Abstract
The goal of this work is to find a suitable method based on Itoh-Sakane model to estimate fatigue life of notched specimens under multiaxial low cycle fatigue under non-proportional loading, accounting of notch sensitivity and crack initiation position. Cylindrical bars of Al6061 aluminum alloy and AISI 316L stainless steel with four values of stress concentration factors referred to the net section Kt,n 1.5, 2.5, 4.2 and 6.0 have been tested. Aluminum alloy features a lower notch sensitivity compared to steel. Cyclic curves evidenced a high additional hardening caused by non-proportional loading for steel and low additional hardening for aluminum. Low cycle fatigue test results evidenced a reduction of fatigue life for non-proportional loading both for aluminum and steel. Furthermore, the crack initiation position resulted moved from the notch tip for low values of Kt,n only in case of steel. The phenomenon has been thought to be dependent on the additional hardening. Stress concentration factor evaluated in the elastic field Kt,n has been included in the Itoh-Sakane parameter to evaluate fatigue life, returning an overestimation for high values of Kt,n Material notch sensitivity and crack initiation position have been taken into account through a new stress concentration factor to further modify the model, returning sound results.
