Experimental and numerical analysis of fatigue crack growth by means of passive thermography during single tooth bending fatigue tests

Abstract Crack propagation at the tooth root leads to one of the most critical failure modes in gears when subjected to bending fatigue conditions. The processes of crack nucleation and propagation had been widely investigated over the years through numerical analysis, and several fatigue crack growth models had been developed and reported in the literature. The objective of this work is to analyse the phenomenon of crack growth in gears during Single Tooth Bending Fatigue tests, with a particular focus on the thermal emissions produced during the fatigue tests. A device for conducting bending fatigue tests on gears was developed with the aim of carrying out the tests at the mechanical pulsator. The crack growth analysis was experimentally conducted by using two thermal cameras positioned in front of the later faces of the tested gear. Thermal maps were acquired in real time during the fatigue tests, enabling the analysis of crack evolution in terms of thermal emissions variations produced during the fatigue process, even when the crack process was still in the gears. Subsequently, the experimental results were compared with the numerical analysis in order to assess the evolution of the crack growth. A dedicated fatigue crack growth model was implemented based on the Paris law through the use of eXtended Finite Element Methods within an open-source software, namely Salome-Meca/Code_Aster. Then, the experimental activity was utilized for a comparison with the corresponding numerical analysis, and the overall results well match in terms of fatigue crack growth.