Original paper(Vol.46 No.10 pp.1155)
Initiation and propagation life distributions of fatigue cracks and the life evaluation in high cycle fatigue of ADI
Ochi Yasuo; Ogata Tomohisa; Kubota Masanobu; Ishii Akira
Abstract:Rotating bending fatigue tests were carried out on austempered ductile cast iron (ADI) in order to investigate the statistical properties of life distributions of crack initiation and propagation, and also the evaluation of fatigue life.
The results are summarized as follows: (1) The size of crack initiation sites of the material was represented by a Weibull distribution without regarding to the kinds of crack initiation sites such as microshrinkage and graphite grain. The crack initiation life scattered widely, but the scatter became much smaller as soon as the cracks grew. (2) The crack propagation life N sub a sub c which was defined as the minimm crack propagation rate showed lower scatter than the crack initiation life. (3) The fatigue life of the material was evaluated well by Nac and the propagation rate after Nac. It was clear that the fatigue life of ductile cast iron was governed by the scatter of Nac.
Key Words:fatigue, crack initiation, life distribution, Weibull distribution, Austempered ductile cast iron