Stage I crack directions under in-phase axial–torsion fatigue loading for AISI 304L stainless steel

摘要: Abstract Smooth AISI 304L stainless steel specimens were tested in fatigue. The tests axial, torsional and in-phase axial–torsional, all of them under load control with R = −1. S–N curves constructed following the ASTM E739 standard fatigue limits obtained method maximum likelihood proposed by Betinelli. ratio between pure torsion tension limits, τ FL / σ , was 0.91, close to 1, which is a typical value for fragile materials. determined biaxial represented on - axes. These experimental values well fitted an elliptical quadrant, although this fitting considered appropriate ductile crack direction along surface analysed using microscope, special attention dedicated initiation zones. first grains, or Stage I, much closer Mode I than II direction.