parameter in the model. In this case, the size parameter is the defect circumference
which is directly proportional to the defect diameter.
120 -IB 120 -CIB
100 -A75 100 A75
8E75 = 8E75
80 80 -
9 60 60
40 40
20 20
0 0
Flash Scan LP-30 LP-45 LP-60 Flash Scan LP-30 LP-45 LP-60
Heating Method Heating Method
A B
160 5 160
140 A75 140
120 BE75 120- E
100 100
2 80 80
60 60
40- 40
20 20
0 0
Flash Scan LP-30 LP-45 LP-60 Flash Scan LP-30 LP-45 LP-60
Heating Method Heating Method
C D
Figure 6-45. Signal half-life for different pulse durations (selected defects only). A)
Specimen A-1. B) Specimen A-2. C) Specimen A-3. D) Specimen A-4.
Figure 6-46 provides a plot of defect circumference C x defect depth D vs. tl/2. The
points on this graph represent data from all of the heating methods for air-filled defects
with ATmax values greater than 2.0C. The sample size for this analysis was 30. A linear
regression analysis resulted in a slope of 4.33 mm2/sec (R2 = 0.97, 95% confidence
interval = 4.03 to 4.63). This value is surprisingly close to slope obtained in the C x d vs.
tmax regression analysis. The resulting curve-fit for the tl/2 data, however, is much better
as evidenced by the higher R2 value (0.81 vs. 0.97) and narrower 95% confidence interval
for the slope. A second regression analysis was performed for the tl/2 data in which the