ABSTRACT
Jago (2012) recently reviewed techniques useful for imaging and surveying crack precursors, not only on the surface of a specimen, but also in the bulk. Crack precursors are seen to occur in a range of sizes, with smaller precursors occurring more frequently, and larger precursors occurring less frequently. For example, Mars & Fatemi (2006) reported observations in which precursors of size 20 microns occurred at a volume density of 5000/mm3, and precursors of size 100 microns occurred at a volume density of 3/mm3.
