53 research outputs found
Analysis of the influence of passenger vehicles front-end design on pedestrian lower extremity injuries by means of the LLMS model
No full textObjective: The work aims at investigating the influence of some front-end design parameters of a passenger vehicle on the behavior and damage occurring in the human lower limbs while impacted in an accident.
Methods: The analysis is carried out by means of finite element analysis using a generic car model for the vehicle and the Lower Limbs Model for Safety (LLMS) for the purpose of pedestrian safety. Considering the pedestrian standardized impact procedure (as in the 2003/12/EC Directive) a parametric analysis, through a DOE plan, was done. Various material properties, bumper thickness, position of the higher and lower bumper beams and the position of pedestrian, were made variable in order to identify how they influence the injury occurrence. The injury prediction was evaluated from the knee lateral flexion, the ligaments elongation, and the state of stress in the bone structure.
Results: The results highlighted that the offset between the higher and lower bumper beams is the most influencing parameter affecting the knee ligament response. The influence is smaller or absent considering the other responses and the other considered parameters. The stiffness characteristics of the bumper are, instead, more notable on the tibia. Even if an optimal value of the variables could not be identified trends were detected, with the potential of indicating strategies for improvement.
Conclusions: The behavior of a vehicle front-end in the impact against a pedestrian can be improved optimizing its design. The work indicates potential strategies for improvement. In this work, each parameter was changed independently one at a time: in future works the interaction between the design parameters could be also investigated. Moreover, a similar parametric analysis can be carried out using a standard mechanical legform model in order to understand potential diversities or correlations between standard tools and human models
Design and analysis of integrated thermal protection system based on lightweight C/SiC pyramidal lattice core sandwich panel
No full textThermal protection system (TPS) plays the key role to successful development of hypersonic vehicles. Here, a novel structurally and thermally integrated thermal protection system (ITPS) based on the lightweight C/SiC pyramidal core lattice sandwich panel is proposed. This ITPS integrates advantages of low areal density and high temperature resistance up to 1600 degrees C. Heat transfer characteristics and compressive responses of the C/SiC sandwich panel are established in advance. The results demonstrate that filling alumina fibers in the pore significantly reduce the effective thermal conductivity from 2.45-4.83 W/m degrees C to no more than 0.7 W/m degrees C. The critical relative density is determinated for the failure models under aerodynamic pressure load. Meanwhile, an analysis procedure of the ITPS is exclusively established under typical aerodynamic heat flux and pressure load. With fulfillment of both temperature and mechanical constraints, minimum areal density is obtained. Compared with current metal corrugated core ITPS, the ITPS proposed here significantly raises the temperature limitation up to 1600 degrees C and reduces the areal density up to 35%, and is very promising for potential application in hypersonic vehicles. (C) 2016 Elsevier Ltd. All rights reserved.fundamental research funds for the central universities; National Natural Science Foundation of China [11602081, 51507106, 51405150]SCI(E)[email protected]; [email protected]
Influence of Vehicle Frontal Structure on Protective Characteristics of Brain Injury of Bicyclist
No full text
Towards lower limbs new injury criteria for pedestrian safety based on realistic impact conditions
No full textLa sécurité du piéton est un problème de santé publique, qui doit être traité tant par les acteurs de la recherche que par l'industrie automobile pour apporter des solutions technologiques innovantes. Dans les accidents impliquant des piétons, le premier contact est généralement localisé sur les membres inférieurs exhibant de fréquentes et nombreuses lésions pouvant être très sévères. Compte tenu des caractéristiques biomécaniques du membre inférieur, comment améliorer les critères de blessures existants pour contribuer au développement d'une voiture moins agressive pour les piétons ? La présente étude vise donc à promouvoir des améliorations significatives de critères de blessure des membres inférieurs pour la sécurité des piétons combinant des essais expérimentaux et des simulations numériques. Un modèle par éléments finis des membres inférieurs (modèle LLMS) a été utilisé et amélioré pour étudier les réponses mécaniques des membres inférieurs dans des conditions de chargement realists. Une attention particulière a été accordée sur la capacité du modèle à prédire séparément les blessures des os longs et celles de l'articulation du genou pour développer deux critères de blessures distincts. Pour le tibia, la nature de sa structure et les conditions de chargement qui lui sont appliquées nous ont conduit à proposer une courbe quadratique de moment en flexion qui tient compte de différents points d'impact. Pour le genou, le critère de blessure a été établi à partir d'une fonction combinant cisaillement latéral et flexion latérale. Ce critère permet de hiérarchiser la nature et la sévérité des lésions en fonction du mécanisme de blessure prépondérant.Pedestrian safety is a worldwide concern, which needs to be investigated by both vehicle manufacturers and researchers to approach innovative solutions. In car-Pedestrian accidents, lower limbs have been demonstrated to be the most frequently injured body region of the pedestrian. Given the biomechanical features of lower limbs, how the existing injury criteria could be improved to aid the development of a pedestrian friendly car? The current study aims to promote significant improvements in the injury criteria of lower limbs for pedestrian safety combining experimental tests and numerical simulations. A finite element lower limb model (LLMS model) was used and improved to investigate the mechanical responses of lower limbs in the loading conditions reflecting the car-Pedestrian impact. A particular attention was paid on the model ability of predicting separately the injuries of long bones and knee joints to develop the corresponding injury criteria. With regard to the tibia structure and its loading condition in pedestrian accidents, we proposed a quadratic curve of bending moments to tibia locations as its injury tolerance. Given dominant injury mechanisms of the ligaments, the knee injury criterion was established as a function of combined joint kinematics including lateral bending and lateral shearing. Moreover, these criteria are relevant with the previous and current experimental test results. Finally, the efficiency of the proposed criteria was evaluated by a parametric study of the realistic car-Pedestrian impact conditions
Incidences of various passenger vehicle front-end designs on pedestrian lower limb injuries
No full textThe present study aims to investigate the influence of various passenger vehicle front-end designs on knee ligaments and tibia injuries of pedestrian lower limbs by finite element simulations. Using a detailed finite element model of the lower limb, this work was focused on tibia fractures and knee ligament ruptures of lower limbs during vehicle?pedestrian impacts. The influences of vehicle front-end structures on the risk of these two injury occurrences were investigated using super mini, small family car, executive car, and multipurpose vehicle passenger vehicle types. The overall results show that the bumper beam design play an important role in inducing pedestrian lower limb injuries. Its height to the road surface, width in the height direction, and the deformable depth between it and the bumper fascia should be all considered in the vehicle design to protect pedestrian lower limbs
Optimization Design of Body-in-White Stiffness Test Rig Based on the Global Adaptive Algorithm of the Hybrid Element Model
No full textOne of the challenging aspects of designing body-in-white stiffness test rigs is measuring test accuracy. This paper proposes a method of integrating the body-in-white stiffness test rig and the body-in-white into an overall model for the optimization design. It establishes an optimization mathematical model based on the overall structure of the stiffness test rig, taking into account the factors affecting the accuracy of the test results of the body-in-white stiffness test rig. The stiffness test rig’s testing accuracy can be significantly increased by designating the degrees of freedom at each connection position as discrete variables. The Hybrid and Adaptive Metamodeling Method (HAM) is used to optimize the mathematical model. This approach uses and integrates three distinct metamodels with various attributes. The body-in-white torsional stiffness test result error is only 1.1%, and the body-in-white bending stiffness test result error is only 3.4%, owing to the optimization result that was used to design and manufacture a set of body-in-white stiffness test rigs and use them for a body-in-white stiffness test verification
Optimizing Vehicle Body Cross-Sections Using a Parametric Mathematical Model
No full textThis paper proposes a fast optimization method of body section at the conceptual design stage, based on the demand for body performance in body concept design. The study first establishes a geometrically simplified model of the truss body structure and uses the transfer matrix method to establish a fully parameterized model of the geometrically simplified body under bending conditions. Then, the stochastic gradient genetic algorithm is used to optimize the solution and determine the geometric parameters of each section. In the example of this paper, after the optimization of the established meshless model, the mass of the whole vehicle is reduced by 30%, and the stiffness of the whole vehicle is greater than that of the benchmark vehicle (5128 N/mm, 4386 N/mm), and at the same time, compared with the conceptual design method of the body of CAE technology, the modeling time is greatly reduced, and the computational efficiency of the analytical method is greatly improved compared with the finite element method
Investigation on risk prediction of pedestrian head injury by real-world accidents
No full textHead injury is the most common and fatal injury in car-pedestrian accidents. Due to the lack of human test data, real-world accident data is useful for the research on the mechanism and tolerance of head injuries. The objective of the present work is to investigate pedestrian head-brain injuries through real car-pedestrian accidents and evaluate the existed injury criteria. Seven car-to-pedestrian accidents in China were selected from the IVAC (Investigation of Vehicle Accident in Changsha) database. Accident reconstructions using multi-body models were conducted to determine the kinematic parameters associated with the injury and were used to measure head injury criteria. Kinematic parameters were input into a finite element model to run simulations on the head-brain and car interface to determine levels of brain tissue stress, strain, and brain tissue injury criteria. A binary logistic regression model was used to determine the probability of head injury risk associated with AIS3+ injuries (Abbreviated Injury Scale). The results showed that head injury criteria using kinematic parameters can effectively predict injury risk of a pedestrians’ head skull. Regarding brain injuries, physical parameters like coup/countercoup pressure are more effective predictors. The results of this study can be used as the background knowledge for pedestrian friendly car design
Injury tolerance of tibia for the vehicle-pedestrian impact
No full textLower limbs are normally the first contacted body region during car-pedestrian accidents, and easily suffer serious injuries. The previous tibia bending tolerances for pedestrian safety were mainly developed from three-point bending tests on tibia mid-shaft. The tibia tolerances of other locations are still not investigated enough. In addition, tibia loading condition under the car-pedestrian impact should be explored to compare with the three-point bending. This work aims to investigate the injury tolerance of tibia fracture with combined experimental data and numerical simulation. Eleven new reported quasistatic bending tests of tibia mid-shaft, and additional eleven dynamic mid-shaft bending test results in the previous literature were used to define injury risk functions. Furthermore, to investigate the influence of tibia locations on bending tolerance, finite element simulations with lower limb model were implemented according to three-point bending and pedestrian impact conditions. The regressive curve of tibia bending tolerance was obtained from the simulations on the different impact locations, and indicated that tibia fracture tolerance could vary largely due to the impact locations for the car-pedestrian crash
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