Influence of Prior Damage by Cyclic Loading Below the Yield Strength on Ship Steels in Marine Environments

摘要

The study examines the extent to which prior cyclic history, which causes a change in mechanical properties through cyclic softening, influences the fatigue crack propagation (FCP) and fracture toughness behavior of ABS EH36 and HY80. The effect of predamage was determined empirically by comparing fracture toughness and FCP behavior developed for virgin materials with that found for predamaged materials. The scope of the study included testing under ambient conditions as well as in seawater at frequencies as low as 0.2 Hz. The data developed have been analyzed to assess whether apparent predamage effects are due to inherent changes in the material or are a consequence of the effects of cyclic softening on the validity and uniqueness of the test methods as applied in past studies. The main conclusion of the study was that apparent predamage effects are due to the influence of cyclic softening on the test methods and related data interpretation.