Full-range fatigue life prediction model for corroded steel rebars: 3D pit-cracks coupling mechanism and validation

Abstract

This paper investigates the influence of the coupled effect of three-dimensional pitting-cracking on the fatigue life of corroded rebars. By introducing the concept of crack propagation ratios (γ_a, γ_c), the extent of crack propagation is quantitatively characterized. Through finite element calculations and analysis, a formula for the stress intensity factor (K) of the pitting-crack model is established, and the mechanism by which pitting significantly reduces the K value when γ_a < 0.3 is revealed (γ_a, ranging from 0 to 1). Based on this, a predictive model for long crack propagation life (N_pl) is constructed using the Forman formula, and the calculation methods for crack initiation life (N_n) and short crack propagation life (N_ps) are modified using the surface defect size (a_s) corrected by pitting characteristics and the critical sizes for short/long cracks (a_sc). The results indicate that when γ_a is less than 0.3, the K value is significantly smaller than the K_EIFS corresponding to the equivalent surface crack method (EIFS), and fatigue failure primarily occurs within this range. This suggests that corrosion pits have a significant impact on N_n, N_ps, and N_pl. Based on experimental data, it has been proven that life is primarily composed of N_ps and N_pl, accounting for 60 %–88 % of the total life. The prediction error of the established model for the total life is generally within 15 %.