Structural Safety Design for Real-World Situations - Using Computer Aided Engineering for Robust Passenger Car Crashworthiness

Doctoral thesis, 2013

Road traffic continues to cause more than a million fatalities worldwide every year. Although many steps have been taken to improve occupant protection in car crashes, challenges still remain for car designers. In the present study, real-world data derived from frontal crashes has been used as a base for identifying crash situations where occupants are severely or fatally injured in cars despite them having been awarded top-ratings in crashworthiness evaluation tests. One situation identified is small overlap crashes, where injuries are commonly related to intrusion. Another is large overlap situations, where injuries are not directly linked to intrusion but rather to vehicle deceleration and interaction with restraint systems. The aim of the studies constituting this thesis was to develop design methods for robust crashworthiness of future passenger cars and propose solutions to mitigate injuries in large overlap situations. Research was performed using simulation models ranging from simple mass-spring elements to detailed Finite Element (FE) models of contemporary passenger cars. A newly developed methodology has been proposed as a main contribution based on the research undertaken, in order to provide a comprehensive way of simulating and visualising structural robustness in car-to-car frontal crashes. The methodology was applied to identify worst-case scenarios both regarding intrusion (oblique small overlap scenarios) and deceleration (large, but not full, overlap scenarios). Further development of this methodology has been proposed in order to address issues of crash compatibility, as well as a tool for securing robustness in future mass reduction scenarios. Another contribution is the proposal of an adaptive front structure to reduce passenger compartment deceleration levels by actively decoupling the front subframe on a contemporary passenger car in a range of frontal car-to-car crash scenarios. Results suggest a deceleration reduction potential equivalent to reducing the velocity change in a frontal crash by up to 44%. The findings of the present study are compared to previous work and future applications are suggested.