Modal passport application for dynamic properties validation and structural health monitoring of helicopter blades

Abstract

The paper considers experimental techniques for research of modal properties of rotating helicopter blades. Sensors of vibration deformations and operational modal analysis techniques are chosen as the optimal tools for evaluation of modal properties of rotating blades. As a complex approach to the study of structural modal properties and its further usage the concept of modal passport is proposed. Authors discuss the setup and technical solutions of the experimental system for determining the modal properties of helicopter blades in statics and rotation. The stages of data processing obtained by the experimental system are described, including preliminary reduction of the periodic component, application of Experimental Modal Analysis (EMA) and Operational Modal Analysis (OMA) algorithms as well as formation of a typical modal passport of the blade. The samples of experimentally determined mode shapes of vibrations and deformations in statics and rotation are considered, as well as the analysis of various factors influence on the modal parameters of the blade. The modal deformation shape parameter, which has a diagnostic value and allows detecting even small changes in the mechanical properties of the blade, is outlined. Authors conclude about OMA techniques capability for deformation sensors application for determination of modal parameters of rotating blades. There are conclusions also about benefits of modal passport approach and its application for structural health monitoring (SHM) of helicopter structures, including blades.