Anisotropic damage mechanics with application to bolt fatigue life estimation

Damage mechanics method is applied to investigate fatigue problems of metallic structure members. Adopting micro-structure model, the anisotropic damage coupled constitutive relations is established for axisymmetric cases to design the procedure considering anisotropic damage with finite element-additional loading method. The damage evolution with a threshold value is utilized to predict the fatigue crack formation and propagation lives of structural members are with damage increment as step length. Then the fatigue life experiment of the bolts with 5mm and 8mm diameters made of 30CrMnSiNi2A are tested and the total lives are estimated the result shows that the theoretical S-N curves well coincide with the experimental ones, the threshold value modifies the agreement of fatigue lives between theoretical data and experimental ones at low stress level.