Based on the experimental fact that the rate of dislocation movement and polymerization to form fatigue crack accelerates with the number of cyclic loads,it is assumed that the fatigue crack initiation rate is a monotonically increasing power function of the number of cyclic loads. The calculation model of fatigue crack initiation life is derived by integrating the power function between the fatigue crack initiation rate and the number of cyclic loads. The fatigue test results of Q460C steel notched plates show that the fatigue crack initiation life,propagation life and total fatigue life increase with the decrease of stress amplitude and nominal maximum stress,and the ratio of fatigue crack initiation life to total fatigue life ranges from 0. 82 to 0. 90. The calculated error of the fatigue life calculation formula recommended in China’s code ‘Standard for design of steel structures’is -17. 0%—+84. 9%. Considering an ellipsoidal fracture model of structural steel originally proposed by the author as the instability propagation (fracture)criterion of fatigue crack,a set of theoretical calculation and numerical simulation were established to investigate the fatigue cracking of the notched plates. Taking a crack length of 0. 05 mm at which the strain over flows at the site of fatigue crack initiation as the critical size of fatigue crack initiation,the calculated errors of the calibrated fatigue crack initiation life formula,propagation life formula and total fatigue life formula of the Q460C steel notched plates are -15. 0%—-1. 2%,-12. 4%—+2. 8% and -12. 1%—-1. 4%,respectively. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.
