Nonlinear dynamics of jointed structures: a multiscale approach to predict fretting wear and its effects on the dynamic response
File(s)
Author(s)
Armand, Jason
Type
Thesis
Abstract
Accurate prediction of the vibration response of friction joints is of great importance
when estimating both the performance and the life of built-up structures. The relative
motion at the frictional interfaces can lead to a highly nonlinear dynamic response and
cause fretting wear at the contact. The latter, by changing the contact surface geometry,
affects the contact conditions of the interface and consequently impacts the nonlinear
dynamic response of the entire assembly, which today is ignored in the analysis.
To address the above issue, a novel multiscale approach that incorporates wear
into the nonlinear dynamic analysis is presented. A contact solver, based on boundary
integral equations, is implemented to compute local contact stresses and stiffness
which, in combination with an energy wear approach, allow to compute fretting wear
at the contact interface. The nonlinear dynamic response of the whole system is
computed using a multi-harmonic balance approach and a continued iteration between
the contact and nonlinear dynamic solvers allows the prediction of the nonlinear
dynamic response over time.
After describing its implementation in detail, the contact solver results are fully
verified against a range of test cases for which an analytical solution is available. A
comparison against finite element simulations demonstrates the accuracy and computational
benefits of the implemented solver. The limitations of the solver due to its
underlying half-space assumption are also discussed.
The proposed multiscale approach is applied to an underplatform damper-blade
system. A significant impact of fretting wear on the nonlinear dynamic behaviour of the
blade-damper system is observed, highlighting the sensitivity of the nonlinear dynamic
response to changes at the contact interface due to wear. A strong effect of rough
interfaces on the wear rate and the resulting interface parameters was also discovered,
making them a crucial component for nonlinear dynamic response predictions over
time.
when estimating both the performance and the life of built-up structures. The relative
motion at the frictional interfaces can lead to a highly nonlinear dynamic response and
cause fretting wear at the contact. The latter, by changing the contact surface geometry,
affects the contact conditions of the interface and consequently impacts the nonlinear
dynamic response of the entire assembly, which today is ignored in the analysis.
To address the above issue, a novel multiscale approach that incorporates wear
into the nonlinear dynamic analysis is presented. A contact solver, based on boundary
integral equations, is implemented to compute local contact stresses and stiffness
which, in combination with an energy wear approach, allow to compute fretting wear
at the contact interface. The nonlinear dynamic response of the whole system is
computed using a multi-harmonic balance approach and a continued iteration between
the contact and nonlinear dynamic solvers allows the prediction of the nonlinear
dynamic response over time.
After describing its implementation in detail, the contact solver results are fully
verified against a range of test cases for which an analytical solution is available. A
comparison against finite element simulations demonstrates the accuracy and computational
benefits of the implemented solver. The limitations of the solver due to its
underlying half-space assumption are also discussed.
The proposed multiscale approach is applied to an underplatform damper-blade
system. A significant impact of fretting wear on the nonlinear dynamic behaviour of the
blade-damper system is observed, highlighting the sensitivity of the nonlinear dynamic
response to changes at the contact interface due to wear. A strong effect of rough
interfaces on the wear rate and the resulting interface parameters was also discovered,
making them a crucial component for nonlinear dynamic response predictions over
time.
Version
Open Access
Date Issued
2017-10
Date Awarded
2018-03
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Schwingshackl, Christoph
Dini, Daniele
Sponsor
Innovate UK
Rolls-Royce plc.
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)