Abstract
Gears are among the most widespread mechanical component. Thanks to new technologies, new production methods and new materials on the market, the use of this component is constantly increasing. This fact outlines the need to understand properly the functioning of such component into different load cases. Nowadays the trend of miniaturization is growing in the mechanical sector and gears that have reduced its size are already used in several fields. This fact brings the necessity to correct analyze and study material properties and the fatigue behavior of this mechanical component. Failures resulting from cyclic stress, thus due to fatigue, must be correctly analyzed. This important aspect reduces the life of a generic component by causing unexpected breaks. For this purpose, in the present manuscript, a combined approach of theoretical calculation and experimental analysis is presented, the aim was to investigate the fatigue comportment of a gear made by 39NiCrMo3 with a fine module equal to 2. Single Tooth Bending Fatigue (STBF) tests were realized with the support of a universal tensile testing machine. New grips have been developed for performing fatigue tests on the tensile test machine and, moreover, dimensions of the new grippers were chosen in order to exploit the Wildhaber W5 property. The fatigue limit was approximated thanks to two different statistic approaches, the classic and the shortest stair-case method proposed by Dixon. Both analyses allow to compute the fatigue limit by performing tests at different loads. The step load used in this research was set at . The Dixon approach allows to use few tests with respect to the classic method, reducing time and material needed for the analyses. Furthermore, by using the standard ISO 6336 it is possible to translate the applied forces into stress values. Afterward, results of the combined theoretical/experimental analyses were related to the one proposed by the ISO standard of the same steel constituent.