Experimental study of temperature heterogeneity in metallic materials under high strain rate sollicitation

Our study deals with the dynamic behaviour of metallic materials and in particular of titanium alloy TA6V. For high strain rates, we can notice the occurrence of a phenomenon called adiabatic shearing. It is about a plastic instability, which results in the appearance of a localisation of the deformation in the narrow bands. The width of these bands is around ten micrometers of broad. The mechanisms concerned in the formation of these bands are partly known, but their modelling remains a complex problem. This article deals with an experimental study of this phenomenon on torsion Hopkinson bars. The surface temperature of the specimen is measured by optical pyrometry with a bar of 32 InSb detectors. This experimental device allows to obtain the time evolution of the temperature along the torsion axis of the specimen. The space resolution is about 50 mum and the measured temperatures vary between 50degreesC and 300degreesC. This measurement makes it possible to study the onset of the localisation precisely.