Analysis of microscopic yielding behaviour of carbon steel under macroscopic loading

Interaction between the microscopic and macroscopic behaviours of pearlite steel was investigated using the homogenization method and elastic-plastic finite element method. Attention was focused upon the microscopic yielding under macroscopically elastic loading state on the tension side. Tangent of macroscopically elastic line at the initial stage of the stress-strain diagram was precisely examined to find that microscopic yielding occurs in the microstructure although macroscopic state is elastic. The zone where microscopic yielding is achieved does not expand throughout the unloading process to the macroscopically-zero stress level, but it expands when the macroscopic stress level exceeds a threshold level in the inverse loading process. The absolute value of this threshold level is equal to the threshold level above which microscopic yielding appears in the initial loading on the tension side. Cyclic loading test was applied to specimens in a laboratory and increase in specimen temperature was measured to check the qualitative validity of the numerical investigation microscopic yielding; macroscopic yielding; interaction; homogenization method; finite element.