Photoelastic analysis of practical mode I fracture test specimens

A photoelastic technique for the evaluation of the isochromatic fringe patterns of practical Mode I fracture test specimen is presented. The new procedure uncouples the expressions for the stress intensity factor K and the non-singular stress term A from the governing maximum shear expression by employing a line perpendicular to the crack-tip in a photoelastic specimen, (this line intersects the isochromatic fringes at the locus of points r i , θ i = π/2 , i = 1,2,…, n, where n is the maximum analizable fringe) in developing the least-squares technique employed in this research. The least-squares expressions developed required no assumption of initial values for the stress intensity factor K and the non-singular stress term A. The accuracy of the approach is then demonstrated by obtaining the K and A values of some practical Mode I specimens under applied uniaxial and biaxial stresses.