HCF notch predictions based on weakest-link failure models

Abstract

Weakest-link models for the prediction of the high cycle fatigue (HCF) limit stress of notched components were investigated. The models employed surface area elements in the high-stress region surrounding the root of a notch. Statistical descriptions of unnotched specimen experimental data were developed using Weibull distributions and median ranking, and incorporated into some of the weakest-link notch formulations. The predictions from each of the failure models were compared to the experimental 10 6 cycle fatigue limit stresses. The fatigue limit stresses were estimated using a step-loading technique at stress ratios from R=−1 to 0.8, for five geometries (elastic stress concentration factors of K t =2.0, 2.8 and 4.1) of circumferentially notched Ti–6Al–4V specimens. The methods were shown to be modestly successful, although data obtained at R=−1 and R>0.65 could not be correlated well with data at intermediate values of R.