AbstractIt was shown in a previous paper(1)that the break‐up time of homogenious ductile metals which elongate due to explosions, is equal to the sample's smallest initial dimension (thickness) divided by the velocity Vplwhich characterizes the metal. It is attempted to explain this rule by suggesting a break‐up mechanism where holes caused by a pile‐up of vacancies are formed at the metal surface and gradually increase until breaking it. This model also predicts the existence of a strain rate threshold below which other mechanisms dominate the break‐up process. Its validity is supported by experimental evidence which is also pr