Computational Study on the Fatigue Behavior of Welded Structures

The major objective of this study is to develop a computational fatigue test method for welded structures. The damage mechanics approach is used to derive explicit expressions for fatigue life estimation within the framework of continuum mechanics. Microdamage model is applied to calculate the quasi-brittle material damage prior to the crack initiation. Based on the two-scale model, that is, micro versus meso (macro) scale linkage scheme is implemented in conjunction with finite element method to describe the crack initiation or propagation. For the material damage model used at microscale, a finite element code is developed. Lemaitre’s unified damage model and constitutive equation were chosen so as to ensure the efficiency for developing finite element algorithm. Identification method for material parameters required to constitutive equation is proposed using inversion of Ramberg-Osgood type constitutive model. In order to consider weld-induced residual stresses, the Ueda’s inherent strain scheme is incorporated into the calculation of residual stresses. Computational procedure based on two-scale model with the use of commercial finite element code is successfully constructed. The numerical results obtained by proposed method are compared with experimental results for validation.