Analyse modale opérationnelle du couple vélo-cycliste (S10)

A l'heure actuelle, le confort du cycliste est devenu primordial, surtout quand on sait que certains cyclistes peuvent parfois passer plus de 6 heures sur leur vélo lors de certaines courses ou encore accumuler plus de 3000km lors de grands tours. Les travaux de Chiementin estiment une durée limite d'exposition de 7 minutes avant d'engendrer des effets délétères sur route pavée. L'objectif du travail est ici d'étudier le comportement dynamique du vélo, de manière à mettre en avant les différents paramètres qui peuvent éventuellement influencer le confort du cycliste. Cette étude du comportement dynamique est réalisée par la mise en place d'une analyse modale opérationnelle

Study of angular cutting conditions using multiple scratch tests onto low carbon steel: An experimental-numerical approach

Multiple parallel scratches are often analyzed to understand the material removal mechanisms due to abrasion. However, successive scratches with different orientations may represent better the conditions found in machining processes, such as honing and belt finishing. The objective of this work was to analyze the cutting forces and the phenomena of material removal due to abrasion, arising from angular scratches in low carbon steel. Experimental and numerical techniques were considered. In both, analyses considered the presence of an initial set of parallel scratches, followed by a second set of scratches with different orientations (10, 20 or 30°) with respect to the previous one. The cutting action was performed by a tool representing an abrasive particle, which had a cono-spherical geometry with 235μm tip radius and 30° apex angle. The cutting settings were: 50m/min scratch velocity and 100μm depth of cut. In the experimental part, scratches were conducted using a shaper machine tool equipped with a tungsten carbide (WC-Co) stylus. Tests were conducted on a Kistler platform, which allowed force measurement. Surfaces were later analyzed with an optical profilometer. The numerical simulations considered a ductile damage model with element deletion to provide the material removal during the scratches. Experimental and numerical results showed that the angle affects the cutting forces, especially when one scratch crosses a previously scratched region. The 20° case was the most critical, especially in terms of the cutting forces, due to the accentuated material strain-hardening for this condition. Likewise, this fact was corroborated by numerical results, which indicated a higher energy necessary to plastic deformation, and a reduced material removal at 20°

Orthogonal cut of SPS-sintered composites with ferrous matrix and Fe Mo S particles: Numerical and experimental analysis

Metal-matrix composites with solid lubricant reinforcements may present a suitable alternative to improve the tribological behavior of sintered components. Besides the performance during the application, the presence of solid lubricants may also modify component manufacture, for example, during machining operations to achieve complex shapes not directly obtained from the sintering process. This work describes a numerical and experimental analysis on the orthogonal cut of metal-matrix composites composed of FeMoS particles embedded in an Astaloy 85 Mo (Höganäes AB) matrix. Specimens were prepared using the Spark-Plasma Sintering (SPS) technique, from mixtures containing powders of Astaloy 85 Mo steel and 2 wt% or 4 wt% of molybdenum disulfide (MoS2). An unreinforced Astaloy 85 Mo specimen (without MoS2) was also included in the analysis. Different microstructures were observed after SPS. The unreinforced specimen presented a ferrite-pearlite structure with a porosity level below 2% and the specimen sintered with 2 wt% of MoS2 presented iron sulfide particles dispersed in the steel matrix. The structure of the specimen sintered with 4 wt % was more complex, with two distinct phases dispersed in the Astaloy 85 Mo matrix. Experimental orthogonal cuts were conducted on the three specimens using a shaper machine tool equipped with a tungsten carbide (WCCo) cutting insert. Tests were recorded using a high-speed camera. The machined surfaces were later analyzed with an optical profilometer and in a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS). The chips were also characterized. The cutting operation was simulated by two-dimensional (2D) finite-element analysis. The meshes were prepared based on the specimen microstructures and considering the properties of the individual phases. Results have indicated significant differences in the cutting process. Observation of the chip surfaces indicates plastic deformation on the unreinforced specimen, in opposition to more uniform scratches on the composite surfaces, especially that of the specimen sintered with 4 wt % of MoS2

Accelerometer analysis for optimizing performance and risk prevention in cycling

Le cycliste a toujours souhaité maintenir et/ou améliorer ses performances. Cependant le confort reste un facteur déterminant au vu du temps passé sur le vélo. Ce confort est notamment altéré par les revêtements et les irrégularités du terrain générant des sollicitations le plus souvent néfastes à la santé. Ainsi, la communauté scientifique s'intéresse à la recherche d'un compromis performance-santé. Cet intérêt la mène à exploiter un grand nombre d'outils caractérisés par la mesure d'une grandeur physique. Parmi ces grandeurs, l'accélération apparaît comme une caractéristique riche en information. Elle permet l'analyse de la performance par un suivi de l'athlète et la prévention de la santé par l'évaluation et la limitation des effets délétères. Ces deux aspects, abordés dans ces travaux de thèse, s'appuient sur les concepts généraux de la mécanique des structures.Cyclists have always wanted to keep and/or improve their performance. However, comfort is still a determinant factor because of the time spend on the bike. This comfort is especially altered by the coverings and the irregularities of the field generating loads that are often harmful to health. Therefore, the scientific community is interested in the research of a compromise between performance and health. This interest leads it to explore a large amount of tools characterized by the measure of a physical quantity. Among these values, the acceleration appears as a quantity rich in information. It allows to analyse the performance through monitoring of the athlete or the prevention of health disorders by the evaluation and limitation of the harmful effects

Adaptation psysiologique à l'altitude et prise en charge du mal aigü des montagnes (enquête effectuée dans les refuges du Mont-Blanc)

REIMS-BU Santé (514542104) / SudocSudocFranceF

Pharmacologie appliquée à la thérapeutique (la progéria)

LILLE2-BU Santé-Recherche (593502101) / SudocSudocFranceF