Thermomechanical constitutive behaviour of a near α titanium alloy over a wide range of strain rates: Experiments and modelling

The constitutive behaviour of a near α Ti3Al2.5 V alloy, conceived for impact resistant turbine engine containment applications, is characterized at quasi-static, medium, and high strain rates ranging from 10⁻³ [s⁻¹] to 10⁶ [s⁻¹] by using the cylindrical compression specimen and shear compression specimen. Systematic tests have been conducted on a screw driven Zwick test machine, a hydraulic Instron machine, a recently designed split Hopkinson pressure bar and a nitrogen 12 [mm] bore gas gun synchronized with high-speed Kirana camera. The adiabatic heating effect from medium to high rates is evaluated experimentally. Digital image correlation technique is employed for strain measurement from simultaneously recorded images. The Ti3Al2.5 V alloy presents noticeable strain rate sensitivity. The strain hardening decreases with increasing strain rate. The microstructural characterization reveals that this alloy fails by dynamic shear localization. A simple constitutive model combining the advantages of Johnson-Cook model and Kuang-Huang-Liang model is proposed for finite element simulations of the impact tests. The model predicts the deformed specimen shapes from Taylor impact experiments with good agreement, indicating the suitability of the constitutive model to predict complex strain rate and temperature dependant impact events.