Pulsed-Active Microwave Thermography

Abstract

Active microwave thermography (AMT) is a thermographic nondestructive testing and evaluation technique that utilizes an electromagnetic-based excitation with a subsequent infrared measurement of the surface thermal profile of the material or structure of interest. AMT has been successfully applied to several aerospace and civil infrastructure applications. This work seeks to expand the performance of AMT by incorporating a signal processing technique common to traditional (flash-lamp) thermography, referred to as pulsed thermography (PT). PT operates on the premise of a pulsed excitation, as opposed to a constant or step excitation (ST) over a given time-period that is typical to traditional active thermography. This work applies the pulsed approach to AMT, herein referred to as P-AMT, and compares the thermal contrast (TC) and signal-to-noise ratio (SNR) of traditional and pulsed AMT inspections as applied to a moisture ingress detection need. The results suggest that the optimal heating time (indicated through SNR) for P-AMT is less than that of traditional AMT with a reduced overall (absolute) temperature. This is important as it relates to any inspection with concerns for thermal damage as well an overall reduction in required inspection time.