Observation and analysis of plastic instability in commercial pure Ti under dynamic simple shear

Modified split Hopkinson pressure bar was applied to realize dynamic simple shear within a limited narrow zone of the tested commercial pure Ti. The phenomenon of plastic flow instability, adiabatic shear band and crack was investigated by SEM, and the critical shear strain to activate unstable deformation was found to be 1.1 according to the deformed pattern of pre-gridded scratch lines on the specimen surface. Johnson-Cook constitute model and temperature rise equation were coupled to derive the adiabatic shear stress and strain curve, according to which critical condition was analyzed and fit well with the experimental values. The relationship between ASB propensity and metallurgical factors were also discussed.