Effect of Non-Metallic Inclusion Size and Residual Stresses on GigacycleFatigue Properties in High Strength Steel
(0) Fatigue fracture of some high-strength steels occurs at small defect in the subsurfacezone of a material at low stress amplitude level and in a high-cycle region of more than 106 cycles(gigacycle fatigue life),whereas surface fatigue crack initiation occurs at high-stress amplitude andlow cycles.There is a definite stress range where the crack initiation site changes from a surface toa subsurface defect,giving a step-wise S-N curve or a duplex S-N curve.From the experimentalresults,fatigue fracture mode was classified into three types,such as,surface inclusion inducedfracture mode,subsurface inclusion induced fracture mode without granular bright facet (GBF) areaand that with the GBF,depending on stress amplitude level and stress ratio.The GBF area wasobserved in the vicinity of a non-metallic inclusion at the fracture origin inside the fish-eye ingigacycle fatigue regime.It was made clear from the discussion with fracture mechanics that thetransition of fracture mode was affected by compressive residual stresses on the specimen surface.Fracture-mode transition diagram was proposed through the experimental and theoreticalinvestigation.Also,from the evaluation of the fatigue life based on the estimated subsurface crackgrowth rate from the S-N data,effect of inclusion size on the dispersion of fatigue life wasexplained,and S-N curve for subsurface inclusion-induced fracture depended on the inclusion sizewas provided.
Gigacycle fatigue Internal failure Inclusion Residual stress Fracture mode
K.Shiozawa L.Lu
Graduate School of Science and Engineering,University of Toyama,Japan State key Laboratory of Traction Power,Southwest Jiaotong University,China
国际会议
成都
英文
2008-08-04（万方平台首次上网日期，不代表论文的发表时间）