Quantitative Estimation of Surface Roughness Affecting the Fatigue Limit

피로한도(疲勞限度)에 영향을 미치는 표면(表面)거칠기의 정량적 평가

Fatigue tests were performed to investigate how much vary the fatigue limit under the different surface conditions on Carbon Steel(SM55C). Four types of specimen which have different surface roughness each other, Series A by turning, Series B by grinding, Series C by polishing and Series D by roller finishing showed the fatigue limit of 265, 320, 335 and 365MPa, respectively. Series D show 36% higher than Series A, which is caused by compressive residential stress on the surface. Therefore, roller finishing machining is helpful not only increase the fatigue limit but also improve the surface roughness. Moreover, to predict the fatigue limit under the conditions of knowing surface roughness and hardness of specimen, ${\sqrt{area}}$ area parameter method is very useful.