Evaluation of materials defect influence on fatigue crack threshold

Abstract

The object of performed investigation is fatigue crack propagation in spheroid graphite cast iron with shrinkage voids. These voids influence on CT specimen’s section properties has been evaluated. The decrease of the threshold Δ K th obtained in specimens with voids compared to specimens without voids during natural tests has been investigated by means of different computational methods. The determined cracking threshold Δ K th of investigated specimens without defects varies from 8.4 MPa √m up to 10 MPa √m, of CT specimens with defects - from 6.3 MPa √m up to 8 MPa √m.The comparison of stress intensity factor values obtained by analytical and numerical calculations shows a satisfactory similarity (with approx. 10 % difference).