High-Cycle and Long-Life Fatigue of 25CrMo4 Under Multiaxial Load Conditions by Three Alternating Stresses

Statistically verified experimental results from high-cycle and long-life fatigue tests (HCF and LLF) on 537 unnotched solid cylindrical and thin-walled hollow specimen are used to demonstrate the fatigue behaviour (S-N-characteristics, scatterband) of 25CrMo4 under uniaxial loading with superimposed static stresses (consideration of the mean stress effect) the under biaxial loadings in variation of phase differences between the three combined normal and torsional stresses sigma sub x , sigma sub y , tau sub xy . The fatigue strength commonly decreases with life time in the high-cycle regime until reaching the fatigue endurance limit in the transition range to infinite life. In comparison with the specific case of biaxial combined loading with synchroneous amplitudes, the fatigue resistance characteristics are detrimentally influenced by out-of-phase normal stresses sigma sub x , sigma sub y ; a phase difference of 180 deg between the normal stress amplitudes is the most critical state of combination, especially in the lower cycle regime caused by a greater slope coefficient. Graphs, Photomicrographs. 40 ref.--AA