Dynamic energy release rate expression for a spreading circular fracture pattern in a plate

An expression for the dynamic energy release rate of a spreading circular fracture pattern in an uniformly stretched plate is derived from a path-independent energy integral. This is equivalent to the energy dissipated in an incremental growth of a constant velocity circular locus in which the radial tension is zero. The relationship to rapid fracture and multiple crack division becomes apparent as the arc distance separating adjacent crack tips becomes small relative to the radius of the circular locus. The condition at some small fixed distance behind the closely spaced crack tips is then well-stimulated by that of zero radial tension on a circular locus. Experiments could be carried out to establish the accuracy of the analytical dynamic energy release rate expression for multiple crack division.