Fatigue characteristics of bearing steel in very high cycle fatigue

Abstract

Very high cycle fatigue (VHCF) tests were carried out to find the fatigue characteristics of a super-long life range by using a cantilever type rotational bending fatigue test machine on three kinds of specimens in bearing steel which were quenched and tempered in air (A: non-shot peened and B: shot peened after heat treatment) and under vacuum environment(C: non-shot peened) in this study. S-N curves obtained from the VHCF tests of the B and C specimens tend to come down again in the super-long life (10 9 cycles) range due to fish-eye type cracking, while most of the A and B specimens were fractured by surface defects such as scratches and slip lines. This duplex S-N behavior of bearing steel has to be reviewed by the change of the fracture modes.

A review about the effects of structural and operational factors on the gigacycle fatigue of steels

“…Other studies show S‐N curve with a duplex shape (Figure ) corresponding to different fracture modes in super‐long life range, beyond 10 6 cycles. In this case, fish‐eye crack initiation was not observed in all the specimens, and crack initiation also occurred at the surface …”

“…Overall, for high strength steels under tension‐compression loading at 20 kHz, the fatigue strength at 10 9 cycles, in terms of stress amplitude, varies from 600 to 1000 MPa. It depends on the specific treatment undergone to the material (Table ). Furthermore, different studies show that for the high strength steels, the difference between the fatigue strength at 10 6 and 10 9 cycles is ranging from 50 to 200 MPa …”

“…Many studies indicate that the microstructure has a significant effect on the VHCF behavior of steels . For example, the quenched and tempered JIS SUJ2 steel shows different S‐N curves corresponding to 2 types of heat treatment in air and in vacuum atmosphere . It can be seen in Figure that decarburization which occurred by the heat treatment processed in air influences greatly the fatigue life.…”

“…The S‐N curves for JIS SUJ2 which were heat treated in vacuum (dark square and red circle marks) and in air (blue triangle marks) under rotating bending fatigue at a loading frequency of 52.5Hz [Colour figure can be viewed at wileyonlinelibrary.com]…”

VHCF Characteristics of SCMH2 Steel Depending on the Surface Treatment Conditions

“…로의 요구가 증대되고 있다 [1][2][3][4][5][6][7][8][9] . 특히 고강도 재료의 표 면특성을 향상시켜 필요한 기계적인 특성을 얻을 수 있 는 표면처리법이 매우 중요시되고 있다 7,8,13) .…”