Energy density zone model and fatigue life prediction considering microscopic effects.

An energy density zone (EDZ) model is developed for the prediction of fatigue life. The microscopic effects can be involved in the EDZ model. Three scale transitional functions in the model are utilized to describe the trans-scale behaviours of fatigue failure from micro-scale to macro-scale. Fatigue failure behaviours of a low-alloy and ultra-high-strength steel material (i.e. 40CrNi2Si2MoVA steel) is investigated. Two fatigue parameters in the model are determined from the experimental S-N curves for the smooth cylinder specimens (the stress concentration factor, SCF, Kt = 1). Then, fatigue lives of notched specimens with SCFs Kt = 2 and Kt = 3 are predicted respectively by the proposed model. The predicted S-N curves are satisfactory in comparison with the experimental results. Scatter of the fatigue test data can be depicted when the microscopic effects are considered. Influences of microscopic effects on the fatigue behaviours are explored by means of numerical simulations. [ABSTRACT FROM AUTHOR]