Non contact measurements of stress fields on rotating mechanical components by thermoelasticity

In this paper the possibility to measure stress fields on rotating mechanical components is demonstrated. The test case used is a plastic fan installed on an electric motor over an electrodynamic exciter in order to rotate and vibrate the fan itself. A special purpouse data processing software has been developed to process the thermal film recorded while the fan is rotating and vibrating. An experimental method to realize thermal markers on the fan is proposed. The software allow to follow the marker movment and to de-rotate the film frames. On the de-rotated film another data processing technique allow to detect temperature time fluctuations on each relevant pixel. The result is a thermal differential image, accordingly to the thernoelastic measurement principal, proportional to the stress on the fan blades surface. The same stress concentration areas and levels has been obtained on the rotating and vibrating or only vibrating fan blade.