Understanding Infrared Thermography Reading 3

Figure 5.12 illustrates a typical infrared materials discontinuity detection
configurat ion using the active (heat injection) method under computer control.
When uniform heat is applied to one surface of a laminar test sample and an
infrared scanner views the opposite surface, two types of defects are
detectable. A metal occlusion within the structure has a higher thermal
conductivity than the ply material and results in a warm (white) spot on the
scanned surface. A void within the structure has a lower thermal conductivity
than the ply material and results in a cool (dark) spot on the scanncd surface.
The computer software can be used. when necessary, to nornlalize the
effective temperature pattern before thermal insertion and to regulate the
timing and intensity of the heat source. Available software also facilitates the
precision timing and recording of test sequences so that they can be repeated
with consistency.
Charlie Chong/ Fion Zhang