3) Detail SEM observation suggests that the AEs during the crack opening operation are produced by mechanical fracture of the coincident grain boundary in case of both austenitic stainless steels and brass, and possibly by the quasi-cleavage trans granular fracture
for the 70Cu/30Zn brass.
Transverse fractures appeared to be brittle fractures; it was very difficult to draw any conclusion from the side view of broken fibre ends, but this may be granular fracture
. Figure 7 shows an idealized view of granular fracture
One of the propeller tips was separated from its propeller blade and exhibited a granular fracture
surface consistent with overload.