A new approach for rapid fatigue limit assessment for C45 steel based on contrast damage parameters

Abstract

In the present work, a different procedure for rapid estimation of fatigue limit is employed for a case of study on C45 steel elements under two fatigue stress ratios. Specifically, three damage parameters are proposed for fatigue limit assessment of metallic materials. These damage factors are estimated employing a simply contrast-based approach that processes raw thermal data to provide dissipative, reversible, or local contrast measurements in selected inspected zones, respectively. Then, the obtained data of three thermal factors are correlated to related loading conditions. Simplified fatigue test campaigns of only 4 ÷ 8 specimens and few testing hours are carried out for both stress ratio conditions employing the ‘stepwise’ loading procedure. The fatigue limit estimation is performed through the standard linear regression approach and a different proposed approach based on the signal to noise ratio data. An interesting agreement between different proposed damage variables and well-established classical methods is observed in terms of fatigue limit estimations for both stress ratio conditions. In addition, a comparative analysis is performed between the obtained results and other research data obtained through thermal or energy methods by different authors, highlighting comparable results and adding robustness and reliability to the proposed approach for the fatigue limit estimation on tempered steel.