The vibration of a turbocharger blade and dynamic characteristics of bladed
packets connected by a lacing wire have been studied. The study was carried out
using three analytical and experimental methods. They are: Modal Testing, Electronic
Speckle Pattern Interferometry (ESPD and Finite Element Analysis (FEA).
Vibration modes of a turbocharger blade with aerodynamic profile, with and
without a lacing wire, were identified using model blades with simplified geometry.
The separation of coupled modes was achieved using ESPI tests.
The modes of vibrations of bladed packets were identified. The effect of
inter-blade coupling through a lacing wire is that a cluster of sub-modes are
generated in bladed packets corresponding to each fundamental mode of the freestanding
blade, the number of the sub-modes being equal to the number of blades in
the packet. Apart from the fundamental sub-mode, the vibration of all other submodes
are out of phase with different phase relations.
The stiffness of the lacing wire and its location with respect to the blade make
great contributions towards certain mode clusters in terms of mode shapes and natural
The nonlinearity of the stiffness of the deformed lacing wire caused by
centrifugal force was established. The coupling of this non linearity with different
vibration amplitudes, due to different phase relation, results in the dynamic mistuning
in lacing wire stiffness. This mistuning is considered to be a major attribute in
reducing the responses at resonance.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.