Bladed discs are very sensitive structures and the amplitude vibration of each
blade can vary significantly from blade to blade due to a series of factors such as
geometrical inhomogeneity between blades or material properties. These factors
lead to bladed disks mistuned thus the forced response amplitudes can be much
higher than the level predicted for a tuned assembly.
Designed models need to be “validate” to predict the response of a real bladed
disc within the tolerances set by the manufactures and this process is very
expensive as well as difficult. The validation process needs “reference data” as
fundamental input against what all predictions can be compared and validated.
Data that can be provided both under stationary conditions and under rotating
conditions and the latter is the most difficult to achieve, especially for bladed
disc assemblies which are very sensitive to any structural modification as it
could be attaching a transducer to measure vibrations. There are contact-less
measurement techniques available which, however, provide limited information
because they can measure only limited areas of the vibrating structures.
The aim of this study is to design measurement methods, using a standard
Scanning Laser Doppler Vibrometer (SLDV) and to integrate it into a software
platform which will be able to handle a series of measurement tasks both under
stationary and rotating conditions. The main contribution of this thesis is to
extend the use of Continuous Scanning LDV (CSLDV) to the rotating structures,
such as bladed discs, thus to perform synchronous measurements. Hence, a
bladed disc is needed to be designed to perform vibration predictions and
measurements and a mathematical model of the measurement test to control,
critically, all possible sources of errors involved in measurement under rotating conditions; all these to produce a robust measurement method. While the
primary focus is the measurement method, the study also extends to evaluation
of the sensitivity properties of the bladed disk test pieces that are the object of
the measurement tool
