Fatigue life prediction of welded joints with artificial corrosion pits based on continuum damage mechanics

An approach based on continuum damage mechanics (CDM) is applied to predict the fatigue life of welded joints with artificial corrosion pits. Full penetration load-carrying fillet cruciform welded joints with a 45° inclined angle were constructed, and artificial corrosion tests and fatigue tests of the welded joints were carried out. A new damage variable based on the crack size was defined to assess the stiffness degradation. Material parameters in the damage evolution equations were obtained from the fatigue experimental data. The CDM model combined with numerical simulations was used to describe the fatigue damage evolution process. A comparison between the fatigue life predicted results and the test results was made. The results show that fatigue life decreases with the increase of pit depth, decreasing by approximately 50% from d = 0 mm to 2 mm at the same stress range. The fatigue damage curves can be divided into three stages: the crack initial growth stage (D < 0.3), the crack slow growth stage (0.3 ≤ D ≤ 0.8), and the crack rapid fracture stage (D > 0.8). The fatigue damage curves for different stress ranges are nearly the same under the same pit depth. In addition to the material and loading conditions, the corrosive environment also has an effect on the material parameters in the fatigue damage evolution process. The fatigue life predicted results agree well with the test results, and the maximum relative error is 10.6%. The crack size can be used to describe the fatigue damage evolution of welded joints with artificial corrosion pits.