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Uniform Heating
With traditional uniform heating (shown below) the heat penetrates straight down into the structure past the hidden flaw. The crack is not detected.
Uniform
Heating
Click image above to view
a short animation (37K).
Forced Diffusion Heating
As demonstrated below, with forced diffusion heating (CTT - Coating Tolerant Thermography) the flaw is easily detected. The basis of this phenomena is that thermal methods correlate structural integrity with thermal diffusivity. If the molecular structure is altered impairing transfer of forces, the conduction of heat energy is also impeded. As demonstrated below, CTT projects a pattern of dynamic heat to force flow across cracks thereby, optimizing the measurable thermal gradient.
Forced Diffusion Heating
Click either image above to view
a short animation (23K).
Heat travels from "hot" stripe to "cool" stripe as the stripes slowly comb the structure for cracks. The in-plane heat flow is impeded by a structural flaw, such as a crack, creating a gradient in the thermal image, which clearly defines the crack. The direction of the heat flow (from the left or from the right) defines the sign of the gradient (positive or negative). In the figure below, the heat flows from the right causing the sign of the gradient to be negative.
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