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

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

Instrumentation for Mechanical Vibration Analysis

International audienc

Physical risk associated with vibration at cycling

The vibrations undergone by men are a well-known and widely studied risk factor in the industrial world. They are transmitted to the whole body or the upper limbs and they are measured, and limited, according to international standards. Disorders resulting from exposure to vibration are varied in nature: osteoarticular, muscular, vascular, and neurological. In this context, an European Directive 2002/44/EC to the protection of workers exposed to vibration, precises thresholds for vibration exposures and defines the procedure for risk prevention. Nevertheless, the effect of vibration is little studied in sports despite the ubiquity of these. Vibration can induce discomfort, degrading performance or causing musculoskeletal disorders. This paper makes an overview of the studies involving the vibrations during cycling. At first, this paper will summarize the different standards and guidelines relating vibration in humans, which present a guide for the measurement and evaluation of the vibration and exposure limits. Secondly, this paper presents a state of the art vibration effects: (i) the physiological and pathological disorders in athletes, (ii) and the performance. A third part will be devoted to the synthesis of numerical studies that represent the biodynamic response and help to predict the effects of human body vibration. Finally, new research and innovations will be discussed based on studies in other sports

Contribution of Bamboo for Vibratory Comfort in Biomechanics of Cycling

Vibrations in cycling produced by road irregularities could cause health problems and affect the cyclist’s comfort and performance. Therefore researchers and manufacturers focus their efforts to reduce the vibrations.Las vibraciones en el ciclismo producidas por las irregularidades de la carretera podrían causar problemas de salud y afectar a la comodidad y el rendimiento del ciclista. Por ello, los investigadores y los fabricantes centran sus esfuerzos en reducir las vibraciones.1. GRESPI, Moulin de la Housse, Université de Reims Champagne Ardenne, Reims, France 2. IN’BO, ZA Les Bouleaux, Les Voivres, France 3. Escuela Colombiana de Ingeniería Julio Garavito, Bogotá D.C., Colombia 4. Montclair State University, Upper Montclair, New Jersey, USA 5. EPF, 3 bis rue Lakanal, Sceaux, France 6. Arts et Métiers ParisTech, MSMP / EA7350, Châlons-en-Champagne, Franc

Relationship between the Pedaling Biomechanics and Strain of Bicycle Frame during Submaximal Tests

The aim of this study was to analyse the effect of forces applied to pedals and cranks on the strain imposed to an instrumented bicycle motocross (BMX) frame. Using results from a finite element analysis to determine the localisation of highest stress, eight strain gauges were located on the down tube, the seat tube and the right chain stay. Before the pedaling tests, static loads were applied to the frame during bench tests. Two pedaling conditions have been analysed. In the first, the rider was in static standing position on the pedals and applied maximal muscular isometric force to the right pedal. The second pedaling condition corresponds to three pedaling sprint tests at submaximal intensities at 150, 300 and 550 W on a cycle-trainer. The results showed that smaller strain was observed in the pedaling condition than in the rider static standing position condition. The highest strains were located in the seat tube and the right chain stay near the bottom bracket area. The maximum stress observed through all conditions was 41 MPa on the right chain stay. This stress was 11 times lower than the yield stress of the frame material (460 MPa). This protocol could help to adapt the frame design to the riders as a function of their force and mechanical power output. These results could also help design BMX frames for specific populations (females) and rider morphology

Contribution of Bamboo for Vibratory Comfort in Biomechanics of Cycling

Vibrations in cycling produced by road irregularities could cause health problems and affect the cyclist’s comfort and performance. Therefore researchers and manufacturers focus their efforts to reduce the vibrations.Las vibraciones en el ciclismo producidas por las irregularidades de la carretera podrían causar problemas de salud y afectar a la comodidad y el rendimiento del ciclista. Por ello, los investigadores y los fabricantes centran sus esfuerzos en reducir las vibraciones.1. GRESPI, Moulin de la Housse, Université de Reims Champagne Ardenne, Reims, France 2. IN’BO, ZA Les Bouleaux, Les Voivres, France 3. Escuela Colombiana de Ingeniería Julio Garavito, Bogotá D.C., Colombia 4. Montclair State University, Upper Montclair, New Jersey, USA 5. EPF, 3 bis rue Lakanal, Sceaux, France 6. Arts et Métiers ParisTech, MSMP / EA7350, Châlons-en-Champagne, Franc