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Technical Paper

Development of a Finite Element Model of the Flex-PLI-GTR

2012-04-16
2012-01-0551
Evaluation of pedestrian leg protection performance using the Flex-PLI-GTR (Flexible Pedestrian Legform Impactor Global Technical Regulation) impactor is initiated in JNCAP in 2011. Therefore, a finite element (FE) model of Flex-PLI-GTR is needed for use in digital car development in order to satisfy pedestrian leg protection performance requirements. This paper describes the FE model of Flex-PLI-GTR that has been developed to meet this need. There are three important features of this FE model for obtaining sufficient simulation accuracy. First, the shapes of all Flex-PLI-GTR structures were modeled in detail. Shape information of the inner structures was obtained by computerized tomography scanning and shape information of the inner structures of the outer skin was obtained by laser measurement. Furthermore, the shape of the wrapped skin was incorporated into the FE model based on a wrapping simulation.
Technical Paper

Numerical Simulation of Out-of-Position Front Passenger Injuries in Frontal Crashes Using an Accurate Finite Element Model of the Cockpit Module

2012-04-16
2012-01-0552
While airbags are effective safety devices for reducing occupant injury level, front Out-of-Position (OOP) passengers can be injured by airbag deployment, for example, when a passenger's head is on the instrument panel surface at the time of the collision. Consequently, FMVSS 208 prescribes In-Position and OOP occupant safety performance, and vehicle manufacturers are continuing to develop optimal restraint systems for reducing injuries under both In-Position and OOP conditions. In this study, a numerical simulation method for OOP front passenger injuries in frontal crashes is presented by using accurate finite element (FE) models of the airbag and the cockpit module. The main characteristics of the airbag model are: (i) the Finite Point Method is employed to simulate the flow of gas; (ii) the initial airbag shape is represented by a folding model; (iii) nonlinear anisotropic material properties of the airbag fabric are identified considering the fiber directions and hysteresis.
Technical Paper

An Application of Cluster Analysis to Dummy Injury Readings in a Frontal Crash

2012-04-16
2012-01-0556
Public concern about the crashworthiness of vehicles has been continuously rising in recent years. Crashworthiness is evaluated under various crash configurations, including frontal collisions, in regulatory testing and in New Car Assessment Programs. Accordingly, vehicle manufacturers must deploy sophisticated product development strategies and redouble their engineering efforts in order to develop vehicles that satisfy the specified requirements for crashworthiness. Computer simulation is one effective approach to resolving this issue in that it provides a valuable tool for conducting multiple parameter studies and iterations in a short period of time. However, it is no easy task for CAE engineers to analyze the large volumes of calculation results obtained in frontal crash simulations and to understand the phenomena involved.
Technical Paper

Early Detection of Reduced Alertness using Subsidiary Behavior

2012-04-16
2012-01-0737
An analysis of drivers' facial expressions and subsidiary behavior events (e.g., yawning, self-touching hand motions, etc.) revealed a significant correlation between the struggle against sleepiness and the frequency of occurrence of such events. We counted drivers' subsidiary behavior events by video analysis and defined nine categories of events related to the mouth, hands, head, shoulders, body and eyes. Mouth-related events were further categorized as yawning, stifling a yawn, exhaling and deep breathing. Yawning and self-touching hand motions in particular were observed in relatively large numbers among subsidiary behavior events. Based on this observation, we created an algorithm for detecting yawning and self-touching hand motions using a monocular camera and calculated the frequency of these subsidiary behavior events. In experiments, we compared the frequency of the subsidiary behavior events at the outset of driving and after the passage of time.
Technical Paper

A Study of Rear Seat 6-year-old Dummy Kinematics in Offset Frontal Crashes

2012-04-16
2012-01-0080
Occupant protection performance in frontal crashes has been developed and assessed for mainly front seat occupants over many years, and in recent years protection of rear seat occupants has also been extensively discussed. Unlike the front seats, the rear seats are often occupied by children seated in rear- facing or forward - facing child restraint systems, or booster seats. In the European New Car Assessment Program (NCAP), child occupant protection assessments using 18-month-old and 3-year-old test dummies in the rear seat are already being conducted. In addition, studies are under way concerning the development and introduction of test dummies of 6-year-old (6YO) and 10.5-year-old children. In this study, we focused on 6-year-old children sitting in belt-positioning booster seats. Offset frontal crash tests were conducted using two types of test dummies, a Hybrid III 6YO and a 6YO Q-series dummy (Q6), positioned in the rear seat.
Technical Paper

Development of Pole Side Impact Sled Test Method using Multiple Actuators for EuroNCAP

2012-04-16
2012-01-0095
The pole side impact test has been mandatory in Euro NCAP since 2009 and it includes, in addition to the head, assessments on other critical body regions that might be affected such as the chest, abdomen and pelvis. This paper describes a new test method for predicting Anthropomorphic Test Device responses to calculate injury index in side impact tests of a rigid pole under Euro NCAP conditions. Simplified sled tests are very effective in reducing the cost and time of development of more advanced side impact safety devices. To accomplish sled tests successfully, it is necessary to reconstruct accurately the combined dynamic deformation behavior of door and seat in pole impact. That behavior varies among different dummy response regions. Conventional sled test methods, published in previous literature, can reconstruct the deformation of the entire door using a single actuator at constant intrusion velocity but actual door velocity isn't constant in full scale vehicle crash tests.
Technical Paper

Effect of Impact-Triggered Automatic Braking in Multiple Impact Crashes

2012-04-16
2012-01-1181
This study proposes an impact-triggered automatic braking system as a potential safety improvement based on the characteristics of the Multiple Impact Crashes (MICs). The system activates with a signal of airbag deployment in a collision to reduce the vehicle speed in the subsequent collisions. The effectiveness was estimated by an in-depth review of the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS). The cases were extracted on the basis of the 3-point lap and shoulder belted occupants, incurring Maximum Abbreviated Injury Scale level 3 to 6 injuries (MAIS 3+), in the crashes occurred from 2004 to 2006, without vehicle rollover or occupant ejection, where the involved vehicles were 2000 and newer model year cars and light trucks.
Journal Article

A Study of the Ditch Fall-over Test Method Using Numerical Simulation

2012-04-16
2012-01-0094
Rollover tests are performed to design the algorithms for deployment of countermeasures to mitigate occupant ejection in rollover situations. The ditch fall-over test is one of the rollover test methods in which a vehicle on a steep slope, representing a ditch embankment, is subjected to a forced steering operation that results in a turnover. An accurate prediction method is needed to determine the specifications of the ditch fall-over test equipment and test conditions because a test-based trial-and-error process involves high cost of performing repeated experiments and preperation for various types of related test equipment. This paper presents a newly developed numerical simulation method for simulating vehicle behavior in ditch fall-over tests.
Journal Article

Different Factors Influencing Post-crash Pedestrian Kinematics

2012-04-16
2012-01-0271
Pedestrian crashes are the most frequent cause of traffic-related fatalities worldwide. The high number of pedestrian accidents justifies more active research work on passive and active safety technology intended to mitigate pedestrian injuries. Post-impact pedestrian kinematics is complex and depends on various factors such as impact speed, height of the pedestrian, front-end profile of the striking vehicle and pedestrian posture, among others. The aim of this study is to investigate the main factors that determine post-crash pedestrian kinematics. The injury mechanism is also discussed. A detailed study of NASS-PCDS (National Automotive Sampling System - Pedestrian Crash Data Study, US, 1994-1998), showed that the vehicle-pedestrian interaction in frontal crashes can be categorized into four types: “Thrown forward”, “Wrapped position”, “Slid to windshield” and “Passed over vehicle”.
Journal Article

Development of Injury Probability Functions for the Flexible Pedestrian Legform Impactor

2012-04-16
2012-01-0277
The goal of this study was to develop injury probability functions for the leg bending moment and MCL (Medial Collateral Ligament) elongation of the Flexible Pedestrian Legform Impactor (Flex-PLI) based on human response data available from the literature. Data for the leg bending moment at fracture in dynamic 3-point bending were geometrically scaled to an average male using the standard lengths obtained from the anthropometric study, based on which the dimensions of the Flex-PLI were determined. Both male and female data were included since there was no statistically significant difference in bone material property. Since the data included both right censored and uncensored data, the Weibull Survival Model was used to develop a human leg fracture probability function.
Journal Article

Effect of Loading Rate Dependence on Unstable Behavior of Thin-Shell Structured Beams under Axial Compression- Elucidation of Mechanism and Effect of Beam Aspect Ratio on Loading Rate Dependence

2012-04-16
2012-01-0554
The thin-shell structured beams that are used extensively in the vehicle body need to satisfy both strength requirements for crash safety and demands for weight reductions for environmental friendliness. This study focused on the loading rate dependence of reaction force, especially the maximum value, which is generated in thin-shell structured beams as a result of axial force inputs in a frontal crash. The mechanism generating the reaction force was made clear through a comparison with classical Euler buckling(1) and von Karman's effective width expression(2). It was observed that a square cross section displays markedly large loading rate dependence, which can be approximated well by considering the effect of inertial force in the high loading rate region and by von Karman's effective width solution in the low loading rate region. Essentially, this dependence is governed by Euler buckling.
Journal Article

An Investigation of Injury Factors Concerning Drivers in Vehicles Involved in Small-Overlap Frontal Crashes

2012-04-16
2012-01-0599
The causes of injuries suffered by drivers in “small-overlap frontal crashes” (SOFC) were examined. These crashes were defined as ones in which vehicles are loaded outside their longitudinal side members. SOFC accident data sets stored in the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) database were investigated. Percentages of cases sustaining injury to each body region of drivers were calculated, and the differences between the percentages of injury by body region were examined. To investigate the injury mechanisms, SOFC tests with two types of rigid barrier were then conducted. Injury values in each body region were analyzed to validate the reproducibility of SOFC test as a relevant test.
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