## 9 Conclusions  
Pulsator/STBF test is a test method employed in the estimation of gear tooth root load-carrying capacity with respect to the tooth root fatigue fracture phenomena. It is widely adopted because it is a cost-efficient method that considers a representative test specimen. Typical applications of pulsator tests are investigating the effects of material heat and surface treatments in gears. However, the pulsator test procedure presents several differences with respect to the real-world case where gears are meshing under load. Therefore, pulsator test results must be elaborated before using them to design a gear pair. Several methodologies have been developed over the years. Considering that all of them have been developed for different test configurations, good agreement has been found. That is, all of them suggest that, in the long-life region, pulsator test results should be reduced by a factor of approximately \(\approx\) 0.77 - 0.83. Figure 17: Trend of normalized \(s_{log(\sigma_{\text{fp}})}\) confidence intervals. Among all the methodologies, two of them have been developed by examining a symmetric (double teeth) pulsator test configuration. These two methodologies are discussed here in detail. The first (method 1: FVA, based on FZG research) elaborates pulsator test data based on typical scattering values obtained from a previous case-hardened gear test, that is, it adopts pre-determined coefficients. It must be noted that this methodology covers the whole testing procedure as additional information is also provided (e.g., gear specimen, testing machine). Most importantly, it also provides the experimenter with indications about the test planning. From a statistical and mathematical point of view, this methodology can be considered the simplest one. The latter (method 2: ML&SoE) adopts ML to estimate the experimental curve; then it estimates the gear SN curve by means of SoE. Different from the previous one, this methodology relies only on the observed data within the analyzed test series. However, no discussions about test planning have been performed so far for method 2, especially concerning specimen numerosity. The two approaches discussed in this paper have been defined, independently and at different times, by all the authors of the paper. Both methodologies are described here in detail. In this way, the designer who wants to undertake the task of gear testing can find indications about the elaboration of pulsator test data. The comparison of the methodologies has been performed on the basis of an actual database composed of 1643 symmetric pulsator test results obtained during 76 different experimental campaigns on case-hardened gears. The comparison was performed by directly examining the final gear SN curve. It has been found that both methods yield completely comparable results. The good agreement between the corresponding outcomes allows us to reaffirm the validity of the two models. However, as it does not rely on previously defined data, method 2 tends to be more sensitive to the presence of outliers. Several cases have been studied; for the sake of simplicity, only a few of them are reported in this paper. As mentioned in Section 4, the validity of method 1 has been reaffirmed recently. Nevertheless, for method 2, both here and in previous works, the validation of method 2 has been performed only by comparing the outcomes of method 1 and method 2. Further validation of method 2 has been conducted here due to the availability of the case-hardened gear database. Parameter confidence intervals have been compared with typical gear data, finding good agreement between the model outcomes and their equivalents presented by the standards. Furthermore, the minimum number of points required for the application of the method has been calculated. This has been calculated as 30 to be on the conservative side. Conceptualization, L.B. and M.G. ; methodology, L.B. and M.G. ; software, L.B. ; supervision, T.T., C.G. and K.S. ; writing, L.B. and M.G.