Temperature field measurement in titanium alloy during high strain rate loading—Adiabatic shear bands phenomenon

This paper concerns the study of the damage and failure mechanisms of metallic materials under dynamic loading. For high strain rates, it appears a strain localization in narrow bands called adiabatic shear bands (ASB). As the loading duration is very short, the dissipation of the mechanical energy into heat generates strong temperature heterogeneities. To study the mechanisms of initiation and propagation of ASB during a dynamic torsion test, we developed an experimental device to measure temperature by pyrometry: for the “low temperatures” ranging between 50 °C and 300 °C, we use a bar of 32 InSb infrared detectors in order to study temperature heterogeneities during the ASB formation. The acquisition frequency is 1 MHz and the spatial resolution is 43 μm. For the “high temperatures” ranging between 800 °C and 1700 °C, we use an intensified camera whose spectral band is in the visible range. The spatial resolution is 2 μm and the aperture time is 10 μs. This device shows that the temperature could exceed 1100 °C with temperature heterogeneity inside the band.The “low temperatures” device allows us to observe the formation of one or two adiabatic shear bands on temperature recording along the torsion axis of the specimen. In order to explain these results, we propose a mechanism of multiple ASB formation followed by interactions and annihilations of the ASB.