Experimental Investigations and Damage Calculations of a Load Time History in the Very High Cycle Fatigue

The main focus of this investigation is to clarify the influence of variable amplitude loadings on subsurface crack initiation and crack growth. Therefore, differently reconstructed load sequences on the basis of a standardized load time history called FELIX are investigated with an R-ratio of -1. The major amount of cycles is situated beneath the fatigue strength. A new damage calculation approach considering inclusion sizes is presented. Thus, the stress amplitude in the S-N curve was normalized with a calculated fatigue limit σw(area), which is defined by Murakami. Afterward, the fatigue life depending on the inclusion size is calculated using a Palmgren/Miner rule. The largest inclusion in the measurement volume was determined using extreme value statistics. Fatigue lives for each investigated load sequence were calculated taking the scatter of inclusion sizes into account.