Transient Thermography

Principle

Transient thermography is well applicable for the detection of deep-seated defects, especially in materials with low temperature conductivity. The sample is heated up over a long time in a furnace (non-destructive temperature, e.g. 50°C). After that it is taken into a normed climate, and at the same time the surface temperature is measured 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 by 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.

Applications

If there is a natural heat source available (e.g. required heating-up during the production process), cooling-down thermography enables a complete, passive and fast testing method for quality assurance purposes (e.g. quality assurance for veneered flake boards, ...)