Refined cyclic R-curve determination through residual crack tip stress reduction by annealing

[Display omitted] •Heat treatments utilized to diminish tensile residual stresses from pre-cracking.•Simple & effective method to reduce effect of residual stresses ahead of pre-cracks.•Significantly more accurate cyclic R-curve determination enabled.•Ambient air and heat treatment do not affect crack extension.•Traditional preparation strategies less effective than proposed strategy. The accurate determination of the cyclic R-curve of the threshold of stress intensity factor range is a demanding experimental task. The main challenge concerns the introduction of a pre-crack that is open under tension loading and free of residual stresses. When pre-cracks are generated by cyclic compression-compression loading, a zone of tensile residual stresses up to the material yield strength is generated ahead of the pre-crack tip. These stresses may affect crack propagation at the beginning of fatigue crack growth and should consequently be removed especially for high-strength materials. However, subsequent stress-relief annealing is impractical for numerous metallic material classes due to undesired microstructural alterations at the temperatures required for stress relief. In the present contribution, the above-described issue is addressed for a high speed steel using single-edge notched bending specimens pre-cracked at various stages of a typical high speed steel heat treatment process. It is shown that stress-relieving via a heat treatment route is a significant improvement compared to the conventional compression pre-cracking procedures to measure material-specific cyclic R-curves.