In this paper we have computed the energy release rate for a crack subjected simultaneously to Mode I and Mode II conditions. The energy was computed by path-independent integrals, using the elastic solution of a deflected crack, having a main branch and a propagation branch. The elasticity solution was obtained from the functional integral equations by the process of iterations. This process leads to a point-wise exact solution in the limit as the propagation branch goes to zero. Interestingly enough, the results indicate that the solution at the tip in the limit as the propagation branch goes to zero is not the same as the solution at the tip with no branch.
Using the Griffith-Irwin criterion, incipient paths of propagation of such a crack were obtained from the maximum value of the energy release rate. To check the validity of the results, an experiment, which gives a pure Mode II condition at the tip of the crack, was devised. The results were in excellent agreement with the theory. The energy release rate, in parametric form, can be used for any crack subjected to Mode I and Mode II loading conditions. To the authors' knowledge, such an expression for the energy release rate does not exist in the literature.