Fatigue Life Estimates for Bluntly Notched Members

Abstract

Methods for estimating the total fatigue lives of bluntly notched members are presented. Analytical estimates are compared to experimental data generated in the Society of Automotive Engineers Cumulative Fatigue Damage Test Program. The crack initiation lives were predicted using strain life concepts and fracture mechanics methods were employed to predict the fatigue crack growth stages. The methods used highlighted the proportions of the total fatigue life spent in crack initiation and propagation. These were found to depend on load amplitude and level of mean load. For the bluntly notched member investigated the initiation and early stages of crack formation formed the major part of the total life, when the loading was predominantly tensile. Conversely for a loading history where most of the cycles were compressive the majority of the fatigue life was expended in crack growth away from the notch.