Abstract
Fatigue tests under rotating bending and reversed torsion were carried out in air, distilled water and 3 percent saltwater, using smooth specimens of high-strength low alloy steel (Cr-Mo steel). The initiation and growth behavior of small fatigue cracks in each environment were evaluated based on detailed observations, and the effect of corrosive environment was also discussed.
The fatigue strength decreased with increasing aggressiveness of test environment. This decrease in corrosive environment was due to the earlier fatigue crack initiation. From the observed locations at which small fatigue cracks began, it was considered that the crack initiation was primarily governed by hydrogen embrittlement in distilled water and also affected by corrosive dissolution in 3 percent saltwater. The validity of the application of linear fracture mechanics for small fatigue cracks was established. The growth rate of small fatigue cracks was higher than that of large through cracks, but not accelerated by the corrosive environment. Moreover, the fatigue life in the corrosive environment was estimated by using the crack growth characteristics in air.
