Cyclic elastic-plastic strain behavior ahead of notches under cyclic tensile load and fatigue life

The strains ahead of notches in steel plate specimens have been investigated using strain gages in order to find the relationship between the cyclic strains under cyclic tensile load and the fatigue life in the range of 10(5)-10(6) cycles. From the cyclic strains measured, the relationships between strain range, mean strain, plastic zone size and the number of cycles, as well as the strain distribution near notches are investigated. Two types of cyclic strain behavior near notch roots have been found;in one type the mean strain and the plastic zone increase as the number of cycles increases and in another type the mean strain and the plastic zone remain constant with increasing cycles. These two types of cyclic strain behaviors show fatigue responses near notches under cyclic tensile load. The experimental results and their discussion are presented.