Volume 2, Issue 3 (March 2005)
Environmentally Influenced Fatigue in High Strength Steels
A study was conducted to identify the environmental influence on fatigue crack growth behavior of three high strength steels: AerMet 100, 300M, and 4340. These steels were subjected to fatigue tests under constant amplitude loading of frequency 10 Hz and stress ratios R = 0.1 and 0.9, in vacuum, air, and 3.5 % NaCl solution. The fatigue crack growth was characterized with two driving force parameters, stress intensity range, ΔK, and maximum stress intensity, Kmax. Especially, the variation of fatigue crack growth per time, da/dt, with Kmax in 3.5 % NaCl solution was evaluated with respect to R, environment, and threshold stress intensity for environmentally assisted cracking (EAC), KIEAC. In addition, the environmental influence on fatigue crack growth was examined with the fractographic features and trajectory path, drawn with the limiting values of ΔK and Kmax, ΔK* and Kmax*.