抄録
Uniaxial tension fatigue tests of high strength steel, SNCM439, were carried out in air and high vacuum environment. As a result, the following were obtained : (1) Compared with surface fractures in air, the fatigue life of surface fractures in high vacuum tended to be longer. (2) High vacuum environment strongly influenced the fatigue fracture surface in the initial stage of crack propagation. (3) High vacuum environment was similar to inner environment of materials. (4) The formation of Optically Dark Area (ODA) closely related to mean stress.
