Below you can find equetion which express flow curve which describes the plastic deformation behavior of a material in a uniaxial tensile (or compression) test. I looking for books, articles which gives me information how values of C and n depends on geometry (eg. diamater and wallthicknes of drawn tube) as well as initial mechanical properties, before material work hardening. Do wires and rods of the same material but with different dimensions have a different form of the flow-curve, or does it depend only on the initial properties of the material?
Hi Konrad,
The Kocks-Mecking parameter (kf) quantifies how strain rate influences strain hardening during plastic deformation. Sample geometry, such as diameter, potentially impact kf. Smaller diameters can lead to strain localization, different stress distributions, and variations in dislocation densities in comparison to larger diameters.
Initial mechanical properties of samples also influence the material's overall strain hardening behaviour and its sensitivity to changes in strain rate, which in turn affects the kf parameter. Higher initial yield strength can lead to greater potential for strain hardening and increased sensitivity to strain rate changes, potentially resulting in a higher kf value. The initial stiffness of a material can influence how it responds to stress. Materials with faster work hardening rates tend to exhibit higher strain hardening responses. Ductile materials deform more uniformly, while less ductile materials may experience localized deformation. The initial microstructure, including grain size and distribution, can also impact dislocation mobility, deformation mechanisms, and consequently kf.
If you look in Materials Science and Engineering Textbooks, such as "Materials Science and Engineering" by William D. Callister and David G. Rethwisch; These text books often cover topics related to plastic deformation, strain hardening, and strain rate sensitivity. Look for chapters on mechanical behaviour of materials.
Hope this helps,
Kind regards
Within testing error the BCC metals (as steel) follow s=Ke^n only for initial state (based on chemistry and thermal history) and n changes upon deformation and K changes to B and s = A +B*e where e=true strain after passing UTS (ultimate tensile stress).
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