The description of resistance to plastic deformation during cold plastic deformation is done through increasing monotonically declined functions σ = σ ( ε ), interpreted by parabolic mathematical expressions of the type σt = K.εtn, σt = K ( ε0 + εt)n and σt = σ0 + K.εtn, known as stress-strain hardening curves of the deformed metal/alloy. These relations are explicit expressions for true stress σt as a function of true plastic strain εt .
The known mathematical relations, that take into account the deformation strengthening cold strain hardening are related to increasing the current yield stress σY and the hardness HV / Hit, without taking into account the anomalous phenomenon strain “softening” occurring at high strain εi ≥ 4 and a negative spherical stress tensor. A new model for anomalous strain hardening for severe plastic deformation is proposed, based on an expanded equation of the stress-strain hardening curve σY = ( Hit, εt), using data from nanoindentation Hit and from uniaxial tension test σ0 of dual ECAE work hardening material (technically pure aluminium).
Key words: stress-strain hardening curves, severe plastic deformation, equal channel angular extrusion
Topic: ENGINEERING SCIENCES