STRENGTH OF TITANIUM DIBORIDE UNDER SHOCK-WAVE LOADING

Strength of TiB2 under plane shock wave loading is assessed in terms of its spall threshold and the shear stress sustained by it under shock compression to 60 GPa. The results of experiments support the thesis that the observed cusp in TiB2 at 4.5-7.0 GPa is of mechanical nature and its effect is to decrease the spall threshold values at stresses above the cusp but below the accepted Hugoniot elastic limit (HEL) value of 13-17 GPa. A comparison of shock Hugoniot data on two different TiB2 obtained from Grady [Dynamic Material Properties of Armor Ceramics, Sandia Laboratories, SAND 91-0147. UC-704 (1991)] and the adiabats constructed from high pressure ultrasonic wave velocity measurements show that these materials sustain increasing shear stresses with increasing values of shock stress. For example, results of data analysis on the denser TiB2 show that it sustains around three times the shear stress at 60 GPa than at its HEL, i.e., 17 GPa.