Rapid estimation of fatigue limit for C45 steel by thermography and digital image correlation

Combining thermography and Digital Image Correlation (DIC) measurements, this paper aims to experimentally capture the fatigue damage phenomenon in steels, with a methodology allowing to rapidly estimate the fatigue limit. Surface temperatures and displacement fields are collected during fatigue tests performed with blocks of progressively increased stress amplitude, at different stress ratios. Results show that both thermography and DIC-based parameters have bilinear trends as a function of the stress amplitude. These changes in the thermal and mechanical behaviours, highly sensitive to the selected stress ratio, are related to damage initiation due to microplasticity and give a precise and rapid estimation of the fatigue limit.