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Technical Paper

A Global and a Detailed Mathematical Model for Head-Neck Dynamics

Two mathematical head-neck models have been developed using MADYMO: a global model and a detailed one. The global model comprises rigid head and vertebrae connected through nonlinear viscoelastic intervertebral joints representing the lumped behaviour of disc, ligaments, facet joints and muscles. The model response to frontal impacts agreed reasonably with volunteer responses. The detailed model comprises rigid head and vertebrae connected through linear viscoelastic discs, nonlinear viscoelastic ligaments, frictionless facet joints and contractile muscles. The model response to lateral impacts agreed excellently with volunteer responses, whereas the response to frontal impacts showed that the model was too flexible. The global model is especially suited for use in complex simulations as occupant behaviour in car crashes, whereas the detailed model is particularly suited for neck injury assessment.
Technical Paper

A Mathematical Human Body Model for Frontal and Rearward Seated Automotive Impact Loading

Mathematical modelling is widely used for crash-safety research and design. However, most occupant models used in crash simulations are based on crash dummies and thereby inherit their apparent limitations. Several models simulating parts of the real human body have been published, but only few describe the entire human body and these models were developed and validated only for a limited range of conditions. This paper describes a human body model for both frontal and rearward loading. A combination of modelling techniques is applied using rigid bodies for most body segments, but describing the thorax as a flexible structure. The skin is described in detail using an arbitrary surface. Static and dynamic properties of the articulations have been derived from literature. The RAMSIS anthropometric database has been used to define a model representing a 50th percentile male.
Technical Paper

A Three-Dimensional Head-Neck Model: Validation for Frontal and Lateral Impacts

The three-dimensional head-neck model of Deng and Goldsmith (J. Biomech., 1987) was adapted and implemented in the integrated multibody/finite element code MADYMO. The model comprises rigid head and vertebrae, connected by linear viscoelastic intervertebral joints and nonlinear elastic muscle elements. It was elaborately validated by comparing model responses with the responses of human volunteers subjected to frontal and lateral sled acceleration impacts. Fair agreement was found for both impacts. Further, a sensitivity analysis was performed to assess the effect of parameter variations on model response. The model proved satisfactory and may be used as a tool to improve restraint systems or dummy necks.
Technical Paper

An Advanced Database of the 50th Percentile Hybrid III Dummy

This paper presents a measurement program of a sitting 50th percentile Hybrid III Dummy to determine a database for computer simulations. Geometrical, inertial, joint property and surface compliance measurements have been carried out. A description of the measuring methodology is given. On the basis of these measurements a 20 segment database for the MADYMO 3D occupant simulation program is developed. The major advancements of this database compared to an earlier 15-segment database developed by TNO [1]* can de summarized as follows: Five additional segments are incorporated in this database to account for the hands, the shoulders(clavicles) and the sternum. The database includes a complete omni-directional description for the neck as well as the lumbar spine. A detailed mathematical surface description is available, for instance to be used for computer animations. Segment ellipsoids for contact interactions have been determined in a more accurate way.
Technical Paper

Comparison of Human Volunteer and Cadaver Head-Neck Response in Frontal Flexion

At the 30th Stapp Conference an analysis was presented of human volunteer head-neck response in omni-directional impact tests. It was shown that the relative head motion can be described by a simple two-pivot analog system. The present study extends this analysis to post-mortem human subject (PMHS) tests conducted at the University of Heidelberg. Two test series similar to the human volunteer frontal impacts tests were carried out. One having an impact severity identical to the most severe human volunteer tests. A second series with higher exposure levels are used to verify the proposed analog system for higher impact levels. Test results including neck injury data for five PMHS tests will be given with special attention to trajectories of the head center of gravity, head rotations and head accelerations. It is concluded that the center of gravity trajectories for the PMHS and volunteer tests are similar for both impact levels.
Technical Paper

Comparison of the Rear Impact Biofidelity of BioRID II and RID2

Researchers worldwide try to define a unique test procedure for the assessment of whiplash protection of seats and restraint systems in low speed rear-end impact. Apart from valid injury criteria and uniform crash conditions, there is no clear answer to the question, which dummy to use. There are two impact dummies currently available, which have been designed for rear-end impact testing: BioRID and RID2. Both dummies have been evaluated in several test programs, however, both dummies have never been compared with each other in the test conditions, which form the basis of their design. BioRID was based on and validated against volunteer tests performed by Davidsson and Ono, while RID2 was designed with and validated against PMHS tests done by Bertholon and compared to volunteer tests reported by Van den Kroonenberg. This paper compares the responses of both rear impact dummies and the Hybrid III for the test conditions mentioned above.
Technical Paper

Development and Evaluation of a New Rear-Impact Crash Dummy: The RID2

Low severity neck injuries due to vehicle accidents are a serious problem in our society. In 1997 the European Whiplash project started with the aim to develop passive safety methodologies to reduce the frequency of neck injuries in rear-end impacts. This project has resulted, among others, in a rear impact crash dummy, the so-called RID2. The objective of this paper is present the design of this dummy and to present its performance in comparison with human volunteer and post mortem human subject (PMHS) tests. Also a comparison is made with the Hybrid III dummy in similar test conditions. In the comparison with human volunteers in a real car seat, both the RID2 and the Hybrid III showed realistic kinematics. Lower neck rotation as well as the typical S-shape in the neck were found in the RID2, but not in the Hybrid III dummy. Ramping up was not found in the Hybrid III, while the RID2 did show limited ramping up.
Technical Paper

ES2 Neck Injury Assessment Reference Values for Lateral Loading in Side Facing Seats

Injury assessment reference values (IARV) predicting neck injuries are currently not available for side facing seated aircraft passengers in crash conditions. The aircraft impact scenario results in inertial loading of the head and neck, a condition known to be inherently different from common automotive side impact conditions as crash pulse and seating configurations are different. The objective of this study is to develop these IARV for the European Side Impact Dummy-2 (ES-2) previously selected by the US-FAA as the most suitable ATD for evaluating side facing aircraft seats. The development of the IARV is an extended analysis of previously published PMHS neck loads by identifying the most likely injury scenarios, comparing head-neck kinematics and neck loads of the ES2 versus PMHS, and development of injury risk curves for the ES2. The ES2 showed a similar kinematic response as the PMHS, particularly during the loading phase.
Technical Paper

Head-Neck Response in Frontal Flexion

At the 27th Stapp Conference an analysis was presented of human head-neck motion in lateral flexion (1)*. Based on this analysis performance requirements for mechanical necks in this type of impact were formulated. This study extends the analysis to head-neck response in frontal flexion. Results will be presented of dynamical tests with human subjects conducted by the Naval Biodynamics Laboratory (NBDL) in New Orleans. Two of these subjects were also included in the analysis of lateral flexion. It will be shown that the mechanical (mathematical) system with two ball and socket joints describing the head-neck response in lateral flexion is also suitable for forward flexion. Geometrical parameters are identical for both impact directions in contrast to the dynamical properties which show significant differences. By this mechanical analog the observed head-neck motions are completely defined. Results will be compared with earlier performance requirements proposed by Mertz et al. (2,3).
Technical Paper

Human Head-Neck Response During Low-Speed Rear End Impacts

Neck injuries resulting from rear-end collisions rank among the top car safety problems and have serious implications for society. Many rear impact sled experiments with volunteers and PMHSs have been performed in the past. However, in most of these studies, T1 kinematics were not obtained so that the kinematic behavior of the neck could not be separated from the motion of the rest of the spine. Also, to the best knowledge of the authors, the effect of anthropometric parameters on the head-neck kinematics was not studied before. The objective of this study is to describe the kinematic response of the head-neck system during low severity rear end impacts. In addition, the effect of anthropometric parameters such as height, weight and neck circumference was investigated. For this purpose, a total of 43 tests with 19 subjects was performed. Values for Δv ranged between 6.5 and 9.5 km/h.
Technical Paper

Motorcycle Crash Test Modelling

This paper concerns the development and validation of a three-dimensional mathematical model representing a motorcycle with rider. As part of this development, several motorcycle to barrier tests were performed at the laboratories of the TNO Crash-Safety Research Centre and several measurements were carried out, including measurements to determine the inertia properties of the motorcycle segments. Results of two full scale tests involving a passenger car were then applied to validate the model in a more realistic crash environment. The resulting MADYMO motorcycle model consists of 7 bodies linked to each other by joints and spring-damper type elements. Special attention was given to the mathematical representation of front fork, front wheel and gastank. A 50th %ile Part 572 dummy with pedestrian pelvis and legs represented the rider. For representation in the model an existing dummy database was updated.
Technical Paper

Performance Requirements for Mechanical Necks in Lateral Flexion

Realistic simulation of the neck response in a dummy is of vital importance to obtain a humanlike dynamical behavior of the head. Trajectories of the head and the nature of head contact with vehicle interior or exterior are critically dependent on the dummy's neck design. Neck performance criteria in literature are limited to the neck response in forward flexion and extension. Recent research programs to develop dummies with omnidirectional biofidelity clearly show a need for additional requirements in lateral and oblique directions. In this study, dynamic lateral flexion tests with human volunteers conducted by the Naval Biodynamics Laboratory (NBDL) in New Orleans are analysed. It follows that the observed head neck motions in this type of impact quite well can be represented by a system with three degrees of freedom: a head and neck rotation in the plane of impact and a head torsion about the head anatomical z-axis.