_y;
eg(3,3,:) = se_z;
eg(2,1,:) = se_xy;
eg(1,2,:) = se_xy;
if( nargin>=6 )
  eg(3,2,:) = se_yz;
  eg(2,3,:) = se_yz;
  eg(3,1,:) = se_xz;
  eg(1,3,:) = se_xz;
  if( nargin<7 )
    icomp = 1;
  end
else
  if( nargin<5 )
    icomp = 1;
  else
    icomp = se_yz;
  end
end

d = zeros( 3, n );
for i=1:n
  d(:,i) = eig( eg(:,:,i) );
end

srt = sort( [ d(1,:); d(2,:); d(3,:) ] );
srt = srt( [3;2;1], : );

se_p = reshape( srt(icomp,:), size(se_x) );