The Influence of Displacement Rate on Environmentally Assisted Cracking of Precracked Ductile Steel Specimens

Sustained load and rising displacement tests were performed on precracked specimens to investigate the environmentally assisted cracking (EAC) behavior of AISI 4340, σ₀ = 1095 MPA (159 ksi), in flowing synthetic seawater. J-R resistance curves were generated in environment over four orders of magnitude in displacement rate and K_IJ (from J_IC) from the slowest test was found to agree closely with the K_IEAC (K_ISCC) value determined from cantilever beam tests. Crack velocity data from the slowest rising displacement test and constant stroke—decreasing K_I—tests fall on the same line suggesting that there is a unique a˙-K_I curve for EAC in this system. A method is suggested to determine the displacement rate needed to obtain a good estimate of K_IEAC from a rising displacement test.