Thermographic inspection

Thermographic inspection refers to the nondestructive testing (NDT) of parts, materials or systems through the imaging of the temperature fields, gradients and/or patterns ("thermograms") at the object's surface.

[11] When compared with other classical NDT techniques such as ultrasonic or radiographic testing, thermographic inspection is safe, nonintrusive, and usually noncontact, allowing the detection of relatively shallow subsurface defects (a few millimeters in depth) under large surfaces (typically covering an area of 30 by 30 cm (12 by 12 in) at once, although inspection of larger surfaces is possible) and quickly (from a fraction of a second to a few minutes depending on the configuration).

In addition, there are two mutually exclusive approaches in thermographic inspection: Typically, passive techniques display information from an infrared sensor on a monitor; these images can be visualized in black and white or in false color.

In vibrothermography, an external mechanical energy source induces a temperature difference between the defective and non-defective areas of the object.

In this case, the temperature difference is the main factor that causes the emission of a broad electromagnetic spectrum of infrared radiation, which is not visible to the human eye.