Thierry Pasquet - Academia.edu (original) (raw)

Papers by Thierry Pasquet

HAL (Le Centre pour la Communication Scientifique Directe), Nov 1, 2010

This paper presents advances in non-linear simulations for systems with contact-friction, with an... more 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 nonlinearities 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.

European Journal of Computational Mechanics, 2010

Handling of large industrial mechanical assemblies implies structure interactions commonly modele... more 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. RÉSUMÉ. La gestion d'assemblages mécaniques complexes nécessite souvent des modèles d'interaction de structure par une formulation en contact. Lorsque la discrétisation élément finis des interfaces est non compatible, les résolutions classiques peuvent êtres non régulières. La méthode présentée dans ce papier donne une mesure pertinente de la compatibilité des interfaces et montre comment l'exploiter pour régulariser les pressions de contact ou limiter la sur-intégration dans la formulation du contact.

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, Feb 23, 2015

The elastic properties of a friction material play a significant role in the vibro-acoustic noise... more The elastic properties of a friction material play a significant role in the vibro-acoustic noise, vibration and harshness behaviour of braking systems on a structural scale. Common testing, such as pad compressibility testing and modal testing, allows identification of the global static and dynamic elastic properties respectively, which generally provide data for finite element numerical models. The present investigation presents static and dynamic testing methodology and focuses on the distribution of the elastic properties of friction materials on a pad scale. Besides trying to determine a correlation with bench testing, the added value in updating friction material models with distributed elastic properties for squeal simulation models is evaluated. For investigation of the distribution of the friction material properties of brake pads, quasi-square friction samples of friction materials were collected from several locations of the pad. The experimental meshing provides data on the inner radius and the outer radius of the brake pads as well as on the inlet and the outlet of the pad. For the purpose of this study, six different materials were tested. In addition to four known prototype friction material formulations obtained using the same production process, two commercial friction materials were investigated. The static stiffness is evaluated with a laboratory compression machine set-up whereas the dynamic stiffness is identified from laboratory ultrasonic investigations. The results and coherence of the static and dynamic stiffness distributions obtained by both approaches are compared. The trends with the noise, vibration and harshness bench testing results are also discussed for selected pads. From ultrasonic testing, it is found that the dynamic stiffness distribution can take several forms (flat, concave or convex) which can be different for the in-plane stiffness and the normal stiffness of the pad. It is mainly noticeable along the tangential direction of the pad, reaching a variation of up to 16% between middle of the pad and the edges. The stiffness can also vary by up to 8% along the radial direction of the pad. The measurements performed during this study confirm also that these stiffness distribution patterns are strongly dependent on the formulation friction of the material and on the production process itself. The above-mentioned stiffness distributions were implemented in finite element brake pad models to estimate the potential frequency shift arising from these considerations. The impact of taking into account such information was shown to be limited for the free–free pad modal properties. Nevertheless, the influence of such distributions on the complex eigenvalue analysis of complete finite element brake models was observed and is discussed. Even if the used pad models take into account to some extent the static and dynamic stiffness distributions for complex eigenvalue analysis, they still do not agree with the non-linear material models regarding the stress and the frequency, as shown experimentally. Even if an additional effort is made to determine these stiffness distributions which provide more detailed information for the brake pad finite element models, this physical degree of freedom could drive, to a certain extent, the noise, vibration and harshness responses of the brake systems. A more mature understanding of the influences of the formulations and the process on these distributions and their control at the pad design stage could add a complementary strategy for reduction in the noise, vibration and harshness issues in brake systems.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2010

Robust design of silent brakes is a current industrial challenge. Braking systems enter in the mo... more 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 integration 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.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 15, 2008

This paper presents a modeling strategy employed to obtain converged results on long time simulat... more This paper presents a modeling strategy employed to obtain converged results on long time simulation of complex finite element brake models. First a novel reduction method, adapted to models showing large interface DOF, is presented. The small finite element area in the vicinity of the contact is treated as fully non-linear and while the remaining of the structure is represented by a superelement. The method is thus suited for large finite element models. A time integration scheme, based on a non-linear Newmark, is then adapted to allow large models to be computed over long time periods. This is achieved mainly by the use of a fixed iteration operator throughout the simulation. This technique is applied first to a simplified brake model for validation purposes, then to a state-of-the-art brake model designed by Bosch Chassis Brake Systems. The simulation results are put in perspective with recent publications on the subject.

Springer eBooks, 2011

Classically Component Mode Synthesis has been used to couple models from different sources (mixed... more Classically Component Mode Synthesis has been used to couple models from different sources (mixed test and analysis, different companies, different software, ...) or reduce models. The focus of this paper is on using component modes in a design cycle. Component modes are the natural representation in the lowest part design cycle. In NVH applications, it is well known that coupling at the system level makes understanding of the impact of component design changes difficult. The paper details and uses the disjoint component synthesis method. Like classical CMS this synthesis method considers reduced component models and couples these models to obtain a system level synthesis. The first novel aspect is that a physical interface is assumed to exist between components. Synthesis thus becomes a trivial application of model assembly. The second novel aspect is that components are reduced using component modes and the trace of nominal system modes, thus allowing exact predictions for the nominal design. Illustrations of the methodology are given for an automotive brake application.

European journal of computational mechanics, Aug 6, 2010

Handling of large industrial mechanical assemblies implies structure interactions commonly modele... more 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. RÉSUMÉ. La gestion d'assemblages mécaniques complexes nécessite souvent des modèles d'interaction de structure par une formulation en contact. Lorsque la discrétisation éléments finis des interfaces est non compatible, les résolutions classiques peuvent êtres non régulières. La méthode présentée dans ce papier donne une mesure pertinente de la compatibilité des interfaces et montre comment l'exploiter pour régulariser les pressions de contact ou limiter la sur-intégration dans la formulation du contact.

Revue européenne de mécanique numérique, 2010

Handling of large industrial mechanical assemblies implies structure interactions commonly modele... more 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. RÉSUMÉ. La gestion d'assemblages mécaniques complexes nécessite souvent des modèles d'interaction de structure par une formulation en contact. Lorsque la discrétisation élément finis des interfaces est non compatible, les résolutions classiques peuvent êtres non régulières. La méthode présentée dans ce papier donne une mesure pertinente de la compatibilité des interfaces et montre comment l'exploiter pour régulariser les pressions de contact ou limiter la sur-intégration dans la formulation du contact.

HAL (Le Centre pour la Communication Scientifique Directe), Feb 1, 2019

SAE Technical Paper Series, 2006

SAE Technical Paper Series, 2007

International Journal of …, 2008

International Journal of …, 2009

This paper demonstrates the influence of the trailing end of the piston, or inboard, pad on the p... more This paper demonstrates the influence of the trailing end of the piston, or inboard, pad on the propensity of a brake to generate audible squeal. The unique technique was employed to measure the dynamic CoP at the pad/disk interface during a normal braking operation. ...

Classically Component Mode Synthesis has been used to couple models from different sources (mixed... more Classically Component Mode Synthesis has been used to couple models from different sources (mixed test and analysis, different companies, different software, ...) or reduce models. The focus of this paper is on using component modes in a design cycle. Component modes are the natural representation in the lowest part design cycle. In NVH applications, it is well known that coupling at the system level makes understanding of the impact of component design changes difficult. The paper details and uses the disjoint component synthesis method. Like classical CMS this synthesis method considers reduced component models and couples these models to obtain a system level synthesis. The first novel aspect is that a physical interface is assumed to exist between components. Synthesis thus becomes a trivial application of model assembly. The second novel aspect is that components are reduced using component modes and the trace of nominal system modes, thus allowing exact predictions for the nominal design. Illustrations of the methodology are given for an automotive brake application.

L'actionneur de freinage (10) de vehicule comporte : - une vis (12), - un carter taraude (18)... more L'actionneur de freinage (10) de vehicule comporte : - une vis (12), - un carter taraude (18) en prise avec la vis (12) au moyen d'une liaison irreversible, et - un moteur electrique (M) de commande d'un mouvement de la vis (12) par rapport au carter (18) ou du carter par rapport a la vis de sorte que ce mouvement actionne un element de freinage (E).

This paper presents advances in non-line ar simulations for systems with contact-friction. Presen... more This paper presents advances in non-line ar simulations for systems with contact-friction. Presented applications deal with squeal analysis of industrial (600,000 DOF) brake models. First a reduction method allowing to keep the exact system real modes is proposed for all simulations. For transient simulat ions a modified non-linear Newmark scheme is used to evaluate the apparition of limit cycles. A space-time limit cycle decomposition is then performed to correlate comple x modes and the limit cycle. Although the shapes are close, the comprehension in the syst m behaviour is much finer in the time domain; in particular, since saturation patterns ar e then available. Since transient computations remain costly (12h), the end of the pa per focuses on quick continuation methods to evaluate saturation threshold based on complex m odes trajectories. Encouraging results are obtained, making the concept viable for industrial systems.

The invention relates to an electromechanical actuator (7) for a motor vehicle brake caliper, com... more The invention relates to an electromechanical actuator (7) for a motor vehicle brake caliper, comprising a housing (8) having an attachment plane face (9) to a caliper body (1), this housing (7) containing a electric motor (19) and a mechanical gearbox (14) coupled to each other and comprising the components rotating about axis (AX) of normal orientation to the planar mounting surface (9). According to the invention, the reducer (14) and the motor (19) and the housing (8) extend all three entirely on the same side of the attachment side (9) planar.

HAL (Le Centre pour la Communication Scientifique Directe), Nov 1, 2010

This paper presents advances in non-linear simulations for systems with contact-friction, with an... more 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 nonlinearities 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.

European Journal of Computational Mechanics, 2010

Handling of large industrial mechanical assemblies implies structure interactions commonly modele... more 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. RÉSUMÉ. La gestion d'assemblages mécaniques complexes nécessite souvent des modèles d'interaction de structure par une formulation en contact. Lorsque la discrétisation élément finis des interfaces est non compatible, les résolutions classiques peuvent êtres non régulières. La méthode présentée dans ce papier donne une mesure pertinente de la compatibilité des interfaces et montre comment l'exploiter pour régulariser les pressions de contact ou limiter la sur-intégration dans la formulation du contact.

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, Feb 23, 2015

The elastic properties of a friction material play a significant role in the vibro-acoustic noise... more The elastic properties of a friction material play a significant role in the vibro-acoustic noise, vibration and harshness behaviour of braking systems on a structural scale. Common testing, such as pad compressibility testing and modal testing, allows identification of the global static and dynamic elastic properties respectively, which generally provide data for finite element numerical models. The present investigation presents static and dynamic testing methodology and focuses on the distribution of the elastic properties of friction materials on a pad scale. Besides trying to determine a correlation with bench testing, the added value in updating friction material models with distributed elastic properties for squeal simulation models is evaluated. For investigation of the distribution of the friction material properties of brake pads, quasi-square friction samples of friction materials were collected from several locations of the pad. The experimental meshing provides data on the inner radius and the outer radius of the brake pads as well as on the inlet and the outlet of the pad. For the purpose of this study, six different materials were tested. In addition to four known prototype friction material formulations obtained using the same production process, two commercial friction materials were investigated. The static stiffness is evaluated with a laboratory compression machine set-up whereas the dynamic stiffness is identified from laboratory ultrasonic investigations. The results and coherence of the static and dynamic stiffness distributions obtained by both approaches are compared. The trends with the noise, vibration and harshness bench testing results are also discussed for selected pads. From ultrasonic testing, it is found that the dynamic stiffness distribution can take several forms (flat, concave or convex) which can be different for the in-plane stiffness and the normal stiffness of the pad. It is mainly noticeable along the tangential direction of the pad, reaching a variation of up to 16% between middle of the pad and the edges. The stiffness can also vary by up to 8% along the radial direction of the pad. The measurements performed during this study confirm also that these stiffness distribution patterns are strongly dependent on the formulation friction of the material and on the production process itself. The above-mentioned stiffness distributions were implemented in finite element brake pad models to estimate the potential frequency shift arising from these considerations. The impact of taking into account such information was shown to be limited for the free–free pad modal properties. Nevertheless, the influence of such distributions on the complex eigenvalue analysis of complete finite element brake models was observed and is discussed. Even if the used pad models take into account to some extent the static and dynamic stiffness distributions for complex eigenvalue analysis, they still do not agree with the non-linear material models regarding the stress and the frequency, as shown experimentally. Even if an additional effort is made to determine these stiffness distributions which provide more detailed information for the brake pad finite element models, this physical degree of freedom could drive, to a certain extent, the noise, vibration and harshness responses of the brake systems. A more mature understanding of the influences of the formulations and the process on these distributions and their control at the pad design stage could add a complementary strategy for reduction in the noise, vibration and harshness issues in brake systems.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2010

Robust design of silent brakes is a current industrial challenge. Braking systems enter in the mo... more 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 integration 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.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 15, 2008

This paper presents a modeling strategy employed to obtain converged results on long time simulat... more This paper presents a modeling strategy employed to obtain converged results on long time simulation of complex finite element brake models. First a novel reduction method, adapted to models showing large interface DOF, is presented. The small finite element area in the vicinity of the contact is treated as fully non-linear and while the remaining of the structure is represented by a superelement. The method is thus suited for large finite element models. A time integration scheme, based on a non-linear Newmark, is then adapted to allow large models to be computed over long time periods. This is achieved mainly by the use of a fixed iteration operator throughout the simulation. This technique is applied first to a simplified brake model for validation purposes, then to a state-of-the-art brake model designed by Bosch Chassis Brake Systems. The simulation results are put in perspective with recent publications on the subject.

Springer eBooks, 2011

Classically Component Mode Synthesis has been used to couple models from different sources (mixed... more Classically Component Mode Synthesis has been used to couple models from different sources (mixed test and analysis, different companies, different software, ...) or reduce models. The focus of this paper is on using component modes in a design cycle. Component modes are the natural representation in the lowest part design cycle. In NVH applications, it is well known that coupling at the system level makes understanding of the impact of component design changes difficult. The paper details and uses the disjoint component synthesis method. Like classical CMS this synthesis method considers reduced component models and couples these models to obtain a system level synthesis. The first novel aspect is that a physical interface is assumed to exist between components. Synthesis thus becomes a trivial application of model assembly. The second novel aspect is that components are reduced using component modes and the trace of nominal system modes, thus allowing exact predictions for the nominal design. Illustrations of the methodology are given for an automotive brake application.

European journal of computational mechanics, Aug 6, 2010

Handling of large industrial mechanical assemblies implies structure interactions commonly modele... more 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. RÉSUMÉ. La gestion d'assemblages mécaniques complexes nécessite souvent des modèles d'interaction de structure par une formulation en contact. Lorsque la discrétisation éléments finis des interfaces est non compatible, les résolutions classiques peuvent êtres non régulières. La méthode présentée dans ce papier donne une mesure pertinente de la compatibilité des interfaces et montre comment l'exploiter pour régulariser les pressions de contact ou limiter la sur-intégration dans la formulation du contact.

Revue européenne de mécanique numérique, 2010

Handling of large industrial mechanical assemblies implies structure interactions commonly modele... more 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. RÉSUMÉ. La gestion d'assemblages mécaniques complexes nécessite souvent des modèles d'interaction de structure par une formulation en contact. Lorsque la discrétisation élément finis des interfaces est non compatible, les résolutions classiques peuvent êtres non régulières. La méthode présentée dans ce papier donne une mesure pertinente de la compatibilité des interfaces et montre comment l'exploiter pour régulariser les pressions de contact ou limiter la sur-intégration dans la formulation du contact.

HAL (Le Centre pour la Communication Scientifique Directe), Feb 1, 2019

SAE Technical Paper Series, 2006

SAE Technical Paper Series, 2007

International Journal of …, 2008

International Journal of …, 2009

This paper demonstrates the influence of the trailing end of the piston, or inboard, pad on the p... more This paper demonstrates the influence of the trailing end of the piston, or inboard, pad on the propensity of a brake to generate audible squeal. The unique technique was employed to measure the dynamic CoP at the pad/disk interface during a normal braking operation. ...

Classically Component Mode Synthesis has been used to couple models from different sources (mixed... more Classically Component Mode Synthesis has been used to couple models from different sources (mixed test and analysis, different companies, different software, ...) or reduce models. The focus of this paper is on using component modes in a design cycle. Component modes are the natural representation in the lowest part design cycle. In NVH applications, it is well known that coupling at the system level makes understanding of the impact of component design changes difficult. The paper details and uses the disjoint component synthesis method. Like classical CMS this synthesis method considers reduced component models and couples these models to obtain a system level synthesis. The first novel aspect is that a physical interface is assumed to exist between components. Synthesis thus becomes a trivial application of model assembly. The second novel aspect is that components are reduced using component modes and the trace of nominal system modes, thus allowing exact predictions for the nominal design. Illustrations of the methodology are given for an automotive brake application.

L'actionneur de freinage (10) de vehicule comporte : - une vis (12), - un carter taraude (18)... more L'actionneur de freinage (10) de vehicule comporte : - une vis (12), - un carter taraude (18) en prise avec la vis (12) au moyen d'une liaison irreversible, et - un moteur electrique (M) de commande d'un mouvement de la vis (12) par rapport au carter (18) ou du carter par rapport a la vis de sorte que ce mouvement actionne un element de freinage (E).

This paper presents advances in non-line ar simulations for systems with contact-friction. Presen... more This paper presents advances in non-line ar simulations for systems with contact-friction. Presented applications deal with squeal analysis of industrial (600,000 DOF) brake models. First a reduction method allowing to keep the exact system real modes is proposed for all simulations. For transient simulat ions a modified non-linear Newmark scheme is used to evaluate the apparition of limit cycles. A space-time limit cycle decomposition is then performed to correlate comple x modes and the limit cycle. Although the shapes are close, the comprehension in the syst m behaviour is much finer in the time domain; in particular, since saturation patterns ar e then available. Since transient computations remain costly (12h), the end of the pa per focuses on quick continuation methods to evaluate saturation threshold based on complex m odes trajectories. Encouraging results are obtained, making the concept viable for industrial systems.

The invention relates to an electromechanical actuator (7) for a motor vehicle brake caliper, com... more The invention relates to an electromechanical actuator (7) for a motor vehicle brake caliper, comprising a housing (8) having an attachment plane face (9) to a caliper body (1), this housing (7) containing a electric motor (19) and a mechanical gearbox (14) coupled to each other and comprising the components rotating about axis (AX) of normal orientation to the planar mounting surface (9). According to the invention, the reducer (14) and the motor (19) and the housing (8) extend all three entirely on the same side of the attachment side (9) planar.