A MACROSCOPIC AND MICROSCOPIC STUDY OF ADIABATIC SHEARING EXTENSION OF MODE-II CRACK AT DYNAMIC LOADING

The in-plane-shear failure of a dynamic Mode-II crack is studied macro - and microscopically for a titanium alloy Ti-6Al-4V. The experimental results show that such a failure essentially results from an interact ion between the precursor adiabatic shear band and the crack extended along the shear band. A two-variable (K-II and K-II) thermo-viscoplast ic instability criterion for the adiabatic in-plane-shear initiation o f a Mode-II crack under dynamic loading is proposed. The theoretical p redictions are in good agreement with the experimental results.