Observaciones Experimentales sobre la Fuerza Motriz en la Propagación de Grietas de Fatiga

the role of the effective and applied stress intensity factors (δkapp and δkeff) as driving forces in fatigue crack growth is analyzed. to make a reliable use of δkeff in design it is needed to show that this parameter depends only on the same parameters that are included in the expression of δkapp (the nominal stress, the crack size and the geometry function). to verify this behavior experimental k-increasing and k-decreasing tests were done with the same specimen. the closure factor u= δkeff/δk showed an accentuated variation with crack size in all the tests, so δkeff should not be used for design purposes. the experimental data are also presented in three dimensions finding similar results, although it is not possible to generalize the results with the data available.