• Novel analysis of the tensile curve with unloadings and hysteresis loops of copper using statistical theory. • Evaluation of the effective stress and the distributions of the internal critical stresses. • TEM and EBSD study of the internal dislocation structures. • Relation of the distribution of the internal critical stresses and internal structure. A novel approach to analyzing the tensile hardening curve is presented. It is based on the premise that, as with cyclic loading, the yield stress is a weighted average of the stresses carried by individual microvolumes (Masing hypothesis). Polycrystalline copper specimens were cyclically deformed with increasing strain amplitudes, while tensile specimens were uniaxially deformed with multiple unloading–reloading sequences. Statistical analysis was applied to the saturated hysteresis loops and to the unloading and reloading segments in interrupted tensile loading. The procedure enables the evaluation of effective stress and probability density functions for microvolumes with critical internal stresses, providing a more comprehensive analysis compared to the representative volume element concept. TEM was utilized to characterize the dislocation arrangement and evaluate the free paths of dislocations in cyclically and unidirectionally deformed specimens. The comparison of the distributions of the free paths and microvolumes indicates that the stress response in both tensile and cyclic loading is given by the probability density of the critical internal stresses. The proposed results provide a basis for a unified approach to stress–strain curve analysis, linking macroscopic mechanical response to the development of the heterogeneous dislocation structures.
Polák et al. (Sun,) studied this question.