Characterization of the temperature evolution during high-cycle fatigue ofthe ULTIMET superalloy: Experiment and theoretical modeling

High-speed, high-resolution infrared thermography, as a noncontact, full-fi eld, and nondestructive technique, was used to study the temperature variat ions of a cobalt-based ULTIMET alloy subjected to high-cycle fatigue. Durin g each fatigue cycle, the temperature oscillations, which were due to the t hermal-elastic-plastic effects, were observed and related to stress-strain analyses. A constitutive model was developed for predicting the thermal and mechanical responses of the ULTIMET alloy subjected to cyclic deformation. The model was constructed in light of internal-state variables, which were developed to characterize the inelastic strain of the material during cycl ic loading. The predicted stress-strain and temperature responses were foun d to be in good agreement with the experimental results. In addition, the c hange of temperature during fatigue was employed to reveal the accumulation of fatigue damage, and the measured temperature was utilized as an index f or fatigue-life prediction.