Structural Safety Design for Real-World Situations
Using Computer Aided Engineering for Robust Passenger Car Crashworthiness
LINUS WÅGSTRÖM
Thesis submitted for the degree of Doctor of Philosophy
in Machine and Vehicle Systems at the Department of Applied Mechanics,
Chalmers University of Technology, Gothenburg, Sweden
To be defended in public, 10.00 a.m., Friday November 8th, 2013
in Omega, Hörselgången 5, Lindholmen, Gothenburg
Faculty opponent
William Thomas Hollowell, Ph.D.
Director (Retired), Office of Applied Vehicle Safety Research,
National Highway Traffic Safety Administration
United States of America
Department of Applied Mechanics
Chalmers University of Technology
SE-412 96 Gothenburg, Sweden
Telephone +46(0)31 772 1000
Structural Safety Design for Real-World Situations
Using Computer Aided Engineering for Robust Passenger Car Crashworthiness
LINUS WÅGSTRÖM
Department of Applied Mechanics
Chalmers University of Technology
ABSTRACT
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 offset 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.
Keywords: passive safety, crash simulation, structural robustness, frontal crashes, structural
adaptivity, crash compatibility, small overlap crashes