Search Results

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.

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.