Stress intensity factor calculation based on the work of external forces

The external forces method is a numerical method for K calculation based on the finite element method. It uses the work of the external forces W-E for the calculation of the energy release rate and is particularly advantageous when that forces are applied far from the crack front. The method was applied to a corner crack geometry with the objective of studying its accuracy. Good results were obtained for a wide range of virtual crack displacements (0.03% < Delta a/a < 6%) considering 4 values of W-E along with a polynomial regression of order 3. For that choice of parameters the inaccuracy of K is mainly due to FEM errors. A great sensitivity of K to FEM errors was observed, however accurate values of K were obtained, with errors lower than 2 percent. So, the use of the external forces method for the calculation of K is recommended, considering its simplicity and accuracy.