EXPERIMENTAL INVESTIGATION OF THE STRAIN-STRENGTHEN EFFECT ON THE EXISTED I+II MIXED MODE FATIGUE CRACK TRANSFORMATION PROPAGATION IN AN AUSTENITE STAINLESS STEEL

摘要

In this paper, I+II mixed mode fatigue crack transformation propagation in austenitic stainless steel 06Crl9Ni10 was tested. Finite element method with displacement approach was employed to calculate stress intensity factors at the crack tip. Strain-strengthening effect on the new crack initiation and propagation of the existed pre-crack was investigated. It is found that under the uni-axial loading, the inclined pre-crack grows in a direction perpendicular to the applied load, making crack mode transferred from I+II mixed mode to Mode I. When strain-strengthened, the new crack initiation from the pre-crack tip is much more difficulty and crack propagation is slower. Finite element non-linear analysis shows that a residual compressive stress distribution is formed around pre-crack tip after strain-strengthening. The residual compressive stress is responsible for the difficult initiation and slow propagation of the new crack.