Effect of biaxial cyclic tension on the fatigue life and damage mechanisms of Cr–Mo steel
Résumé
Combined cyclic tension and internal pressure tests with various proportions of each loading were run on
a 2.5%Cr–1%Mo steel to investigate the effect of positive stress biaxiality on fatigue lives and damage
mechanisms. While moderate stress biaxiality had a beneficial effect on fatigue lives, attributed mainly
to a retardation of crack initiation, equibiaxial tension had a slightly detrimental effect, attributed to a
‘‘pseudo size effect”. Intergranular facets associated with temper and hydrogen embrittlement were
observed on the fracture surfaces. The evolutions of their surface fraction with DK and load biaxiality
suggested a possible reduction in crack growth rate at moderate biaxialities. Several popular multiaxial
fatigue criteria failed to describe all fatigue data. Thus, a new fatigue criterion based on Gerber’s parabola
has been proposed. It captures the evolution of the endurance limit under the combined effects of a
positive mean stress and positive biaxiality.