15 Research Lab › Live physics
An explicit finite difference solver for the heat equation, running in your browser. Fire the flash and watch a buried air gap change the surface temperature above it.
Solver output, not recorded data. Conductivity ratio of the air gap to the solid is 0.052 to 1.
The upper panel is a cross section of a solid with a thin air gap buried inside it. The flash deposits heat across the top surface, and that heat then drains downward through the material.
An air gap conducts about twenty times worse than the solid around it, so it blocks the drain. Heat piles up above the gap and that patch of surface stays warmer than its neighbours.
The lower panel is the surface temperature line scan. That single line is the only thing a real infrared camera can see, and the bump in it is the entire finding.
Change the depth selector and fire again. A shallow defect blooms early and fades quickly. A deep one arrives late, weaker, and spread wider across the surface.
That arrival time is what encodes depth. Flash thermography is not a photograph of a defect, it is a timed measurement of when contrast appears, which is why the instrument needs a camera fast enough to catch the arrival rather than one with the highest resolution.
It is also why the method reports depth at all, instead of only telling you that something is wrong somewhere underneath.
This page is the numerical version. The GT-1 is the physical one: a FLIR camera at 60 Hz, a xenon flash, and an agent that runs the instrument and writes the report.
Alongside it are ultrasonically verified reference defect panels, so a detection can be checked against a gap whose depth and size are already known. That is the part of a machine learning pipeline that is usually synthetic.
$8,500 for the GT-1 instrument, here
$45,000 and up for a flash thermography system, elsewhere
Incumbent systems run $45,000 to $300,000. Certified defect panels are $800 to $1,500 here.
A two dimensional finite difference solver for the heat equation, running in your browser. The upper panel is a cross section of a material with a low conductivity air gap buried inside it. The lower panel is the surface temperature line scan, which is the only thing a real infrared camera can see.
The flash deposits heat on the surface, and that heat drains downward. An air gap conducts roughly twenty times worse than the surrounding solid, so it blocks the drain. Heat piles up above it and that patch of surface stays warmer than its neighbours. The camera sees a bloom.
A shallow defect blooms early and fades fast. A deep one blooms late and weakly. The arrival time of the contrast is what encodes depth, which is why flash thermography is a timed measurement rather than a single photograph.
The GT-1 instrument and certified defect panels sit on the rate board with everything else. Posted before opening, not after.