Thermographic investigation of the fatigue behavior of reactor pressure vessel steels

The fatigue behavior of reactor pressure vessel (RPV) steels during fatigue testing was monitored by an advanced, high-speed, high-sensitivity, nondestructive evaluation (NDE) technique called infrared (IR) thermography. Five stages of temperature profiles during fatigue were recorded: an initial increase of the mean specimen temperature followed by a temperature decrease, a constant (equilibrium) temperature region, an abrupt temperature increase, and a temperature drop after the specimen failure. Using the state-of-the-art IR camera, the temperature profiles were recorded cycle by cycle during 20 Hz fatigue testing. A theoretical model combining the thermoelastic, inelastic, and heat-conduction effects were used to explain and predict the temperature evolution during fatigue. Specifically, the temperature evolution was predicted, and the results were found to be in good agreement with the experimental data.