We briefly review a number of important recent experimental and theoretical
developments in the field of dynamic fracture. Topics include experimental
validation of the equations of motion for straight tensile cracks (in both
infinite media and strip geometries), validation of a new theoretical
description of the near-tip fields of dynamic cracks incorporating weak elastic
nonlinearities, a new understanding of dynamic instabilities of tensile cracks
in both 2D and 3D, crack front dynamics, and the relation between frictional
motion and dynamic shear cracks. Related future research directions are briefly
discussed.Comment: Added refs. & figs., minor textual change