Publications
137 results found
Salles L, Staples B, Hoffmann NP, et al., 2016, 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
Grolet A, Hoffmann N, Thouverez F, et al., 2016, Travelling and standing envelope solitons in discrete non-linear cyclic structures, Mechanical Systems and Signal Processing, Vol: 81, Pages: 75-87, ISSN: 0888-3270
Envelope solitons are demonstrated to exist in non-linear discrete structures with cyclic symmetry. The analysis is based on the Non-Linear Schrodinger Equation for the weakly non-linear limit, and on numerical simulation of the fully non-linear equations for larger amplitudes. Envelope solitons exist for parameters in which the wave equation is focussing and they have the form of shape-conserving wave packages propagating roughly with group velocity. For the limit of maximum wave number, where the group velocity vanishes, standing wave packages result and can be linked via a bifurcation to the non-localised non-linear normal modes. Numerical applications are carried out on a simple discrete system with cyclic symmetry which can be seen as a reduced model of a bladed disk as found in turbo-machinery.
Di Maio D, Schwingshackl C, Sever IA, 2016, Development of a test planning methodology for performing experimental model validation of bolted flanges, Nonlinear Dynamics, Vol: 83, Pages: 983-1002, ISSN: 0924-090X
This work presents a strategy for testing and validating structures connected together with bolted joints, which are the most common components in mechanical structures. Considering the great number of coupled mechanical structures and research studies on this subject, the authors focused this research work on bolted flanges of aircraft engine casings. In fact, the coupling of engine casings is generally obtained by a large number of joints which assure the correct sealing at the flanges’ interfaces. From a finite element (FE) modelling perspective, joints are often modelled by either rigid connections or springs, otherwise incurring a very expensive computational time. This modelling approach is not a problem when dealing with low amplitude levels of vibrations. For higher levels of vibrations, joints and flanges cannot be considered rigidly connected and that exerted flexibility at the joints’ area can determine nonlinear dynamic behaviour. This work aims to study the dynamic behaviour of bolted flanges by using modal testing performed under controlled response amplitude. Two test structures, (1) a simple bolted flange test case and (2) a sector of a Rolls-Royce aero-engine casing, are tested under high level of vibrations. Both test structures are modelled by FE method, and nonlinear elements are used for modelling the flanges’ interfaces so as to perform prediction of nonlinear responses. These predictions are eventually correlated with the measured data.
Armand J, Pesaresi L, Salles L, et al., 2016, A multi-scale approach for nonlinear dynamic response predictions with fretting wear
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.
Salles L, Swacek C, Lacayo RM, et 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.
Stender M, Papangelo A, Allen M, et al., 2016, Structural Design with Joints for Maximum Dissipation, 34th IMAC Conference and Exposition on Structural Dynamics, Publisher: SPRINGER, Pages: 179-187, ISSN: 2191-5644
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- Citations: 6
Ondra V, Riethmueller R, Brake M, et al., 2016, Comparison of nonlinear system identification methods for free decay measurements with application to MEMS devices, International Conference on Noise and Vibration Engineering (ISMA) / International Conference on Uncertainty in Structural Dynamics (USD), Publisher: KATHOLIEKE UNIV LEUVEN, DEPT WERKTUIGKUNDE, Pages: 2547-2547
Gross J, Armand J, Lacayo RM, et 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
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- Citations: 7
Lacayo RM, Pesaresi L, Fochler D, et al., 2016, A numerical round robin to predict the dynamics of an experimentally-measured Brake-Reuss beam, International Conference on Noise and Vibration Engineering (ISMA) / International Conference on Uncertainty in Structural Dynamics (USD), Publisher: KATHOLIEKE UNIV LEUVEN, DEPT WERKTUIGKUNDE, Pages: 2545-2545
Grolet A, Hoffmann NP, Schwingshackl C, 2015, Solitons in Non-Linear Cyclic Systems, Euromech Colloquium 573: Coupling and Nonlinear Interactions in Rotating Machinery
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.
Ruffini V, Schwingshackl C, Green J, 2015, Experimental and Analytical Study of Coriolis Effects in Bladed Disk, ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Publisher: American Society of Mechanical Engineers
Modern aero-engines have reached a high level of sophistication and only significant changes will lead to the improvements necessary to achieve the economic and environmental targets of the future. Open rotors constitute a major leap in this direction, both in terms of efficiency and of technological innovation. This calls for a revision of the accepted design practices, and a new focus on phenomena that have been little investigated in the past, such as the Coriolis effect, or the gyroscopic coupling of the blades with the shaft. Experimental results from modern fans, with large blades and strong stagger angles, are showing dependence on Coriolis gyroscopic effects already, an effect that is expected to be strongly enhanced with the proposed open rotor designs.For an accurate prediction of the Coriolis and gyroscopic effects in rotating assemblies a fully experimentally validated approach is needed. Today’s FE models can capture the basic physical phenomena, but experimental confirmation is still needed for the evolution of the mode shapes with angular speed, and the influence of damping and geometric nonlinearities when gyroscopic coupling is considered. To support this validation effort a new rotating test rig will be introduced, initial measurement data will be discussed, and a comparison with a finite element analysis presented.Different forcing patterns, including forward and backward travelling-wave engine order excitation could be experimentally excited in the new rig, Coriolis-induced frequency splits were found in the dynamic response, showing a significant change in the dynamic behaviour of the investigated dummy disk, and only a minor impact of the mistuning was observed on the frequency splits due to Coriolis effects. The experimental results have been compared to a finite element analysis, and after some updating a good agreement between the predicted and measured Campbell diagrams could be obtained, demonstrating the reliability of the modelling
Ruffini V, Schwingshackl CW, Green JS, 2015, Prediction capabilities of coriolis and gyroscopic effects in current finite element software, Pages: 1853-1862, ISSN: 2211-0984
The progress towards a whole-engine design philosophy and the development of new technologies like open rotors, where coupled behaviour due to Coriolis and gyroscopic effects could be more pronounced, calls for an assessment of the prediction capabilities currently available in commercial FE software packages. Finite element models including these rotational effects are rarely used in simulations of bladed disc-shaft assemblies, and the confidence in FE codes to provide reliable frequency and mode shape data can therefore be improved. Different models were used as benchmark test cases in the evaluation, including the classic Stodola-Green rotor, and a blade-disc-shaft assembly, and the resulting Campbell diagrams were compared to analytical solutions from the literature. The ability of the codes to exploit the cyclic symmetry of bladed discs for computational efficiency was also assessed. The results show that all investigated codes are able to capture the Coriolis-induced frequency splits, but discrepancies arise at high speeds and in the vicinity of instabilities.
Panunzio AM, Salles L, Schwingshackl C, et 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
Peradotto E, Panunzio AM, Salles L, et al., 2015, STOCHASTIC METHODS FOR NONLINEAR ROTORDYNAMICS WITH UNCERTAINTIES, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
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- Citations: 6
Pesaresi L, Schwingshackl CW, 2014, Automated Measurement Grid Generation for Scanning Laser Doppler Vibrometers, Pages: 645-653, ISSN: 2191-5644
Full field measurement techniques can provide fast, accurate and detailed vibration response data for finite element model validation and are being wildly used in industrial applications. A Scanning Laser Doppler Vibrometer (SLDV) measures the full field operating deflection shapes of a structure by changing the location of the laser spot on the target surface. However the setup of a measurement and in particular the measurement grid definition, can take up a significant part of the overall measurement time. To optimise the setup time a novel technique for SLDV measurement grids has been developed. The suggested method includes an automated identification of the vibrating target, based on the measured vibration signal of a scan covering the entire field of view of the LDV. Alpha-shape techniques for target identification and geometric algorithms for shape recognition are used to define the measurement area. Novel approaches for symmetry and orientation capture allow the generation of point grids and continuous patterns for various target shapes. The introduced approach allows a quick SLDV setup of the full field scan with a minimum input from the user. © The Society for Experimental Mechanics 2014.
Schwingshackl CW, Joannin C, Pesaresi L, et al., 2014, Test method development for nonlinear damping extraction of dovetail joints, ISSN: 2191-5644
The traditional measurement techniques to acquire the linear dynamic response of a single component are well established and have been in use for many decades to provide reliable input data for model updating. The measurement of assembled structures normally follows a very similar approach, although the presence of joints can introduce a nonlinear dynamic behaviour, which impacts the measurement results. Applying traditional linear test methods to a highly nonlinear structure, such as a dovetail joint in an aircraft engine blade-disk connection, does not necessarily take the special features of the nonlinear response into account and may lead to unreliable data. This is particularly true, if modal information such as damping are required. The influence of the measurement setup and the test procedures must be well understood for an accurate measurement. In this paper the influence of the different measurement components on a simple clamped beam and a compressor blade dove tail test rig will be investigated. A particular focus will be on the support of the test rig, the location and control of the excitation and the influence of the accelerometer on the response. Based on the findings an approach will be recommended that allows a reliable measurement of the dynamic behaviour of this heavily nonlinear structure.
Schwingshackl CW, D'Antonio G, Tacconelli S, et al., 2014, Automated full field measurement system for nonlinear model validation, International Conference on Noise and Vibration Engineering (ISMA), Publisher: KATHOLIEKE UNIV LEUVEN, DEPT WERKTUIGKUNDE, Pages: 885-893
Botta F, Dini D, Schwingshackl C, et al., 2013, Optimal Placement of Piezoelectric Plates to Control Multimode Vibrations of a Beam, Advances in Acoustics and Vibration, Vol: 2013, ISSN: 1687-627X
Damping of vibrations is often required to improve both the performance and the integrity of engineering structures, for example, gas turbine blades. In this paper, we explore the possibility of using piezoelectric plates to control the multimode vibrations of a cantilever beam. To develop an effective control strategy and optimize the placement of the active piezoelectric elements in terms of vibrations amplitude reduction, a procedure has been developed and a new analytical solution has been proposed. The results obtained have been corroborated by comparison with the results from a multiphysics finite elements package (COMSOL), results available in the literature, and experimental investigations carried out by the authors. © 2013 Fabio Botta et al.
Schwingshackl CW, Di Maio D, Sever I, et al., 2013, Modeling and Validation of the Nonlinear Dynamic Behavior of Bolted Flange Joints, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 135, ISSN: 0742-4795
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- Citations: 55
Di Maio D, Bennett P, Schwingshackl C, et al., 2013, Experimental non-linear modal testing of an aircraft engine casing assembly, Pages: 15-36, ISSN: 2191-5644
This paper aims to present experimental work on an aircraft engine casing assembly. Nowadays single components of casings can be modeled with such high accuracy that they can be validated by carrying out the model validation process using measured data from a sector of the entire assembly. This smart validation process can be achieved by carrying out the modal analysis with a Scanning LDV (Laser Doppler Vibrometer) system which allows good spatial resolution of the measured mode shapes. The validation process can be assumed valid under linear response conditions obtainable for low vibration amplitudes. Casings are typically connected together by joints which may or may not respond non-linearly under high levels of vibration. Therefore, prior to conducting any non-linear validation, the mode(s) responding non-linearly must be identified beforehand in order to correctly specify the non-linear modal testing required. The work presented here will use a large civil engine casing assembly comprising a Combustion Chamber Outer Casing (CCOC), High Intermediate Pressure Turbine Casing (HIPTC) and Low Pressure Turbine Casing (LPTC.) The Fine Mesh Finite Element Model (FMFEM) was successfully validated using linear modal analysis test data. One of the objectives of this work is to define the key points for conducting non-linear modal testing of such large casing assemblies and sub-assemblies. One outcome of the experimental work was a set of recommendations for performing measurements, which should be carried out within the frequency bandwidth selected during the model validation process. Experimentally derived non-linear response curves arc presented in this paper. © The Society for Experimental Mechanics, Inc. 2013.
Ruffini V, Schwingshackl CW, Green JS, 2013, LDV measurement of local nonlinear contact conditions of flange joint, Pages: 159-168, ISSN: 2191-5644
The traditional approach to evaluating the linear dynamic behavior of structures for modal validation is based on the acquisition of frequency response functions and their modal analysis. With small modifications, a similar technique can be used to validate nonlinear response predictions. The use of nonlinear dynamic analysis of flange joints for sealing and wear predictions makes it necessary to also provide validation information for the localised nonlinear mechanisms at the contact surface. For this purpose, a technique based on two Laser Doppler Vibrometers has been developed. The experimental set-up can provide data of the relative out-of-plane displacement of the bolted flange joint during a vibration cycle, which indicates contact separation and permanent gap locations. The observed influence of different excitation levels and bolt torques on the global and local dynamic response led to an understanding of the nonlinear behaviour of the flange and of the local contact conditions. © The Society for Experimental Mechanics, Inc. 2013.
Giuliani P, Di Maio D, Schwingshackl CW, et al., 2013, Six degrees of freedom measurement with continuous scanning laser doppler vibrometer, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, Vol: 38, Pages: 367-383, ISSN: 0888-3270
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- Citations: 25
Salles L, Schwingshackl C, Green J, 2013, Modelling friction contacts in nonlinear vibration of bladed disks
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- Citations: 1
Schwingshackl CW, Di Maio D, Green JS, 2013, MODELLING AND VALIDATION OF THE NONLINEAR DYNAMIC BEHAVIOUR OF BOLTED FLANGE JOINTS, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
Botta F, Marx N, Schwingshackl C, et al., 2013, A WIRELESS VIBRATION CONTROL TECHNIQUE FOR GAS TURBINE BLADES USING PIEZOELECTRIC PLATES AND CONTACTLESS ENERGY TRANSFER, PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2013, VOL 7A
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- Citations: 6
Schwingshackl CW, Petrov EP, 2012, Modeling of Flange Joints for the Nonlinear Dynamic Analysis of Gas Turbine Engine Casings, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 134, ISSN: 0742-4795
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- Citations: 25
Schwingshackl CW, 2012, Measurement of friction contact parameters for nonlinear dynamic analysis, Pages: 167-177, ISSN: 2191-5644
Detailed linear finite element simulations and accurate modal testing techniques ensure a reliable validation of linear dynamic response predictions of engineering structures. The good agreement between simulation and measurement for single components is often diminished when an assembly is considered, since nonlinear effects of the joints influence the response behaviour. To re-establish the agreement between analysis and measurement the nonlinear behaviour must be included in the simulation. Analysis tools are available today to take these nonlinear effects into account which require accurate input parameters, to represent the nonlinear contact interface. Research at Imperial College London has focused on the reliable measurement of the dynamic friction contact parameters for over a decade. The extraction of the dynamic friction coefficient, μ, and the tangential contact stiffness, k t, requires the measurement of the nonlinear hysteresis loop with a minimum interference from the test rig. A newly developed friction, with a high test accuracy and a large test range will be presented and its behaviour compared to previous data. © The Society for Experimental Mechanics, Inc. 2012.
Schwingshackl CW, Petrov EP, Ewins DJ, 2012, Measured and estimated friction interface parameters in a nonlinear dynamic analysis, Mechanical Systems and Signal Processing, Vol: 28, Pages: 574-584, ISSN: 0888-3270
The modelling of nonlinear friction contact interfaces in structural dynamics currently attracts large research interest since the accurate characteristics of the friction interfaces are required in the nonlinear dynamic analysis of assembled structures. For an accurate representation of friction contact interfaces it is important to ensure that a sufficient number of parameters are provided to characterise all aspects of the friction contacts that the measured values are accurate and reliable, and that the contact parameters are interpreted and used correctly in the numerical modelling of the contact interfaces. This investigation focused on three major parameters used in the nonlinear friction contact analysis: (i) the friction coefficient, (ii) the tangential contact stiffness, and (iii) the normal load distribution in the contact. The accuracy of the measured friction input parameters is evaluated and possibilities to obtain reliable normal load distributions for a successful prediction of the measured frequency response function are investigated. Average friction input parameters, based on a large set of experimental data, are introduced, and their effect on the nonlinear resonance response is discussed.
Schwingshackl CW, Petrov EP, Ewins DJ, 2012, Effects of Contact Interface Parameters on Vibration of Turbine Bladed Disks With Underplatform Dampers, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 134, ISSN: 0742-4795
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- Citations: 48
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