Material forces as a simple criterion for the description of crack-turning problems☆

Crack-path prediction for crack-turning problems in stiffened structures is an important issue in modern aircraft design processes because the ability of modeling a crack-path correctly allows the engineer to predict lifecycles and maintenance cycles more appropriate. In this paper the method of material forces as a simple method to describe crack-turning problems is introduced. At first, simple problems are examined, in order to make sure that the computed numerical results are comparable to known analytical results. Thereafter a simple academic example of a stiffened structure is shown and the crack-path is predicted by means of an implementation of the material force method in a finite element analysis formulation. The results of these computations have been compared to the results achieved by several known methods for computing the stress intensity factors, the crack-path and the energy release rate. It can be seen that computations of the material force deliver all necessary information to describe a crack by linear elastic fracture mechanics.