Effect of bimodal harmonic structure on fatigue properties of austenitic stainless steel under axial loading

•Harmonic structure design increases the fatigue limit of stainless steel.•Harmonic structured stainless steel fails from the coarse-grained structure.•Harmonic structured stainless steel exhibits low resistance of long crack growth.•Crack path is not influenced by the harmonic structure. Axial fatigue tests and fatigue crack propagation tests were conducted to investigate the fatigue properties of austenitic stainless steel (JIS-SUS304L) with a harmonic structure (HS), which is defined as a coarse-grained structure surrounded by a network of fine grains. Fatigue cracks initiated at the coarse-grained structure in the HS SUS304L, but the fatigue limit was increased by the HS design due to the grain refinement. In contrast, the crack growth rates for the HS material for long cracks were constantly higher, and its threshold stress intensity range were lower compared to a material with a homogenous coarse-grained structure.