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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 01 Oct 2023 05:18:19 GMT2023-10-01T05:18:19ZCharacterization of identification errors and uses in localization of poor modal correlation
http://hdl.handle.net/10985/11675
Characterization of identification errors and uses in localization of poor modal correlation
MARTIN, Guillaume; BALMES, Etienne; CHANCELIER, Thierry
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.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/116752017-01-01T00:00:00ZMARTIN, GuillaumeBALMES, EtienneCHANCELIER, ThierryWhile 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.Review of model updating processes used for brake components
http://hdl.handle.net/10985/10921
Review of model updating processes used for brake components
MARTIN, Guillaume; BALMES, Etienne; VERMOT DES ROCHES, Guillaume; CHANCELIER, Thierry
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.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/109212015-01-01T00:00:00ZMARTIN, GuillaumeBALMES, EtienneVERMOT DES ROCHES, GuillaumeCHANCELIER, ThierryTo 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.Squeal measurement with 3D Scanning Laser Doppler Vibrometer: handling of the time varying system behavior and analysis improvement using FEM expansion
http://hdl.handle.net/10985/13856
Squeal measurement with 3D Scanning Laser Doppler Vibrometer: handling of the time varying system behavior and analysis improvement using FEM expansion
MARTIN, Guillaume; CHANCELIER, Thierry; VERMOT DES ROCHES, Guillaume; BALMES, Etienne
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 variations with wheel position and reproducibility tests. To obtain a high spatial density measurement, 3D Scanning Laser Doppler Vibrometer is interesting but leads to iterative measurements on a time-varying system. An algorithm to merge sequential measurement and extract main shapes is detailed. Even with a high-density 3D SLDV measurement, shapes characterizing the squeal event are still only known on accessible surfaces. Minimum Dynamic Residual Expansion (MDRE) is thus finally used to estimate motion on a full FE mesh which eases interpretation and highlights areas where the test and the model contain errors.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/138562018-01-01T00:00:00ZMARTIN, GuillaumeCHANCELIER, ThierryVERMOT DES ROCHES, GuillaumeBALMES, EtienneIn 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 variations with wheel position and reproducibility tests. To obtain a high spatial density measurement, 3D Scanning Laser Doppler Vibrometer is interesting but leads to iterative measurements on a time-varying system. An algorithm to merge sequential measurement and extract main shapes is detailed. Even with a high-density 3D SLDV measurement, shapes characterizing the squeal event are still only known on accessible surfaces. Minimum Dynamic Residual Expansion (MDRE) is thus finally used to estimate motion on a full FE mesh which eases interpretation and highlights areas where the test and the model contain errors.The Component Mode Tuning (CMT) method. A strategy adapted to the design of assemblies applied to industrial brake squeal
http://hdl.handle.net/10985/10920
The Component Mode Tuning (CMT) method. A strategy adapted to the design of assemblies applied to industrial brake squeal
VERMOT DES ROCHES, Guillaume; REJDYCH, Gabriel; BALMES, Etienne; CHANCELIER, Thierry
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.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/109202014-01-01T00:00:00ZVERMOT DES ROCHES, GuillaumeREJDYCH, GabrielBALMES, EtienneCHANCELIER, ThierryNumerical 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.Updating and design sensitivity processes applied to drum brake squeal analysis
http://hdl.handle.net/10985/10922
Updating and design sensitivity processes applied to drum brake squeal analysis
MARTIN, Guillaume; BALMES, Etienne; VERMOT DES ROCHES, Guillaume; CHANCELIER, Thierry
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.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/109222016-01-01T00:00:00ZMARTIN, GuillaumeBALMES, EtienneVERMOT DES ROCHES, GuillaumeCHANCELIER, ThierrySqueal 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.Damping characterization of a high speed train catenary
http://hdl.handle.net/10985/10918
Damping characterization of a high speed train catenary
VO VAN, Olivier; BALMES, Etienne; LORANG, Xavier
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.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/109182015-01-01T00:00:00ZVO VAN, OlivierBALMES, EtienneLORANG, XavierCatenary 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.Numerical design and test on an assembled structure of a bolted joint with viscoelastic damping
http://hdl.handle.net/10985/10455
Numerical design and test on an assembled structure of a bolted joint with viscoelastic damping
HAMMAMI, Chaima; BALMES, Etienne; GUSKOV, Mikhail
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.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/104552015-01-01T00:00:00ZHAMMAMI, ChaimaBALMES, EtienneGUSKOV, MikhailMechanical 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.Squeal complex eigenvalue analysis, advanced damping models and error control
http://hdl.handle.net/10985/10915
Squeal complex eigenvalue analysis, advanced damping models and error control
VERMOT DES ROCHES, Guillaume; CHIELLO, Olivier; BALMES, Etienne; LORANG, Xavier
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.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/109152015-01-01T00:00:00ZVERMOT DES ROCHES, GuillaumeCHIELLO, OlivierBALMES, EtienneLORANG, XavierEstimation 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.Validation of a reduced model of railway track allowing long 3D dynamic calculation of train-track interaction
http://hdl.handle.net/10985/10916
Validation of a reduced model of railway track allowing long 3D dynamic calculation of train-track interaction
ARLAUD, Elodie; COSTA D'AGUIAR, Sofia; BALMES, Etienne
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.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/109162014-01-01T00:00:00ZARLAUD, ElodieCOSTA D'AGUIAR, SofiaBALMES, EtienneIn 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.Pantograph catenary dynamic optimisation based on advanced multibody and finite element co-simulation tools
http://hdl.handle.net/10985/8223
Pantograph catenary dynamic optimisation based on advanced multibody and finite element co-simulation tools
LAURENT, Christophe; MASSAT, Jean-Pierre; NGUYEN TAJAN, T.M.L.; BIANCHI, Jean-Philippe; BALMES, Etienne
This paper presents recent developments undertaken by the 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. The FE catenary models from the SNCF software are coupled with a full flexible MB representation with pneumatic actuation of pantograph. These advanced functionalities allow new kind of numerical analysis such as dynamic improvements based on a passive pneumatic suspension or assessment of crash risks in crossing areas, that demonstrate the powerful capabilities of this computing approach.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/82232013-01-01T00:00:00ZLAURENT, ChristopheMASSAT, Jean-PierreNGUYEN TAJAN, T.M.L.BIANCHI, Jean-PhilippeBALMES, EtienneThis paper presents recent developments undertaken by the 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. The FE catenary models from the SNCF software are coupled with a full flexible MB representation with pneumatic actuation of pantograph. These advanced functionalities allow new kind of numerical analysis such as dynamic improvements based on a passive pneumatic suspension or assessment of crash risks in crossing areas, that demonstrate the powerful capabilities of this computing approach.