Threshold Characteristics of Stress Corrosion Cracking under Dynamic Combined Multiaxial Loading Conditions

点击翻译按钮获取中文摘要

Cyclic stress corrosion cracking (SCC) tests of smooth specimens were conducted on 4135 high-strength steels in 3.5% NaCl solution. Loading types were bendin (R = -1), torsion (R = -1), and combined in-phase tensio( (R = 0) and torsion (R = 0). The ratio of <tau>_<max> to <sigma>_<max> ranged from zero (tension) to infinity (torsion). In torsion at <tau>_<max> <greater than or equal> 780 MPa, specimens were fractured by transgranular cracking normal to the longitudinal direction. At 500 MPa <equal or less than> <tau>_<max> < 780MPa, a longitudinal creack by shear stresses, which is considered to be caused by dissolution, was initiated at the bottom of corrosion pit, and then intergranular cyclic SCC crack dominated by maximum proincipal stress was started at the tip of it. In torsion at <tau>_<max> < 500 MPa and in bending and combined tension and torsion loading, however, cyclic SCC crack dominated by maximum principal stress or maximum tensile stress range was initiated at the bottom of corrosion pits. Mechanical condition dominating crack initiation at the bottom of corrosion pit was determined by stress intensity factor range <DELTA>_<IFSCC>, which was obtained by assuming the corrosion pit as a sharp crack. Similarly, a longitudinal crack by dissolution was initiated when a K_<III> value of a pit exceeded the K_<IIIFSCC>.