A new approach, in which the only information is the area of isochromatic f
ringe loop, is presented to determine mode-I and mode-II stress intensity f
actors(SIFs). For a mixed-mode crack, the expressions for SIFs K-I and K-II
in terms of the area inside an isochromatic fringe loop and the area insid
e an iso-sum fringe loop are given. A comparison of the present results wit
h the previous results shows that the proposed method is stable and efficie
nt.