A COMPARISON OF CRACK-FLANK DISPLACEMENT FITTING FOR ESTIMATING K WITH A PATH-INDEPENDENT INTEGRAL

Predicting crack growth under cyclic loading in applications usually r equires the efficient extraction of stress intensity factors from fini te element analyses of mixed mode situations. Two approaches to this e nd are examined: one, a competitive fitting procedure using crack-flan k displacement data, the other, a path independent integral which can readily distinguish between modes. A protocol is established for compa ring the two on a set of about forty test problems which have exact so lutions. Analysis is via quarter point elements on a common sequence o f three successively refined meshes for each problem. Results show tha t the path independent integral is more consistently accurate and reli ably convergent, yet comparable in implementation effort.