A two-strain-gage technique for determining mode I stress-intensity factor

A finite element analysis and a experimental test were performed to show that the terms with r^−1/2 and ^1/2 in the eigenfunction expansion of the strains can describe the crack tip strain distribution with sufficient accuracy. A set of two linear equations can be obtained to determine the stress intensity factor K_I using only two strain-gages. Errors within 5% can be achieved provided that the two strain-gages are placed at the appropriate locations. The technique can be developed to treat crack bodies with irregular geometry and complex loading.