Imperial College London

DrLoicSalles

Faculty of EngineeringDepartment of Mechanical Engineering

Research Fellow
 
 
 
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Contact

 

+44 (0)20 7594 2243l.salles Website

 
 
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Assistant

 

Mr Peter Higgs +44 (0)20 7594 7078

 
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Location

 

556City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

59 results found

Lu Y, Zhao F, Salles L, Vandati Met al., 2017, AEROELASTIC ANALYSIS OF NREL WIND TURBINE, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Panunzio AM, Salles L, Schwingshackl CW, 2016, Uncertainty propagation for nonlinear vibrations: A non-intrusive approach, JOURNAL OF SOUND AND VIBRATION, Vol: 389, Pages: 309-325, ISSN: 0022-460X

Journal article

Salles L, Vahdati M, 2016, Comparison of Two Numerical Algorithms for Computing the Effects of Mistuning of Fan Flutter, ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition

Conference paper

Pesaresi L, Salles L, Jones A, Green JS, Schwingshackl CWet al., 2016, Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications, Mechanical Systems and Signal Processing, Vol: 85, Pages: 662-679, ISSN: 1096-1216

Underplatform dampers (UPD) are commonly used in aircraft engines to mitigate the risk of high-cycle fatiguefailure of turbine blades. The energy dissipated at the friction contact interface of the damper reduces the vibrationamplitude significantly, and the couplings of the blades can also lead to significant shifts of the resonance frequenciesof the bladed disk. The highly nonlinear behaviour of bladed disks constrained by UPDs requires an advancedmodelling approach to ensure that the correct damper geometry is selected during the design of the turbine, and thatno unexpected resonance frequencies and amplitudes will occur in operation. Approaches based on an explicit modelof the damper in combination with multi-harmonic balance solvers have emerged as a promising way to predict thenonlinear behaviour of UPDs correctly, however rigorous experimental validations are required before approaches ofthis type can be used with confidence.In this study, a nonlinear analysis based on an updated explicit damper model having different levels of detail isperformed, and the results are evaluated against a newly-developed UPD test rig. Detailed linear finite element modelsare used as input for the nonlinear analysis, allowing the inclusion of damper flexibility and inertia effects. The nonlinearfriction interface between the blades and the damper is described with a dense grid of 3D friction contact elementswhich allow accurate capturing of the underlying nonlinear mechanism that drives the global nonlinear behaviour. Theintroduced explicit damper model showed a great dependence on the correct contact pressure distribution. The use ofan accurate, measurement based, distribution, better matched the nonlinear dynamic behaviour of the test rig. Goodagreement with the measured frequency response data could only be reached when the zero harmonic term (constantterm) was included in the multi-harmonic expansion of the nonlinear problem, highlighting its importance when thecontact inter

Journal article

Armand J, Pesaresi L, Salles L, Schwingshackl CWet al., 2016, A Multiscale Approach for Nonlinear Dynamic Response Predictions With Fretting Wear, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 139, ISSN: 0742-4795

Journal article

Salles L, Staples B, Hoffmann N, Schwingshackl Cet al., 2016, Continuation techniques for analysis of whole aeroengine dynamics with imperfect bifurcations and isolated solutions, Nonlinear Dynamics, Vol: 86, Pages: 1897-1911, ISSN: 0924-090X

The analysis of whole engine rotordynamic models is an important element in the design of aerojet engines. The models include gyroscopic effects and allow for rubbing contact between rotor and stator components such as bladed discs and casing. Due to the nonlinearities inherent to the system, bifurcations in the frequency response may arise. Reliable and efficient methods to determine the bifurcation points and solution branches are required. For this purpose, a multi-harmonic balance approach is presented that allows a numerically efficient detection of bifurcation points and the calculation of both continuous and isolated branches of the frequency response functions. The method is applied to a test case derived from a commercial aeroengine. A bifurcation structure with continuous and isolated solution branches is observed and studied in this paper. The comparison with time marching based on simulations shows both accuracy and numerical efficiency of the newly developed approach.

Journal article

Papangelo A, Grolet A, Salles L, Hoffmann N, Ciavarella Met al., 2016, Snaking bifurcations in a self-excited oscillator chain with cyclic symmetry, Communications in Nonlinear Science and Numerical Simulation, Vol: 44, Pages: 108-119, ISSN: 1007-5704

Snaking bifurcations in a chain of mechanical oscillators are studied. The individual oscillators are weakly nonlinear and subject to self-excitation and subcritical Hopf-bifurcations with some parameter ranges yielding bistability. When the oscillators are coupled to their neighbours, snaking bifurcations result, corresponding to localised vibration states. The snaking patterns do seem to be more complex than in previously studied continuous systems, comprising a plethora of isolated branches and also a large number of similar but not identical states, originating from the weak coupling of the phases of the individual oscillators.

Journal article

Armand J, Pesaresi L, Salles L, Schwingshackl CWet al., 2016, A multi-scale approach for nonlinear dynamic response predictions with fretting wear, Journal of Engineering for Gas Turbines and Power, Vol: 139, ISSN: 0742-4795

Accurate prediction of the vibration response of aircraft engine assemblies is of great importance when estimating both the performance and the lifetime of their individual components. In the case of underplatform dampers, for example, the motion at the frictional interfaces can lead to a highly nonlinear dynamic response and cause fretting wear at the contact. The latter will change the contact conditions of the interface and consequently impact the nonlinear dynamic response of the entire assembly. Accurate prediction of the nonlinear dynamic response over the lifetime of the assembly must include the impact of fretting wear. A multi-scale approach that incorporates wear into the nonlinear dynamic analysis is proposed, and its viability is demonstrated for an underplatform damper system. The nonlinear dynamic response is calculated with a multiharmonic balance approach, and a newly developed semi-analytical contact solver is used to obtain the contact conditions at the blade-damper interface with high accuracy and low computational cost. The calculated contact conditions are used in combination with the energy wear approach to compute the fretting wear at the contact interface. The nonlinear dynamic model of the blade-damper system is then updated with the worn profile and its dynamic response is recomputed. A significant impact of fretting wear on the nonlinear dynamic behaviour of the blade-damper system was observed, highlighting the sensitivity of the nonlinear dynamic response to changes at the contact interface. The computational speed and robustness of the adopted multi-scale approach are demonstrated.

Journal article

Krack M, Salles L, Thouverez F, 2016, Vibration Prediction of Bladed Disks Coupled by Friction Joints, Archives of Computational Methods in Engineering, Pages: 1-48, ISSN: 1134-3060

The present review article addresses the vibration behavior of bladed disks encountered e.g. in aircraft engines as well as industrial gas and steam turbines. The utilization of the dissipative effects of dry friction in mechanical joints is a common means of the passive mitigation of structural vibrations caused by aeroelastic excitation mechanisms. The prediction of the vibration behavior is a scientific challenge due to (a) the strongly nonlinear contact interactions involving local sticking, sliding and liftoff, (b) the model order required to accurately describe the dynamic behavior of the assembly, and (c) the multi-disciplinary character of the problem associated with the need to account for structural mechanical as well as fluid dynamical effects. The purpose of this article is the overview and discussion the current state of the art of vibration prediction approaches. The modeling approaches in this work embrace the description of the rotating bladed disk, the contact modeling, the consideration of aeroelastic effects, appropriate model order reduction techniques and the exploitation of the rotationally periodic nature of the problem. The simulation approaches cover the direct computation of periodic, steady-state externally forced and self-excited vibrations using the high-order harmonic balance method, the formulation of the contact problem in the frequency domain, methods for the solution of the governing algebraic equations and advanced simulation approaches, including the concept of nonlinear modes.

Journal article

Salles L, Staples B, Hoffmann NP, Schwingshacklet al., Nonlinear dynamic analysis of whole aeroengine models with harmonic balance method and continuation techniques for imperfect bifurcations and isolated solutions., Nonlinear Dynamics, ISSN: 1573-269X

The analysis of whole engine rotor-dynamic models is an important element in the design of aerojetengines. The models include gyroscopic effects and allow for rubbing contact between rotor and statorcomponents such as bladed discs and casing. Due to the non-linearities inherent to the system, bifurcationsin the frequency response may arise. Reliable and efficient methods to determine the bifurcation pointsand solution branches are required. For this purpose a multi-harmonic balance approach is presented thatallows a numerically efficient detection of bifurcation points and the calculation of both continuous andisolated branches of the frequency response functions. The method is applied to a test-case derived from acommercial aero-engine. A bifurcation structure with continuous and isolated solution branches is observedand studied in this paper. The comparison with time-marching based on simulations shows both accuracyand numerical efficiency of the newly developed approach

Journal article

Salles L, Swacek C, Lacayo RM, Reuss P, Brake MRW, Schwingshackl CWet al., 2016, Numerical round robin for prediction of dissipation in lap joints, 33rd IMAC, A Conference and Exposition on Structural Dynamics, 2015, Publisher: Springer, Pages: 53-64, ISSN: 2191-5644

Joints, interfaces, and frictional contact between two substructures can be modelled as discrete nonlinearities that connect the substructures. Over the past decade, a number of phenomenologically different approaches to modelling and simulating the dynamics of a jointed structure have been proposed. This research focuses on assessing multiple modelling techniques to predict the nonlinear dynamic behaviour of a bolted lab joint, including frequency based sub-structuring methods, harmonic balance methods, discontinuous basis function methods, and high fidelity FEA approaches. The regimes in which each method is best suited are identified, and recommendations are made for how to select a modelling method and for advancing numerical modelling of discrete nonlinearities.

Conference paper

Gross J, Armand J, Lacayo RM, Reuss P, Salles L, Schwingshackl CW, Brake MRW, Kuether RJet al., 2016, A Numerical Round Robin for the Prediction of the Dynamics of Jointed Structures, Editors: Allen, Mayes, Rixen, Publisher: SPRINGER, Pages: 195-211, ISBN: 978-3-319-29762-0

Book chapter

Armand J, Pesaresi L, Salles L, Schwingshackl CWet al., 2016, A multi-scale approach for nonlinear dynamic response predictions with fretting wear

© Copyright 2016 by ASME. Accurate prediction of the vibration response of aircraft engine assemblies is of great importance when estimating both the performance and the lifetime of its individual components. In the case of underplatform dampers, for example, the motion at the frictional interfaces can lead to a highly nonlinear dynamic response and cause fretting wear at the contact. The latter will change the contact conditions of the interface and consequently impact the nonlinear dynamic response of the entire assembly. Accurate prediction of the nonlinear dynamic response over the lifetime of the assembly must include the impact of fretting wear. A multi-scale approach that incorporates wear into the nonlinear dynamic analysis is proposed, and its viability is demonstrated for an underplatform damper system. The nonlinear dynamic response is calculated with a multiharmonic balance approach, and a newly developed semi-Analytical contact solver is used to obtain the contact conditions at the blade-damper interface with high accuracy and low computational cost. The calculated contact conditions are used in combination with the energy wear approach to compute the fretting wear at the contact interface. The nonlinear dynamic model of the blade-damper system is then updated with the worn profile and its dynamic response is recomputed. A significant impact of fretting wear on the nonlinear dynamic behaviour of the blade-damper system was observed, highlighting the sensitivity of the nonlinear dynamic response to changes at the contact interface. The computational speed and robustness of the adopted multi-scale approach are demonstrated.

Conference paper

Wu L, Krattiger D, Zacharczuk M, Buck M, Kuether R, Allen M, Brake M, Tiso P, Reuss P, Salles Let al., 2016, Evaluation of interface reductions for Craig Bampton substructured models, International Conference on Noise and Vibration Engineering (ISMA) / International Conference on Uncertainty in Structural Dynamics (USD), Publisher: KATHOLIEKE UNIV LEUVEN, DEPT WERKTUIGKUNDE, Pages: 2549-2549

Conference paper

Vahdati M, Salles L, 2015, The effects of mistuning on Fan flutter, The 14th International Symposium on Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines

The aim of this paper is to study the effects ofmistuning on fan flutter. The computations are basedon a three-dimensional, whole assembly, timeaccurate,viscous, finite-volume compressible flowsolver. The unsteady flow cases are computed asReynolds-averaged Navier–Stokes, with the basicassumption that the frequencies of interest aresufficiently far away from the frequencies ofturbulent flow structures. The overall solutionmethod is implicit, with second-order accuracy inspace and time. A rig wide-chord fan blade, typical ofmodern civil designs, was used as the benchmarkgeometry for this study. There are 20 blades in thefan assembly. A random pattern frequency mistuningwas used in most of analysis undertaken in thispaper. The 1F mode shapes are the same for allmistuned blades. The objectives of this work are:1. To check if the introduction of mistuning wouldbring the experimental and computed flutterboundaries closer2. To explain how mistuning provide stability3. Establish a relationship between mistuning anddamping4. Provide a data base which can be used in futurefor testing simple mistuning models

Conference paper

Armand J, Salles L, Schwingshackl CW, 2015, Numerical Simulation of Partial Slip Contact Using a Semi-Analytical Method, 27th Conference on Mechanical Vibration and Noise, Publisher: American Society of Mechanical Engineers

Almost all mechanical structures consist of an assembly of components that are linked together with joints. If such a structure experiences vibration during operation, micro-sliding can occur in the joint, resulting in fretting wear. Fretting wear affects the mechanical properties of the joints over their lifetime and as a result impacts the non-linear dynamic response of the system. For accurate prediction of the non-linear dynamic response over the lifetime of the structure, fretting wear should be considered in the analysis.Fretting wear studies require an accurate assessment of the stresses and strains in the contacting surfaces of the joints. To provide this information, a contact solver based on the semi-analytical method has been implemented in this study. By solving the normal and tangential contact problems between two elastic semi-infinite bodies, the contact solver allows an accurate calculation of the pressure and shear distributions as well as the relative slips in the contact area. The computed results for a smooth spherical contact between similar elastic materials are presented and validated against analytical solutions. The results are also compared with those obtained from finite element simulations to demonstrate the accuracy and computational benefits of the semi-analytical method. Its capabilities are further illustrated in a new test case of a cylinder with rounded edges on a flat surface, which is a more realistic contact representation of an industrial joint.

Conference paper

Panunzio AM, Salles L, Schwingshackl C, Gola Met al., 2015, ASYMPTOTIC NUMERICAL METHOD AND POLYNOMIAL CHAOS EXPANSION FOR THE STUDY OF STOCHASTIC NON-LINEAR NORMAL MODES, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Peradotto E, Panunzio AM, Salles L, Schwingshackl Cet al., 2015, STOCHASTIC METHODS FOR NONLINEAR ROTORDYNAMICS WITH UNCERTAINTIES, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Salles L, Schwingshackl C, Green J, 2013, Modelling friction contacts in nonlinear vibration of bladed disks

Conference paper

Temis YM, Salles L, 2012, Efficient CSM/CFD method for aeroelasticity stability analys of turbomachne blades

The problem of blade flutter prediction is relevant on the engine design stage. Modern technology of multidisciplinary simulation that combines the vibrating blade model and the response model of gas flow in gas dynamic tract is used in present paper to determine the influence of flow parameters on natural modes and frequencies. Geometrically nonlinear aeroelastic blade models (pre-twisted beam, shell and 3D solid body) that consider aerodynamic stiffness in the blade assembly are implemented. Aerodynamic stiffness coefficients are calculated on the base of CFD simulation results. Stability analysis for typical compressor and turbine blades is carried out. It is demonstrated, that centrifugal loads and flow speed change blade natural frequencies and modes, what has an influence on blade sensitivity to flutter. It is shown that connection between blade second bending and first torsion natural modes defines the condition of blade bending-torsion flutter initiation.

Conference paper

Salles L, Blanc L, Thouverez F, Gouskov AM, Jean Pet al., 2012, DUAL TIME STEPPING ALGORITHMS WITH THE HIGH ORDER HARMONIC BALANCE METHOD FOR CONTACT INTERFACES WITH FRETTING-WEAR, ASME Turbo Expo 2011, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 913-921

Conference paper

Salles L, Blanc L, Thouverez F, Gouskov AM, Jean Pet al., 2011, Dual Time Stepping Algorithms With the High Order Harmonic Balance Method for Contact Interfaces With Fretting-Wear, Journal of Engineering for Gas Turbines and Power, Vol: 134, Pages: 032503-032503, ISSN: 0742-4795

Journal article

Salles L, Blanc L, Thouverez F, Gouskov AMet al., 2011, Dynamic analysis of fretting-wear in friction contact interfaces, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, Vol: 48, Pages: 1513-1524, ISSN: 0020-7683

Journal article

Salles L, Blanc L, Thouverez F, Gouskov AM, Jean Pet al., 2010, Multiscale analysis of fretting-wear under dynamical loading, MECANIQUE & INDUSTRIES, Vol: 11, Pages: 277-282, ISSN: 1296-2139

Journal article

Salles L, Blanc L, Thouverez F, Gouskov AMet al., 2010, Dynamic Analysis of Fretting-Wear in Friction Contact Interfaces, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 132, ISSN: 0742-4795

Journal article

Salles L, Gouskov AM, Blanc L, Thouverez F, Jean Pet al., 2010, DYNAMIC ANALYSIS OF FRETTING-WEAR IN JOINT INTERFACE BY A MULTISCALE HARMONIC BALANCE METHOD COUPLED WITH EXPLICIT OR IMPLICIT INTEGRATION SCHEMES, ASME Turbo Expo 2010, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1003-1013

Conference paper

Salles L, Blanc L, Thouverez F, Gouskov AM, Jean Pet al., 2009, DYNAMIC ANALYSIS OF A BLADED DISK WITH FRICTION AND FRETTING-WEAR IN BLADE ATTACHMENTS, 54th ASME Turbo Expo 2009, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 465-476

Conference paper

Salles L, Blanc L, Thouverez F, Gouskov AMet al., 2008, DYNAMIC ANALYSIS OF FRETTING-WEAR IN FRICTION CONTACT INTERFACES, 53rd ASME Turbo Expo 2008, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 543-554

Conference paper

Laxalde D, Salles L, Blanc L, Thouverez Fet al., 2008, NON-LINEAR MODAL ANALYSIS FOR BLADED DISKS WITH FRICTION CONTACT INTERFACES, 53rd ASME Turbo Expo 2008, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 457-467

Conference paper

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