Finite element implementation of nearly-incompressible rheological models based on multiplicative decompositions

International audienceThe present work is concerned with the numerical integration of finite viscoelastic or viscoplastic models. A numerical integration scheme based on the definition of a flow direction and a flow amplitude as in elastoplasticity is proposed. The most original feature of this approach resides in a local correction of the direction and amplitude with a sub-stepping strategy. Comparisons with the results obtained using a classical tensorial integrator based on a Runge-Kutta-Fehlberg scheme are provided. The reliability of the present numerical scheme is investigated with three rheological models two are viscoelastic (Zener and Poynting-Thomson) and one is viscoplastic

Substructure method for an assembly of structures invariant in one direction

International audienceThis study deals with the modeling by finite elements of an elastomeric composite structure. The main difficulties lie in the heterogeneity of the piece and in the geometrical non-linearity due to the centrifugal forces. We use the combination of two different methods of level sub-structuring. The first one is a multi-level sub-structuring method and the second is a more classical sub-structuring. After computation, the complete solution in displacement, the complete stress field and the global dumping of the structure (by an energetic method) are obtained

A micro-mechanically based continuum damage model for fatigue life prediction of filled rubbers

International audienceThis paper presents a continuum damage model based on two mechanisms: decohesion between fillers and matrix at a micro-scale followed by a crack nucleation at a macro-scale. That scenario was developed considering micro observations conduced with a SEM and an original experimental procedure based on simple shear and tension specimens. Damage accumulation is related to fatigue life using the continuum damage mechanics (CDM). The material behavior is investigated using the statistical framework introduced by Martinez et al. (2011). A Finite Element implementation is proposed and some numerical examples are provided

Le rôle des réseaux d’acteurs dans l’innovation publique complexe : le cas du vote électronique dans le canton de Genève

Actor networks play an essential role on innovation processes. In the public sector, innovations are often highly complex. This complex nature substantially affects innovation processes, their barriers, levers and their outcomes. Complexity also subverts the role of actor networks in each phase of innovation processes. These changes are illustrated through an exemplary case study of the highly complex project of e-voting in the canton of Geneva

Analyse du comportement hyperélastique d'un tuyau en EPDM : Application pour distribuer de l'eau en irrigation

International audienceDans le domaine de l'irrigation avec des eaux usées, bon nombre de travaux portent sur les aspects sanitaires. Cependant un des verrous à la diffusion de ces techniques demeure le système d'épandage. Il doit assurer une distribution homogène et durable. En s'inspirant des dispositifs agricoles, on observe que la régulation est souvent assurée par une membrane de type élastomère. Pour cela, il nous faut comprendre le comportement des matériaux de type élastomère et de définir leurs lois de comportement. La famille des élastomères est remarquable par la multiplicité de ses propriétés mécaniques. Trois d'entre eux : l'effet Mullins, l'hystérésis et l'effet visqueux, ont été mis en évidence durant les expériences en laboratoire. Dans ces travaux, nous avons cherché à nous affranchir de ces effets pour caractériser le comportement réversible de ces matériaux. Pour cela plusieurs types d'essais de traction ont été réalisés : uniaxiale, biaxiale et équibiaxiale, afin d'identifier le comportement du matériau. / In the field of the irrigation with waste water, a lot of works concern the sanitary aspects. However one of the bolts in the distribution of these techniques remains the system of manuring. It has to assure a homogeneous and sustainable distribution. Being inspired by agricultural devices, we observe that the regulation is often guaranteed by a membrane of an elastomer type. We need to understand the behaviour of the elastomer materials and the definition of their laws of behaviour. The family of elastomers is characterized by the multiplicity of its mechanical properties. Three of them: the Mullins effect, the hysteresis and the viscous effect, were noticed during the experiments in the laboratory. In these works, we tried to disengage from these effects in order to characterize the reversible behaviour of these materials. Therefore a series of tension tests were realized in order to identify the behaviour of material: uniaxial, biaxial and equibiaxial

A Coupled SFM-ASCRIBE Model To Investigate the Influence of Emotions and Collective Behavior in Homogeneous and Heterogeneous Crowds

The understanding of crowd behavior dynamics holds immense significance in ensuring public safety across a range of situations, including emergency evacuations and large-scale events. Our research focuses on two primary objectives: investigating the impact of emotions on crowd movement and gaining valuable insights into collective behavior within crowds. To achieve this, we present a coupled model, incorporating an enhanced ASCRIBE model with an agent displacement model. We introduce heterogeneity into our model by incorporating specific mobility laws for different categories of panicked crowds, considering the influence of emotions on both speed and direction. Through numerical simulations, we analyze the model's parameters, observe the behavior of uniform crowds, and explore the collective dynamics within diverse crowds. By conducting comprehensive simulations and analyses, the findings from this study can contribute to the development of more effective crowd management strategies and emergency evacuation protocols

Linearized behavior of a dissipative rubber with large static preloads

International audienceThe dynamic behavior of filled rubber has been intensively studied during the last 20 years and a large number of finite strain models have been developed. However, many industrial applications involve small vibrations superimposed on large static preloads. In this specific case, the dynamic problem can be treated as a small amplitude problem near a finite strain state. In this paper, we discuss how to extend previous approaches by taking arbitrary (large) dynamic rotations into account. A general approach is proposed as well as a finite element implementation. Results show that large rotations are required in some tests, even at small dynamic amplitudes

Les freins culturels à l'innovation dans l'administration publique : spécificités helvétiques

Les processus d’innovation au sein des organisations publiques sont souvent soumis à plusieurs freins, et notamment des freins culturels. Cette étude explore la nature des freins culturels à l’innovation publique en Suisse. Elle se base sur l’analyse inductive d’entretiens semi-directifs menés auprès de quinze cadres de la fonction publique et chefs de projets, dans les cantons de Vaud et Genève. Les résultats montrent que plusieurs freins culturels préalablement décrits par la littérature internationale, tels que l’aversion au risque, la dépendance au sentier et la tendance à donner peu d’autonomie aux collaborateurs, se retrouvent aussi en Suisse. Cependant deux freins inédits ressortent de notre étude : la recherche du consensus, qui modère l’innovation pour la rendre acceptable, et la non personnification des projets d’innovation, qui les empêche d’être portés par un leader. Innovation processes in public sector organizations (PSO) are often hindered by various barriers, including cultural barriers. This study explores the very nature of the cultural barriers to innovation in Swiss PSO, and potential Swiss particularities. An inductive analysis of fifteen semi-structured interviews has been conducted with public managers in the cantons of Vaud and Geneva. The results show that various cultural barriers previously identified in the international literature, such as risk aversion, path dependency and employees’ lack of autonomy, are active in the Swiss context. Two additional barriers appear in the Swiss context: the propensity for consensus, which moderates innovations to make them acceptable, and the anonymization of projects, which prevents innovations to be driven by a leader

Les treize postulats de l’innovation publique : identification et discussion dans le champ de la santé

Cet article vise à identifier et discuter les postulats véhiculés par la littérature sur l’innovation dans le secteur public. Il s’intéresse plus particulièrement aux organisations de santé. En se basant sur une revue de la littérature (98 études) sur l’innovation publique, treize postulats – affirmations sans preuve empirique – ont été identifiés. Ils portent sur la désirabilité de l’innovation et sur sa raison d’être (le pourquoi de l’innovation), sur sa nature (le quoi), sur son contexte (le où et le quand), et sur ses méthodes de développement (le comment et avec qui). Ces postulats se retrouvent dans la plupart des études analysées, que celles-ci soient consacrées au champ de la santé ou non. Or, le champ de la santé présente des spécificités qui mettent en doute la pertinence de ces postulats. C’est pourquoi ces derniers sont discutés à la lumière de ce champ. The Hidden Assumptions behind Public Sector Innovation: Implications for the Health Sector This article aims to identify and discuss the hidden assumptions of the literature on innovation of public organizations, with a special focus on studies about the health sector. Based on a systematic literature review (98 studies) we identified thirteen hidden assumptions on public sector innovation. These assumptions concern the desirability of public innovation and its legitimacy (the why of innovation), its nature (the what), its context (the where and when), and its methods of development (how and with whom). Our study shows that these assumptions are used in most studies, whether they are devoted to the health sector or not. However, the health sector has specificities that question the relevance of these assumptions. For this reason, the hidden assumptions are discussed in the light of this sector