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Rollover crashes are often difficult to reconstruct in detail because of their chaotic nature. Historically, vehicle speeds in rollover crashes have been calculated using a simple slide-to-stop formula with empirically derived drag factors. Roll rates are typically calculated in an average sense over the entire rollover or a segment of it in which vehicle roll angles are known at various positions. A unified model to describe the translational and rotational vehicle dynamics throughout the rollover sequence is lacking. We propose a pseudo-cylindrical model of a rolling vehicle in which the rotational and translational dynamics are coupled to each other based on the average frictional forces developed during ground contacts. We describe the model as pseudo-cylindrical because vertical motion is ignored but the ground reaction force is not constrained to act directly underneath the center of gravity of the vehicle.

This article compares the results of automotive accident reconstructions to event data recorder (EDR) data from vehicles involved in rear-end collisions. Accident reconstructions in the Crash Investigation Sampling System (CISS) database calculate crash severity expressed as the impact-related change in velocity (delta-V) experienced by a vehicle. The accuracy of the CISS-reconstructed delta-V in rear impacts was assessed by comparison to the delta-V recorded during the crash by the EDR on board the rear-ended vehicles. The CISS database was searched for single rear impact cases with a CISS-reconstructed delta-V as well as an EDR download. A total of 256 cases met these criteria. On average, the CISS-reconstructed delta-V was 4.0% lower than the delta-V recorded by the EDR. The accuracy of the CISS reconstructions varied with crash configuration, vehicle type, collision partner, and crash severity.

This paper reports on seventy additional tests conducted using a mechanical device described by Bonugli et al. [4]. The method utilized quasi-static loading of bumper systems and other vehicle components to measure their force-deflection properties. Corridors on the force-deflection plots, for various vehicle combinations, were determined in order to define the system stiffness of the combined vehicle components. Loading path and peak force measurements can then be used to evaluate the impact severity for low speed collisions in terms of delta-v and acceleration. The additional tests refine the stiffness corridors, previously published, which cover a wide range of vehicle types and impact configurations. The compression phase of a low speed collision can be modeled as a spring that is defined by the force-deflection corridors. This is followed by a linear rebound phase based on published restitution values [1,5].

This paper investigates the role that load-limiters play with respect to the performance of occupant protection systems, with focus on performance in frontal crashes. Modern occupant protection systems consist of not just the seat belt, but also airbags, interior vehicle surfaces and vehicle structure. Modern seat belts very often incorporate load-limiters as well as pretensioners. Published research has established that load-limiters and pretensioners increase the effectiveness of occupant protection systems. Some have argued that load-limiters with higher deployment thresholds are always better than load-limiters with lower deployment thresholds. Through testing, modeling and analysis, we have investigated this hypothesis, and in this paper we present test and modeling data as well as a discussion to this data and engineering mechanics to explain why this hypothesis is incorrect.

Further stringent emission legislation requires advanced technologies, such as sophisticated engine management and advanced catalyst and substrate to achieve high catalytic performance, especially during the light-off phase. This paper presents the results of calculations and measurements of hydrocarbon and carbon monoxide light-off performance for substrates of different wall thickness, cell density and cell shapes. The experimental data from catalyst light-off testing on an engine dynamometer are compared with theoretical results of computer modeling under different temperature ramps and flow rates. The reaction kinetics in the computer modeling are derived from the best fit for the performance of conventional ceramic substrate (6mil/400cpsi), by comparing the theoretical and experimental results on both HC and CO emissions. The calibrated computer model predicts the effects of different wall thickness, cell density and cell shape.

New ultra-low vehicle emission legislation requires advanced catalyst systems to achieve high conversion requirements. Manufacturers have to improve both the washcoat formulations and the catalyst substrate technology to meet these new regulations. This paper will present the results of a computer modeling study on the effects of ultra-thinwall catalysts on hydrocarbon and carbon monoxide light-off performance improvement. The experimental data from catalyst light-off testing on an engine dynamometer are compared with theoretical results of advanced substrate modeling for ultra-thin wall ceramic substrates. Results show that thermal mass has the greatest effect on light-off performance. Decreases in wall thickness offer the greatest benefit to light-off performance by lowering the thermal mass of the substrate, thus allowing it to reach light-off temperature faster.

Industry standards and practices define a number of mathematical and physical methods to estimate the cargo carrying volume capacity of a vehicle. While some have roots dating back decades, others try to assess the utility of the space for cargo by subjective measurements. Each these methods have their own inherent merits and deficiencies. The purpose of this paper is to highlight the differences in calculated cargo volume amongst the following practices: Society of Automobile Engineers (SAE) J1100[1] International Organization for Standardization (ISO 3832)[2], Global Car manufacturer's Information Exchange group (GCIE)[3], Consumer Reports[4]. This paper provides a method and associated rationale for constructing a new cargo volume calculation practice that attempts to harmonize these procedures into a more contiguous practice. This homologation will benefit publishing industry, vehicle manufacturers and customers alike.