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- Title
Influence of inclusion size on S-N curve characteristics of high-strength steels in the giga-cycle fatigue regime.
- Authors
LU, L. T.; ZHANG, J. W.; SHIOZAWA, K.
- Abstract
Fatigue fracture of high-strength steels often occurs from small defect on the surface of a material or from non-metallic inclusion in the subsurface zone of a material. Under rotating bending loading, the S-N curve of high-strength steels consists of two curves corresponding to surface defect-induced fracture and internal inclusion-induced fracture. The surface defect-induced fracture occurs at high stress amplitude levels and low cycles. However, the subsurface inclusion-induced fracture occurs at low stress amplitude levels and high-cycle region of more than 106 cycles (giga-cycle fatigue life). There is a definite stress range in the S-N curve obtained from the rotating bending, where the crack initiation site changes from surface to subsurface, giving a stepwise S-N curve or a duplex S-N curve. On the other hand, under cyclic axial loading, the S-N curve of high-strength steels displays a continuous decline and surface defect-induced or internal inclusion-induced fracture occur in the whole range of amplitudes. In this paper, influence factors on S-N curve characteristics of high-strength steels, including size of inclusions and the stress gradient of bending fatigue, were investigated for rotating bending and cyclic axial loading in the giga-cycle fatigue regime. Then, based on the estimated subsurface crack growth rate from the S-N data, effect of inclusion size on the dispersion of fatigue life was explained, and it was clarified that the shape of S-N curve for subsurface inclusion-induced fracture depends on the inclusion size.
- Subjects
STRENGTH of materials; MATERIALS testing; MATERIAL fatigue; FRACTURE mechanics; STEEL
- Publication
Fatigue & Fracture of Engineering Materials & Structures, 2009, Vol 32, Issue 8, p647
- ISSN
8756-758X
- Publication type
Article
- DOI
10.1111/j.1460-2695.2009.01370.x