EFFECT OF DISPLACEMENT RATES ON EAC OF AISI 4340 STEEL
The environmentally assisted cracking (EAC) of AISI 4340 steel in synthetic ocean water was investigated using the rising displacement test method. The stress intensity factor for crack initiation, Kinit , in precracked compact tension specimens, was observed to increase with the displacement rates. However, a critical displacement rate existed which was associated with the KIEAC of the steel in the environment. Here, KIEAC is the threshold value of the stress intensity factor below which no EAC is expected. Constant load and constant deflection tests resulted in similar KIEAC values. The method pursued in this investigation for the determination of the initial displacement rate needed to obtain a valid KIEAC was found to be quite effective for the rapid and satisfactory evaluation of KIEAC , requiring a minimum number of tests.