Time/frequency analysis of contact-friction instabilities. Application to automotive brake squeal.

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

Design oriented simulation of contact-friction instabilities in application to realistic brake assemblies

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

Compatibility measure and penalized contact resolution for incompatible interfaces

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

Étude des variations des paramètres cliniques lors de l'entraînement des chiens au Centre national d'instruction cynophile de la gendarmerie

Les chiens de la gendarmerie sont amenés à produire des efforts tels que des exercices de mordant ou de pistage. Il arrive que certains d'entre eux deviennent insuffisants à l'effort. Ils doivent alors être réformés. Après un état des lieux relatifs aux connaissances concernant la physiologie de l'effort et les pathologies pouvant apparaître suite à l'entraînement, ce travail se penche sur l'entraînement dispensé au Centre National d'Instruction Cynophile de la Gendarmerie. Un groupe de 17 chiens a été suivi lors des 3 mois de stage. Un examen clinique a été effectué à deux reprises au début et à la fin du stage dans le but de trouver un paramètre clinique pouvant permettre d'évaluer le devenir du chien vis-à-vis de l'effort. Cet examen comprenait la prise de la fréquence cardiaque, de la fréquence respiratoire, de la température rectale et du poids ainsi qu'un tracé électrocardiographique. Aucun chien du groupe n'ayant présenté d'insuffisance à l'effort, cette étude a permis de trouver certains paramètres pouvant servir au suivi de l'entraînement des chiens. La fréquence respiratoire semble peu exploitable dans le contexte de la gendarmerie étant donné le port de la muselière lors de l'examen clinique. La température rectale peut, quand à elle, être suivie avec attention notamment lors d'efforts produits lors de fortes chaleurs. L'évolution de la fréquence cardiaque lors d'un effort est modifiée suite à l'entraînement. Il semble que les intervalles ébauchés dans cette étude peuvent être affinés afin de suivre et d'adapter l'entraînement des chiens

Time/frequency analysis of contact-friction instabilities. Application to automotive brake squeal.

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

Design oriented simulation of contact-friction instabilities in application to realistic brake assemblies

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

Frequency Doubling Nanocrystals for Cancer Theranostics

A novel bio-photonics approach based on the nonlinear optical process of second harmonic generation by non-centrosymmetric nanoparticles is presented and demonstrated on malignant human cell lines. The proposed method allows to directly interact with DNA in absence of photosensitizing molecules, to enable independent imaging and therapeutic modalities switching between the two modes of operation by simply tuning the excitation laser wavelength, and to avoid any risk of spontaneous activation by any natural or artificial light source.Comment: 16 pages, 7 figure

New polymer coating to visualize surgical mesh by MRI

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