Unstable behavior of the dynamic fracture toughness

It is shown that the dynamic fracture toughness of materials substantially depends on the history of loading; this determines instability in the behaviour of this quantity under shock-wave loading. It is found that the minimal value of the dynamic fracture toughness can amount to 50% of the corresponding static value. In engineering practice, this quantity can be regarded as the initial critical parameter, which must be taken into account while choosing materials working under pulsed loading.