Corrosion-Fatigue Crack Initiation Behavior of Four Structural Steels

作者：S. R. Novak · 年份：1983 · DOI：10.1520/stp44805s · 被引用次数：15 · 研究领域：Fatigue and fracture mechanics、Non-Destructive Testing Techniques、Material Properties and Failure Mechanisms

This study was undertaken to investigate the corrosion-fatigue crack initiation (CFCI) behavior of steels with nominal yield strengths from 248 to 1034 MPa (36 to 150 ksi). Notched specimens were exposed to a 3.5% NaCl solution under constant-load-amplitude conditions at a stress ratio R of 0.10 and at a cyclic frequency of 12 cycles per minute (0.2 Hz). Results of crack-initiation life (NI) were characterized in terms of cyclic stress-intensity range normalized relative to notch-tip root radius [(ΔK/√ρ)] and in terms of cyclic-stress range at the notch tip (Δσmax). Results showed that the CFCI behaviors for the A36, A588-A, A517-F, and V-150 steels investigated were virtually identical. Each steel exhibited a linear relationship of (ΔK/√ρ) versus log NI for cyclic lives from NI ≊ 104 to 3 × 106 cycles, where the latter value reflects a continuous testing period of about 180 days (6 months). All four steels exhibited about the same cyclic-stress range of (ΔK/√ρ) ≊ 207 ± 21 MPa (30 ± 3.0 ksi) at NI = 3 × 106 cycles. No evidence of a CFCI threshold behavior was determined or apparent up to 3 × 106 cycles. Compared with the respective estimated values of fatigue-crack-initiation (FCI) threshold in air [(ΔK/√ρ)th ≊ 448, 552, 758, and 1138 MPa (65, 80, 110, and 165 ksi)], such values of (ΔK/√ρ) for CFCI behavior correspond to degradations of about 54, 62, 72, and 82% for the A36, A588-A, A517-F, and V-150 steels, respectively. The cited values of (ΔK/√ρ) at 3 × 106 cycles were als...