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http://hdl.handle.net/10985/23306
A Structural Dynamics Modification Strategy based on Expanded Squeal Operational Deflection Shapes
MARTIN, Guillaume; BALMES, Etienne; CHANCELIER, Thierry; THOUVIOT, Sylvain; LEMAIRE, Rémi
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.
Sun, 01 May 2022 00:00:00 GMThttp://hdl.handle.net/10985/233062022-05-01T00:00:00ZMARTIN, GuillaumeBALMES, EtienneCHANCELIER, ThierryTHOUVIOT, SylvainLEMAIRE, RémiTo 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.Time/frequency analysis of contact-friction instabilities. Application to automotive brake squeal.
http://hdl.handle.net/10985/8232
Time/frequency analysis of contact-friction instabilities. Application to automotive brake squeal.
VERMOT DES ROCHES, Guillaume; BALMES, Etienne; PASQUET, Thierry; LEMAIRE, Rémi
Robust design of silent brakes is a current industrial challenge. Braking systems enter in the more general context of unstable systems featuring contact friction interaction. Their simulation requires time integra- tion schemes usually not adapted to combination of large industrial models (over 600,000 DOF) and long simulations (over 150,000 time steps). The paper ﬁrst discusses selection of the contact/friction model and adaptations of the integration scheme. The relation between the nominal steady state tangent modes and the system evolution over time is then evaluated. The time response shows a nearly periodic response that is analyzed as a limit cycle. It is shown that instantaneous dynamic stability predictions show stable/unstable transitions due to changes in the contact/friction state. These transitions are thought to give an understanding of the mechanism that limits levels for these self sustained vibrations. The concept is exploited to suggest novel ways to analyze complex modes.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/82322010-01-01T00:00:00ZVERMOT DES ROCHES, GuillaumeBALMES, EtiennePASQUET, ThierryLEMAIRE, RémiRobust design of silent brakes is a current industrial challenge. Braking systems enter in the more general context of unstable systems featuring contact friction interaction. Their simulation requires time integra- tion schemes usually not adapted to combination of large industrial models (over 600,000 DOF) and long simulations (over 150,000 time steps). The paper ﬁrst discusses selection of the contact/friction model and adaptations of the integration scheme. The relation between the nominal steady state tangent modes and the system evolution over time is then evaluated. The time response shows a nearly periodic response that is analyzed as a limit cycle. It is shown that instantaneous dynamic stability predictions show stable/unstable transitions due to changes in the contact/friction state. These transitions are thought to give an understanding of the mechanism that limits levels for these self sustained vibrations. The concept is exploited to suggest novel ways to analyze complex modes.Compatibility measure and penalized contact resolution for incompatible interfaces
http://hdl.handle.net/10985/8096
Compatibility measure and penalized contact resolution for incompatible interfaces
VERMOT DES ROCHES, Guillaume; BALMES, Etienne; BEN DHIA, Hachimi; LEMAIRE, Rémi; PASQUET, Thierry
Handling of large industrial mechanical assemblies implies structure interactions commonly modeled with contact formulations. In cases where component interfaces are discretized using non conforming meshes, classical contact solutions have difﬁculties producing correct contact pressure ﬁelds. The method presented in this paper gives a relevant measure of interface compatibility and shows how it can be exploited to obtain regular contact pressures or limit over-integration in the contact formulation.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/80962010-01-01T00:00:00ZVERMOT DES ROCHES, GuillaumeBALMES, EtienneBEN DHIA, HachimiLEMAIRE, RémiPASQUET, ThierryHandling of large industrial mechanical assemblies implies structure interactions commonly modeled with contact formulations. In cases where component interfaces are discretized using non conforming meshes, classical contact solutions have difﬁculties producing correct contact pressure ﬁelds. The method presented in this paper gives a relevant measure of interface compatibility and shows how it can be exploited to obtain regular contact pressures or limit over-integration in the contact formulation.Design oriented simulation of contact-friction instabilities in application to realistic brake assemblies
http://hdl.handle.net/10985/8108
Design oriented simulation of contact-friction instabilities in application to realistic brake assemblies
VERMOT DES ROCHES, Guillaume; BALMES, Etienne; LEMAIRE, Rémi; PASQUET, Thierry
This paper presents advances in non-linear simulations for systems with contact-friction, with an application to brake squeal. A method is proposed to orient component structural modifications from brake assembly simulations in the frequency and time domains. A reduction method implementing explicitly component-wise degrees of freedom at the system level allows quick parametric analyses giving modification clues. The effect of the modification is then validated in the time domain where non-linearities can be fully considered. A reduction method adapted for models showing local non-linearities is purposely presented along with an optimization of a modified non linear Newmark scheme to make such computation possible for industrial models. The paper then illustrates the importance of structural effects in brake squeal, and suggests solutions.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/81082010-01-01T00:00:00ZVERMOT DES ROCHES, GuillaumeBALMES, EtienneLEMAIRE, RémiPASQUET, ThierryThis paper presents advances in non-linear simulations for systems with contact-friction, with an application to brake squeal. A method is proposed to orient component structural modifications from brake assembly simulations in the frequency and time domains. A reduction method implementing explicitly component-wise degrees of freedom at the system level allows quick parametric analyses giving modification clues. The effect of the modification is then validated in the time domain where non-linearities can be fully considered. A reduction method adapted for models showing local non-linearities is purposely presented along with an optimization of a modified non linear Newmark scheme to make such computation possible for industrial models. The paper then illustrates the importance of structural effects in brake squeal, and suggests solutions.