Research on a quantitative fault diagnosis method for rotor rub-impact

The rotor system during its operation is susceptible to various faults such as unbalance, rub-impact, crack, and misalignment, which usually induce the rotor system to exhibit nonlinear behavior. Some linear diagnosis methods are unable to extract nonlinear characteristics of the faulty rotor system. However, existing nonlinear fault diagnosis methods can describe the nonlinear characteristics but cannot quantitatively indicate the severity of rub-impact faults. To address this issue, this study combines the nonlinear output frequency response functions weighted contribution rate (WNOFRFs) and JS divergence to develop an improved fault diagnosis approach, WNOFRFs based on the JS divergence (WNOFRFs-JS). And a superior NOFRFs-associated index JSRm is developed to indicate the severity of faults. In addition, a sensitive factor is defined to evaluate the sensitivity of the index. The performance of this approach is verified by an established dynamic model and a rotor rub-impact experimental rig. The results prove the effectiveness and merits of this approach for the identification of rotor rub-impact. JSRm is especially sensitive to rub-impact and can also quantitatively detect the severity of faults. The present approach can accurately and quantitatively identify the rub-impact rotor system. These advantages enable the improved WNOFRFs to be applied in the fault diagnosis and condition monitoring of rotating machinery and even other nonlinear systems.