Effect of Low Cycle Fatigue Damage on Ultimate Strength of Aged Ship Structures

The main objective of this paper is to study the effects of general low cycle fatigue (LCF) damage on ultimate strength of unstiffened ship plates under uniaxial compression. A nonlinear LCF damage model has been derived on basis of continuum damage mechanics (CDM) coupled with plastic mechanics in order to define the deterioration of materials. The theoretical results show that the damage variable D can be measured by a simple procedure and it can be related to the mechanical property of material directly. Formulae predicting ultimate strength reduction have been proposed based on amended Faulkner’s simple and useful expression. Nonlinear finite element analyses (FEA) of panels with various material damages have been carried out. The results indicate that the deterioration of materials is important factors determining the amount of strength reduction. It was also found that the proposed formulae can accurately predict the residual ultimate strength of unstiffened plate with general fatigue damage.