Reliable Gear Design: Translation of the Results of Single Tooth Bending Fatigue Tests Through the Combination of Numerical Simulations and Fatigue Criteria

Abstract

Establishing the actual gear root bending strength is a fundamental aspect in gear design. With this respect, gears materials can be characterized through two types of tests, i.e. on Running Gears (RG) or Single Tooth Bending Fatigue (STBF). The former is able to reproduce the loading conditions of the actual gears and, therefore, leads to the most accurate results. The latter excels in terms of efficiency and simplicity of the experimental campaign but as a drawback, tends usually to overestimate the material strength due to the different stress state histories it induces on the tooth root. Therefore, a common practice is to carry out STBF tests and apply a correction coefficient () for exploiting the results in the design of actual gears. In the present paper, an approach to estimate centered on the combination of numerical simulations and multi-axial fatigue criteria based on the critical plane capable of taking into account non-proportional loading conditions has been proposed. In particular, the same gear geometry has been simulated through Finite Element (FE) models in two conditions, i.e. STBF and RG. The outcomes of the simulations, in terms of stress histories in the tooth root region, have been analyzed with five different fatigue criteria, i.e. Findley, Matake, McDiarmid, Papadopoulos, and Susmel et al.has been calculated as the ratio between the maximum damage parameter observed in the STBF and RG conditions according to the different fatigue criteria. Results show that , calculated for three different materials (i.e. 18NiCrMo5, 42CrMoS4, 31CrMo12), differs up to 22% between the RG and the STBF conditions (depending on the criterion considered). Therefore, future studies should aim to understand which fatigue criterion is the most appropriate for this type of analysis.

Early Crack Propagation in Single Tooth Bending Fatigue: Combination of Finite Element Analysis and Critical-Planes Fatigue Criteria

“…In recent studies, the authors pointed out that the FE simulation results of the STBF configuration can be analyzed and elaborated via different fatigue criteria based on the critical plane approach [41][42][43]. These allow for evaluating the criticality of each point along the ρ f P .…”

“…Moreover, it permits to individuate the potential propagation direction of the crack after nucleation. Nevertheless, it has been observed that different fatigue criteria could lead to different results in terms of TBS and/or crack propagation direction [42].…”

Gear Tooth Root Bending Strength Estimation under the Assumption of Fatigue Limit Existence

“…Material Design & Processing Communications case and the actual case [23, 36-39, 52, 53]. On the one hand, the lack of the rolling/sliding condition implies that the loading condition occurring within the toot root is different [11,54,55]. On the other hand, the fact that the tests are performed on the teeth rather that gear implies a statistical difference [17,18].…”

Experimental Study on Vibration Fatigue Behavior of Aircraft Aluminum Alloy 7050

“…By considering the modal parameters of the structures and the influence of structural dynamic characteristics on micro-structural deformation, the factors that influence vibration fatigue damages were studied. Concli, F. [ 17 ] studied the different fatigue criteria according to different results of crack propagation direction. Poursaeidi and Arhani [ 18 ] investigated the failure of an auxiliary steam turbine.…”