부산대학교 도서관

In order to investigate the properties of interior originating fractures, uniaxial tension fatigue tests were carried out in air and vacuum environments using pieces high strength steel (SNCM439) with various finishing conditions. As result, the following were obtained : (1) All of the fractures occurred from small inclusions located in the interior of the test pieces. (2) The interior originating fractures were not affected by surface conditions and environment. (3) △ K values at the inclusions of fracture origins were mach smaller than △ Kth of surface originating fractures. (4) Rough and strongly structure sensitive fracture surface were observed around the origins and almost all of the fatigue lives were estimated to be spent in these regions.