Efeito da frequência cíclica na nucleação e propagação da trinca por fadiga da liga ABNT 304 recozida e pré-deformada

Abstract

Austenitic stainless steel is a versatile alloy widely used in the industrial, aerospace and food sectors due to its high ductility, resistance to corrosion and high temperatures. However, despite its noble properties, its components are subject to failure, mainly due to fatigue, considered an engineering problem that affects several mechanical components. Numerous variables influence fatigue performance, however recent studies indicate that loading frequency, previously considered not influential, can impact mechanical responses. In this scenario, the study in question sought to evaluate the effect of conventional test frequencies (3 and 30 Hz) on the fatigue performance of ABNT 304 steel under load control in order to identify the fatigue stage in which the effect is outstanding. To this end, chemical, mechanical and microscopic characterization tests were carried out, as well as fatigue and fracture mechanics tests with samples without deformation and previously deformed. The analyses showed that increasing frequency reduces fatigue performance, especially in previously deformed samples. This effect was preponderant in the nucleation of the crack, that is, in stage I of fatigue, which is conditioned by the microstructure of the alloy. The results indicate that the observed difference may be linked to martensitic transformation, as the investigated alloy is metastable. Additionally, due to its high plasticity, the presence of twins and deformation bands, added to the alloy's high strain-hardening coefficient, also are micromechanisms with contribute to responding to the difference in fatigue behaviour.