SDNews: January-February 2025
Newsletter summary:
?? [Research] Scientific research at SDTools
??? [Software] Automatic reporting
??? [Software] Reduced model animation on reduced mesh through cuts (slices)
?? [Thesis] Guilherme Malacrida Alves – Phd Defense
?? [Expertise] Quality modelling hints: simplification pitfalls with modal analysis. The case of pressure application for brake squeal.
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?? More information about SDTools on our website
??[Research] Scientific research at SDTools
SDTools is involved in vibration research at multiple levels, either through R&D projects for its customers, or as a member of research programs, or by supervising PhD students.
??? We have gathered recent?publications?involving SDTools on our website: https://www.sdtools.com/publications_wp/
You will be able to download them and, based on your fields of interest, to filter them by:
?? Some of these publications were written in the context of PhD theses and presented by the PhD students themselves at scientific conferences. The list of past PhD theses supervised by @Etienne Balmes is available here?https://www.sdtools.com/phd-thesis-supervision/
?? One of the benefits we provide is a scalable simulation framework where academic investigations and development of new tools is possible, with or without our support. This can also be performed as a contribution to our OpenFEM core.
?? Do not hesitate to contact us if you want to discuss research topics opportunities!
??? [Software] Automatic reporting
??Classical off the shelves analyses in SDT (EMA, numerical modal analysis, shape correlation, …) are integrated with automated report generation. Tables, animations, pictures, text… can then be easily analyzed with main results displayed at the same time and same place with a unified formatting.
??Default output formats are Microsoft Word or Power Point. Depending on the data type, we also support Excel, HTML, LaTeX, MarkDown…
??Formatting and exporting strategies are tunable, so that we can build dedicated outputs using customized templates.
?In today’s video, we illustrate this functionality applied to the Experimental Modal Analysis results. The default report shows
Sections and captions can be separately activated by checking the desired boxes and captions can be edited on the fly!
??? [Software] Reduced model animation on reduced mesh through cuts (slices)
Are you suffering from slow animations with large FEM results? Do you need to navigate into huge FEM DoE where full result would be TB of data?
?? Rather than storing full results and animating the usual skin mesh, #SDTools is finding many industrial reasons to store reduced models, perform restitution on the fly and animate cuts (slices)
?? These reasons are illustrated on a full brake FEM from #HitachiAstemo with 1.8 million DOF
?? Lighter animations
?? 836 nodes rather than 607 000 nodes using cuts + to feature preserving mesh coarsening
?? View internal motion / hide less surfaces
?? The piston and pins are only visible with the cuts
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?? Limit memory usage and file sizes
?? Interactive viewing of large data sets: use generalized DOF (1 GB = 400 000 complex shapes on 168 generalized DOF, but <40 on all 1.8 million DOF)
?? Restitution on the fly (simulations #MATLAB, #SimuLink) or expand test results (#testlab, #Polytec, #SDT, #HybridTwin) takes micro-seconds since display mesh is small
??Animation file: reduced DOF superelement allowing restitution of any shape on the reduced mesh (3.4 MB in comparison with initial FEM superelement with restitution on full mesh 2.3 GB)
?? This strategy integrates fluently in your processes
?? FEM software neutral format, imported from #NASTRAN, #Ansys, #Abaqus, … superelements in any form (free-modes with residual vectors, Craig-Bampton, …) or generated with #SDT
?? Share your animation without giving your model. As a supplier you may want to preserve your intellectual property: mesh slicing and coarsening hides much detail
??[Thesis] Guilherme Malacrida Alves: PhD defense
Congratulations to Guilherme Malacrida Alves who successfully defended his PhD thesis on “Experimental modal analysis of time varying non-linear systems. Application to brake squeal”
The jury was composed of
M. Franck MASSA , Professeur, Université Polytechnique Hauts-de-France, LAMIH - Rapporteur
M. Ga?l Chevallier , Professeur, Ecole de l’Air et de l’Espace - Rapporteur
M. Jean-Luc Dion , Professeur, ISAE-Supmeca, Quartz - Examinateur
M. Etienne Balmes , Professeur, Arts et métiers science et technologies, PIMM - Examinateur
M. Guillaume Martin , Docteur, SDTools – Examinateur
This thesis has been directed by Etienne Balmes with industrial support by Guillaume Martin for SDTools and the contribution of Hitachi Astemo .
Etienne Balmes and Guillaume Martin want to deeply thank the other jury for their interest in this work. We are also grateful to our industrial partner Hitachi Astemo (that allowed Guilherme to perform the full brake squeal measurement campaigns) and to thierry chancelier for giving us the industry viewpoint on the work performed.
We wish you all the best Guilherme Malacrida Alves !
?? Keywords: Brake squeal instability, Nonlinear vibrations, Limit cycle, Parameter-varying systems, Signal model, Experimental modal analysis, 3D-SLDV, Instant stiffness, clustering.
?? 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.
?? Publications:
Analysis of a brake squeal functional model using a linear parameter varying perspective G. Malacrida Alves, E. Balmes, G. Martin INTER-NOISE 2024
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
A time varying system perspective on rubber mount tests G. Malacrida Alves, E. Balmes ISMA 2022 https://sdtools.com/pdf2/22ISMA%20A%20time%20varying%20system%20perspective%20on%20rubber%20mount%20tests.pdf
?? [Expertise] Quality modelling hints: simplification pitfalls with preloaded modal analysis.
?Verification and Validation is at the foundation of numerical analysis ensuring modelling quality. “All models are wrong but some are useful” is a common saying, but focusing on usefulness, a quality model is expected to be mistakes free regarding implementation and input values, and capable of approaching the physics at play.
??All models are then a simplification of reality, and simplification levels must be assessed for each procedure. For multi-step analyses such as preloaded modal analysis, implications may vary so that intermediate adaptations may be needed.? This is the case for brake squeal, where pressure actuation is simplified not to model the brake fluid. Its behavior however induces different main characteristics in statics and dynamics. Not altering the initial simplified model input suited to statics will lead to quality problems in dynamics!
?? Ensuring quality can thus be a challenging task, that can be eased by appropriate tools. SDTools develops original tools for this purpose, for implementation verification and validation through experimental correlation and updating.
??Check out our latest website post about this subject to get more insights, and what this means for a brake actuator simplification : https://www.sdtools.com/quality-modelling-hints-simplification-pitfalls-with-preloaded-modal-analysis-the-case-of-pressure-application-for-brake-squeal/
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