Evaluation of notch size effect on LCF life of TA19 specimens based on the stress gradient modified critical distance method

摘要

In the present study, the stress gradient modified critical distance method is proposed to predict the low-cycle fatigue lifetime of notched TA19 specimens by introducing a weight function of relative stress gradient into conventional critical distance theories. The accuracy and reliability of the proposed method were validated based on the experimental data by performing low-cycle fatigue tests on smooth bar TA19 specimens as well as geometrically similar plate specimens containing a bore hole (BHP). Predicted results demonstrate that the mean absolute errors for entire tested specimens using the stress gradient modified critical distance method on the basis of the point method and the line method are 7.49% and 7.41% respectively. Furthermore, the fatigue striation width at the fracture surface was determined by scanning electronic microscope observations to examine the stress gradient effect on the crack growth rate. Highlights 1. The effect of circular hole size on the LCF life is investigated experimentally. 2. SEM observations reveal that stress gradient inhibits the fatigue crack growth. 3. The conventional CDTs extended to the LCF regime fail to evaluate the notch size effect. 4. A novel method is proposed by combining weight function of relative stress gradient and CDTs.