Experimental and numerical analysis of low-cycle tooth bending fatigue in case-carburized gears

• Experimental low-cycle fatigue tests were performed on case-carburized AISI 8620 gears. • FEM simulations included residual stresses and elastic–plastic material behavior. • Critical plane strain-based criteria predicted fatigue life, point of crack nucleation and initial crack trajectory. • Numerical predictions agreed well with experimental crack location and orientation. • Chen-Xu-Huang model provided accurate estimates of fatigue life to crack nucleation. Tooth root bending fatigue represents one of the main failure modes of gears. While most of the available literature focuses on tooth root bending under high-cycle fatigue, little has been researched regarding tooth root bending under low-cycle fatigue, even though it is encountered in high-demand industrial sectors. This work evaluates the single tooth bending low-cycle fatigue behaviour of case-carburized gears and presents a novel framework for its prediction, based on the combination of experiments and numerical analysis. Specifically, pulsator single tooth bending tests were performed on case-carburized AISI 8620 spur gears instrumented with strain gages to detect crack initiation. The same tests were replicated in a finite element simulation framework capable of accounting for residual stresses induced by case-carburizing. Simulation results were numerically processed through critical plane criteria for multiaxial fatigue, obtaining predictions about fatigue life, location of crack nucleation and crack initial trajectory, which were compared with test results. Numerically predicted crack initiation locations and trajectories agreed with the experimental means, with errors of 2.6 % and 8 %, respectively. This study presents a new use of critical plane criteria implemented with residual stresses for the analysis of tooth bending fatigue, providing a novel and comprehensive framework for the prediction of such phenomenon, supported by experimental validation.