Prediction of Fatigue Strength in HSS-Co , S55C and the Friction Welded Materials Based on Statistical Evaluation of Inclusion Size

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) In this paper, the effects of nonmetallic inclusions on the fatigue strength of medium and high strength steels are quantitatively investigated by considering the relationship between the Vickers hardness, Hv and the maximum size of nonmetallic inclusion,... The maximum size of nonmetallic inclusion defined by the square root of the projected area in an inclusion can be estimated by the statistics of extreme values with a definite number of specimens or structural components. While most of other studies using the parameter... have performed the experiments with the specimens with small artificial defects or notches, this study investigates the possibility of prediction on fotigue strength in the unnotched smooth specimens. The results show that strength of the friction welded joints of HSS-Co to S55C carbon steel is almost equal to that of the weaker material in the optimum welding conditions. Under the limiting condition for the nonpropagating cracks emanating from defects or inclusions, the threshold stress intensity factor range °K^sub th^ and the lower limit of fatigue strength σ^sub w1^ were successfully estimated from the largest inclusion size... From the analysis of SEM fractographs, it can be concluded that the fatigue fractures of the specimens are associated primarily with the inclusions located at the outer periphery of the specimens.[PUBLICATION ABSTRACT]