On the failure of shocked titanium diboride

The failure of brittle materials in uniaxial compressive shock loading has been the subject of extensive recent discussion. The physical interpretation of the yielding process in titanium diboride and its Hugoniot elastic limit remain poorly defined. Titanium diboride is known to exhibit an anomalous Hugoniot containing cusps at 4.5-7 and 13-17 GPa, according to the production route adopted for the material. These features are additionally observed on the free-surface wave profiles. Various experimental and microstructural variables have been investigated to find an explanation for these features. In other ceramics, failure has been seen to occur behind a travelling boundary that follows a shock front, called a failure wave, across which the strength of the material has been shown to dramatically decrease. In order to elucidate whether the cusps in titanium diboride are related to failure processes, gauges were embedded in order to measure the lateral stress behind the shock front. As in other materials, the stress in titanium diboride was seen to rise across a failure front. However, this process only occurred over certain stress ranges. A mechanical interpretation of the shock response of titanium diboride as a function of peak shock pressure is suggested relating to the cusps observed.