Model-based Inversion for Pulse Thermography
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Pulse or flash thermography is a method of nondestructive evaluation that finds subsurface flaws in materials by observing a heat pulse and subsequent cooldown using a thermal camera. A fundamental constraint of pulse thermography is lateral heat diffusion that tends to blur the shapes of defects. It can be difficult to interpret the thermal image sequence from a pulse thermography test. This paper presents a model-based inversion for pulse thermography that uses the known physics of heat conduction to as a basis for representing the recorded thermal image sequence. The technique provides a means to solve for the reflectivity distribution of defects across multiple layers, such as delaminations in a composite material. The layer reflectivity distributions provide a compact and concrete representation of the thermal image sequence. The technique gives excellent interpretability and resolution with minimal noise gain. Model-based inversion is demonstrated on several carbon fiber reinforced plastic (CFRP) specimens.
KeywordsPulse thermography Flash thermography Non-destructive evaluation Composites Model-based inversion Inverse problems
This research was funded by NASA Early Stage Innovation under award NNX15AD75G.
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