23. Nonlinear Vibration Phenomena in Aero-Engine Measurements

Measured aero engine vibration responses vary in character and amplitude depending on the operating environment and prevailing loading conditions. When these responses are limited to linear dynamics range, existing analysis tools which are mostly targeted at such responses, can be used to analyse and characterise the underlying mechanisms. However when responses are nonlinear, use of the same tools may result in nontrivial errors or may not at all be applicable. Some methods have been put forward with the premise of dealing with nonlinearities in measured data. However, they are often very simplistic and cannot effectively deal with complexities an aero engine environment can produce. With designs getting more complex and non-traditional materials, such as composites, becoming more widely used; strong nonlinearities are becoming a more common occurrence. Therefore from industrial perspective, development of effective tools that can deal with identification, classification and eventually quantification of nonlinear features is a very real and present need.

In this paper, a number of scenarios, in which sufficiently strong nonlinear responses have been measured, will be presented. Approaches available to an industrial practitioner in such cases will be discussed. Areas that need development of new methods, as well as the degree of robustness with which such methods need to be deployed, will be outlined from an industrial perspective.