THE KINETICS AND MECHANISM OF THE FATIGUE FRACTURE OF SAMPLES OF 40H AND 38H2N2MA STEELS

Abstract

: It is known that the most of breakdown fractures of the structures or machine parts are related either to the fatigue fracture or brittle fracture caused by the fatigue crack. For this reason, to reduce the possibility of the fatigue crack initiation and development, the expensive medium and highly alloyed steels are often used. This paper presents the com-parative analysis of the parameters of the fatigue fracture of samples of low alloyed 40H steel and medium alloyed 38H2N2MA steel. The fatigue tests of 10×15×80 mm prism samples made of 40H steel with the U - and V-shaped stress concentrators and of 38H2N2MA steel samples with the U-shaped stress concentrator were carried out on the Instron 8802 installation at the temperature of 20 °C according to the three -point bending scheme with ⱱ =10 Hz, R =0.1 and various Δ