where \(S_{{a,R}_{0}}\) and \(S_{{m,R}_{0}}\) are the nominal stress
amplitude and mean nominal stress when a load ratio is \(R_{0}\).\(\ \)
The equivalent life curve was obtained by using the Goodman curve, and
based on the working stress of the fan provided by the supplier, the
stress of the fan structure was modified [43]. The modified curve
was shown in Fig. 6 and Eq. (12). The predicted life of four different
rotating speeds was shown in Table 4.