An experimental-modelling pitch link formulation for an induced ice damaged blade and its usage in vibration-based rotorcraft-blade health monitoring

Abstract

Rotorcraft blades and harmonically controlled mechanisms as Pitch Links, are integrated in main rotor, these substructures are highly important because they directly influence helicopter control, performance and stability. As these rotor blade system begin to accumulate damage, structural dynamics of main rotor hub and its substructures progressively changes. In this thesis, an MBB Bo-105’s rotorcraft blade model configuration was excited harmonically to obtain frequency response functions for non-rotating and rotating frames of references, different Pitch Link damages and also a few parametric uncertainties thought out blade were adopted. In parallel, an experimental case study was explored on 2 Aluminium beams, deepening experimental-modelling comparisons were carried out in only 1 beam since both are quite similar. Four models are used to perform harmonic forced vibration analysis which features coupling on both flapping-torsional deflections. This thesis covers and shows computational insights, ways how solver works, its functionality and how the model frameworks can be exploited on aero elastic rotating blades exposed to Aerodynamic and Vacuum effects. The aim behind this research is to apply sequential damages on the Pitch Link model configuration and modify the Pitch Link’s properties while rotor experiences systematically changes. Monitoring results indicates that damage identifications are plausible done by using different exploration routes and suggest that by controlling Pitch Link properties, one can fully govern blade’s dynamics. It was found that increasing damages in Pitch Link arm and adding Ice on the blade’s tip promotes substantial changes on both first fundamental bending and torsional resonant frequencies, these were found to be highly sensitive to rotorcraft blade configurations