Original Date: 11/03/1996
Revision Date: 01/18/2007
Best Practice : High Speed Infrared Camera System
Typically high-speed infrared (IR) cameras perform non-destructive evaluations to look for subsurface oxide scales, cracks, delaminations, plugged cooling holes in turbine blades, and spallation (the separation of the thermal barrier coating in turbine blades). However, Oak Ridge National Laboratory’s (ORNL’s) High Temperature Materials Laboratory (HTML) developed a unique capability for its Raytheon high-speed IR camera. The speed and sensitivity of this camera allows, for the first time, quantitative thermal diffusivity mapping.
Other features of the Raytheon high-speed IR camera include a 256 x 256 pixel resolution, up to 142 full frames per second, temperature resolution greater than or equal to 0.015°C, a snapshot mode, a motorized, five-position filter wheel, and a closed-cycle, sterling linear cooler. These capabilities far exceed other IR cameras currently on the market.
The thermal diffusivity mapping feature works by recording the thermal response of the sample to an external heat source. Heat sources include lasers, xenon flash lamps, quartz lamps, and xenon illuminators. Thermal diffusivity is measured by supplying the heat to the side of the sample which lies opposite to the camera. The sample must be planar. The sensitivity of the IR camera can recognize microstructural changes in the sample.
HTML’s IR camera demonstrated its value through a project with the Ford Motor Company. Ford suspected that a micro-material problem existed in its brake rotors. Whenever the brakes were applied, hot spots occurred in the rotors and caused the vehicle to vibrate. Warranted repairs created an expensive cost for the company. HTML investigated the problem by using its IR camera to analyze a brake rotor setup on a brake dynamometer at the Ford laboratory. Within minutes, the IR camera revealed the hot spots and provided valuable data to the automotive engineers for solving this problem. Previously, Ford had tried to investigate the brake problem by using three other IR cameras, but with no success.
Other projects performed with HTML’s IR camera include thermal diffusivity mapping of carbon-carbon composites; identification of subsurface flaws in turbine engine coatings; and thermal image of voltage breakdown in a varistor. Current projects include monitoring cyclic, fatigue testing of metals; heat spreading in electronic packaging substrates; thermal shock damage to composites; and process optimization in the pulp and paper industry.
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