(a)
(b)
Figure 7: Microscopic cracking process with the field of view of 0.8 mm × 1.0 mm around notch tip under the typical loading rates of (a) 0.6 mm/min (TPB-0.6-1) and (b) 3.0 mm/min (TPB-3.0-1) observed using the microscopic visualization monitoring system. “Pre70” denotes the 70% of Ppeak prior to the peak, while “Post90” denotes the 90% of Ppeak after the peak.