Quantification and propagation of uncertainty in critical speeds and mode shapes of rotating structures

Parametric uncertainties are ubiquitous in engineering structures in a variety of forms. Specifically, the most significant sources of uncertainties in rotating structures include the manufacture errors, assemble tolerance, boundary conditions and geometrical properties of critical components. The uncertain parameters have irreducible influences on inherent modal properties of the rotating systems. It is required to consider the variabilities of uncertainties for a robust evaluation of natural characteristics. This paper employed a polynomial surrogate method to track the propagation of parametric uncertainties in an overhung rotating structure. The method is non-probabilistic in nature, which alleviates the hash requirement of strict probabilistic density functions that could be difficult to obtain for real applications. The critical speeds and mode shapes of the rotor-bearing system were investigated based on the surrogate model considering different uncertain parameters. The results were validated with the crude scanning method. It was demonstrated that the surrogate method used has superiority in computation efficiency over traditional methods while maintaining enough accuracy, which will be beneficial for large-scale engineering structures. Moreover, the analysis procedure is adaptable to other uncertain structures with little change.