Infrared Thermography -

Thermography is the use of an infrared imaging and measurement camera to "see" and "measure " thermal energy emitted from an object.

Thermal, or infrared energy, is light that is not visible because its wavelength is too long to be detected by the human eye; it's the part of the electromagnetic spectrum that we perceive as heat. Unlike visible light, in the infrared world, everything with a temperature above absolute zero emits heat. Even very cold objects, like ice cubes, emit infrared. The higher the object's temperature, the greater the IR radiation emitted. Infrared allows us to see what our eyes cannot.

Passive Thermography -

The objective of conventional thermography is the measurement of surface temperatures. Using passive thermography, one can get contactless information about the surface.

Transient Thermography -

Transient thermography is applicable for the detection of deep-seated defects in materials with low temperature conductivity. The sample is heated up over a long period of time in a furnace (non-destructive temperature, e.g. 50°C). After that it is brought into a normal climate and at the same time the surface temperature is gathered with an infrared camera. Because the sample is losing heat to the environment due to convection and radiation, the surface is cooling down. Heat is flowing from the inside to the surface of the sample. A defect, typically a delamination or a cavity, is a thermal barrier for the heat flow. This leads to an inhomogeneous temperature distribution on the surface, which is detected from the infrared camera. Only one way, from the defect to the surface of the sample, is relevant for the measurement: The heat has to cover only half the distance compared to other thermal methods. This explains, why it is possible to detect deep-seated defects in short time with this method.

Laser Shearography -

Shearography is a variation of holography specifically designed for NDT applications. Shearography provides full-field, non-contact nondestructive testing for rapid wide-field inspection of composites, bonded structures and other advanced materials. Shearography is an optical video strain gauge and an appropriately applied stress is used to locate strain concentrations caused by internal defects.

Optical Holography -

Optical holography is an imaging method, which records the amplitude and phase of light reflected from an object as an interferometric pattern on film. It thus allows reconstruction of the full 3-D image of the object. In HNDT, the test sample is interferometrically compared in two different stressed states. Stressing can be mechanical, thermal, vibration etc. The resulting interference pattern contours the deformation undergone by the specimen in between the two recordings. Surface as well as sub-surface defects show distortions in the otherwise uniform pattern. In addition, the characteristics of the component, such as vibration modes, mechanical properties, residual stress etc. can be identified through holographic inspection. Applications in fluid mechanics and gas dynamics also abound.