Issue34

R. Citarella et alii, Frattura ed Integrità Strutturale, 34 (2015) 554-563; DOI: 10.3221/IGF-ESIS.34.61 559 for both the control and noise factors. This matrix is suitable for the cases in question, since, in addition to providing a variation on two levels as required, it provides a number of simulations equal to the degrees of freedom and therefore just sufficient to ensure the conditions at the base of a correct use of the Taguchi method. Figure 5 : Von Mises stress (MPa) state induced by the combined action of interference and torque, with the highlight of circumferential reciprocal sliding. Regarding the equivalent (Von Mises) stress peaks, it is worth considering the following: - there is an optimal exploitation of the material when said peaks reache the maximum value allowed for the material in question, for which the problem is considered as “nominal the best” ; - the length of the hub can be chosen as calibration factor because useful in bringing the mean stress value to the target value after optimization, thanks to its characteristics (presumed but eventually verifiable) of not affecting the sensitivity of the coupling to considered noises. Thus, in the choice of the optimum combination of the design parameters, it is possible to neglect the distance between the target value and the effective mean value in the quality function. Only at the end the length of the hub is defined, upon which the stress peaks depend in an inversely proportional manner. Figs. 6-10 show the effects of the control factors on the mean values and on the scatter of the performance parameters: with reference to the latter, each bar of the histogram is representative of the mean (Fig. 10) or the signal/noise ratio (Figs. 6-9), recalculated in decibels (dB), when the control factor, indicated on the abscissa, assumes a given value. Thus, the individual contributions of the control factors on the performance of the overall mean and S/N ratio are identified, assuming no interaction between the control factors. Tabs. 1-4 present all the simulation results. Figure 6 : S/N ratio for the radial expansion of the hub upon varying the design parameters .