It is generally recognized that enhance crack growth in fatigue crack, stress corrosion cracking and even SSRT(slow strain rate test) loading can be uniquely explained by synergistic results of materials and environment interaction for a given material/environment system. The difference in loading modes such as cyclic load, monotonic rising load, constant load and constant displacement has significant effects on crack tip strain rate which control a film rupture frequency and resultant metal dissolution and/or hydrogen evolution at crack tip. These processes can enhance a crack advance either slip dissolution type cracking or hydrogen cracking or both of them. In this paper, environmentally assisted cracking behavior of pressure vessel steels was investigated under different loading mode by use of trapezoidal wave form with different holding time and very slow rising load. Emphasis was focused on the effects of cyclic loading effects on crack growth under constant load. Results showed that with increasing holding time, crack growth rate during holding time of trapezoidal wave form become slower. This results implies that dynamic loading during fatigue cycle can enhance the crack growth rate at early stage of constant load. These crack growth rate are compared with those obtained by SSRT tests performed on compact tension specimens. The significance of loading mode in various testing on crack growth rates was summarized in terms of crack tip strain rate. The synergistic effects of corrosion fatigue and stress corrosion on crack growth is emphasized.
|Number of pages
|American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP
|Published - 1995
|Proceedings of the 1995 Joint ASME/JSME Pressure Vessels and Piping Conference - Honolulu, HI, USA
Duration: 1995 Jul 23 → 1995 Jul 27