Understanding Infrared Thermography Reading 3

■ The Stimulated Measurement Approach to Infrared Materials Flaw
Detection
When the desired characteristic thermal pattern on the product surface
cannot be made to occur, or when the material samples or products are to be
evaluated after manufacture, the stimulated, or thermal injection, approach is
necessary. The stimulated approach can also involve thermal extraction, or
the removal of heat from the sample, by introducing some form of cooling.
Devices used for heat injection or extraction include the sun, air blowers,
flood lamps, flash lamps, lasers, refrigerants, hot and cold water, chemical
reactions, thermoelectric devices and mechanical heat sinks. In order for the
stimulated approach to be effective, it requires the generation of a controlled
flow of thermal energy across the Structure of the sample material under test.
This is accompanied by thermographic monitoring of one of the surfaces (or
sometimes both) of the sample, and the seareh for the anomalies in the
thermal patterns so produced that will indicate a defect in accordance with
established accept-reject criteria.
Charlie Chong/ Fion Zhang