SM45C 균열부의 피로거동에 관한 연구 = A Study on Fatigue Behavior of Crack Part in SM45C

다국어 초록 (Multilingual Abstract)

Through the rotary bending fatigue experiment of SM45C, widely applicable material to the machine, ship-building and airplane engineering, some mechanical properties were investigated such as fatigue limit, crack propagation, notch coefficient and fracture surface according to various type of notched specimen.

Based on this study, the obtained results are summarized as follows:

1. Fatigue limit for Non-notched specimen was found 32.2kgf/㎟ and for U-notch and V-notch specimen, the limit values were 22.8kgf/㎟ 15.5kgf/㎟ respectively.
In the case of transverse hole notch specimen, for 0.8㎜ and 1.6㎜ diameter of hole notch specimen the values were 17.6kgf/㎟ and 18.5kgf/㎟ respectively. Therefore, fatigue limit of notched specimen was 29.2-51.7% smaller than Non-notched specimen.

2. It was certified a fatigue crack length was more increase according to the repetition number of cycles. The slope was more steep in the S-N curve diagram and fatigue crack according time was more faster according to the stress level changed from lower stress level to high.