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: #journal #conference #thesis
- Application: #brake #rail #panto #piezo
- Research field: #damping #reduction #HybridTwin #HBVSig #ParamTesting #SHM
- Authors: Balmes ; Vermot des Roches ; Martin ; Bianchi ; …
- Any other key word: updating ; sensitivity ; …
| Illustration | Publication | #Tags | Links |
|---|---|---|---|
 | Squeal occurrence classification using a Harmonic Balance Vector signal model E. Balmes, G. Martin, G. Malacrida Alves, G. Vermot des Roches JSD 2025 Abstract[...]Brake squeal is an instability that generates self-excited limit cycles which vary with time and operating conditions in real experiments. To analyze test results, it is proposed to use a Harmonic Balance Vector (HBV) signal model. It combines Harmonic Balance Method and analytic signal methodologies. From the Harmonic Balance Method, one uses the space-time decomposition where spatial distribution of each harmonic is described by a complex vector and frequency is common to all sensors. From analytic signal, one keeps the assumption that quantities are slowly varying in time. Synchronous demodulation and principal coordinate definitions are combined in a multistep algorithm that provides an HBV estimation.On an industrial brake test matrix, HBV estimation is shown to be robustly applicable. The HBV signal being slowly varying, time sub-sampling reduces the volume of test data by two orders of magnitude. Limit cycle frequency, amplitude and shapes can thus be added to the parallel coordinates that associate to each time sample the operating parameters: pressure, velocity, temperature, torque, disk position, disk/bracket distance, ... This opens a path to a range of analyzes otherwise difficult to perform. Classification of squeal occurrences is first discussed showing pressure and amplitude dependence. The effect of amplitude on both frequency and shape is next demonstrated. The entry and exit of instability when parameters change are then analyzed by proposing a transient root locus built from test. Thus squeal test results are related to the classical complex eigenvalue analysis. Intermittent growth/decay events are shown to be correlated with wheel position. Furthermore, distance measurements indicate that disk shape variations of a few microns play a clear parametric role. Parametric testing and clustering are then used to map the instability region and its edges. Pressure is shown to have an effect dominating other variations. Prospective uses of these results to combine test results and finite element models are discussed last. | #brake #HBVSig #journal | Download Graphical summary |
 | Experimental modal analysis of time varying non-linear systems. Application to brake squeal G. Malacrida Alves PhD Thesis 2025 Abstract[...]Brake squeal is a complex phenomenon resulting from a mode coupling instability. Despite being a subject of study for many years, no robust design method exists for its prevention and correcting measures are heavily based on prototyping and validation, which is time-consuming and expensive. Squeal testing can be separated into three main activities: classification of squeal occurrences based on acoustic levels, detailed spatial characterization of limit cycles, and modal characterization of components and assemblies. This work thus seeks to propose and analyze the usefulness of different methodological changes to testing methods. A specificity of squeal is that vibration depends on multiple operating parameters pressure, wheel speed, temperature, … which vary in time relatively slowly compared to the frequencies of squeal limit cycles. It is thus necessary to take this specificity into consideration to design testing methods and analyze their results. As a mean to gain further insight on the effects of slowly changing operating conditions, a new functional model for squeal is proposed based on the well-known Hoffmann model. The novelty lies in replacing the variable friction assumption by a nonlinear contact law, which introduces a sensitivity to the applied pressure (as the static-state is modified), and amplitude (through its effect on the mean pressure). Analyzing and comparing the response of this model in frequency and time domain provides a path to understanding the relations between squeal limit cycle vibration and parameters. The definition of a Harmonic Balance Vector (HBV) signal model and the use of demodulation for its estimation, then allows tracking of quasi-periodic squeal signals without resolution limitations of the Fourier transform. For parametric squeal tests, this method improved occurrence classification by extracting the evolutions of features such as instantaneous frequency, global vibration amplitude, generalized coordinates and shape. For the detailed shape analysis using 3D-SLDV measurements, the HBV signal estimates led to results improved over current methods based on short time Fourier transforms. Applications are illustrated in a contact test bench to obtain the evolution of shapes with pressure, and in a full-scale brake test to obtain the limit cycle shapes. The HBV signal estimation can also extract spatially detailed shapes for higher harmonics. Two indicators (harmonic modulation and harmonic perturbation) are then proposed, based on the notion of instant stiffness, as a mean of evaluating where in a period the system is stiffer or softer. Finally, for in operation parametric Experimental Modal Analysis (EMA), full scale tests showed that modes away from squeal can be consistently identified and tracked. Near squeal, however, the presence of a coherence loss indicates that other methods are required such as the feedforward phase resonance tracking proposed in the analysis of the simplified contact test bench. | #brake #HBVSig #thesis | Download PhD defense |
 | Hybrid FEM/test twin building, an electric engine case history E. Balmes, G. Vermot Des Roches , S. Nacivet CSMA 2024 Abstract[...]An electric engine case history illustrates issues in the hybrid use of models and test data. Having fast online models for many query evaluations of responses of interest is a traditional topic. Rather than focusing on IA related inverse methodologies, one evaluates the performance of current versions of component mode synthesis leading to direct generation of parametric reduced order models. Discussions address geometry, contact and high modal densities. Finally, model and test errors are considered for hybrid estimations of motion. | #HybridTwin #conference | Download |
 | Analysis of a brake squeal functional model using a linear parameter varying perspective G. Malacrida Alves, E. Balmes, G. Martin INTER-NOISE 2024 Abstract[...]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, limit cycle saturation, vibration decay and parametric dependence. The proposed functional model differs from the well-known Hoffmann model by the introduction of a nonlinear contact law and a quasi-static pressure loading. First, using a harmonic balance perspective, non-linear forces are shown to lead to a pressure and amplitude dependent contact stiffness. This Linear Parameter Varying perspective allows complex mode computations in the pressure/amplitude domain which are then correlated with a series of transient responses of the nonlinear modes for three different pressure profiles. The chosen profiles represent usual experiments: drag where a constant pressure is applied, pressure ramps and pressure oscillations mimicking the effect of wheel spin on the contact surfaces. | #brake #HBVSig #conference | Download |
 | Parametric modal testing using slow but continuous variation of operating conditions. Illustration on a contact bench. G. Malacrida Alves, E. Balmes, G. Martin, T. Chancelier, E. Kassa SURVISHNO 2023 Abstract[...]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 characteristics. A lot of test configurations may thus be required to finely characterize the influence of environmental parameters on the system dynamics. The novel point of view taken here is to consider that in a number of applications, one can generate a slow variation of the operating condition that is sufficiently below the frequencies of interest to allow continuous monitoring of vibration properties. The application chosen as illustration of the process is a test bench seeking to characterize contact stiffness properties in a brake subassembly focusing on piston/backplate and piston/chamber contacts. A first rough estimate of the relation between modal frequency and pressure is obtained by traditional modal tests. A series of tests then changes pressure and excitation frequency continuously seeking to track phase resonance and thus update the estimates of resonance frequency, damping and shape changes at a very large number of pressure points. The proposed methodology using a feed-forward approach results in tests that are inherently certain to provide a result in a controlled amount of time | #brake #ParamTesting #conference | Download |
 | A time varying system perspective on rubber mount tests G. Malacrida Alves, E. Balmes ISMA 2022 Abstract[...]Rubber tests typically only consider the first harmonic of responses and thus ignore additional information about variation of properties during a cycle. The Payne effect is then only described as a decrease of modulus with amplitude. An harmonic modulation is introduced as a novel way to look at the classical harmonic balance characterization of periodic signals in an effort to answer the question of when in the period is the system close to being linear ? In the case of enforced displacement tests, the harmonic modulation of force signals corresponds to an instant material stiffness or instant modulus. Sine test results are thus interpreted as trajectories in a complex modulus / strain plane that are much more discriminating than the traditional representation as a complex modulus and gives indication of coupling between hyperelastic, hysteretic and viscoelastic behaviors. This new interpretation of classical results is shown to be relevant as a correlation tool and a constitutive model for rubber is validated in its ability to reproduce the instant modulus behavior in a wide range of cases. | #damping #HBVSig #conference | Download |
 | A unified non-linear system model view of hyperelasticity, viscoelasticity and hysteresis exhibited by rubber R. Penas, E. Balmes, A. Gaudin MSSP 2022 Abstract[...]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 used to identify parametric models, whose accuracy can be controlled by order selection or by numerical implementation considerations. A full test campaign, including multi-step relaxation, low speed triangular and sine tests, on a large deformation compression sample is used to illustrate the need to model and combine the base behaviors known as hyperelasticity, viscoelasticity, and rate independent hysteresis. The equivalence between linear viscoelasticity and linear time invariant systems is used to clarify the link between order selection and accuracy of a generalized Maxwell model. Rate independent hysteresis is analyzed using a convolution product like the one used for viscoelastic transients by introducing a relaxation modulus. Measurements of the hysteretic relaxation modulus are used to propose strategies to measure the asymptotic hyperelastic modulus and discriminate between different hysteretic model forms. A parallel between Iwan and Maxwell models is detailed, and non-parametric models are used to show that the two overlap in the low frequency small deformation regime. Regularized rate independent hysteresis and non-linear viscoelasticity are finally shown to lead to a similar view allowing a transition between the rate independent and linear relaxation models. The instantaneous ratio analytic force and displacement signals, or instant complex modulus, is introduced as novel non-parametric estimation of sine measurements and shown to be a powerful tool to analyze and validate the fact that a force rate relaxation with non-linear relaxation frequencies is most appropriate to represent the non-linear coupling of all three effects. | #damping #journal | Download |
 | Expansion in structural dynamics : a perspective gained from success and errors in test/FEM twin building E. Balmes, G.Martin, G. Vermot Des Roches, T. Chancelier, S. Thouviot CSMA 2022 Abstract[...]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 seeking a trade-off between test and model error. The case of a measured brake squeal limit cycle is used to illustrate implementation details found to be important. | #brake #HybridTwin #conference | Download |
 | A Structural Dynamics Modification Strategy based on Expanded Squeal Operational Deflection Shapes G. Martin, E. Balmes, T. Chancelier, S. Thouviot, R. Lemaire EUROBRAKE 2022 Abstract[...]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 difficult to propose system modifications from test alone. Historical Structural Dynamics Modification (SDM) techniques need mass normalized shapes which is not available from an ODS measurement. Furthermore, it is very difficult to translate mass, damping or stiffness modification between sensors into physical modifications of the real system. On the model side, FEM methodology gives access to fine geometric details, continuous field over the whole system. Simple simulation of the impact of modifications is possible, one typical strategy for squeal being to avoid unstable poles. Nevertheless, to ensure accurate predictions, test/FEM correlation must be checked and model updating may be necessary despite high cost and absence of guarantee on results. To combine both strategies, expansion techniques seek to estimate the ODS on all FEM DOF using a multi-objective optimization combining test and model errors. The high number of sensors compensates for modeling errors, while allowing imperfect test. The Minimum Dynamics Residual Expansion (MDRE) method used here, ensures that the complex ODS expanded shapes are close enough to the measured motion but have smooth, physically representative, stress field, which is mandatory for further analysis. From the expanded ODS and using the model, the two underlying real shapes are mass-orthonormalized and stiffness-orthogonalized resulting in a reduced modal model with two modes defined at all model DOFs. Sensitivity analysis is then possible and the impact of thickness modifications on frequencies is estimated. This provides a novel structural modification strategy where the parameters are thickness distributions and the objective is to separate the frequencies associated with the two shapes found by expansion of the experimental ODS. | #brake #HybridTwin #conference | Download Presentation |
 | Bending waves focusing in arbitrary shaped plate-like structures: Study of temperature effects, development of a digital twin and of an associated neural-network based compensation procedure N. Benbara, G. Martin, M. Rébillat, N. Mechbal JSV 2022 Abstract[...]Advanced automotive audio applications are more and more demanding with respect to the visual impact of loudspeakers while still requiring more and more channels for high quality spatial audio rendering. Removing classical heavy and large electrodynamic loudspeakers and using car interior plate-like structures driven by state of the art spatial sound algorithms appear as a promising solution to tackle both issues. However, to meet spatial audio rendering constraints, the bending waves generated within car interior plate-like structures must be focused at a given position and to a certain extent within the host structure. Theoretically, this means being able to invert in a robust manner the spatio-temporal wave propagation operator for the generated bending waves to fit a given target shape. The propagation operator inversion method considered here is the spatio-temporal inverse filtering (STIF) method based on the knowledge of the propagation operator on a regular spatial grid over the structure at a given temperature. However, in a car interior a high temperature variations exist and can adversely impact the performances of the STIF method, mainly because dynamical properties of the host structure (built up with polypropylene in most cases) largely vary within this temperature range. Even if the STIF method has already been adapted and assessed in the context of automotive audio reproduction, no study dealing with the effects of temperature on the STIF method and providing potential mitigation procedures avoiding experimental measurements at each temperature has been reported. To address that issue, the influence of temperature on the behavior of a polypropylene plate is first experimentally quantified. A model updating method is used to build a finite-element model of the plate taking into account temperature effects. This digital twin of the host-structure is then used to assess the influence of the temperature on the STIF method. A neural network based controller is finally trained and validated on the digital twin in order to compensate for the effects of temperature on STIF filters. Obtained results demonstrate that this procedure successfully allows to compensate for temperature effects on the STIF method applied to polypropylene plate with very limited experimental needs, thus paving the way through an industrial development of such approaches. | #ParamTesting #HybridTwin #journal | Download |
Showing 1 to 10 of 64 entries
This table does not contain publications published before 2014.
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