Some Physical Characteristics of Strain Hardening in Severe Plastic Deformation

Abstract

It is shown here using group theory principles that the Hencky strain is not an appropriate measure for tests involving simple shear, for which the von Mises formulation should be used exclusively. It is also shown analytically that the application of self-similarity principles to Stages III-IV indicates that these obey power laws, while the same principles do not apply to the other stages. As a result, they do not develop self-similar microstructures. Finally, the effect of strain path on the work hardening rates themselves is also examined. It is shown that the lowest rates are again associated with simple shear because this is the path along which the number of intersecting slip systems is the lowest.

Analytical and numerical approaches to modelling severe plastic deformation

“…The relative 'universality' of the grain structure development appears to be at odds with the analysis of Tomé et al [465] who argued that strain hardening behaviour should be strain path dependent. A similar view is held by Beygelzimer et al [167], whose point is that the intrinsic strain hardening derived from deformation tests for different strain paths should be different due to differences in texture and in the complexity of dislocation slip. At this stage, the issue is not fully resolved and more work is needed to establish whether saturation in grain fragmentation under SPD does take place and if so, whether it is strain path dependent or not.…”

Large and Severe Plastic Deformation of Metals: Similarities and Differences in Flow Mechanics and Structure Formation

“…[27,28] However, for structure formation in polycrystals, the rotational strain modes, also known as vortex or turbulent modes, are important as well. [29,30] The contribution of these modes into deformation was recently considered through the example of ECAP processing. [7] Here, the movement of material points along Lagrange's physical paths was used, i.e., along the physical paths of mass transfer.…”

The self-similarity theory of high pressure torsion

“…In [22] the scaling nature of the power-law interval of the hardening curve was established based on the self-similarity of the microstructure. Therefore, self-similarity at the micro-level is a physical reason of self-similarity at the macro-level.…”