A comparison of gear tooth bending fatigue lives from single tooth bending and rotating gear tests

Being able to properly predict gear failure is a key aspect to achieve a reliable light-weight gearbox. Among the several gear failures, tooth root bending fatigue is considered as the most dangerous one because it implies the stoppage of the whole gearbox. In order to characterize a gear for this phenomena, Single Tooth Bending Fatigue (STBF) tests are the most performed ones. However, as in STBF test THERE IS no sliding/rolling contact and as the specimens are teeth rather than gears, some differences occur between the test conditions and those of the real case. This paper deals with the statistical ones that is the estimation of the gear SN curve starting from the teeth one. The teeth SN curve has been estimated by means of a statistical model developed considering Murakami’s idea of nonpropagating crack. Then, a methodology based on statistic of extreme is adopted for the purpose of estimating the gear SN curve.

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“…al. [52]. Interested readers are referred to [17,52] for a comprehensive review about how the literature deals with the aforementioned passages.…”

Section: Gear Testing For Tooth Root Bending Fatiguementioning

confidence: 99%

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

Bonaiti

Gorla

2022

Material Design & Processing Communications

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“…This is a clear economic advantage towards the experimentation on MG. In addition, in STBF tests the lubrication is not required since there is no meshing [34].…”

Section: Introductionmentioning

confidence: 99%

Effect of Gear Design Parameters on Stress Histories Induced by Different Tooth Bending Fatigue Tests: A Numerical-Statistical Investigation

et al. 2022

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The characterization of new materials for enabling gear design is definitely a fundamental objective in the gear industry and research. Single Tooth Bending Fatigue (STBF) tests can be performed to speed up this process. However, it is well known that STBF tests tend to overestimate material strength compared to tests performed directly on meshing gears (MG) which, in turn, require an excessively long test time. Therefore, it is common practice to use a constant correction factor fkorr of 0.9 to translate STBF results for designing actual MG (e.g., via ISO 6336). Recent works involving a combination of Finite Element Models (FEM) and multiaxial (non-proportional) fatigue criteria based on the critical plane concept have highlighted that the assumption of considering fkorr as a constant independent of the gear design parameters leads to inaccurate results. However, in previous studies, no correlation between fkorr and gear design parameters has emerged. In the present paper, the influence of the normal pressure angle (αn), the profile shift coefficient (x*), and the normal module (mn) on fkorr was investigated by analyzing FEM simulations with the Findley fatigue criterion. 27 gear geometries were studied by varying the above 3 parameters in 3 levels (full factorial DOE). These geometries were simulated in both MG and STBF configurations. The results of the 54 FEM simulations were analyzed by applying the Findley fatigue criterion and the corresponding fkorr were calculated. The correlation between fkorr and αn, x* and mn was investigated using the Analysis of Variance (ANOVA) technique. The results show that the only gear design parameter influencing fkorr is x* hence, a regression model for fkorr including x* has been developed. This latter has been then adopted for calculating and comparing fkorr values from other combination of the parameters found in literature, giving good correspondence.

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“…To consider the above-mentioned difference, it is possible to introduce a corrective factor (f korr ) to translate STBF results into the RG ones [32]. The coefficient f korr is the ratio between the σ Flim obtained with the STBF approach and the σ Flim calculated through RG tests.…”

Section: Introductionmentioning

confidence: 99%

Exploiting a numerical method to translate single tooth bending fatigue results into meshing gears design data: the influence of material properties

Concli¹,

Maccioni²,

Fraccaroli³

2022

Int. J. CMEM

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According to standards, a fundamental gear design parameter, which heavily influences the sizing of these mechanical components, is the gear tooth root bending strength. To establish this parameter in a reliable way, tests should be performed on running gears (RG) manufactured with the same material and heat treatments under investigation. However, it is common practice in industry and in academia to perform single tooth bending fatigue (STBF) tests, which, on the one hand, are simpler and cheaper to perform, on the other hand, the stress history (V V t ) they induce is not identical to that obtained during RG meshing. Therefore, it is necessary to apply a correction coefficient (f korr ) to translate data obtained via STBF in RG design data. In recent studies, a method to estimate f korr through the combination of finite element (FE) simulations and the implementation of multiaxial fatigue criteria (MFC) based on the critical plane concept has been proposed. This method consists of simulating through FE a gear geometry both in the RG load case and in the equivalent STBF condition. Through the load histories recorded on the nodes belonging to the critical area, it is possible, by implementing different MFC, to identify the most critical node and the relative Damage Parameter (DP). The ratio between the obtained critical DP of the STBF case and RG provides the value of f korr . However, different MFC can lead to different results in terms of f korr . This is because different MFC differs in the definition of the DP. More specifically, DPs are both functions of material properties, such as the fatigue limit of the material related to symmetric sinusoidal bending stresses (σ f ) and the fatigue limit at sinusoidal cyclic torsional stresses (τ f ), and load-dependent characteristics. The goal of this paper is to investigate the effect of different material properties, i.e. σ f and τ f , on the estimation of f korr highlighting differences between the various MFC implemented, i.e. Findley, Matake, Papadopoulos, and Susmel et al. To this respect, the above-mentioned numerical method has been applied to a specific gear geometry whose material properties have been systematically varied. Results show that the criteria of Findley and Papadopoulus lead to very similar results and a monotonically increasing relationship between f korr and τ f /σ f . A similar trend is observed for the Susmel et al. criterion but with higher value of f korr Differently, the criterion of Matake leads to a monotonic decreasing relationship between f korr and τ f /σ f .

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A comparison of gear tooth bending fatigue lives from single tooth bending and rotating gear tests

Cited by 7 publications

References 23 publications

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

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

Effect of Gear Design Parameters on Stress Histories Induced by Different Tooth Bending Fatigue Tests: A Numerical-Statistical Investigation

Exploiting a numerical method to translate single tooth bending fatigue results into meshing gears design data: the influence of material properties

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