Stress distribution calculation of notched fatigue specimens of TC21 alloy

The stress distribution at the notch root of round notched fatigue specimens of TC21 alloy under monotonic loading and cyclic loading was calculated by adopting FEM. The results indicate that the axial stress concentration factor K_σ and strain concentration factor K_ε are related to the magnitude of cyclic stresses, but the variation trends are different. The notch root region is in three-dimensional stress state, and the position of the maximum von mises equivalent stress is at the surface of the notch root, though the positions of the maximum values of three directional stresses change with the cyclic stress. Furthermore, the ratio between the tangent stress and the axial stress at the notch root changes due to the variation of the cyclic stresses. Because of the plastic deformation at the notch root, the cyclic stress ratio decreases with the increase of nominal cyclic stress, but when the cyclic stress is higher than 1100 MPa, the cyclic stress ratio increase with the increase of cyclic stress. During the fatigue process, the cyclic stress ratio slightly alters when the cyclic stress is high enough.