Cyclic softening and hardening of a steel using a logistic curve

Abstract

The plastic strain range of stress-strain curve during fatigue process was measured for an annealed and a rolled steel for general structure SS400. The movable dislocation density was estimated from the plastic strain range. It was found that variation in movable dislocation density ρ was expressed as a function of the number of stress cycles n by following equation using a model based on the multiplication and annihilation process of dislocations. [numerical formula] It was concluded that the calculation using this equation corresponds well with the movable dislocation density estimated from the plastic strain range.