The Effect of Stress Amplitude on Multi-axial High-cycle Fatigue Failure under Constant Amplitude Loading

摘要

Studies about the effect of stress characteristics on multi-axial high-cycle fatigue of metals are still insufficient. Up to now, little work about the effect of different ratio of stress amplitude has been done on multi-axial fatigue under the same equivalent stress. In this paper, the effect of ratio of stress amplitude, λ = τ_o/ σ_o under the same Von-Mises equivalent stress is studied from theory and experiment. The results show that the main factor of multi-axial high-cycle fatigue failure is the maximum principal stress. For proportional loading, fatigue life raises when ratio of stress amplitude increase. The variety of fatigue life is not obvious when λ is larger than a certain value and its value closes to that of pure torsion. For non-proportional loading, when ratio of stress amplitude increases, fatigue life raise at first, then has an inflection point. The value of λ at the inflection point changes with phase difference and its value is 0.5 while phase angle is 90°. Fatigue life of uniaxial tension was lower than that of pure torsion.