Technical Skills Influences on Front Crawl Tumble Turn Performance in Elite Female Swimmers

International audienceThe objective of this research was to compare technical skills composed of kinematic and kinetic variables in the complex motor task of a tumble turn between 9 elites and 9 sub-elite female swimmers. The best tumble turn among three attempts was analyzed using a three-dimensional underwater protocol. A total of 37 kinematic variables were derived from a Direct Linear Transformation algorithm for 3D reconstruction, and 16 kinetic variables measured by a piezoelectric 3D force platform. Data were analyzed by Student's t-test and effect size statistics. Pearson correlations were applied to the data of the eighteen swimmers to relate the association of 53 kinematic, kinetic variables to the performance of the tumble-turn (3 meters Round Trip Time, 3m RTT). The approach and the whole turn times were faster for elite swimmers compared to sub elites (1.09±0.06 vs. 1.23±0.08 sec, and 2.89±0.07 vs. 3.15±0.11 sec.), as well as the horizontal speeds of the swimmers’ head 1 m before the rotation (1.73±0.13 vs. 1.57±0.13 m/sec.), at the end of the push-off on force platform (2.55±0.15 vs. 2.31±0.22 m/sec.) and 3 m after the wall (2.01±0.19 vs. 1.68±0.12 m/sec.). Large differences (|d| > 0.8) in favor of the elite swimmers were identified for the index of upper body extension at the beginning of the push-off, the lower limb extension index at the end of push-off, and among the kinetic variables, the horizontal impulse and lateralization of the push-off. Correlations for the whole group revealed a moderate to strong relationship between 6 body extension indices and 3mRTT performance. For the kinetic variables, the correlations indicated the fastest swimmers in 3mRTT showed large lateral impulse during placement (r=0.46), maximum horizontal force during the push-off (r=0.45) and lateralization of the push-off (r=0.44) (all p<0.05). Elite female swimmers had higher approach and push-off speeds, were more streamlined through the contact, and showed a higher horizontal impulse and lateralization of the push-off, than their sub-elite counterparts

Optimisation des structures lattices : une comparaison entre le layout optimization et l'optimisation topologique

International audienceNous discutons et comparons deux méthodes d'optimisation structurale pertinentes pour les structures lattices : l'optimisation topologique et le layout optimization. Nous présentons une application originale de ces deux méthodes dans le cadre de la minimisation de la masse structures lattices cellules masse en tenant compte d'un critère de rupture en contrainte. Nous proposons ensuite une comparaison qualitative de ces deux méthodes et discutions de leur pertinence respective pour l'optimisation des structures lattices

Technical Skills Influences on Front Crawl Tumble Turn Performance in Elite Female Swimmers

International audienceThe objective of this research was to compare technical skills composed of kinematic and kinetic variables in the complex motor task of a tumble turn between 9 elites and 9 sub-elite female swimmers. The best tumble turn among three attempts was analyzed using a three-dimensional underwater protocol. A total of 37 kinematic variables were derived from a Direct Linear Transformation algorithm for 3D reconstruction, and 16 kinetic variables measured by a piezoelectric 3D force platform. Data were analyzed by Student's t-test and effect size statistics. Pearson correlations were applied to the data of the eighteen swimmers to relate the association of 53 kinematic, kinetic variables to the performance of the tumble-turn (3 meters Round Trip Time, 3m RTT). The approach and the whole turn times were faster for elite swimmers compared to sub elites (1.09±0.06 vs. 1.23±0.08 sec, and 2.89±0.07 vs. 3.15±0.11 sec.), as well as the horizontal speeds of the swimmers’ head 1 m before the rotation (1.73±0.13 vs. 1.57±0.13 m/sec.), at the end of the push-off on force platform (2.55±0.15 vs. 2.31±0.22 m/sec.) and 3 m after the wall (2.01±0.19 vs. 1.68±0.12 m/sec.). Large differences (|d| > 0.8) in favor of the elite swimmers were identified for the index of upper body extension at the beginning of the push-off, the lower limb extension index at the end of push-off, and among the kinetic variables, the horizontal impulse and lateralization of the push-off. Correlations for the whole group revealed a moderate to strong relationship between 6 body extension indices and 3mRTT performance. For the kinetic variables, the correlations indicated the fastest swimmers in 3mRTT showed large lateral impulse during placement (r=0.46), maximum horizontal force during the push-off (r=0.45) and lateralization of the push-off (r=0.44) (all p<0.05). Elite female swimmers had higher approach and push-off speeds, were more streamlined through the contact, and showed a higher horizontal impulse and lateralization of the push-off, than their sub-elite counterparts

Optimisation des structures lattices : une comparaison entre le layout optimization et l'optimisation topologique

International audienceNous discutons et comparons deux méthodes d'optimisation structurale pertinentes pour les structures lattices : l'optimisation topologique et le layout optimization. Nous présentons une application originale de ces deux méthodes dans le cadre de la minimisation de la masse structures lattices cellules masse en tenant compte d'un critère de rupture en contrainte. Nous proposons ensuite une comparaison qualitative de ces deux méthodes et discutions de leur pertinence respective pour l'optimisation des structures lattices

Vers des structures treillis manufacturées : une comparaison entre l'optimisation de layout et l'optimisation topologique

International audienceThe repetitive nature of cellular lattice structures brings various interesting features among which fast assembly and repair time, reduced tooling, and manufacturing costs are major advantages. Additionally, as the mechanical performances of the structure are heavily influenced by the topology and materials of the cell, the designers can optimize the cell to tailor the structure for various scenarios. In this paper, we discuss and compare two relevant structural optimization methods for lattice structures: topology optimization and layout optimization. In the first part of the article, we presented an innovative cellular topology optimization formulation that minimizes the structural mass taking into account the internal stresses. The cellular implementation is based on the full-scale method called variable linking. In the second part, a qualitative comparison of topology and layout optimization is carried out, analysing the strength and the weakness of the two methods when applied to a lattice structure context.La nature répétitive des structures en treillis cellulaires apporte diverses caractéristiques intéressantes parmi lesquelles un temps d'assemblage et de réparation rapide, un outillage et une fabrication à faible coût sont des avantages majeurs. De plus, comme les performances mécaniques de la structure sont fortement influencées par la topologie et les matériaux de la cellule, les concepteurs peuvent l'optimiser pour adapter la structure à divers scénarios. Dans cet article, nous discutons et comparons deux méthodes d'optimisation structurelle pertinentes pour les structures en treillis : l'optimisation topologique et l'optimisation de layout. Dans la première partie de l'article, nous présentons une formulation cellulaire d'optimisation topologique innovante qui minimise la masse structurelle en tenant compte des contraintes internes. La mise en œuvre cellulaire est basée sur la méthode à grande échelle appelée variable linking. Dans la deuxième partie nous avons mené une comparaison qualitative de l'optimisation topologique et de l'optimisation de layout, en analysant les avantages et les inconvénients des deux méthodes lorsqu'elles sont appliquées à un contexte de structure en treillis

Efficient 3D truss topology optimization for aeronautical structures

International audienceTruss lattices are potential candidates for the design of innovative aerostructures, thanks to their high stiffness-to-weight ratio, modularity, and aeroelastic properties. However, when designing ultralight structures, multiple mechanical constraints, such as maximum internal stress or local buckling constraints, must be taken into account since the early design phase. In response to this, a volume minimization problem for 3D structures, subject to multiple load cases, maximum stress, and topological buckling constraints, is formulated in this work. The optimization is solved using a two-step optimization strategy. First, a relaxed formulation is solved by a Sequential Linear Programming algorithm and is used to explore the vast design space of the optimization. During this phase, a heuristic is proposed to reduce the influence of the starting point on the optimized structure. The solution is refined in a second optimization step in which the full non-linear problem is solved using IPOPT, making sure that all the mechanical constraints are respected. The proposed method is validated on multiple two-dimensional classical benchmarks, showing robust behavior with respect to random starting point initializations. Later, the three-dimensional wingbox of the Common Research Model subject to multiple load cases is optimized. The results show that the proposed method can deal with real-sized structures with thousands of candidate members, all while being computationally efficient, optimizing the structure in minutes on a consumer notebook.<br/

Optimisation topologique des treillis (TTO) appliquée à un caisson d'aile cellulaire

International audienceCellular architectured structures' most appealing characteristic is that they are able to create large structures assembling small repetitive components. Thanks to their modular nature, they bring interesting features among which reduced tooling, fast assembly, and short repair time. In the first part of the article, we formulate an optimizing method that minimizes the mass of a cellular architectured structure taking into account internal stresses, local buckling, and pattern repetition constraints. The proposed solving algorithm mitigates the appearance of local minima, a critical problem for discrete trusses. In the second part, the optimization method is applied to a real-size aeronautic application: the minimization of the mass of a cellular 3D wing box subject to lift and torsion loads. Compared to classic cell topologies, the proposed method found a cell 10-times lighter, at the cost of increased manufacturing difficulty.La caractéristique la plus attrayante des structures à architecture cellulaire est qu'elles sont capables de créer de grandes structures en assemblant de petits composants répétitifs. Grâce à leur nature modulaire, elles apportent des caractéristiques intéressantes parmi lesquelles un outillage réduit, un assemblage rapide, et un temps de réparation réduit. Dans la première partie de l'article, nous formulons une méthode d'optimisation qui minimise la masse d'une structure à architecture cellulaire en tenant compte des contraintes internes, du flambage local et de la répétition des motifs. L'algorithme de résolution proposé atténue l'apparition de minima locaux, un problème critique pour les structures en treillis discrètes. Dans la deuxième partie, la méthode d'optimisation est appliquée à une application aéronautique de taille réelle : la minimisation de la masse d'un caisson alaire cellulaire 3D soumis à des charges de portance et de torsion. Par rapport aux topologies de cellules classiques, la méthode proposée a permis de trouver une cellule 10 fois plus légère, au prix d'une difficulté de fabrication accrue