Corrosion fatigue of V-shaped welded and cast specimens in seawater under variable amplitude loading

Investigations on V-shaped welded joints of normal and high strength steels and of cast V-shaped specimens were conducted in seawater under spectrum loading (simulated sea state sequence of the North Sea). Seawater reduces fatigue life by a factor of two compared with results in air while cathodic protection compensates the effect of seawater i.e. fatigue life values as those in air were reached. Mean test frequencies between 1 Hz and 10 Hz showed no significant influence on fatigue strength. Post treatment of the welded joints by TIG dressing or shot peening led to a remarkable increase of the fatigue loading withstood in seawater especially by shot peening of the high strength steels. Fatigue strength of the cast specimens was about twice that of the untreated welded joints in seawater for the given geometry. (LBF)