## 4 Conclusions  
The section test approach for the fatigue life evaluation of structural components was applied to wheel rims for off-highway applications. Additional aspects related to the production process of the component were also considered. The following conclusions can be drawn:  
1. The rim section test approach was confirmed to be a valid approach which can be used in fatigue testing when standard dynamic radial tests on the complete wheel are not feasible. Customized specimen geometry was studied by FEA and specimens were subjected to bending fatigue tests. The target of creating a S-N curve for the component in the most critical area was achieved. Specimens from two different rims showed slightly different fatigue strength at 2 \(\times\) 10\({}^{6}\) cycles. As a result, further investigations are planned to improve the knowledge about the influence of the production process parameters on the fatigue properties of this component;
2. Bending test results of rim section specimens were compared to traction test results of hourglass specimens obtained from the base material. The comparison was made to consider the shortcomings that can be derived from the improper use of standard fatigue data from the technical literature. The results show a ratio between 1.36 and 1.5 between the fatigue strength of rim section specimens and the hourglass specimens from the base material. This is due not only to the different load condition but also to the effects of the production process on the final surface condition of the material. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Rim 1** & **Rim 1** & **Rim 2** & **Rim 2** \\ \hline
**Zone** & **Specimen A** & **Specimen B** & **Specimen C** & **Specimen D** \\ \hline Flat & 425 & 415 & 395 & 415 \\ Radius & 440 & 450 & 415 & 425 \\ \hline \end{tabular}
\end{table} 
Table 6: Approximate tensile strength of the rim sections specimens, in unit [MPa]. Values are converted from Rockwell B hardness scale according to ASTM A370. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Rim 1** & **Rim 1** & **Rim 2** & **Rim 2** \\ \hline
**Zone** & **Specimen A** & **Specimen B** & **Specimen C** & **Specimen D** \\ \hline Flat & 71 & 69 & 66 & 69 \\ Radius & 73 & 74 & 69 & 71 \\ \hline \end{tabular}
\end{table} 
Table 5: Hardness measurement of the rim sections specimens. Scale: Rockwell B (HRB). Therefore, the section test approach seems more appropriate to consider the local geometry of the component and its surface condition;
3. The residual stress state of the component after the production process was investigated, both on the complete rim and on section specimens obtained from the same rim. The results show the presence of mainly compressive residual stresses along the axial direction for the complete rim. They should be beneficial for the fatigue strength of the component in service conditions. However, the compressive residual stresses were released after the manufacturing of the rim section specimens. Therefore, it seems that this aspect is not considered properly by the section test approach;
4. Surface hardness was measured on four specimens to assess the effect of the local plastic deformation on the material properties. The results show a slight increase of the hardness in the radius, where plastic deformation occurs, leading to increased material strength in that area. This was confirmed by the fatigue test results of Section 3.1. Also, on average, the results are better for specimens from Rim 1, which, in fact, had better fatigue life results. More extensive hardness measurements are planned to investigate this aspect further;
5. The section test approach, here investigated to compensate the shortcomings of standard fatigue testing for off-highway wheels, could also be tailored to different components subjected to fatigue in service. As a future development of this research, the rim section test approach should be applied to a specific case where the fatigue failure of the complete wheel is easily achievable through standard fatigue tests.