| Summary: | Developing accurate design data to enable the effective use of new materials is undoubtedly an essential goal in the gear industry. To speed up this process, Single Tooth Bending Fatigue (STBF) tests can be conducted. However, STBF tests tend to overestimate the material properties with respect to tests conducted on Running Gears (RG). Therefore, it is common practice to use a constant correction factor <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>k</mi><mi>o</mi><mi>r</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula>, of value 0.9 to exploit STBF results to design actual gears, e.g., through ISO 6336. In this paper, the assumption that this coefficient can be considered independent from the gear material, geometry, and loading condition was questioned, and through the combination of numerical simulations with a multiaxial fatigue criterion, a method for the calculation of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>k</mi><mi>o</mi><mi>r</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula> was proposed. The implementation of this method using different gear geometries and material properties shows that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>k</mi><mi>o</mi><mi>r</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula> varies with the gears geometrical characteristics, the material fatigue strength, and the load ratio (R) set in STBF tests. In particular, by applying the Findley criterion, it was found that, for the same gear geometry, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>k</mi><mi>o</mi><mi>r</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula> depends on the material as well. Specifically, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>f</mi><mrow><mi>k</mi><mi>o</mi><mi>r</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula> increases with the ratio between the bending and torsional fatigue limits. Moreover, through this method it was shown that the characteristics related to the material and the geometry have a relevant effect in determining the critical point (at the tooth root) where the fracture nucleates.
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