Asymmetric friction: Modelling and experiments

International audienceThe effect of asymmetry with respect to sliding direction has been recently proved to be important in the analysis of static contact interactions of some automotive mechanical structures. In the present paper, we consider a nonclassical friction law, based on a dissymmetry of friction in a given sliding direction. A simple analytical micro-model has been adopted to derive the macroscopic model via averaging. Not only does it allow the law macroscopic characteristics to be determined but it also theoretically proves the existence of such dissymmetry of friction. The thermodynamic admissibility of the law is then shown from the derivation of a generalized standard model including friction. To complete the analysis, the existence of asymmetric friction conditions is confirmed from an experimental point of view. We then compare theoretical computations resulting from the analytical model with experimental results

One year OSIRHYS IV project synthesis: mechanical behaviour of 700 bar type iv high pressure vessel code qualification.

International audienceIn this paper we present results of the OSIRHYS IV French project which aims to develop andvalidate models and methods for composite high pressure design and optimization withbehavior uncertainties knowledge. Models of the five partners of this project are presentedand burst simulation results are compared for three test temperatures (-40°C, 15°C and85°C)

A four-layered self-consistent scheme applied to two-phase composites

International audienceFor both particulate and unidirectional composites, the traditional scheme describing one phase as the matrix and the other as the reinforcement is not completely satisfactory for high reinforcement content. This article proposes the use of De Larrard and Le Roy's geometric model [1] to better define the morphological characteristics of a two-phase composite, in conjunction with the selfconsistent method, thanks to the recent development of n+l layered models. The comparison of results with experimental data has proved promising

OPTIMISATION DU COUSSINET DE BIELLE: CARACTERISATIONS, SIMULATIONS ET MISE EN FORME

Crank bearings are present in all car internal combustion engines. Apart from the generation of a torque on the crankshaft due to the strain applied on the latter, the crank has to ensure the smooth running of its articulations with the piston and the crankshaft. To guarantee this last function, we therefore use bearings. The kind of bearing used for this investigation has an aluminum-tin alloy plating on a steel foil.The main questions which manufacturers have to solve include the following :- knowledge of the bearing antifriction material's thermo mechanical characteristics ;- knowledge of the factors at work during the bearing forming process ;- validity of length measurement controls, particularly the importance of the margin of error caused by the bearing's friction in its test seating.Thus, initially and also taking into account the multiphase aspect of the material, we studied the different homogenization techniques associated with this kind of material. To answer this question as accurately as possible, we developed a four phase model. The validity of these models has been tested by experimental comparison with different types of specimens and across a range of temperatures.Armed with this knowledge of thermo mechanical properties, we then undertook the study of the bearing's friction in its sealing and in particular the effect of this phenomenon on the developed length bearing control operation. A calculation/measurement correlation enabled us lo identify what friction coefficient values needed to be consider.Knowing the characteristics of the materials and the friction coefficient of the bearing/steel seating, we were finally able to study the forming of the bearing itself. A numerical simulation of the different stages in the forming process was developed with the help of the SYSTUS software program. A simplified model of RDM type was used in order to confirm orders of size obtained by the code. To conclude, the calculation/test comparison is proving very satisfactory in each of the experimental tests we carried out.Les coussinets de bielles sont présents clans tous les moteurs thermiques a combustion interne de véhicules automobiles. Outre la génération d'un couple sur le vilebrequin dû a !'effort qu'elle applique sur ce dernier, la bielle doit aussi garantir le bon fonctionnement de ses articulations avec le piston et avec le vilebrequin. Pour assurer cette dernière fonction, on utilise précisément des coussinets. Le type de coussinet ayant servi a cette étude possède un revêtement en alliage d'aluminium-étain plaqué sur un feuillard d'acier.Les principales questions que se pose l'industriel concernent les points suivants:- la connaissance des caractéristiques thermomécaniques du matériau antifriction du coussinet ;- la connaissance des facteurs influents !ors de l’opération de mise en forme du coussinet ;- la validité des contrôles de mesure de longueur, en particulier l'importance de l'erreur induite par le frottement du coussinet clans son logement de contrôle.Ainsi dans une première partie et compte tenu de l'aspect multiphase du matériau, nous avons étudié les différentes techniques d'homogénéisation relatives a ce type de matériau. Pour répondre le plus fidèlement à la question posée, nous avons aussi développé un modèle a quatre phases. Ces modèles ont été validés par confrontation avec des essais sur différentes familles d'éprouvettes et sur toute une gamme de températures.Fort de cette connaissance des propriétés thermomécaniques, nous avons abordé, dans une seconde partie, l'étude du frottement du coussinet dans son logement et plus particulièrement l'effet de ce phénomène sur l'opération de contrôle de longueur développée du coussinet. Une corrélation calcul/mesure nous a permis d'identifier les valeurs des coefficients de friction a considérer.Connaissant les caractéristiques des matériaux et le coefficient de frottement coussinet/logement en acier, nous avons pu. dans une dernière partie, étudier la mise en forme du coussinet lui-même. Une simulation numérique des différentes étapes de la mise en forme a été réalisée a l'aide du logiciel SYSTUS. Un modèle simplifié de type RDM a été employé pour confirmer les ordres de grandeur obtenus par le code. In fine, la comparaison calcul expérience s’avère tout a fait satisfaisante pour chacun des contrôles expérimentaux que nous avons réalisés

OPTIMISATION DU COUSSINET DE BIELLE: CARACTERISATIONS, SIMULATIONS ET MISE EN FORME

Crank bearings are present in all car internal combustion engines. Apart from the generation of a torque on the crankshaft due to the strain applied on the latter, the crank has to ensure the smooth running of its articulations with the piston and the crankshaft. To guarantee this last function, we therefore use bearings. The kind of bearing used for this investigation has an aluminum-tin alloy plating on a steel foil.The main questions which manufacturers have to solve include the following :- knowledge of the bearing antifriction material's thermo mechanical characteristics ;- knowledge of the factors at work during the bearing forming process ;- validity of length measurement controls, particularly the importance of the margin of error caused by the bearing's friction in its test seating.Thus, initially and also taking into account the multiphase aspect of the material, we studied the different homogenization techniques associated with this kind of material. To answer this question as accurately as possible, we developed a four phase model. The validity of these models has been tested by experimental comparison with different types of specimens and across a range of temperatures.Armed with this knowledge of thermo mechanical properties, we then undertook the study of the bearing's friction in its sealing and in particular the effect of this phenomenon on the developed length bearing control operation. A calculation/measurement correlation enabled us lo identify what friction coefficient values needed to be consider.Knowing the characteristics of the materials and the friction coefficient of the bearing/steel seating, we were finally able to study the forming of the bearing itself. A numerical simulation of the different stages in the forming process was developed with the help of the SYSTUS software program. A simplified model of RDM type was used in order to confirm orders of size obtained by the code. To conclude, the calculation/test comparison is proving very satisfactory in each of the experimental tests we carried out.Les coussinets de bielles sont présents clans tous les moteurs thermiques a combustion interne de véhicules automobiles. Outre la génération d'un couple sur le vilebrequin dû a !'effort qu'elle applique sur ce dernier, la bielle doit aussi garantir le bon fonctionnement de ses articulations avec le piston et avec le vilebrequin. Pour assurer cette dernière fonction, on utilise précisément des coussinets. Le type de coussinet ayant servi a cette étude possède un revêtement en alliage d'aluminium-étain plaqué sur un feuillard d'acier.Les principales questions que se pose l'industriel concernent les points suivants:- la connaissance des caractéristiques thermomécaniques du matériau antifriction du coussinet ;- la connaissance des facteurs influents !ors de l’opération de mise en forme du coussinet ;- la validité des contrôles de mesure de longueur, en particulier l'importance de l'erreur induite par le frottement du coussinet clans son logement de contrôle.Ainsi dans une première partie et compte tenu de l'aspect multiphase du matériau, nous avons étudié les différentes techniques d'homogénéisation relatives a ce type de matériau. Pour répondre le plus fidèlement à la question posée, nous avons aussi développé un modèle a quatre phases. Ces modèles ont été validés par confrontation avec des essais sur différentes familles d'éprouvettes et sur toute une gamme de températures.Fort de cette connaissance des propriétés thermomécaniques, nous avons abordé, dans une seconde partie, l'étude du frottement du coussinet dans son logement et plus particulièrement l'effet de ce phénomène sur l'opération de contrôle de longueur développée du coussinet. Une corrélation calcul/mesure nous a permis d'identifier les valeurs des coefficients de friction a considérer.Connaissant les caractéristiques des matériaux et le coefficient de frottement coussinet/logement en acier, nous avons pu. dans une dernière partie, étudier la mise en forme du coussinet lui-même. Une simulation numérique des différentes étapes de la mise en forme a été réalisée a l'aide du logiciel SYSTUS. Un modèle simplifié de type RDM a été employé pour confirmer les ordres de grandeur obtenus par le code. In fine, la comparaison calcul expérience s’avère tout a fait satisfaisante pour chacun des contrôles expérimentaux que nous avons réalisés

Effects of mechanical quality of the concrete between steel and FRP in CFRP strengthening : theoretical analysis.

International audienceThere are many studies on the strengthening of works done with Fibre Reinforced Polymer (FRP). Most of these concern beams, techniques for bonding and effects of bonded fibre-reinforced composites in the strengthening of structural materials [1]. None of these studies considers the effect of the concrete, between the steel rods and the FRP, on the behaviour of the strengthened structure. This work aims to analyze the effects of mechanical quality of the concrete between steel and FRP. Therefore, a theoretical analysis is developed, simulating the bending behaviour of slabs reinforced by FRP strips. In this analysis, the concrete of the area between FRP strips and lower steel reinforcements is regarded as multi-layer non-linear concrete. The proposed model, based on commercially Finite Element Code Ansys [2], is used to analyse the effects of the layer of concrete covering the steel on the bending behaviour of FRP-strengthened slabs

Optimization of blended composite structures: parametric study

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Single- and multi-objective optimization of composite structures: the influence of design variable

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Comparison of optimal design methods for type 3 high-pressure storage tanks.

International audienceThis study compares different optimal design methods for producing two-angle filament-wound structures able to withstand under internal pressure. In recent years, studies have concentrated on materials and their damage behaviour as well as winding optimisation techniques in relation to vessel geometry and manufacturing processes, but none of these studies has established a definitive design rule. In the present paper, two developed methods, one based on a basic CPT with gradual damage and enumerative optimisation, the other a more sophisticated finite element (FE) method with Reddy's progressive damage law and genetic algorithm (GA) optimisation are compared to recent results based on CDM theory and a 3D FE technique incorporating a modified GA. The results were used to compare the advantages and limitations of each method and to derive simple design rules and calculation strategies that would reliably obtain a very good CPU cost/efficiency ratio

Cumulative microslip at the interface of mechanical assemblies under cyclic loading

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