Constitutive modelling of CK45N, AlZnMgCu1.5 and Ti-6Al-4V in a wide range of strain rate and temperature

Abstract
Continuous constitutive equations for wide ranges of strain rates and temperatures are gaining increasing importance for adequate simulation of dynamic deformation processes. The flow behaviour of the carbon steel CK45N, the Aluminium Alloy AIZnMgCul.5 and the Titanium Alloy Ti6A14V is studied at different strain rates between 0.001 s ^-1 and 10000 s ^-1 with temperatures varying between 23 C and 1000 C at CK45N and Ti6A14V. AIZnMgCul.5 was investigated in a temperature range from 23 C up to 500 C. The mechanical behaviour of the three materials over this wide range needs the consideration of different physical deformation mechanisms. In the range of high temperatures and low strain rates stress relaxation due to creep deformation processes are superimposed to the plastic deformation process with a relatively low strain rate sensitivity and temperature dependence. In the range of high strain rates, the damping controlled deformation mechanism is additionally active leading to a high increase of the strain rate sensitivity. In case of steel, a dynamic age hardening mechanism is superimposed causing a stress increase between 300 C and 600 C according to strain rate. The correlation between the material parameters and the instability, localisation and damage is studied on the bases of simple models.