T. Kobayashi et al., DEDUCING CRACK HISTORY IN AN AGED BOILER TUBE FROM FRACTURE SURFACE-TOPOGRAPHY, Journal of testing and evaluation, 22(4), 1994, pp. 309-317
A new fractographic technique, FRActure Surface Topography Analysis (F
RASTA), was applied to a crack in a boiler tube of a fossil-fired powe
r plant in an attempt to determine when in its 22-year service history
the crack initiated and the rate at which it grew. By comparing the t
opographies of the conjugate crack surfaces, we estimated that the cra
ck nucleated about 68 000 h after onset of service and experienced sev
eral periods of accelerated and decelerated growth with rates ranging
from 5 x 10(-5) to 9.5 x 10(-5) mm/h. These findings correlated roughl
y with chemical cleanings and startup/shutdown cycles. A similar analy
sis of a corrosion fatigue specimen tested under controlled conditions
in the laboratory provided results consistent with measured values. T
hese results suggest that fractography can be used to extract valuable
information on cracking kinetics in aged systems and, thereby, lead t
o new ways to predict, monitor, and extend component life.