<title>Time-resolved infrared radiometry (TRIR) using a focal-plane array for characterization of hidden corrosion</title>

Abstract

A time-resolved infrared radiometry technique is developed which is applicable to detection of hidden corrosion in airframe structures and which implements an InSb focalplane array. The TRIR method can measure the loss of skin thickness due to corrosion and can also detect second layer corrosion when a sealant material is present at a lap joint. It has also been shown that the presence of corrosion product can be detected on the back surface of an aluminum plate free standing in air. Other experimental studies suggest that the presence of corrosion product, corrosion thinning of the plate and morphology changes at the aluminum-corrosion layer interface all affect the TRIR temperature-time signature. This raises the possibility of separating these contributions experimentally.

Quantitative analysis and defect assessment using infrared thermographic approaches

“…Slow phenomena are better investigated under step heating stimulation, while fast phenomena are better monitored with pulsed thermography. Specific advantages of this technique include the ability to determine either defect depth or material's thermal characteristics from a single test without the need for a calibration measurement made on a defect-free region of the specimen [82]. Moreover, by applying heating of low energy, the time varying temperature change on the surface of the specimen can be maintained at a high level throughout the measurement process and simultaneously the parallel nature of the detection process (excitation and monitoring) allows large areas to be studied in a single test.…”