The table below gathers publications involving SDTools.
It can be filtered using the search field at the top of the table. Here are for instance relevant key words that can be combined:
- Publication type: #paper #conference #thesis
- Application: #brake #rail #panto #piezo
- Research field: #damping #reduction #HybridTwin
- Authors: Balmes ; Vermot des Roches ; Martin ; Bianchi ; …
- Any other key word: updating ; sensitivity ; …
| Illustration | Publication | #Tags | Links |
|---|---|---|---|
 | Squeal measurement using operational deflection shape. Quality assessment and analysis improvement using FEM expansion G. Martin, E. Balmes, G. Vermot des Roches, T. Chancelier Eurobrake 2017 Abstract[...]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 even in the presence of variations with wheel position as well as for reproducibility tests. For a proper relation with the model, it is desirable to also extract modes. The test campaign is used to illustrate how this can be quite difficult due to reproducibility problems. Finally, shapes characterizing the squeal event are fundamentally limited by measurable quantities. Minimum Dynamic Residual Expansion (MDRE), which estimates test motion at all FE degrees of freedom, is shown to be applicable for industrial models and gives insight of test and model imperfections. | #HybridTwin #conference #brake | Download |
 | Characterization of identification errors and uses in localization of poor modal correlation G. Martin, E. Balmes, T. Chancelier MSSP 2017 Abstract[...]While modal identification is a mature subject, very few studies address the characterization of errors associated with components of a mode shape. This is particularly important in test/analysis correlation procedures, where the Modal Assurance Criterion is used to pair modes and to localize at which sensors discrepancies occur. Poor correlation is usually attributed to modeling errors, but clearly identification errors also occur. In particular with 3D Scanning Laser Doppler Vibrometer measurement, many transfer functions are measured. As a result individual validation of each measurement cannot be performed manually in a reasonable time frame and a notable fraction of measurements is expected to be fairly noisy leading to poor identification of the associated mode shape components. The paper first addresses measurements and introduces multiple criteria. The error measures the difference between test and synthesized transfer functions around each resonance and can be used to localize poorly identified modal components. For intermediate error values, diagnostic of the origin of the error is needed. The level evaluates the transfer function amplitude in the vicinity of a given mode and can be used to eliminate sensors with low responses. A Noise Over Signal indicator, product of error and level, is then shown to be relevant to detect poorly excited modes and errors due to modal property shifts between test batches. Finally, a contribution is introduced to evaluate the visibility of a mode in each transfer. Using tests on a drum brake component, these indicators are shown to provide relevant insight into the quality of measurements. In a second part, test/analysis correlation is addressed with a focus on the localization of sources of poor mode shape correlation. The MACCo algorithm, which sorts sensors by the impact of their removal on a MAC computation, is shown to be particularly relevant. Combined with the error it avoids keeping erroneous modal components. Applied after removal of poor modal components, it provides spatial maps of poor correlation, which help localizing mode shape correlation errors and thus prepare the selection of model changes in updating procedures. | #HybridTwin #journal | Download |
 | Waves, modes and properties with a major impact on dynamic pantograph-catenary interaction O. Vo Van, J.P. Massat, E. Balmes JSV 2017 Abstract[...]Understanding the dynamic behavior of the pantograph-catenary system is crucial for design improvement, but many factors inuence the contact force, which is the main design objective. To give a proper un-derstanding of dynamic characteristics, the paper uses a combination of mass drop tests on a catenary, analytic models and parametric _nite element model simulations allowing a ne analysis of the inuence of train speed. The _rst contributor to contact force variations is the geometry of the catenary under gravity loading. This parameter is however shown to be insu_cient to explain higher frequency e_ects. The second contributor is the propagation of waves in the contact and messenger wires. The inuence of wave dis-persion is _rst demonstrated, which emphasizes the importance of considering the bending sti_ness. Wave compensation by droppers and reections at the mast are then shown to be important. Characteristic times associated with wave group velocities are _nally used to explain the series of harmonic contributions visible in spectra in the catenary and pantograph frames. Finally, modes are shown to play a role particularly when their frequencies coincide with other contributions. The notion of mode groups, associated wave velocities and relevant design variables are discussed. Several observations pave the way for future work on catenary design. | #panto #journal | Download |
 | Calculation/Test methods for the analysis squeal G, Martin PhD thesis 2017 Abstract[...]Brake squeal is a nuisance commonly encountered in the car industry which often results in financial penalties towards brake manufacturers, even if no robust solution exists for the conception. Numerical simulation and experimental characterizations are the classical two-track approaches to analyze squeal phenomena. Numerical simulation allows a fine analysis of vibration behaviors and the evaluation of conception modification impacts, but models are not perfect and their validity domain must be defined. Measurement guarantees that every parameter is taken into account, but it is often spatially poor and not really suited for modification prediction. In this context, the thesis objectives are to make an overview of test operating methods, to provide tools allowing an easier interaction between both test and simulation teams and to enforce the developments in a business application.After a review of the hypotheses and methods for modal identification, a critical analysis of the identification results leads to the characterization of biases and the introduction of detailed criteria to evaluate the quality of the result. Calculation/test correlation allows to qualify the models and tools are integrated to facilitate its implementation. Several criteria are defined to highlight the sources of bad correlation coming from the measure on the one hand and the model on the other hand. Sources of poor correlation are also identified with the MDRE expansion algorithm, whose limitations are compared with those of static and dynamic expansions.Model updating is then processed by a systematic procedure imbricating the steps of updating of geometry, material properties and contacts between components. A contact parametrization is proposed with a multi-model reduction allowing calculation times compatible with industrial time. It also allows sensitivity studies with the introduction of the notion of component modes in an assembly.Finally, a detailed analysis of a measurement campaign on a braking system under squeal conditions is carried out. A parallel between the changes of the limit cycle and the degree of coupling of the complex modes is proposed. In the time-frequency domain, variability, repeatability, reproducibility and the ability to aggregate sequential measurements are evaluated. The result is finally extended on the finite element model, which allows useful interpretations. | #brake #thesis #HybridTwin | Download |
 | Wave damping and evanescence: how to combine the spatial and temporal visions of the same problem? E. Balmes, M. Rebillat, E. Arlaud VISHNO 2016 Abstract[...]It is proposed to analyze the forced response of periodic structures using a 2D Fourier transform using continuous time and discrete space.The simple example of compression waves is used to show that this response can be used to define poles in the wavenumber domain corresponding to evanescent waves or poles in the frequency domain corresponding to damped periodic modes. Link with classical computational methods based on FEM models of cells was done for both the periodic solution and wave based approach (SAFE, WFE). Two examples are analyzed in more detail: a simple train track model exhibiting a band-gap and the more complex case of a honeycomb panel where cell wall bending occurs within the band of interest. | #damping #conference #rail | Download |
 | Updating and design sensitivity processes applied to drum brake squeal analysis G. Martin, E. Balmes, G. Vermot des Roches, T. Chancelier Eurobrake 2016 Abstract[...]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 junctions. A modeling strategy allowing the practical analysis of the impact of junctions is proposed and illustrated on the case of a drum brake assembly. As the level of uncertainty/design freedom is fairly large for junctions, the evolution of modal properties is difficult to interpret. The notion of component modes within a rigid assembly is thus introduced and shown to provide an appropriate interpretation of changes in a system with multiple modal crossings. The analysis of possible forced responses is finally shown to lead to relevant interpretation of possibly interesting designs or problematic instances of a variable component. | #HybridTwin #conference #brake | Download |
 | Error localization and updating of junction properties for an engine cradle model G. Vermot des Roches, E. Balmes, S. Nacivet ISMA 2016 Abstract[...]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 modeling side, weld spots and lines and variations of thickness due to press forming are shown to have relatively minor impact when compared to the contact surfaces. Usual junction simplifications are also shown to play a major role particularly at higher frequencies where more localized modeshapes occur. | #HybridTwin #conference | Download |
 | Numerical Study of Railway Track Dynamics : Case of a Transition Zone E. Arlaud, S. Costa d'Aghuiar, E. Balmes, G. Faussurier Railways 2016 Abstract[...]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 based on the Finite Element Method (FEM), adapted to the railway track using model reduction techniques. Taking advantage of the periodicity of the track introduced by the regular sleeper spacing, one or several basic slices containing all the geometric properties of the structure can be identified. Static and periodic responses of these slices are computed. Then, reduction is performed using these deformations.Thus the number of degrees of freedom of the model is highly reduced. This reduction induces a decrease in computation time with limited accuracy loss in the representation of track dynamics. The methodology will be further described in this paper. The second novelty of this work is to use this model to analyze the dynamic behavior of a transition zone located in a French high speed line. | #reduction #conference #rail | Download |
 | Sensitivity analysis of catenary geometry on current collection quality O. Vo Van, E. Balmes, A. Capitaine, X. Lorang Railways 2016 Abstract[...]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 theinput parameters to the output variability is quantified. It is shown that the dynamicinteraction is mainly sensitive to the mechanical tensions in contact and messenger wires whereas existing geometric criteria are mainly dependent on height of messenger wire at masts. Moreover, selected geometric criteria available using geometry measurements are hardly correlated with dynamic criteria. | #panto #conference | Download |
 | Introduction of variability into pantograph-catenary dynamic simulations O. Vo Van PhD Thesis 2016 Abstract[...]In railways, electrical current is generally collected by the train through a complex coupledmechanical system composed of a pantograph and a catenary. Dynamic phenomena that occur duringtheir interaction are still not fully understood. Furthermore, the system behaviour is sensitive to numerousparameters and thus highly variable. The first contribution of this thesis is a detailed analysis of thepantograph-catenary dynamic interaction separating phenomena due to the dynamic response of the pantographto the catenary geometry from wave propagations, reflections and transmissions that occur in thecatenary. The coincidence of frequencies or characteristic times is then shown to explain most variationsin the quantities of interest. Moreover, droppers surrounding the mast have been shown to be particularlyimportant in dynamic interaction. Ratio of wire impedances and sum of wave velocities also appeared tobe dimensioning quantities for catenary design. The second contribution was to reduce epistemic uncertaintylinked with model parameters such as catenary damping, contact stiffness and element size. Thefinal contribution was to use the model in a configuration with random parameters. An initial step was tostatistically characterise physical catenary parameters using available measurements. From this randommodel, ranking of uncertainties using Sobol indices on static and dynamic criteria was shown to be possible.An absence of correlation between geometric and dynamic criteria was also found, which has notableimplications for maintenance policies. The high number of sensitivity studies also gave the occasion tohighlight the maturity of simulation tool and propose directions for further work on design, maintenance orcertification of pantographs and catenaries. | #panto #thesis | Download |
 | Use of FEM models to study fatigue of overhead contact wires J.P. Massat, E. Balmes, J-P. Bianchi Railways 2016 Abstract[...]Fatigue cracks can induce fracture of the catenary Contact Wire (CW) and thus huge costs for the operator. Nowadays the wear criterion to replace the CW leads to lifespan over than 50 years, and the catenary can see a very high number of cycles so that fatigue life must be taken into account. A full process to compute the multiaxial transient stress field in the CW has been developed. A fatigue criticality indicator to assess the risk of crack initiation was introduced. This elaborate indicator is used to validate a simplified fatigue indicator based on the uniaxial Euler-Bernoulli beam stresses that are much faster to compute. This indicator is then used to assess parameters influencing the risk of fatigue in the case of junction claws. | #panto #conference | Download |
 | Simultaneous Influence of Static Load and Temperature on the Electromechanical Signature of Piezoelectric Elements Bonded to Composite Aeronautic Structures M. Rebillat, M. Guskov, E. Balmes, N. Mechbal JVA 2016 Abstract[...]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 temperature variations that affect the metrics commonly used for damage detection and sensor diagnostics. However, the effects of load and temperature on these metrics have mostly been addressed separately. This paper presents experimentations conducted to investigate the simultaneous influence of static load and temperature on these metrics for two kinds of piezoelectric elements (lead zirconate titanate (PZT) and macrofiber composite (MFC)) bonded on sandwich composite materials, for the full range of real-life conditions encountered in aeronautics. Results obtained indicate that both factors affect the metrics in a coupled manner in particular due to the variations of the mechanical properties of the bonding layer when crossing its glass transition temperature. Furthermore, both piezoelectric elements globally behave similarly when subjected to temperature variations and static loads. Simultaneous accounting of both temperature and static load is thus needed in practice in order to design reliable structural health-monitoring systems based on these metrics. | #piezo #journal | Download |
 | Validation and verification of FE models of piezo based SHM systems. E. Balmes, M. Guskov, M. Rebillat, J.-P. Bianchi ISMA 2016 Abstract[...]The idea of generating and sensing Lamb waves through piezoelectric sensor/actuator configurations is common for Structural Health Monitoring (SHM) applications. Methods using time of flight analysis require the prediction of the first incoming waves. Computations on small periodic patterns are shown to be usable to determine which waves will actually be relevant. For the considered applications, these are the first membrane waves propagating at fairly high speeds. Parametric FEM computations are then used to analyze important parameters (mesh size, time step, damping) and it is shown that accurate predictions can be obtained in a few CPU minutes. | #piezo #conference | Download |
 | Effects of temperature on the impedance of piezoelectric actuators used for SHM E. Balmes, M. Guskov, M. Rebillat, N. Mechbal VISHNO 2016 Abstract[...]- 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. | #piezo #conference | Download |
 | Numerical design and test on an assembled structure of a bolted joint with viscoelastic damping C. Hammami, E. Balmes, M. Guskov MSSP 2015 Abstract[...]Mechanical assemblies are subjected to many dynamic loads and modifications are often needed to achieve acceptable vibration levels. While modifications on mass and stiffness are well mastered, damping modifications are still considered difficult to design. The paper presents a case study on the design of a bolted connection containing a viscoelastic damping layer. The notion of junction coupling level is introduced to ensure that sufficient energy is present in the joints to allow damping. Static performance is then addressed and it is shown that localization of metallic contact can be used to meet objectives, while allowing the presence of viscoelastic materials. Numerical prediction of damping then illustrates difficulties in optimizing for robustness. Modal test results of three configurations of an assembled structure, inspired by aeronautic fuselages, are then compared to analyze the performance of the design. While validity of the approach is confirmed, the effect of geometric imperfections is shown and stresses the need for robust design. | #damping #journal | Download |
 | Review of model updating processes used for brake components G. Martin, E. Balmes, G. Vermot des Roches, T. Chancelier Eurobrake 2015 Abstract[...]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 geometry measurements and vibration tests are considered. The study seeks to perform a systematic review of how test quality is evaluated, and models are correlated and then updated. This will give a solid basis to define clear and easily used validations protocols for brake components where prediction of modes and their stability in the manufacturing process is often deemed critical. Updating the geometry before updating the material properties is shown to be very important: the residual error on frequencies is smaller and no bias is introduced in the estimated material properties. Proper pairing of modeshapes is important for broadband comparisons and the MAC criterion is used. Intermediate steps: experimental topology correlation using easy tools with accuracy evaluation, estimation of errors on test shapes, handling of mode crossing, are sources of errors that are analyzed. For the updating of contact properties, where many parameters may need update, the use of model reduction is shown to allow a major speed-up of parametric studies. | #HybridTwin #conference #brake | Download |
 | OSCAR Statement of Methods J.P. Massat, E. Balmes, J.P. Bianchi, Van Kalsbeck, G, VSD 2015 Abstract[...]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 conventional or high-speed lines. It is a representative of the real overhead line geometry, with contact wire (CW) irregularities, staggered alignment of the CW, dropper spacing, wire tension, etc. Nonlinearities, such as slackening of droppers and unilateral contact between the pantograph and the CW, are taken into account. Several pantograph models can be used, with a complexity level growing from the three-lumped-mass model to the multibody model. In the second case, a cosimulation between the FE method catenary and the multibody pantograph models has been developed. Industrial features for pre- and post-treatments were developed to increase robustness of results and optimise computation time. Recent developments include volume meshing of the CW for stress computation or statistical analysis and lead to new fields of studies such as fatigue failure or design optimisation. OSCAR was fully validated against in-line measurements for its different AC and DC catenary models as well as its different pantograph models (with independent strips for instance) and has continuously been certified against EN50318 since 2008. | #panto #journal | Download |
 | Dynamic stress prediction in catenary wires for fatigue analysis J.P. Bianchi, E. Balmes, Nguyen-Tajan M.L, IAVSD 2015 Abstract[...]Fatigue cracks in the contact wire are a possible cause of fracture which can induce huge costs. Fatigue study is thus of a great interest but requires an accurate computations of stress distributions. OSCAR is a SNCF software used to study coupled pantograph / catenary dynamics. It is based on Euler-Bernoulli beam meshes. This formalism is accurate to study the catenary displacements, but is not sufficient to compute multi-axial stresses, in particular in parts that can concentrate stresses such as the junction claws. This paper details and illustrates the strategy developed to compute a full multi-axial transient stress field, in any point of the contact wire. The dynamic displacement computed by OSCAR is expanded and combined with a precise nonlinear static state of a mixed model of beams and volume elements. | #panto #conference | Download |
 | Damping characterization of a high speed train catenary O. Vo Van, E. Balmes, X. Lorang IAVSD 2015 Abstract[...]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 shows a very low level of damping for a large frequency range. A fitted Rayleigh model and a combined modal and Rayleigh model are proposed and compared with a reference damping model found in literature as well as with the tests. Finally, the consequences on a typical contact force simulation are analysed and the most relevant model is chosen. | #panto #conference | Download |
 | Squeal Complex Eigenvalue Analysis, Advanced Damping Models and Error Control G. Vermot des Roches, O. Chiello, E. Balmes, X. Lorang Eurobrake 2015 Abstract[...]Estimation of brake systems stability related to noise emission is part of the industry state-of-the-art for brake design. Improved assessment of stability would allow better NVH performance from early design stages thus reducing costs related to late redesign and testing. The prediction capability however remains challenged due to the complexity of brake noise phenomena. In particular, integration and resolution of complex systems with damping is a difficult task that is commonly overlooked. This paper proposes two ideas to improve stability estimation. From the solver side, a convergence indicator is proposed to quantify the convergence of the complex eigenvalues for subspace based methods. The error obtained can be directly used to enhance the computation subspace and a priori enhancement is suggested. From the modelling side, a damping strategy based on sub-assembly modal damping ratios is proposed allowing direct exploitation of test measurements or refined sub-assembly simulations for damping estimation. Sub-assembly damping can thus be accounted for at the system level including all possible effects like joint dissipation or composite materials. | #brake #conference | Download |
 | Meta-models of repeated dissipative joints for damping design phase C. Hammami, E. Balmes ISMA 2014 Abstract[...]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 reduction methods make computation of models with detailed non-linear parts accessible although costly although allowing the generation of a small size model for the linear part. One is, thus, interested in introducing meta-models of the behavior in the non-linear part by determining a basis of principal joint deformations. In this work, one seeks to validate the ability to predict macro-forces associated with the principal deformation shapes. Taking the case of aeronautic structures as cylindrical ones with multiple joints, one seeks to validate the construction of a meta-model associated to the joint. The ability to use such a meta-model to predict damping associated with viscoelastic behavior in a specifically designed bolted joint will be illustrated. | #damping #conference | Download |
 | The Component Mode Tuning (CMT) method. A strategy adapted to the design of assemblies applied to industrial brake squeal. G. Vermot des Roches, G. Rejdych, E. Balmes, T. Chancelier Eurobrake 2014 Abstract[...]Numerical prototyping is widely used in industrial design processes, allowing optimization and limiting validation costs through experimental testing. Industrial applications nowadays focus on the simulation of complex component assemblies that are generally mass produced. Coupling properties thus have to be modelled, updated and accounted for variability. For squeal applications, simulations still fail at robustly producing exploitable results due to the systems complexity, while experimentations are limited for diagnostic and design improvement. This paper presents a new application of the Component Mode Tuning, an efficient model reduction method adapted to quick system level reanalysis as function of component free modes, to study the effect of coupling. The impact of component coupling stiffness and coupling surface topology is thus assessed on a drum brake subassembly which design is sensitive to squeal. It is shown that significant system differences can come from coupling surface variations with patterns close to experimental observations. This emphases the need for refined analyses to control coupling in the perspective of robust modelling. | #reduction #brake #conference | Download |
 | Validation of a reduced model of railway track allowing long 3D dynamic calculation of train-track interaction E. Arlaud, S. Costa d'Aghuiar, E. Balmes IACMAC 2014 Abstract[...]In order to face challenges of increased traffic and speed on their infrastructures, railway companies 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 equivalent springs, the second one is a FEM model or FEM/BEM model of track in which the train is simply modeled as a moving load but the complexity of track taken into account. Dynavoie software studied in this work aims to offer a new approach by representing in details both track and train. Understanding train-track interaction requires transients on long track segments, leading to very large finite element models and high computation time. The specificity of Dynavoie software is to use periodic properties of the track to generate a reduced slice model, and then build the track as a combination of these slices. Computation time is then highly reduced. The present work focuses on the initial step of the model reduction where computations in the frequency and wave domains are used. The resulting 3D periodic computations are compared to 2.5D FEM/BEM results from the literature and the content of the receptance curve is discussed in relation with dispersion curves. | #reduction #conference #rail | Download |
 | Statistical identification of geometric parameters for high speed train catenary O. Vo Van, E. Balmes, J.P. Massat ISMA 2014 Abstract[...]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 measurements. One then seeks to solve the statistical inverse problem using the maximum entropy principle and the maximum likelihood method. Two methods of multivariate density estimations are presented, the Gaussian kernel density estimation method and the Gaussian parametric method. The results provide statistical information on the significant parameters and show that the messenger wire tension of the catenary hides sources of variability that are not yet taken into account in the model. | #panto #conference | Download |
 | Pantograph catenary dynamic optimisation based on advanced multibody and finite element co-simulation tools J.P. Massat, C. Laurent, J.P. Bianchi, E. Balmes VSD 2014 Abstract[...]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 pneumatic actuation of pantograph. These advanced functionalities allow new kind of numerical analyses such as dynamic improvements based on innovative pneumatic suspensions or assessment of crash risks crossing areas that demonstrate the powerful capabilities of this computing approach. | #panto #journal | Download |
 | Understanding friction induced damping in bolted assemblies through explicit transient simulation. G. Vermot des Roches, E. Balmes ISMA 2014 Abstract[...]The design of joints is seeing increased interest as one of the ways of controlling damping levels in lighter and more flexible aeronautic structures. Damping induced by joint dissipation has been studied for more than a decade, mostly experimentally due to the difficulty of simulating large structures with non-linearities. Experimentally fitted meta-models were thus used for damping estimation at design stage without a possible optimization. The aim of this paper is to demonstrate that damping estimation using local friction models is feasible and that it can be usable for design. The simulation methodology is based on an explicit Newmark time scheme with model reduction and numerical damping that can be compensated for the modes of interest. Practical simulation times counted in minutes are achieved for detailed models. The illustration on a lap-joint shows how simulations can be used to predict the amplitude dependence of modal damping, answer long standing questions such as "does the modeshape change?" or analyze the evolution of pressure fields during a cycle. | #brake #conference | Download |
 | Frequency and time simulation of squeal instabilities. Application to the design of industrial automotive brakes. G. Vermot des Roches PhD thesis 2011 Abstract[...]Brake squeal is a common noise problem encountered in the automotive industry. Higherfriction coefficients and weight reduction recently led to higher vibration levels in the audiblefrequency range. This quality issue becomes economic due to penalties imposed to the brakesupplier although no robust design method exists. The industrial practice thus relies on costlyprototyping and adjustment phases. The evolution of computational power allows computationof large mechanical assemblies, but non-linear time simulations generally remain out of reach.In this context, the thesis objective is to provide numerical tools for squeal resolution at earlydesign stages.Parameterized reduction methods are developed, using system real modes as Rayleigh-Ritzvectors, and allow very compact reduced models with exact real modes. The proposed ComponentMode Tuning method uses the components free/free modes as explicit degrees of freedom.This allows very quick sensitivity computation and reanalyzes of an assembly as function oflocal component-wise parameters. Non-linear time simulations are made possible through twoingredients. A modified non-linear implicit Newmark scheme and a fixed Jacobian are adaptedfor contact vibrations. The brake is reduced keeping a superelement with exact real modes anda local non-linear finite element model in the vicinity of the pad/disc interaction.A set of design tools is illustrated for a full industrial brake model. First, instant stabilitycomputations and complex mode trajectories are studied. Modal interactions and non-linearphenomena inside the limit cycles are thus well understood. Time/frequency correlations areperformed using transient modal identification and space-time decomposition. A time domainmodal damping model is also shown to be very useful. The modification of a critical componentfor squeal resolution is finally tested and validated. | #brake #reduction #thesis | Download |
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