KLIBER Jiří VŠB - Technická univerzita

Spoluautoři KUNČICKÁ Lenka, MAMUZIC Ilja

Investigations of metal materials properties were always based on performing tests, for mechanical properties confirmation it have been mainly tensile tests. But, due to complicated state of stress after neck occurrence, these cannot be used for practical forming processes application. So that plastometric tests (torsion, press) are further utilized, their outcomes are curves of stress-strain dependence. After applications of large strains tests always result in curves with σ_p maximum stress value corresponding to peak strain value ε_p. Reaching of this strain value induces (dynamic) recrystallization or recovery start. It is, mostly, one single point on the stress-strain curve which can be defined unambigiously and mathematically described depending on the basic parameters. Single curves may vary in accordance with various ways of plotting, basic parameters (temperature T, strain ε and strain rate ε ̇), additional conditions (chemical composition influence and history of the material – residual strain after incomplete recrystallization or recovery), structure influence (phases portions, grain size) etc.. The paper is focused on various methods of peak stress description on the basis of Gleeble plastometer tests results and Plane Strain Compression tests.