How is thermography defined in the context of NDT?

Thermography, in the context of Non-Destructive Testing (NDT), is accurately defined as the process of mapping thermal patterns non-intrusively using infrared technology. This technique allows for the detection of temperature variations on a surface, which can indicate underlying issues such as poor insulation, electrical faults, or structural anomalies without any physical contact with the object being tested.

This method relies on infrared cameras that detect infrared radiation emitted from an object. Since objects emit heat based on their temperature, thermography can visualize these thermal patterns effectively. Such an approach is particularly valuable in industries where maintaining the integrity of components is crucial, and where traditional inspection methods may be impractical or damaging.

Other methods mentioned—like using contact methods or inspecting visual surfaces—are distinct from thermography as they either involve direct interaction with the materials or do not utilize thermal imaging technology at all. Thus, the essence of thermography lies in its non-invasive nature and its reliance on infrared technology to assess thermal conditions, making the correct answer focused on its non-intrusive capability.