Efficacité des équipements de protection 'légers' pour les usagers de 2RM en cas de glissade

Journées scientifiques 'Deux-roues motorisés', Bron, France, 15-/10/2013 - 16/10/2013Cette recherche porte sur les problèmes de sécurité passive des usagers de 2RM lorsque les conditions climatiques sont chaudes. L'objectif est d'analyser et d'évaluer les équipements de protection vestimentaire (à savoir blousons, pantalons et gants) dits « légers » en configuration de glissade sur la chaussée. Le travail s'est décomposé en deux parties complémentaires : une approche expérimentale et une approche numérique. Concernant l'approche expérimentale, elle concernait des essais de glissade sur bitume réalisées avec des corps donnés à la science. Deux campagnes de trois tests (soit au total 6 essais) ont été réalisées à des vitesses de 30km/h et 50 km/h. Pour chaque campagne, un essai a été effectué avec des vêtements légers, un avec des vêtements lourds et un sans équipement spécifique. Les résultats montrent qu'à des vitesses de l'ordre de 30 km/h, le sujet glisse sur environ 4 mètres pour un temps de glissade inférieur à la seconde. A 50 km/h, le sujet glisse durant 1,5 secondes sur une distance d'environ 10 mètres. Concernant la protection offerte par les équipements, si des zones de frottement ont été constatées de manière plus importante sur les vêtements légers que lourds, les résultats montrent toutefois que ces équipements (qu'ils soient légers ou lourds) offrent une protection suffisante dans le cas de glissade courte (moins de 10 mètres) puisqu'aucune lésion notamment de brûlure n'a été constatée. Ce qui n'est pas le cas lors des essais sans protection individuelle où des abrasions de la peau ont été constatées sur les sujets. D'un point de vue numérique, 360 simulations ont été effectuées afin d'identifier l'influence de différents paramètres sur la glissade tels que la vitesse du motocycliste au sol (de 10 à 60 km/h), son orientation (0°, 30°, 90°, 180°), sa position par rapport au sol (dos au sol, de profil, de face, allongé, recroquevillé). Les résultats montrent des distances de glissade jusqu'à 30 mètres pour un temps inférieur à 3 secondes. Les simulations ont également permis de quantifier une force de frottement moyenne d'environ 4000N pouvant aller jusqu'à 12000N. Les segments corporels subissant le plus de frottement sont le tronc et les membres inférieurs. Enfin, ce travail s'est conclu par une réflexion sur les retombées de cette étude concernant les normes existantes sur les équipements

Relations de dépendance entre la configuration d'un accident VL-piéton et le déroulement du choc

Cette étude porte sur la compréhension des phénomènes mis en jeu lors d'un accident où un véhicule percute un piéton. L'objectif est de déterminer les relations de dépendance entre certains paramètres de configuration d'un accident tels que la vitesse du véhicule ou la position du piéton au moment de l'impact et le déroulement du choc (impact du piéton sur le véhicule, projection au sol). Ce travail est basé sur la réalisation de nombreuses simulations numériques d'accident véhicule-piéton à l'aide d'un modèle multicorps et en suivant un plan d'expériences. Une étude paramétrique a ainsi été réalisée en faisant varier les facteurs d'entrée suivants: la vitesse et l'accélération du véhicule, l'orientation du piéton par rapport au véhicule, la position des jambes du piéton au moment de l'impact, le critère de rupture des tibias, le coefficient de frottement entre le piéton et le sol, la modélisation du contact entre le piéton et le véhicule. L'influence de ces paramètres sur le déroulement du choc a ensuite été analysée au travers des paramètres de sortie suivants : la position, la vitesse et l'angle de l'impact de la tête sur le véhicule, les critères lésionnels au niveau de la tête et des jambes, le type de projection observé et les distances de projection au sol du piéton. Un des caractères innovant de cette étude est la prise en compte des phénomènes d'interaction entre les différents facteurs. Les résultats montrent ainsi que la projection au sol du piéton est essentiellement déterminée par les valeurs de l'accélération du véhicule, la vitesse du véhicule, les choix de modélisation du contact entre le piéton et le véhicule, mais aussi par leurs interactions respectives. Le sens de projection du piéton dépend principalement de son orientation par rapport au véhicule au moment de l'impact et de la position de ses jambes. D'une manière plus générale, les résultats de cette recherche permettent de mettre en avant de nombreux facteurs d'influence et introduit la notion d'interaction entre ces facteurs. Ces résultats peuvent, par exemple, servir de base lors de choix de modélisation ou être utilisés lors de la détermination de la configuration la plus probable d'un accident réel

Assessment methodology of Active Pedestrian Safety Systems: an estimation of safety impact

SIMBIO-M 2014, SIMulation technologies in the fields of BIO-Sciences and Multiphysics: BioMechanics, BioMaterials and BioMedicine, Marseille, France, 19-/06/2014 - 20/06/2014Devoid of any protection, pedestrians are highly vulnerable to road accidents against a vehicle. To enhance their protection, new safety-based technologies have been introduced in the vehicle market. These on-board systems are developed to prevent crashes from occurring or reduce their severity by reducing the impact speed. Several methods assessing these systems have been presented. This research is focusing on assessing the benefit of Active Pedestrian Safety Systems (APSS's) for pedestrian injury mitigation. Researchers have established a relationship between impact severity and variations in speed impact. This project is examining the effect of speed reduction on variations in impact conditions. Outlines of the assessment method are presented here illustrated with one example. The first step consists of gathering a sample of real vehicle/pedestrian crashes provided by in-depth crash investigation. A considerable level of details is required to reconstruct numerically the pre-crash sequence including trajectories of the vehicle and pedestrian prior to the collision and the eventual obstacles. Each crash is modelled by representing the vehicle and pedestrian involved and the road environment. An APSS is then virtually represented by the parameters of the sensor and actuator. Once modelling has been set up, all the required components of each sub-model (crash environment, vehicle, pedestrian, and sensor and actuator technology) are implemented through a computational simulation and so interacting in a virtual environment identical to the real world crash scenario. This batch simulation provides a set of data displaying a new impact speed distribution. This distribution is estimated according to the actuation of the emergency braking manoeuvre. The last step is to estimate change in injury outcome using the HIC. These changes are calculated through the use of multi-body system (MBS) software, MADYMO®. The real accident is firstly simulated in order to obtain the actual risk. Finally, by adding the effect of the emergency braking manoeuvre, the simulation enables to find out if the risk is reduced. To show the possibilities of this assessment method, an accident case has been selected. In the original configuration of the crash, the HIC was 1645.6 for an impact speed of 37 km/h. With an APSS fitted in the vehicle, the impact speed is reduced to 8.9 km/h and the pedestrian head doesn't hit any part of the vehicle and hit the ground resulting in a very low HIC value of 28.2. In this research, a formalized assessment methodology has been presented and illustrated with one case to forecast the safety benefits of APSS. This method is based on confronting these systems to real accident configurations through computational simulations. The safety impacts of these systems is then estimated by comparing injury outcome with and without the system enabled for the crash set

Methodology for a global bicycle real world accidents reconstruction

The use of the bicycle on a large scale encouraged in the context to develop an eco friendly environment is facing today on a range of barriers. One of these barriers identified by researchers and governments is observed to include ‘road safety’. Hence, it is necessary to set up a protection system for bicyclists especially for the cephalic segment. Currently only few studies are available concerning the head impact loading in case of real accidents. Therefore, the objective of this work is to identify the initial condition of head impact in case of real accident. Head impact velocity and head impact area are extracted and implemented in the last generation of head injury prediction tool to simulate the head trauma by impacting directly the Strasbourg University Finite Element Head Model (SUFEHM) on the vehicle structures. The present study can be divided into three activities i.e. obtain real bicyclist accidents data issued from in depth accident investigation databases, cyclist body kinematic reconstruction to obtain the initial conditions of the head just before the impact and head impact simulation to evaluate the head loading during impact and the injury risk. A total of 26 bicyclists’ accident cases with head injuries have been collected from both a French and a German accident database. For each accident case, body kinematic has been simulated using Madymo® software. Two methodologies and human multibody models were used: 10 accident cases have been reconstructed by IFSTTAR using its owned developed human model and 16 accident cases have been reconstructed by Unistra using the human pedestrian TNO model. The results show that the head is impacted more often on top parietal zone, and the mean impact velocity is 6.8 ± 2.7 m/s with 5.5 ± 3.0 m/s and 3.4 ± 2.1 m/s for normal and tangential components respectively. Among these real accidents, 19 cases have been selected to be simulated by finite element computations by coupling the human head model and a windscreen model whose properties were extracted from literature. All reconstructed head impact gave results in accordance with the damage actually incurred to the victims. The objective of this study is to demonstrate the feasibility of numerical reconstruction as an understanding tool of the head impact conditions in bicyclist's accident cases, and hence providing knowledge for helmet optimization using biomechanical criteria

Head injury criteria in child pedestrian accidents

Improved protection for the child pedestrian requires a precise knowledge of the biomechanics of specific injury mechanisms for this particular category of pedestrian. In the absence of tests on cadaver subjects, numerical models are a possible route of investigation for developing a predictive model for the severity of injuries. The purpose of this study was to develop an Abbreviated Injury Scale-head (AIS-head) prediction model from numerical simulations of real accident configurations between a vehicle and a child pedestrian. Fifteen real accident configurations were collected from three different databases and simulated in order to identify a realistic injury criterion. For each configuration, a complete multi-body simulation of the accident, followed by a finite element simulation of the head/hood contact, was performed. Sixteen numerical indicators of injury, related to both the kinematics and the stress distribution, were recorded at the end of each reconstruction. To assess the predictive capacity of our model, four new cases of real accidents were also simulated. Statistical analysis showed that a combination of different numerical indicators predicted the AIS-head of an accident accurately, with a mean error of 0.25

Real-Time Analysis of the Dynamic Foot Function: A Machine Learning and Finite Element Approach

International audienceAbstract Finite element analysis (FEA) has been widely used to study foot biomechanics and pathological functions or effects of therapeutic solutions. However, development and analysis of such foot modeling is complex and time-consuming. The purpose of this study was therefore to propose a method coupling a FE foot model with a model order reduction (MOR) technique to provide real-time analysis of the dynamic foot function. A generic and parametric FE foot model was developed and dynamically validated during stance phase of gait. Based on a design of experiment of 30 FE simulations including four parameters related to foot function, the MOR method was employed to create a prediction model of the center of pressure (COP) path that was validated with four more random simulations. The four predicted COP paths were obtained with a 3% root-mean-square-error (RMSE) in less than 1 s. The time-dependent analysis demonstrated that the subtalar joint position and the midtarsal joint laxity are the most influential factors on the foot functions. These results provide additionally insight into the use of MOR technique to significantly improve speed and power of the FE analysis of the foot function and may support the development of real-time decision support tools based on this method

Are custom-made foot orthoses of any interest on the treatment of foot pain for prolonged standing workers?

Background The prolonged standing position is an important factor in the onset of foot musculoskeletal disorders among workers. Safety shoes, designed to protect against the physical constraints of the work environment, do not address this issue to date. Objectives The goal of this study is to assess the possible benefits of custom-made foot orthoses among prolonged standing workers. Study design repeated measures without control group. Methods Thirty-four standing workers who suffer from foot pain volunteered for the study. Custom-made foot orthoses, designed by a podiatrist, were 3D-printed and distributed to each volunteer. Static balance as well as static and dynamic plantar pressure measurements were carried out with sensors inserted in the safety shoes, before and after three weeks of wearing foot orthoses daily. A questionnaire on pain and comfort was also distributed before and after treatment. Results Feelings of pain, discomfort and heavy legs were found to be significantly reduced after wearing 3D-printed orthoses (