Impact of anisotropy and viscosity to model the mechanical behavior of Ti-6A1-4V alloy

This paper compares the predictions of an isotropic-thermo-elasto-viscoplastic approach and of an anisotropic-thermo-elastoplastic one with experimental results representative of the mechanical behavior of Ti-6Al-4V at moderate temperatures and low strain rates. The first model is the well known Norton-Hoff viscoplastic constitutive law with isotropic von Mises yield locus identified by using monotonic tension tests performed at strain rates from 10-3 s-1 to 10-1 s-1 and at temperatures up to 400°C. The second model is a thermo-elasto-plastic one defined by the orthotropic yield criterion CPB06. It takes into account the anisotropy and the strength differential (SD) effect in tension-compression of Ti-6Al-4V at RT, 150°C and 400°C. The identification of the SD effect is done by using tension and compression tests and the anisotropy behavior is identified by using shear, plane strain, tension and compression tests performed in three orthogonal material directions. The accuracy of the load and displacements predictions of the two macroscopic constitutive models are compared to experimental results obtained from tests performed on specimens with multiaxial loadings and large strain at several temperatures.