Etienne Balmes

SDTools

Brake squeal is a limit cycle vibration induced by mode coupling instability that depends on operating conditions such as applied pressure, temperature, and disc velocity. This work proposes a simplified functional model of brake squeal that reproduces the main characteristics observed in a full-scale industrial test campaign: vibration growth, lim...

Viscoelastic materials are widely used in many industries for their ability to undergo large deformation and dissipate energy. Pads placed between rail and sleeper experience large deformation when the train passes. This is important for load distribution to the sleepers. They also strongly contribute to vibration damping, and thus to lowering nois...

NVH compliance issues related to brake squeal constitute nowadays a major cost in industry. Simulation remains very challenging, brake systems being complex assemblies operating in various conditions. Industrial applications rely on Complex Eigenvalue Analysis (CEA) whose recurrent correlation to squeal measurements makes it a relevant working basi...

Many systems have vibration properties, modes and non-linear limit cycles, that are significantly affected by environmental properties such as temperature, pressure, rotation speed, ... The classical testing strategy is to select a number of fixed operating conditions, wait for the system to stabilize at each condition and extract the vibration cha...

Since tests only provide measurements at sensors, it is interesting to use models to estimate the response at all degree of freedom, correct measurement errors and possibly allow updating of model parameters. The paper gives an integrated perspective on methods developed by the control and structural dynamics communities and in particular methods s...

To analyze brake squeal, measurements are performed to extract Operational Deflection Shapes (ODS) characteristic of the limit cycle. The advantage of this strategy is that the real system behavior is captured, but measurements suffer from a low spatial distribution and hidden surfaces, so that interpretation is sometimes difficult. It is even more...

Rubber modeling is an old subject and so many models exist that it is difficult to have a clear vision of what exists and is more appropriate. Rather than attempting a standard review, this paper proposes classification using the traditional system modeling strategy, where raw measurements are either processed to obtain non-parametric models, or us...

Estimation of damping can be of great importance for turbomachines, where vibration based instabilities like flutter occur. The paper discusses a numerical method to predict the homogenized viscoelastic behavior of 3D woven composites, used in fan blades, from elementary constituent behavior. Yarn and weave microstructures are considered in a two s...

Structures composed of repetitions of multiple identical cells are common and have been the object of a large body of literature on waveguides, periodic media, and cyclic symmetry. Starting from a cell model, possibly with a large number of Degrees of Freedom both inside the cell and on its edges, the objective of this paper is to propose a Ritz-Ga...

In brake FEM, model updating is often needed to improve the model accuracy and well describe problematic phenomena such as the squeal. To avoid performing a full model updating which is often time consuming, the use of the Minimum Dynamic Residual Expansion method is proposed to help building the updating strategy. The procedure proposed in this pa...

NVH compliance issues related to brake squeal constitute nowadays a major cost in industry. Simulation remains very challenging, brake systems being complex assemblies operating in various conditions. Industrial applications rely on Complex Eigenvalue Analysis (CEA) whose recurrent correlation to squeal measurements makes it a relevant working basi...

In the presence of squeal, Operational Deflection Shapes (ODS) are classically performed to analyze behavior. A simple numeric example is used to show that two real shapes should dominate the response. This justifies an ad-hoc procedure to extract main shapes from the real brake time measurements. The presence of two shapes is confirmed despite var...

Understanding the dynamic behavior of the pantograph-catenary system is crucial for design improvement, but many factors influence the contact force, which is the main design objective. To give a proper understanding of dynamic characteristics, the paper uses a combination of mass drop tests on a catenary, analytic models and parametric finite elem...

In presence of squeal, Operational Deflection Shapes (ODS) are classically measured to gain understanding of brake behavior. A simple numeric example is analyzed to justify the use of time-frequency analysis and shows that two real shapes should probably dominate the response. Using measurements on a real brake, this expectation is shown to hold ev...

Extending the bandwidth of validity of FEM models used in vibroacoustic design is a generic objective of model generation processes. Achieving this objective requires a critical review of both testing and modeling processes. Using the case study of an engine cradle, tools used to detect modal test inconsistencies are first illustrated. On the model...

Electromechanical (EM) signature techniques have raised a huge interest in the structural health-monitoring community. These methods aim at assessing structural damages and sensors degradation by analyzing the EM responses of piezoelectric components bonded to aeronautic structures. These structures are subjected simultaneously to static loads and...

This paper presents numerical simulations and experimental studies on the frequency domain behaviour of railway track below 100 Hz, focusing on the link between the substructure properties of the track and its global dynamic response. A numerical method in the frequency domain is first proposed and used to understand the frequency response of a rai...

Squeal occurrences are quite common in brakes in production and involve coupling of modes. Detailed understanding of vibration patterns typically requires FEM models updated using test results. The process used at Chassis Brakes International typically starts by updating components so that the main sources of variability are associated with junctio...

The main objective of this paper is to present an innovative numerical tool to represent the track and platform dynamic behavior under passing trains. Dynavoie is currently being developed for engineering purposes at SNCF. It is specifically designed to correctly reproduce the track and platform dynamic behaviors in the time domain. This model is b...

A global sensitivity analysis is led on catenary parameters such as dropper lengths, height of the messenger wire at masts and mechanical tensions in the wires thanks to the Sobol indices. All parameters are defined using experimental measurements. A set of geometric and dynamic criteria is selected as output and the contribution of the input param...

Catenary damping has long been a tuning parameter in pantograph-catenary dynamic interaction models. As the computed contact force is highly sensitive to the choice of damping model or coefficients, it became critical to measure it independently of the pantograph. Original tests have been conducted on a real catenary and damping identification show...

Receptance tests are widely used, in-situ, to get information experimentally on the global dynamic behaviour of tracks. As a complement to this measurement, numerical models can be of great use to the diagnose of existing tracks, especially in zones presenting unexpected response to passing trains or in zones with specific design, providing a more...

To be confident in the prediction capability of a model, verification and validation steps are classically performed. Verification checks that the model is properly solved. Since the model used are fairly standard, this is not issue for brake components. Validation checks the relation between model and experiments on actual structures. Here geometr...

OSCAR (Outil de Simulation du CAptage pour la Reconnaissance des défauts) is the pantograph–catenary dynamic software developed by Société Nationale des Chemins de fer Français (SNCF) since 2004. A three-dimensional finite element (FE) mesh allows the modelling of any catenary type: alternating current (AC) or direct current (DC) designs, and conve...

Currently, pantograph–catenary dynamic simulations are mainly based on deterministic approaches. However, the contact force between catenary and pantograph depends on many key parameters that are not always quantified precisely and can vary in time and space. To get a better chance of addressing extreme or combined critical conditions, methodologie...

Developing tools to predict dissipation in mechanical assemblies starting from the design process is a subject of increasing interest. Design phases imply numerous computations resulting from the use of families of models with varying properties. Model reduction is thus a critical tool to make such design studies affordable. Existing model reductio...

Scanning laser vibrometer measurements generate detailed maps of modal characteristics in normal or 3D directions. Since many points are measured, individual validation of cannot be performed manually in a reasonable time frame and a notable fraction of measurements is expected to be fairly noisy. The key new notion of the paper is a quantification...

In order to face challenges of increased traffic and speed on their infrastructures, railway compa- nies need to develop numerical tools able to predict the dynamic behaviour of the track. Currently, two approaches are widely used: the first one is a train-based methodology in which train dynamic is well reproduced but track is only represented as...

Pantograph/catenary interaction is known to be strongly dependent on the static geometry of the catenary, this research thus seeks to build a statistical model of this geometry. Sensitivity analyses provide a selection of relevant parameters affecting the geometry. After correction for the dynamic nature of the measurement, provide a database of me...

-- FEM modeling of piezoelectric patches used as actuators and sensors for SHM applications. -- Test/analysis correlation of temperature effects in piezoelectric materials and glue -- Numerical methods associated with the prediction of electric transfers.

Design of damping in multi-jointed structures is studied here. − Dissipation sources are viscoelastic behavior and contact/friction at joints interfaces. − Reduction on meta-models of nonlinear joints models is investigated. − Experimental characterization of nonlinear forces.

This paper presents recent developments undertaken by SNCF Innovation & Research Department on numerical modelling of pantograph catenary interaction. It aims at describing an efficient co-simulation process between finite element (FE) and multibody (MB) modelling methods. FE catenary models are coupled with a full flexible MB representation with p...

Currently, pantograph-catenary dynamic simulations codes are mainly based on deterministic approaches. However, the contact force between catenary and pantograph depends on many key parameters that are not always quantified precisely. To get a better chance of addressing extreme or combinations of critical conditions, methodologies to consider vari...

Brake squeal impacts trains during station parking, generating over 110 dB at the wheel vicinity. This disturbance is a problem for commuters and employees working close to trains and limits exploitation times. The only adjustable parameter is here the brake pad, since it is the only part with frequent replacement regarding the railway equipment li...

On présente ici une méthodologie de conception d'une liaison boulonnée dissipative ainsi que sa validation par une étude expérimentale. Un premier calcul statique permet de caractériser la zone de compression induite à l'interface par le serrage. Cette zone contribue seule à la tenue statique de la liaison et est conservée en liaison métallique. On...

Classical vibration design uses modes and transfer functions generated with the superposition principle to allow the verification of design objectives. If redesign is needed, one optimizes mass and stiffness in order to modify the transfer until the specification is met. Integrating damping and non-linearities in the optimization of detailed industri...

25th International Conference on Noise and Vibration engineering (ISMA2012), LEUVEN, BELGIQUE, 17-/09/2012 - 19/09/2012

Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A ge...

L'expansion par minimisation du résidu dynamique (MDRE) cherche à estimer la réponse de modes propres expérimentaux sur tous les Degrés De Liberté (DDLs) d'un modèle éléments Finis (EF) en minimisant la somme pondérée d'une erreur de modèle et d'une erreur sur les mesures. On présente ici une méthode de résolution itérative de ce problème d'expansi...

In Pressurized Water Reactors of nuclear power plants, steam generators act as heat exchangers between primary and secondary coolant fluids. They consist of a bundle of U-tubes in which flows the primary coolant fluid. Several support plates guide these tubes vertically. Secondary coolant fluid flows along the U-tubes and passes through the space b...

Constrained viscoelastic damping treatments are fairly common in many applications but have not been industrially applied to aerospace engines. New engine designs tend to use BLISK (integrally bladed disks) machined from a single part and thus showing less friction damping than earlier designs. Constrained viscoelastic treatments are considered as...

The fatigue fracture is one of the most critical failures which may occur on the high speed network because it is undetectable and it has a huge impact on traffic disruption. The contact wire lifespan of a high speed line is estimated at more than 50 years and thus it is necessary to consider the risk of fatigue. The Railway Technical Research Inst...

This paper presents advances in non-linear simulations for systems with contact-friction, with an application to brake squeal. A method is proposed to orient component structural modifications from brake assembly simulations in the frequency and time domains. A reduction method implementing explicitly component-wise degrees of freedom at the system...

Experimentally, modal damping is known to allow a relatively accurate representation of damping for wide frequency ranges. For transient simulation of full finite element models, viscous damping is very often the only formulation that is associated with an acceptable computation time. In the absence of a proper material damping model, it is common...

Rotating structures typically have stages with cyclo-symmetric geometries that are periodic by rotation. The spatial Fourier transform of fields at periodic positions leads to multiple uncoupled low cost problems for each Fourier harmonic. Real rotors are assemblies of stages that have different number of sectors. This motivated the extension of cy...

Robust design of silent brakes is a current industrial challenge. Braking systems enter in the more general context of unstable systems featuring contact friction interaction. Their simulation requires time integra-tion schemes usually not adapted to combination of large industrial models (over 600,000 DOF) and long simulations (over 150,000 time s...

Handling of large industrial mechanical assemblies implies structure interactions commonly modeled with contact formulations. In cases where component interfaces are discretized using non conforming meshes, classical contact solutions have difficulties producing correct contact pressure fields. The method presented in this paper gives a relevant me...

Handling of large industrial mechanical assemblies implies structure interactions commonly modeled with contact formulations. In cases where component interfaces are discretized using non conforming meshes, classical contact solutions have difficulties producing correct contact pressure fields. The method presented in this paper gives a relevant me...

Classically Component Mode Synthesis has been used to couple models from different sources (mixed test and analysis, different companies, different software, ...) or reduce models. The focus of this paper is on using component modes in a design cycle. Component modes are the natural representation in the lowest part design cycle. In NVH application...

Active control has often been considered for low frequency noise control of aircraft or helicopter trim panels. The present study proposes a methodology for numerical homogeneization of honeycombs and shell models of piezoelectric patches. These models are validated experimentally. The considered honeycomb is shown to be significantly viscoelastic...

On pr´esente et utilise une généralisation des méthodes d'analyse modale prenant en compte de manière appropriée des éléments viscoélastiques localisés, dont les propriétés varient en fréquence et température. Ces méthodes modales étendues sont issues d'itérations sur résidus considérant les efforts viscoélastiques comme perturbation non-linéaire d...

L'utilisation de modèles éléments finis d'objets industriels complexes pose une problématique de compatibilité des maillages aux interfaces, en particulier dans le cas du contact. Cette incompatibilité génère des problèmes de convergence et de régularité des solutions. L'étude présentée ici étend le concept de la (1-e)-compatibilité introduite par...

Monitoring the vibrations of a structure has been recognized as a useful monitoring approach. However, the temperature and other environmental factors are known to affect the way a civil structure vibrates. A vibration monitoring method based on a subspace residual and χ2-type global and sensitivity tests has been proposed by some of the authors. I...