A computor system of principal stress-analysis and automatic tracing of stress trajectories employing a micro-computor is described. The boundary condition and interior distribution of principal stress-difference, both obtained from two-dimensional photoelastic pattern, are put in the computor using a digitizer and Laplace's equation with respect to sum of principal stresses is solved numerically by the iteration procedure at 25×25 points over the model area. The stress trajectories are automatically traced form the obtained σ1 and σ2 without recourse to isoclinics which tend to be blurred and troublesome to determine accurately.
