Increase in residual lifetime due to low amplitude cycles and dwell times at room temperature: Observations and suspected mechanisms

With the onset of VHCF research, material behavior inconsistent with conventional versions of the Miner rule started occurring repeatedly: instead of decreasing the residual lifetime of a specimen, load cycles just below the so-called endurance limit increase lifetime compared to CA tests even if only the cycles of the highest load step are counted; the low load cycles contribute a negative amount of damage in damage accumulation computations. We give an overview over related observations on carbon steel, martensitic precipitation–hardening steel and aluminum and discuss conditions of occurrence and possible mechanisms. We show experimentally that tensile dwell stresses enhances static strain aging compared to dwelling at zero stress.