Estimation of the damage in doubly notched A36 steel specimens, as a function of the reduction rate of Nf under a loading level Δ σ

In this paper, which is a part of a whole series of researches, we deal with the study of a damage approach of an A36 steel material subjected alternately to fatigue and static tests. The aim is to quantify the material residual resistance under controlled cyclic loading with R = −1. Indeed, the prediction of the lifetime of ordinary A36 steel by using the method based on the rate of reduction of the number of cycles at break (RRCB) corresponding to a given loading level has been detailed. Then, the developed method has been compared to the damage approach using the unified theory. Furthermore, the experimental results have been obtained from fatigue tests on doubly notched specimens, combined to static tests results. The calculated values are analysed, discussed and compared. These approaches will allow us both to quantify the impact of unexpected damage on the lifetime of A36 steel and to predict its residual lifetime or even improve it.