Low and High Cycle Fatigue and Cyclic Elasto-Plastic Behavior of the P355NL1 Steel

A normalized fine grain carbon low alloy steel, P355NL1 (TStE355), intended for service in welded pressure vessels, where notch toughness is of high importance, has been investigated. Low and high cycle fatigue tests have been conducted on several series of smooth specimens under both strain and stress control. The monotonic and cyclic elasto-plastic behavior of the material is characterized and described using relations available in the literature. The shape of hysteresis loops are conveniently modeled, taking into account the observed non Masing behavior of the steel. Some important cyclic phenomena, observed for the studied steel, such as the cyclic creep and the cyclic stress relaxation, are illustrated. Strain, stress, and energy based relations for fatigue life prediction until crack initiation, are evaluated based on experimental results. The adequacy of several rules for damage accumulation is also investigated. Finally, along the paper, some comparisons are performed between the cyclic elasto-plastic and fatigue behaviors of the steels P355NL1 and ASTM A516 Gr. 70.