Abstract：Combined with digital image correlation method (DIC) and microscopic metallurgical observation of " freezing" samples, this paper experimentally discuses about the initiation and propagation of adiabatic shear localization of Ta2 titanium alloy in a closed flat hat-shaped specimen struck by Split Hopkinson Pressure Bars. The results show that the width of shear zone in hat-shaped specimen is continually narrow-down until the formation of adiabatic shear band, and the crack will propagate along this band from the end to the center of shear zone. It is also shown that the critical shear strain of initiation sensitivity increase with an increasing loading rate. Furthermore, the results of DIC show that the initiation of adiabatic shear localization can be taken as the time when the elastic strain of element located near the plastic shear zone begins to rebound according to the stress unloading theory, and the adiabatic shear band initial in that localization area and cracks propagation along the band. The evolution of heat in shear zone converted by plastic work shows that the temperature of initiation is only 86℃, this result means that the heat softening of material may not the key condition of initiation of adiabatic shear localization, however, the sharp increase of temperature is the result of high-plastic-strain in adiabatic shear band.
2015, Vol. 36 
