Linus Wågström

STRUCTURAL ADAPTIVITY FOR ACCELERATION LEVEL REDUCTION IN PASSENGER CAR FRONTAL COLLISIONS

A mathematical model was developed to explore and demonstrate the injury reducing potential of an adaptable frontal stiffness system for full frontal collisions. The model was validated by means of crash tests and was found to predict the peak accelerations of the crash test vehicles well, whereas correlation concerning mean acceleration or residual crush was not found. Vehicles were divided into three mass classes, and a test matrix was established in order to evaluate different combinations of vehicles involved in frontal crash at three closing velocities. In a baseline simulation setup, constant stiffness values were used and the results were compared to the corresponding simulations using adaptable frontal stiffness. Results show promising acceleration peak reductions at low speeds, implying that injury risk reductions are possible.

A methodology for improving structural robustness in frontal car-to-car crash scenarios

There has been significant development in passenger car crashworthiness over the last few decades. However, real-world crashes often occur in scenarios dissimilar to laboratory barrier crash set-ups. Further knowledge is required on how different impact scenarios affect vehicle structural response and occupant injury risk in real-world scenarios. This study introduces a methodology for assessing crash configuration parameters that influence the structural response in car-to-car frontal collisions by using finite element models of two identical vehicles. The crash configuration parameters included in this study were initial velocities, oblique angle and lateral offset distance. An evaluation was made in terms of passenger compartment intrusion and crash pulse severity. Special focus was directed towards investigating whether these input parameters can be used to define incompatible scenarios, i.e. where the structural response in one vehicle is significantly different compared to the other vehicle. Results indicate that collision scenarios with large overlap as extreme in terms of crash pulse severity, and incompatible car-to-car crash scenarios were found at small overlap and an oblique angle of 15°. An outlook for future model and method validation work is described.

Adaptive structure concept for reduced crash pulse severity in frontal collisions

From accident statistics in real-world frontal collisions, it has been shown that a considerable portion of injuries occur in situations without major passenger compartment intrusions and that these injuries can be attributed to the occupant interaction with the restraint systems. To address these types of injuries, a novel front structure concept is proposed. This structure includes a partly detachable front subframe that can actively be released from the passenger compartment and thereby reduce the crash forces and related decelerations. The aim of this study was to quantify the effect of an adaptive front structure on occupant loading in a modern passenger car in frontal crash situations. A simplified finite element model was derived from a full vehicle model in order to run a large simulation matrix spanning from full overlap to small overlap situations. Occupant loading was estimated by using two simplified occupant chest deceleration models, the Volvo Pulse Index and the Occupant Load Criterion. Results suggest that modifying the crash pulse shape can be equivalent to reducing the velocity change in a crash by up to 44%. In relation to scenarios without subframe release, this indicates a considerably lower force required to be applied to the occupant from the restraint system.