CARATTERIZZAZIONE A FATICA AD ALTISSIMO NUMERO DI CICLI DI UN ACCIAIO AISI H13 AD ELEVATO GRADO DI PUREZZA

Experimental results recently obtained by testing high-strength steels at a very high number of cycles showed that failures could occur at stress amplitudes below the conventional fatigue limit with nucleation of cracks from defects or inclusions inside the material. Therefore, the size and density of inclusions or defects significantly affect the VHCF behavior of materials. The article presents the experimental results of VHCF tests carried out on a high-strength steel (Örvar Supreme) characterized by a high level of purity. Fully reversed tension-compression fatigue tests were performed by using the ultrasonic testing machine developed at Politecnico di Torino. The experimental results showed that, even if characterized by a high level of purity, the tested steel could fail at a very high number of cycles with nucleation of the fatigue cracks from inclusions found inside the material.