[Society of Automotive Engineers International Congress and Exposition, March 2000]

There is little debate that reconstructing a rollover crash presents complex multi-dimensional challenges to the reconstructionist. Real world rollovers often cover large amounts of various terrains and typically involve multiple ground impacts. The possible vehicle orientations throughout the roll are almost unlimited. It is also clear that the complexities of these events have placed practical limitations on the abilities for both analytical and experimental models to accurately recreate specific real world rollover collisions.

The fundamentals of accident reconstruction do still apply, however, and much valuable and insightful test data is available. This paper will describe a practical methodology and protocol to assist reconstructionists in reconstructing both on-road and off-road rollover accidents. It will point to previously published rollover studies relevant to the reconstructionist; present a methodology and protocol for documenting and analyzing field data, most specifically accident vehicle damage; and, lastly, it will review various presentation techniques useful for explanation and validation of the reconstructionist’s conclusions.

[Society of Automotive Engineers International Congress and Exposition, March 2000]

In this study we continue and build upon previous research conducted with various production three-point restraint systems; studying resulting vertical excursion on restrained inverted occupants. Vertical excursions will be reported for various sized occupants restrained by both production vehicle belt systems as well as systems incorporating alternative designs. Vertical excursions have been reduced by an average of 77% with optimized belt geometry combined with belt pretensioning.

Modeling of Frontal and Rollover Collisions and Restraint Analysis

[12^th International Conference on Mathematical and Computer Modeling and Scientific Computing, August 1999]

The Articulated Total Body (ATB) computer model is a dynamic multi-body simulation program which has been utilized to model and analyze occupant motion, injury mechanisms and injury mitigation in a variety of automotive impact environments. ATB has been used extensively to model actual automotive accidents in order to better understand injury mechanisms and to investigate alternative scenarios. In this paper, 3 examples of this methodology are presented. First, a real-world frontal impact accident is analyzed. This accident resulted in a rear seat occupant submarining under a lap belt. The simulation demonstrated that the addition of a shoulder belt would eliminate the likelihood of submarining and related injuries in this accident. Next to be analyzed was a real-world frontal offset accident. The effectiveness of padding on an automotive A-pillar and the effectiveness of door-mounted restraints were analyzed. Finally, a simulation of a large truck rollover was created to understand the restraint performance and occupant motions experienced in a rollover. An analysis of restraints in frontal and rollover collisions is given.

[Vol. 43; 1999; Advances in Bioengineering; ASME 1999]

Padding materials are routinely used to reduce the potential for head injury. The interior of vehicles has been identified as an area where injury can occur in the absence of padding. Head impacts with roof, pillars and support structures have been studied by Fan, Monk, and Friedman. Recent rulemaking by the National Highway Traffic Safety Administration has identified padding as a potential mechanism for reduction in head injury. Helmets utilize padding for energy management so as to reduce the potential for head injury. *(Meyers, Becker). The occurrence of diffuse axonal injury with direct impacts and translational accelerations have been evaluated by Nishimoto. Mclean has suggested that brain injury does not occur without head impact. The padding studies were conducted to evaluate the effect of padding on the Head Injury Criterion (HIC), linear acceleration and angular acceleration.

[Biomedical Engineering Society, Engineering in Medicine and Biology, 1^st Joint Conference, October 1999]

ABSTRACT

Potential injury mitigation of padding on vehicular roll bars was evaluated. After market and metal air gap padding markedly reduced the head injury criterion (HIC) angular acceleration and angular velocity compared to the stock foam roll bar padding.

[Society of Automotive Engineers International Congress and Exposition, February 1998]

This paper describes some human subject experiments in occupant response to rollover with reduced headroom. The results suggest that with a nominal 10 cm of head room, 7.5 to 15 cm of torso excursion in production belts and more than 15 cm of roof intrusion, serious neck injury is likely. Brain damage/head injury is more likely from a combination of roof rail crush and high change of angular roll rate.

[Society of Automotive Engineers International Congress and Exposition, February 1998]

Rollover accidents account for a large number of serious to fatal injuries annually. In the past, these injuries were often the result of unrestrained occupant ejection. Subsequent to mandatory belt use laws, a larger percentage of these injuries occur inside the vehicle, and the head and neck areas sustain a substantial number of these injuries. Rollovers have been characterized as violent events, roof crush as the natural consequence of such violence. Further, head and neck injury have been thus considered unavoidable, even with occupant use of the production restraints.

This paper will describe the relationship between the three dimensional extent (severity) of roof crush and the equivalent drop test contact velocity as derived from physical experiments and tests. The drop test contact velocity is directly related to the cumulative change of velocity experienced by a vehicle as a result of roof contact deformation during a rollover accident by validated computer simulations. The conclusion is that a summary range of impact velocities to produce more than 15 cm of roof crush for most on-the-road cars and light trucks from 1988 to 1992, is approximately 1 to 2 m/s.

[Society of Automotive Engineers International Congress and Exposition, February 1998]

Rollover accidents account for a large number of serious to fatal injuries annually. In the past, these injuries were often the result of unrestrained occupant ejection. Subsequent to mandatory belt use laws, a larger percentage of these injuries occur inside the vehicle, and the head and neck areas sustain a substantial number of these injuries.

An analytical effort to understand rollover injuries, using the field accident data of the NASS files and residual headroom as an indicator, was reported by the authors at the 1996 ESV conference in Melbourne, Australia. This paper describes the relationship between roof crush and restrained occupant injury in rollover accidents as derived from the analysis of 1988-1992 NASS files. It extends the residual headroom parameter to the entire population of head, face and neck occupants injured inside the compartment.

[Society of Automotive Engineers International Congress and Exposition, February 1998]

ABSTRACT

Experimental results from three point bending and axial compression tests of common automotive roof elements are presented. Modifications of these components were also tested to evaluate the effect of structural reinforcements and void filling.

Under three-point bending, an open hat section side header (or side rail) was tested and failed in a manner consistent with observed failures in real world accidents. Modifying the hat section to create a closed section increased load capacity and energy absorption, and demonstrated some gains in strength to weight performance. Two epoxy compounds in a similar closed section configuration resulted in substantial increases in peak load, energy absorption and strength-to-weight ratio.

In the axial compression tests, a open "c" section front header were tested in axial compression and failed just past a sheet metal reinforcement consistent with observed failures in real world accidents. The void filled header was successful at resisting local section collapse at the sheet metal reinforcement and material holes. Peak axial strength, energy absorption and strength to weight were increased for the void filled header relative to the production component. A metal reinforced front header and a production closed side header from the same vehicle also generated considerable increases in peak strength, energy absorption and strength to weight ratio.

Both void filling and structural reinforcements demonstrated structural advantages in peak load capacities and energy absorption properties. Optimization of the proper void filling density and amount of metal reinforcement is required on an individual design basis to maximize the effectiveness. Both techniques demonstrated an ability to improve upon existing automotive components and repair some of their inherent weaknesses.

[National Academy of Forensics Engineers Conference, July 1997]

3-point safety belts are designed and provided with a primary objective being to control and limit occupant motions within the vehicle. These systems function differently in different accident modes. In frontal impacts, the safety belts primarily limit forward occupant motion towards interior vehicle components. In rollover crashes, the belts should provide both restraint from vertical motion towards dangerous upper interior contacts as well as prevent ejection. Controlling the severity of the occupant’s "second collision" within the vehicle is critical to injury reduction. This paper will report on our continued research in this area, concentrating on the effects of belt pretensioning in rollovers.