Abstract: The rupture modes of thin metal circular plates struck by conical-nosed missiles were experimentally studied at the critical rupture speeds. The modes of piercing, petalling and plugging appeared respectively with increasing cone half-angles. A failure map was established to distinguish these rupture modes according to the cone half-angle of the missile and the target material properties. In the analysis, the missile tip penetration, the wall deformation and the rupture process in local contact region were also considered. For a missile with cone half-angle 30, the rupture of a thin metal plate was always due to piercing. It was found that there was a critical cone half-angle c=arcsin(exp(－0.5f)) that plugging occured for a missile with ＞c and ＞30, and petalling occurs for a missile with 30＜＜c.